INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 152
POLYBROMINATED BIPHENYLS
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization.
First draft prepared by Dr. W. Gross, Dr. J. Kielhorn
and Dr. C. Melber, Fraunhofer Institute for
Toxicology and Aerosol Research, Hanover, Germany
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
World Health Orgnization
Geneva, 1994
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venture of the United Nations Environment Programme, the International
Labour Organisation, and the World Health Organization. The main
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carried out by the IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
epidemiological studies, and promotion of research on the mechanisms
of the biological action of chemicals.
WHO Library Cataloguing in Publication Data
Hexachlorobutadiene.
(Environmental health criteria: 152)
1. Polybromobiphenyl compounds - adverse effects
2. Polybromobiphenyl compounds - toxicity
3. Environmental exposure
4. Environmental pollutants I.Series
ISBN 92 4 157152 7 (NLM Classification QV 633)
ISSN 0250-863X
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR POLYBROMINATED BIPHENYLS (PBBs)
1. SUMMARY AND EVALUATION, CONCLUSIONS AND RECOMMENDATIONS
1.1. Summary and evaluation
1.1.1. Identity, physical and chemical properties,
analytical methods
1.1.2. Sources of human and environmental exposure
1.1.3. Environmental transport, distribution, and
transformation
1.1.4. Environmental levels and human exposure
1.1.5. Kinetics and metabolism
1.1.6. Effects on organisms in the environment
1.1.7. Effects on experimental animals and
in vitro test systems
1.1.8. Effects on humans
1.1.9. Overall evaluation of toxicity and
carcinogenicity
1.2. Conclusions
1.3. Recommendations
1.3.1. General
1.3.2. Future research
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.1.1. Primary constituents
2.1.2. Technical products
2.1.2.1 Major trade names
2.1.2.2 Composition of the technical products
2.2. Physical and chemical properties
2.2.1. Physical and chemical properties of individual
congeners
2.3. Conversion factors for PBB in air
2.4. Analytical methods
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Man-made sources
3.2.1. Production levels and processes
3.2.1.1 World production figures
3.2.1.2 Manufacturing processes
3.2.1.3 Loss into the environment during
normal production
3.2.1.4 Methods of transport, accidental
release, and disposal of production
wastes
3.2.2. Uses
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1. Transport and distribution between media
4.1.1. Air
4.1.2. Water
4.1.3. Soil
4.1.4. Biota
4.1.4.1 Terrestrial ecosystems
4.1.4.2 Aquatic ecosystems
4.1.4.3 Accidental contamination of the
food chain
4.2. Degradation
4.2.1. Photolytic degradation
4.2.2. Microbial degradation
4.2.3. Degradation by plants and animals
4.2.4. Bioaccumulation
4.2.4.1 Aquatic organisms
4.2.4.2 Terrestrial organisms
4.3. Ultimate fate following use
4.3.1. Disposal of PBB-contaminated animals
and wastes from the Michigan disaster
4.3.2. Thermal decomposition of PBBs
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water and sediments
5.1.2.1 Surface waters
5.1.2.2 Sediments
5.1.2.3 Groundwater
5.1.3. Soil
5.1.4. Feed and food
5.1.4.1 Feed
5.1.4.2 Food
5.1.5. Other products
5.1.6. Terrestrial and aquatic organisms
5.1.6.1 Aquatic and terrestrial plants
5.1.6.2 Animals
5.2. General population exposure
5.2.1. Quantified data on human exposure
5.2.1.1 Worldwide
5.2.1.2 The Michigan accident
5.2.2. Human monitoring methods for PBBs
5.2.3. Human monitoring data
5.2.4. Subpopulations at special risk
5.3. Occupational exposure during manufacture, formulation, or
use
6. KINETICS AND METABOLISM
6.1. Absorption
6.1.1. Animal studies
6.1.1.1 Gastrointestinal absorption
6.1.1.2 Dermal and inhalation absorption
6.1.2. Human studies
6.2. Distribution
6.2.1. Animal studies
6.2.1.1 Levels in organs and blood
6.2.1.2 Transfer to offspring
6.2.2. Human studies
6.3. Metabolic transformation
6.3.1. In vitro studies
6.3.2. In vivo studies
6.3.3. Metabolic pathway
6.4. Elimination and excretion in expired air, faeces,
urine
6.4.1. Animal studies
6.4.2. Human studies
6.5. Retention and turnover
6.5.1. Animal studies
6.5.1.1 Time trends, retention:
2,2',4,4',5,5'-hexabromobiphenyl
(BB 153)
6.5.1.2 Biological half-lives
6.5.1.3 Differences between individual
congeners
6.5.1.4 Octabromobiphenyl
6.5.2. Human studies
6.6. Reaction with body components
6.6.1. Animal studies
6.6.2. Human studies
7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
7.1. Microorganisms
7.2. Aquatic organisms
7.3. Terrestrial organisms
7.3.1. Wildlife
7.3.2. Farm animals
7.3.2.1 Cattle
7.3.2.2 Other farm animals
7.4. Population and ecosystem effects
7.5. Effects on the abiotic environment
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
8.1. Lethality
8.2. Single and short-term exposures: general signs of
toxicity
8.2.1. PBB mixtures
8.2.1.1 Overt clinical signs, food intake,
and body weight changes
8.2.1.2 Haematology and clinical chemistry
8.2.1.3 Morphological and histopathological
changes
8.2.2. Individual PBB congeners and comparative
studies
8.2.2.1 Food intake, overt clinical signs,
body weight changes
8.2.2.2 Haematology and clinical chemistry
8.2.2.3 Morphological and histopathological
changes
8.3. Skin and eye irritation, sensitization, dermal
lesions, and acne
8.4. Long-term toxicity
8.4.1. Rat
8.4.1.1 Overt clinical signs, body weight
changes, food intake
8.4.1.2 Haematology and clinical chemistry
8.4.1.3 Morphological changes
8.4.1.4 Histopathological changes
8.4.2. Mouse
8.4.3. Cattle
8.4.4. Mink
8.4.5. Rhesus monkey
8.4.6. Pre- and perinatal exposure
8.5. Reproduction, embryotoxicity, and teratogenicity
8.5.1. PBB mixtures
8.5.1.1 Mammals
8.5.1.2 Avian species
8.5.2. Individual PBB congeners
8.6. Mutagenicity and related end-points
8.7. Carcinogenicity
8.7.1. Carcinogenicity in long-term toxicity studies
8.7.2. Mechanisms of carcinogenicity
8.7.2.1 Tumour initiation
8.7.2.2 Tumour promotion
8.7.2.3 PBBs acting as complete carcinogens
8.8. Biochemical toxicity
8.8.1. Induction of microsomal enzymes
8.8.1.1 Commercial PBB mixtures
8.8.1.2 Individual PBB congeners
8.8.2. Endocrine interactions
8.8.2.1 Thyroid hormones
8.8.2.2 Sex hormones
8.8.2.3 Prostaglandins
8.8.3. Interaction with drugs and toxicants
8.8.4. Effect on vitamin A storage
8.8.5. Porphyria
8.8.6. Miscellaneous effects
8.9. Effects on intercellular communication
8.10. Immunotoxicity
8.11. Neurotoxicity
8.11.1. Exposure of adult animals
8.11.2. Perinatal exposure
8.12. Factors modifying toxicity, toxicity of metabolites
8.12.1. Contaminants affecting toxicity
8.12.1.1 Polybrominated naphthalenes (PBNs)
8.12.1.2 Mixed polybromo-chlorobiphenyls
8.12.2. Toxicity of metabolites
8.12.3. Toxicity of photolysis and pyrolysis products
8.12.3.1 Photolysis products
8.12.3.2 Pyrolysis products
8.13. Mechanism of toxicity including carcinogenicity
9. EFFECTS ON HUMANS
9.1. General population exposure
9.1.1. Acute toxicity-poisoning incidents
9.1.2. Epidemiological studies
9.1.2.1 Studies conducted by the Michigan
Department of Public Health
(MDPH studies)
9.1.2.2 Studies conducted by the
Environmental Science Laboratory,
Mount Sinai School of Medicine,
New York (ESL studies)
9.1.3. Special studies
9.1.3.1 Examination of subjects with
complaints
9.1.3.2 Cutaneous effects
9.1.3.3 Effects on liver function
9.1.3.4 Porphyria
9.1.3.5 Effects on spermatogenesis
9.1.3.6 Paediatric aspects
9.1.3.7 Neurological and neuropsychiatric
aspects
9.1.3.8 Lymphocyte and immune function
9.1.3.9 Carcinogenic embryonic antigen
plasma levels
9.1.3.10 Biochemical effects
9.2. Occupational exposure
9.2.1. Epidemiological studies
9.2.2. Clinical studies
9.2.3. Special studies
9.2.3.1 Cutaneous effects
9.2.3.2 Memory performance
9.2.3.3 Thyroid effects
9.2.3.4 Reproductive effects
9.2.3.5 Lymphocyte function
9.2.3.6 Mortality
10. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
ANNEX 1
RESUME ET EVALUATION, CONCLUSIONS ET RECOMMANDATIONS
RESUMEN Y EVALUACION, CONCLUSIONES Y RECOMENDACIONES
WHO TASK GROUP ON ENVIRONMENTAL HEALTH
CRITERIA FOR POLYBROMINATED BIPHENYLS
Members
Dr L. Albert, Consultores Ambientales Asociados, S.C., Xalapa,
Veracruz, Mexico
Dr J. Alexander, Department of Toxicology, National Institute of
Public Health, Oslo, Norway
Dr W. Gross, Fraunhofer Institute for Toxicology and Aerosol
Research, Hanover, Germany
Dr R.F. Hertel, Federal Health Department CV 2.1, Berlin,
Germany (Co-Rapporteur)
Dr B. Jansson, Swedish Environmental Protection Agency,
Environmental Impact Assessment Department, Solna, Sweden
Dr J. Kielhorn, Fraunhofer Institute for Toxicology and Aerosol
Research, Hanover, Germany
Dr R.D. Kimbrough, Institute for Evaluating Health Risks (IEHR),
Washington, DC, USA (Chairman)
Dr C. Melber, Fraunhofer Institute for Toxicology and Aerosol
Research, Hanover, Germany (Co-Rapporteur)
Dr K. Mitsumori, Division of Pathology, Biological Safety
Research Center, National Institute of Hygienic Sciences,
Tokyo, Japan
Dr S. Sleight, Department of Pathology, Michigan State
University, East Lansing, Michigan, USA
Professor P. Yao, Institute of Occupational Medicine, Chinese
Academy of Preventive Medicine, Beijing, People's Republic of
China (Vice-Chairman)
Observers
Dr B. Savanne, ELF ATOCHEM, Paris La Défense, France
Mr S. Tsuda, Environmental Health and Safety Division,
Environment Directorate, Organisation for Economic
Co-operation and Development, Paris, France
Secretariat
Dr H. Galal-Gorchev, International Programme on Chemical
Safety, World Health Organization, Geneva, Switzerland
(Secretary)
Dr K.W. Jager, International Programme on Chemical Safety,
World Health Organization, Geneva, Switzerland
NOTE TO READERS OF THE CRITERIA MONOGRAPHS
Every effort has been made to present information in the
criteria monographs as accurately as possible without unduly
delaying their publication. In the interest of all users of the
Environmental Health Criteria monographs, readers are kindly
requested to communicate any errors that may have occurred to the
Director of the International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland, in order that they may be
included in corrigenda.
* * *
A detailed data profile and a legal file can be obtained from
the International Register of Potentially Toxic Chemicals, Case
postale 356, 1219 Châtelaine, Geneva, Switzerland (Telephone
No. 9799111).
* * *
This publication was made possible by grant number 5 U01
ES02617-14 from the National Institute of Environmental Health
Sciences, National Institutes of Health, USA.
ENVIRONMENTAL HEALTH CRITERIA FOR POLYBROMINATED BIPHENYLS
A WHO Task Group on Environmental Health Criteria for
Polybrominated biphenyls (PBBs) met at the Fraunhofer Institute for
Toxicology and Aerosol Research, Hanover, Germany, from 22 to 26
June 1992. Dr H. Galal-Gorchev, IPCS, welcomed the participants on
behalf of Dr M. Mercier, Director of the IPCS, and the three IPCS
cooperating organizations (UNEP/ILO/WHO). The Group reviewed and
revised the draft and made an evaluation of the risks for human
health and the environment from exposure to PBBs.
The first draft was prepared by Dr W. Gross, Dr J. Kielhorn
and Dr C. Melber of the Fraunhofer Institute for Toxicology and
Aerosol Research, Hanover, Germany, who also prepared the second
draft, incorporating comments received following circulation of the
first drafts to the IPCS Contact Points for Environmental Health
Criteria monographs.
Dr H. Galal-Gorchev and Dr K.W. Jager of the IPCS Central Unit
were responsible for the scientific content of the monograph, and
Mrs M.O. Head of Oxford for the technical editing.
The efforts of all who helped in the preparation and
finalization of the monograph are gratefully acknowledged.
1. SUMMARY AND EVALUATION, CONCLUSIONS AND RECOMMENDATIONS
1.1 Summary and evaluation
1.1.1 Identity, physical and chemical properties, analytical
methods
The term polybrominated biphenyls or polybromobiphenyls (PBBs)
refers to a group of halogenated hydrocarbons, formed by
substituting hydrogen by bromine in biphenyl. PBBs are not known to
occur as natural products. They have a molecular formula of C12
H(10-x-y)Br(x+y) where both x and y = 1 to 5. Theoretically 209
congeners are possible. Only a few have been synthesized
individually and characterized. PBBs, manufactured for commercial
use, consist mainly of hexa-, octa-, nona-, and decabromobiphenyls,
but also contain other homologues. They are additive type flame
retardants, and when blended with the dry solid or liquid polymeric
material, provide filter-type, flame retardant action with the
chemical release of hydrogen bromide if ignited.
PBBs are manufactured using a Friedel-Crafts type reaction in
which biphenyl is reacted with bromine with, or without, an
organic solvent, using, e.g., aluminium chloride, aluminium
bromide, or iron as catalyst.
Most research has been carried out on FireMaster BP-6 and
FF-1, which were involved in the Michigan disaster when this
compound was inadvertently added to animal feed instead of
magnesium oxide. The ensuing contamination of farm animals resulted
in the destruction of thousands of cattle, pigs, and sheep, and
millions of chickens.
The composition of FireMaster(R) changes from batch to
batch, but its main constituents are
2,2',4,4',5,5'-hexabromobiphenyl (60-80%), and
2,2',3,4,4',5,5'-heptabromobiphenyl (12-25%) together with lower
brominated compounds because of incomplete bromination reaction.
Mixed bromochlorobiphenyls and polybrominated naphthalenes have
also been observed as minor components of FireMaster(R).
FireMaster FF-1 (white powder) is FireMaster BP-6 (brown flakes) to
which 2% calcium silicate has been added as an anti-caking agent.
PBBs are solids with a low volatility that decreases with
increasing bromine number. PBBs are virtually insoluble in water,
soluble in fat, and slightly to highly soluble in various organic
solvents; solubility also decreases with increasing bromine number.
These compounds are relatively stable and chemically unreactive,
though highly brominated PBB mixtures are photodegraded with
reductive debromination upon exposure to ultraviolet radiation
(UVR).
The products of the experimental thermal decomposition of PBBs
depend on the temperature, the amount of oxygen present, and a
number of other factors. Investigations into the pyrolysis of
FireMaster BP-6 in the absence of oxygen (600-900 °C) have shown
that bromobenzenes and lower brominated biphenyls are formed, but
no polybrominated furans. In contrast, pyrolysis in the presence of
oxygen (700-900 °C) yielded some di- to heptabromodibenzofurans. In
the presence of polystyrene and polyethylene, higher levels were
found. Pyrolysis of FireMaster BP-6 with PVC at 800 °C yielded
mixed bromochlorobiphenyls. There is no information on the nature
of the products of incineration of PBB-containing material. Little
is known about the toxicities of brominated and
brominated/chlorinated dioxins and furans, but they are estimated
to be of about the same order as those of chlorinated dioxins and
furans.
The primary analytical technique used for the biological
monitoring of PBBs in environmental samples and biological tissues
and fluids, after the Michigan disaster, was gas chromatography
with electron capture detection. Individual congeners can be
determined by capillary gas chromatography and more specific
detection can be obtained with selected ion monitoring mass
spectrometry. Because of the large numbers of congeners possible,
investigations are hampered by lack of suitable synthetic
standards. Methods for extracting PBBs from biological samples have
been based on those for pesticides. PBBs are extracted with the
fat, and then purified.
The recent finding of PBB congeners in background biological
samples does not necessarily mean that concentrations are
increasing in the environment. The development of more sensitive
analytical techniques, such as negative ion chemical ionization
mass spectrometry, may be the explanation. Thus, the need for
retrospective studies is urgent. With improved clean-up methods, it
is possible to carry out specific analyses of the toxic co-planar
PBB congeners and such data are also needed.
1.1.2 Sources of human and environmental exposure
The commercial production of FireMaster(R) was started in
the USA in 1970. After the Michigan disaster, production was
discontinued (November 1974). The estimated production of PBBs in
the USA between 1970 and 1976 was 6000 tonnes (commercial
quantities). Octabromobiphenyl and decabromobiphenyl were produced
in the USA until 1979. A mixture of highly brominated PBBs called
Bromkal 80-9 D was produced in Germany until mid- 1985. Technical
grade decabromobiphenyl (Adine 0102) is currently produced in
France. As far as is known, this is the only current production of
PBBs.
PBBs were introduced as flame retardants in the early 1970s.
Prior to November 1974, hexabromobiphenyl was the most commercially
significant PBB in the USA and was incorporated into
acrylonitrile-butadiene-styrene (ABS) plastics (PBB content 10%),
used mainly in small appliance and automotive applications,
coatings, lacquers, and polyurethane foam. The other PBB flame
retardants have similar uses.
Losses of PBBs into the environment during normal production
can occur through emission into the air, waste waters, losses into
the soil, and to landfills, and have been found to be generally
low.
These chemicals can also enter the environment during
shipping and handling, and accidentally, as occurred in Michigan.
There is also the possibility of their entrance into the
environment as a result of the incineration of materials containing
PBBs as well as during accidental fires with the formation of other
toxic chemicals, such as polybromodibenzofurans or mixed
bromochloro derivatives.
The major part of the total volume of these compounds produced
will ultimately enter into the environment, as such, or as
breakdown products.
1.1.3 Environmental transport, distribution, and transformation
Long-range transport of PBBs in the atmosphere has not been
proven, but the presence of these compounds in Arctic seal samples
indicates a wide geographical distribution.
The principal known routes of PBBs into the aquatic
environment are from industrial waste discharge and leachates from
industrial dumping sites into receiving waters and from erosion of
polluted soils. PBBs are almost insoluble in water and are
primarily found in sediments of polluted lakes and rivers.
Pollution of soils can originate from point sources, such as
PBB plant areas and waste dumps. Once introduced into the soil,
PBBs do not appear to be translocated readily. PBBs have been found
to be 200 times more soluble in a landfill leachate than in
distilled water; this may result in a wider distribution in the
environment. The hydrophobic properties of PBBs make them easily
adsorbed from aqueous solutions onto soils. Preferential adsorption
of PBB congeners was noted, depending on the characteristics of the
soil (e.g., organic content) and the degree and position of bromine
substitution.
PBBs are stable and persistent, lipophilic, and only slightly
soluble in water; some of the congeners are poorly metabolized and
therefore accumulate in lipid compartments of biota. Once they have
been released into the environment, they can reach the food chain,
where they are concentrated.
PBBs have been detected in fish from several regions.
Ingestion of fish is a source of PBB transfer to mammals and birds.
Degradation of PBBs by purely abiotic chemical reactions
(excluding photochemical reactions) is considered unlikely. The
persistence of PBBs under field conditions has been reported. Soil
samples from a former PBB manufacturing site, analysed several
years after the Michigan incident, still contained PBBs though the
PBB congener composition was different, indicating a partial
degradation of the PBB residues in the soil sample.
Under laboratory conditions, PBBs are easily degraded by UVR.
Photodegradation of the commercial FireMaster(R) mixture led to
diminished concentrations of the more highly substituted PBB
congeners. The rates and extent of photolytic reactions of PBBs in
the environment have not been determined in detail, though field
observations indicate a high persistence of the original PBBs, or
a partial degradation to the less brominated congeners.
In laboratory investigations, mixtures of PBBs appear to be
fairly resistant to microbial degradation.
Neither uptake nor degradation of PBBs by plants has been
recorded. In contrast, PBBs are easily absorbed by animals and
though they have been found to be very persistent in animals, small
amounts of PBB metabolites have been detected. The main metabolic
products were hydroxy-derivatives, and, in some cases, there was
evidence of partially debrominated PBBs. No investigation of
sulfur-containing metabolites analogous to those of PCBs have been
reported.
The bioaccumulation of PBBs in fish has been investigated.
Bioaccumulation of PBBs in terrestrial animals has been
investigated in avian and mammalian species. Data were obtained
through field observations, evaluation of the Michigan disaster and
through controlled feeding studies. Generally, the accumulation of
PBBs in body fat depended on the dosage and duration of exposure.
Bioaccumulation of individual PBB congeners has been found to
increase with degree of bromination up to at least tetrabromo
biphenyls. Higher brominated congeners can be expected to
accumulate to an even greater extent. However, no information is
available for decabromobiphenyl; it is possible that it is poorly
absorbed.
Brominated dibenzofurans or partially debrominated PBBs have
been reported as products of the thermal decomposition of PBBs.
Their formation depends on several variables (e.g., temperature,
oxygen).
1.1.4 Environmental levels and human exposure
Only one report is available on PBB levels in air. In this
study, concentrations in the vicinity of three PBB-manufacturing or
PBB-processing plants in the USA were measured.
Levels in surface waters in the same vicinity and in the
Gratiot County landfill (Michigan, USA), which received over a
hundred thousand kg of waste containing 60-70% PBBs between 1971
and 1973, were monitored.
Groundwater monitoring data from the Gratiot County landfill
showed trace levels of PBBs even outside the landfill area,
however, PBBs were not detected in drinking-water wells in the
area.
Data on soil pollution by PBBs are available for areas of
manufacture, use, or disposal of PBBs, and for soils from fields of
the PBB-contaminated Michigan farms.
In the Michigan disaster, FireMaster(R) was inadvertently
added to animal feed. It was almost a year later that the mixing
error was discovered and the analyses indicated that PBBs were
responsible. During this time (summer 1973 - May 1974),
contaminated animals and their produce entered the human food
supply and the environment of the state of Michigan. Hundreds of
farms were affected, thousands of animals had to be slaughtered and
buried, as well as thousands of tons of farm produce.
Most data available on the PBB-contamination of wildlife refer
to fish and birds in the USA and Europe, primarily waterfowl, in
the vicinity of industrial sites, and marine mammals.
Recent reports on the PBB-contamination of fish, terrestrial
and marine mammals, and birds in the USA and Europe indicate a wide
distribution of these compounds. The congener pattern found in fish
samples is quite different from that found in commercial products.
Many of the major peaks could well be the result of the
photochemical debromination of decabromobiphenyl (BB 209), but this
has not been confirmed.
Occupational exposure was found in employees in chemical
plants in the USA, and in farm workers, as a result of the Michigan
PBB incident. Median serum and adipose tissue PBB levels were
higher among chemical workers. Information from other
countries/companies on occupational exposure associated with
manufacturing, formulation, and commercial uses is not available.
For most human populations, direct data on exposure to PBBs
from various sources have not been documented. Widespread human
exposure resulting from direct contact with contaminated feed and,
primarily, from the consumption of PBBs in meat, eggs, and dairy
products has been reported from Michigan, USA. At least 2000
families (primarily farmers and their neighbours) received heavy
exposure. Recently, PBBs have been detected in cows' milk and human
milk in Germany.
The congener patterns in these samples are different from that
in fish. The relative concentration of BB 153 is higher in human
milk than in fish.
The routes of exposure of the general population to PBBs are
not well known. Present knowledge indicates that ambient air and
water do not contain high levels. Lipid-rich food, especially from
contaminated waters, is probably of great importance. There is no
information on levels of exposure in indoor air and dermal exposure
levels from materials containing PBB flame retardants.
The PBB congener pattern found in human milk, collected in
Germany, resembled that found in cows' milk from the same region,
but levels in the human samples were substantially higher.
An estimate of the daily intake of PBB via food by the general
population has to be based on very few data. If it is assumed that
fish contains 20 µg PBB/kg lipid and 5% lipid and that a 60-kg
person eats 100 g fish/day, the intake will be 0.002 µg/kg body
weight per day. A PBB concentration of 0.05 µg/kg lipid in milk
(4% lipid) and a milk consumption of 500 ml/day will give the same
person a PBB intake of about 0.00002 µg/kg body weight per day.
An infant of 6 kg body weight consuming 800 ml human milk
(3.5% lipid) per day will have an intake of 0.01 µg PBB/kg body
weight per day, if the milk contains 2 µg PBB/kg lipid.
1.1.5 Kinetics and metabolism
Gastrointestinal absorption of PBBs varies according to the
degree of bromination, the lower brominated compounds being more
easily absorbed.
There is inadequate information on the absorption of DeBB and
OcBB/NoBB.
PBBs are distributed throughout the animal species and human
beings, the highest equilibrium concentrations being in adipose
tissues. Relatively high levels have also been found in the liver,
particularly of the more toxic congeners, which appear to be
concentrated in the liver. The partitioning ratios of the various
PBB congeners appear to differ between several tissues. Generally,
there is a marked tendency for bioaccumulation. In mammals,
transfer of PBBs to offspring occurs through transplacental and
milk routes. Human milk was found to contain levels of
2,2',4,4',5,5'-hexabromobiphenyl that were more than 100 times the
maternal serum levels. During a multigeneration study on rats,
administration of PBBs to a single generation resulted in
detectable residues in more than two subsequent generations. Eggs
of avian species were also affected by maternal PBB body burden.
Many PBB congeners are persistent in biological systems. There
was no evidence for significant metabolism or excretion of the more
abundant components of the FireMaster(R) mixture or for octa- and
decabromobiphenyl. In vitro-metabolism studies showed that
structure-activity relationships exist for the metabolism of PBBs.
PBBs could be metabolized by PB (phenobarbital)-induced microsomes
only if they possessed adjacent non-brominated carbons, meta and
para to the biphenyl bridge on at least one ring. Metabolism by
MC (3-methylcholanthrene)-induced microsomes required adjacent
non-brominated ortho and meta positions on at least one ring of
lower substituted congeners and higher bromination appeared to
prevent metabolism. Hydroxylated derivatives as major in vitro-
and in vivo-metabolism products of lower brominated biphenyls
have been identified in vertebrates. The metabolic yield was
relatively low. The hydroxylation reaction probably proceeds via
both arene oxide intermediates and by direct hydroxylation.
Humans, rats, rhesus monkeys, pigs, cows, and chickens
eliminate PBBs mainly in the faeces. In most cases, excretion rates
seem to be slow. Concentrations of 2,2',4,4',5,5'-hexabromobiphenyl
observed in the bile and faeces of humans were about 1/2 to 7/10 of
the serum levels and approximately 0.5% of the adipose levels.
Treatment to enhance elimination of PBBs in animals or humans had
no, or little, success. Another pathway of elimination is excretion
through milk.
Complex and varied relationships were found in PBB tissue
concentrations with time after PBB administration to rats and other
animals. They are described by several compartmental models. A
half-life of approximately 69 weeks was calculated for the
elimination of 2,2',4,4',5,5'-hexabromobiphenyl from the body fat
of rats. A half-life of more than 4 years was found in rhesus
monkeys. Average half-lives in humans have been estimated to be
between 8 and 12 years for 2,2',4,4',5,5'-hexabromobiphenyl. Ranges
of 5-95 years have been suggested in the literature. There are some
differences in retention and turnover between individual PBB
congeners. Results of analyses of serum from farmers and chemical
workers for 2,3',4,4',5-pentabromobiphenyl were inconsistent. This
inconsistency was probably because of the different sources of
exposure. The workers were exposed to all compounds of
FireMaster(R), while the Michigan population was exposed to
contaminated meat and milk containing a different PBB mixture as a
result of metabolic processes in farm animals. Bromine levels did
not decrease in the adipose tissue of rats, when technical
octabromobiphenyl was given. No information is available on the
retention of decabromobiphenyl.
Humans may have a greater tendency to retain certain PBB
congeners than experimental animals. This factor should be taken
into consideration in evaluating the human health hazards from
these chemicals.
In conclusion, all available data indicate that PBBs have a
marked tendency to bioaccumulate and persist. Metabolism is poor
and half-lives in humans are of the order of 8-12 years or longer.
1.1.6 Effects on organisms in the environment
Only few data are available on the effects of PBBs on
organisms in the environment. They refer to microorganisms, water
fleas, waterbirds, and farm animals.
Waterbirds nesting on islands in northwestern Lake Michigan
were studied to see if environmental contaminants were producing
effects on reproduction. Seventeen contaminants, including PBBs,
were measured, but none seemed to have a pronounced effect on
reproduction.
Farm animals that ingested feed inadvertently containing
Firemaster(R) FF-1 instead of magnesium oxide became sick. The
estimated average exposure of cows on the first identified highly
contaminated farm was 250 mg/kg body weight. The clinical signs of
toxicity were a 50% reduction in feed consumption (anorexia) and a
40% decrease in milk production, a few weeks after ingestion of the
contaminated feed. Although the supplemented feed was discontinued
within 16 days, milk production was not restored. Some cows showed
an increased frequency of urination, and lacrimation, and developed
haematomas, abscesses, abnormal hoof growth, lameness, alopecia,
hyperkeratosis, and cachexia; several died within 6 months of
exposure. Altogether, the death rate on this farm was 24/400. The
death rate of 6- to 18-month- old calves was much higher. About 50%
died within 6 weeks, only 2 out of 12 surviving after 5 months.
They developed hyper keratosis over their entire bodies. There were
also a variety of reproductive problems.
Necropsy findings have been reported for some of the mature
cows that died in the 6 months following exposure.
Histopathological studies revealed variable liver and kidney
changes.
Several clinical signs and pathological changes noted above
were later confirmed in controlled feeding studies (anorexia,
dehydration, excessive lacrimation, emaciation, hyperkeratosis,
reproductive difficulties, some clinical chemistry changes, and
renal damage).
A drop in production and sterility were reported in herds with
low-level contamination. This contrasts with results of controlled
studies, which did not show any significant differences between
herds with low-level contamination and control herds.
Although it was cattle feed that was originally involved in
the accidental substitution, other animal feeds became involved by
cross contamination, e.g., in the mixing machinery of feed
companies. It is likely that the exposure was not as high as that
of cattle. Although other animals (poultry, swine, horses, rabbits,
goats, and sheep) were reported as being contaminated and were
killed, details of ill effects were not recorded.
No information is available on the effects of PBBs on the
ecosystem.
1.1.7 Effects on experimental animals and in vitro test systems
The LD50 values of commercial mixtures show a relatively low
order of acute toxicity (LD50 > 1 g/kg body weight) in rats,
rabbits, and quails, following oral or dermal administration.
Deaths and acute manifestations of toxicity were delayed after
administration of PBB. The total dose administered determined the
extent of toxicity, whether given as a single dose or as repeated
doses over short periods (up to 50 days). The toxicity of PBBs was
higher with multiple-dose rather than single-dose administration.
Deaths after exposure to PBBs are delayed.
The few studies performed with commercial octa- and deca
bromobiphenyl mixtures did not result in mortality in rats and
fish. Of the individual PBB congeners, only three hexa isomers have
been tested, 3,3',4,4',5,5'-HxBB; and 2,3',4,4',5,5'-HxBB being
more toxic for rats than 2,2',4,4',5,5'-HxBB. On the basis of
limited, available data, OcBB and DeBB appear to be less toxic than
the PBB mixtures and less well absorbed.
In many acute and short-term studies, signs of PBB (mostly
FireMaster) toxicity have included reductions in feed consump tion.
At lethal doses, the cause of death cannot be ascribed to pathology
in a particular organ but rather to a "wasting syndrome" that the
animals develop as a first indication of toxicity. At death, the
loss in body weight can be as great as 30-40%. The few studies with
technical OcBB and DeBB did not show any such effects.
Morphological and histopathological changes, caused by PBB
exposure, are most prominent in the liver. Enlargement of the liver
frequently occurred at doses lower than those required to produce
body weight changes. The principal histopathological alterations in
rodent species may consist of extensive swelling and vacuolation of
hepatocytes, proliferation of smooth endoplasmatic reticulum, and
single-cell necrosis. The severity of the lesions depends on the
dose and the composition of the PBB material given.
Decreases in thymus weights were observed in rats, mice, and
cattle after doses of FireMaster(R), but not OcBB or DeBB.
There are some reports of increase in thyroid weight and
histological changes in the thyroid of rats, which have been
observed at low concentrations.
It is evident that individual PBB congeners differ in their
pattern of toxicity. The more toxic isomers and congeners cause a
decrease in thymus and/or body weight and produce pronounced
histological changes in the liver and thymus. Categorization of
halogenated biphenyls has been made on a structural basis.
Category 1 comprises isomers and congeners lacking ortho-
substituents (coplanar PBBs). Mono-ortho-substituted derivatives
constitute the second category. Other PBBs (mainly those with two
or more ortho-bromines) have been organized into the third
category. Congeners of Category 1 tend to elicit the most severe
effects, while the congeners of the second and third categories
show decreasing toxicological changes. Within the category, the
degree of bromination may also influence toxicity.
In all combinations tested, 3,3',4,4',5,5'-HxBB was found to
be the most toxic PBB. This congener is present in low
concentrations as a constituent of FireMaster(R). Of the major
FireMaster(R) constituents, 2,3,3',4,4',5-HxBB appeared to be the
most toxic one followed by 2,3',4,4',5,5'-HxBB and
2,3',4,4',5-PeBB. The main component of the FireMaster(R)
mixture, 2,2',4,4',5,5'-HxBB was relatively non-toxic as was
2,2',3,4,4',5,5'-HpBB, the second most abundant constituent.
The toxicity of technical OcBB and DeBB mixtures in relation
to their contents of various PBB congeners (and other possible
contaminants) is not so well elucidated.
Common skin and eye irritation tests and sensitization tests
resulted in no, or only mild, reactions to the technical PBB
mixtures tested (OcBB and DeBB). However, hyperkeratosis and hair
loss were seen in cattle, and lesions resembling chloracne were
seen in Rhesus monkeys, following the ingestion of a
FireMaster(R) mixture. Hyperkeratosis of the inner surface of the
rabbit ear was produced by FireMaster, but not by its main
components (2,2',4,4',5,5'-HxBB and 2,2',3,4,4'5,5'-HpBB).
Fractionation of FireMaster(R) revealed that most activity was
associated with the more polar fractions containing minor
components. Treatment with sunlight-irradiated HxBB caused severe
hyperkeratosis in rabbit ears.
Low dose, long-term feeding of technical OcBB to rats did not
affect food consumption and body weight, but an increase in the
relative liver weights of exposed rats was found at 2.5 mg/kg body
weight for 7 months. Long-term feeding of FireMaster(R) to rats
at doses of 10 mg/kg body weight for 6 months did not affect food
consumption. Doses of 1 mg/kg body weight over a 6-month period
affected liver weight. The thymus weight was decreased in female
rats administered 0.3 mg/kg body weight. Histopathological changes
were also noted. Controlled, long-term feeding studies on cattle
exposed to low doses of FireMaster(R) did not reveal any adverse
effects as indicated by food intake, clinical signs,
clinicopathological changes, or performance. Minks, guinea-pigs,
and monkeys appeared to be more susceptible to PBB toxicity.
Long-term effects related to the retention of administered
PBBs following pre- or perinatal exposure to high doses of
FireMaster(R) have been recorded in rats.
The most common adverse effects on reproduction were fetal
wastage and decrease in viability of offspring. Some effects were
still noted in mink at concentrations of 1 mg/kg diet. Decreases in
the viability of the offspring were observed in Rhesus monkeys
following a 12.5 month exposure to FireMaster(R) (0.3 mg/diet).
The monkeys received a daily dose of 0.01 mg/kg body weight and a
total dose of 3.8 mg/kg body weight. Reproduction and
neurobehavioural studies on monkeys and rats with low-level
exposure could not be evaluated since insufficient information was
given in the published papers on the experimental design of the
studies. A weak teratogenic potential was seen in rodents at high
doses that may have caused some maternal toxicity.
PBBs interact with the endocrine system. Rats and pigs showed
dose-related decreases in serum thyroxine and triiodo-thyronine.
PBBs have also been reported to affect the levels of steroid
hormones in most cases. The extent depends on the species as well
as the dose and time administered.
PBBs produced porphyria in rats and male mice at doses as low
as 0.3 mg/kg body weight per day. The no-effect level was 0.1 mg/kg
body weight per day. There was a pronounced influence of PBBs on
vitamin A storage as well as effects on the intermediary
metabolism.
Atrophy of the thymus was a frequent observation following PBB
exposure, and other lymphoid tissues have been shown to be
affected. Further indicators of a suppressed immune function have
also been demonstrated for FireMaster(R). Data on OcBB, NoBB,
DeBB, or individual PBB congeners are lacking.
One of the most intensively studied effects of PBBs is their
induction of mixed function oxidase (MFO) enzymes. Consistently,
FireMaster(R) was found to be a mixed-type inducer of hepatic
microsomal enzymes in rats and all other animal species tested.
Induction was also found to a lesser extent in other tissues. The
ability to induce hepatic microsomal enzymes differed for
individual PBB congeners. Correlations between structure and
microsomal enzyme inducing activity have been demonstrated.
Several studies have revealed that PBBs are able to alter the
biological activity of a variety of drugs and toxic substances.
This may partly be because of the ability of PBBs to induce
microsomal enzymes involved in the activation or deactivation of
xenobiotics.
The FireMaster(R) mixture, and some of its major components,
were found to be capable of inhibiting intercellular communication
in vitro. This inhibition occurs at non-cytotoxic concentrations.
Both the cytotoxicity and metabolic cooperation-inhibiting
properties of PBB congeners seem to be related to their structure,
i.e., presence or lack of ortho-substitution.
In vitro and in vivo assays (microbial and mammalian cell
mutagenesis, mammalian cell chromosomal damage, mammalian cell
transformation, and DNA damage and repair) have failed to indicate
any mutagenicity or genotoxicity of individual PBB congeners or
commercial mixtures.
Long-term toxicity studies have shown the liver to be the
principal site of the carcinogenic effects of PBB. The incidences
of hepatocellular carcinoma were significantly increased in both
male and female mice and rats receiving oral doses of the
FireMaster(R) mixture. Carcinogenic effects in the liver have
been reported in mice receiving diets containing Bromkal 80-9D
(technical nonabromobiphenyl) at 100 mg/kg (5 mg/kg body weight per
day) or more for 18 months. The lowest dose of PBB that produced
tumours (mostly adenomas) in rodents was 0.5 mg/kg body weight per
day for 2 years. The rats receiving 0.15 mg/kg body weight per day
in addition to pre- and perinatal exposure did not suffer any
adverse effects. The carcinogenicity of technical octabromobiphenyl
and decabromobiphenyl has not been studied.
Neither Firemaster BP-6 nor 2,2',4,4',5,5'-hexabromobiphenyl
showed tumour-initiating (using TPA as promotor) or
tumour-promoting (using DMBA as initiator) activity in a mouse skin
bioassay. However, in other mouse skin models (using DMBA or MNNG
as initiators), FM FF-1, 3,3',4,4',5,5'-hexabromobiphenyl, but not
2,2',4,4',5,5'-hexabromobiphenyl, showed tumour promoting activity.
In a two-stage rat liver bioassay using phenobarbital as promotor,
3,3',4,4'-tetrabromobiphenyl showed a weak initiating activity. In
the two-stage rat liver model using diethylnitrosamine and partial
hepatectomy, FM, 3,3',4,4'-tetra bromobiphenyl, and
2,2',4,4',5,5'-hexabromobiphenyl, but not
3,3,',4,4',5,5'-hexabromobiphenyl, showed tumour promoting
activity.
The results of the studies on cell communication, the negative
results of studies on genotoxicity and mutagenicity, and the
results of tumour promotion assays indicate that the mixtures and
congeners studied cause cancer by epigenetic mechanisms. No
information is available on technical octa-, nona-, or decabromo
biphenyl.
The mechanisms of action underlying the many manifestations of
the toxicity of PBBs and related compounds are not known. However,
some of the effects, such as the wasting syndrome, thymus atrophy,
hepatotoxicity, skin disorders, and reproductive toxicity may be
related to interaction with the so-called Ah- or TCDD-receptor
causing alteration in the expression of a number of genes.
Different PBB congeners vary in their interaction with the
receptor, the coplanar congeners being more active.
Many of the effects of PBB are seen after long-term exposure.
The reason for this may be the pronounced accumulation of some PBB
congeners and the poor ability of the body to metabolize and
eliminate them. This results in a build-up of the chemical in the
body overcoming compensatory mechanisms leading to adverse effects.
Some polybrominated naphthalenes (PBNs), known contaminants of
the FireMaster(R) mixture, are potent toxic substances and
teratogens. Although PBNs are only present at low levels in the
FireMaster(R) mixture, it is possible that they may contribute to
its toxicity.
Studies on the FireMaster(R) mixture and its main component,
2,2',4,4',5,5'-HxBB showed that the photolysis products were more
toxic than the original PBB. The pyrolysis products of FM caused
MFO enzyme induction, body weight loss, and thymic atrophy. Liver
enlargement was observed with pyrolysis products of technical OcBB.
1.1.8 Effects on humans
There was no example of acute PBB toxicosis in humans with
which to compare the potential effects at lower exposures following
the poisoning incident in Michigan, USA, 1973. The main
epidemiological studies were conducted by the Michigan Department
of Public Health (MDPH) and the Environmental Science Laboratory,
Mount Sinai School of Medicine, New York (ESL).
It was estimated that the most highly exposed people consumed
5-15 g PBB over a 230-day period through milk. Some additional
exposure may have occurred through meat. The exposure levels among
some of the farmers and most of the general population in Michigan
were much lower, i.e., the total exposure was 9-10 mg. However,
some people in this group may have received a total exposure of
about 800-900 mg. (A total dose of 9 mg corresponds to 0.15 mg/kg
body weight, and 900 mg-15 mg/kg body weight for a 60-kg average
adult; the dose/kg body weight would be higher for children).
In 1974, the first MDPH study compared the health status of
people on quarantined farms with people on non-quarantined farms in
the same area. Although a variety of symptoms were reported by both
groups, there was no pattern of differences between the groups. No
unusual abnormalities of the heart, liver, spleen, nervous system,
urinanalysis, blood counts, or any other medical conditions
examined could be found. In a later comprehensive MDPH study
including groups with different levels of exposure, there was no
positive association between serum concentrations of PBB and
reported symptom or disease frequencies. The ESL studies involved
about 990 farm residents, 55 chemical workers, and a group of
Wisconsin dairy farmers who were used as a control. The incidence
of symptoms in Michigan farmers was greater than the incidence in
Wisconsin farmers. The greatest differences were in the broad
classification of neurologi cal and musculoskeletal symptoms.
Elevated serum concentrations of some liver enzymes and
carcinoembryonic antigen were more prevalent in Michigan farmers
than in Wisconsin farmers. Chemical workers had a higher prevalence
of chest and skin symptoms and a lower prevalence of
musculoskeletal symptoms than farmers.
Although results of ESL studies were at times interpreted
differently from results of comparable studies, there was one area
of consistent agreement. Neither sets of studies demonstrated a
positive dose-response relationship between PBB levels in serum or
adipose tissue and the prevalence of symptoms or abnormal clinical
measurements. Several clinical areas were investigated using more
intensive special studies. Examination of neurological aspects by
means of objective performance tests revealed in one study a
negative correlation of serum PBB levels with performance test
scores, particularly in males in older age groups. The other
studies showed no association between serum or fat concentrations
of PBBs and performance in a battery of tests measuring memory,
motor strength, coordination, cortical-sensory perception,
personality, higher cognitive functioning, and other functions.
Paediatric aspects of PBB exposure were examined in families
of the ESL studies. Although many symptoms were reported, physical
examination failed to reveal any objective alteration that could be
attributed to PBB. There were different views about the more subtle
neuropsychological effects in the offspring and the results of
investigations of developmental abilities remain controversial,
too. The same is true for the investigation of lymphocyte and
immune function. One set of authors found no differences in
lymphocyte count or functions between groups with high and low
serum PBB levels, the other found a significant decrease in T- and
B-lymphocyte subpopulations in about 40% of an exposed Michigan
group, compared with unexposed groups, and impaired lymphocyte
function, i.e., decreased response to mitogens.
In the epidemiological studies reviewed, efforts have been
made to evaluate the relationship between PBB exposure and a large
number of adverse effects including behavioural effects and
subjective complaints. However, most studies suffer from major
failures in design introducing confounders that make it difficult,
or impossible, to draw conclusions about the relationship between
PBB exposure and possible health effects. The follow-up time has
not been long enough to evaluate possible carcinogenic effects.
Two small groups of workers with occupational exposure to a
mixture of PBBs or to DeBB and DBBO were identified. Lesions
resembling chloracne were found in 13% of the workers exposed to
the PBB mixture, such lesions were not seen in the DeBB- exposed
workers. However, a significantly higher prevalence of
hypothyroidism was seen in the latter group.
1.1.9 Overall evaluation of toxicity and carcinogenicity
The only lifetime study with a PBB mixture was conducted on
rats and mice in a recent NTP bioassay. The lowest dose tested that
still produced carcinogenic effects was 0.5 mg/kg body weight per
day (liver tumours in rodents). In other carcinogenicity studies,
3 mg/kg body weight per day given for 6 months resulted in a
carcinogenic response. The 6-month study demonstrates that less
than lifetime exposure at similar doses will also result in similar
adverse effects. Effects on reproduction in subhuman primates and
mink may occur at lower doses.
In addition, in the 2-year NTP rat study, a daily dose of
0.15 mg/kg body weight per day and prenatal and perinatal exposure
of the dam to 0.05 mg/kg body weight per day did not result in any
adverse effects. Thus, the total daily intake from food, water,
air, and soil should be less than 0.15 µg/kg body weight per day,
extrapolating from a NOAEL (no-observed- adverse-effect level) of
a positive carcinogenicity study, using an uncertainty (safety)
factor of 1000, since these compounds probably produce cancer by an
epigenetic mechanism.
The total dose received by the subpopulation in Michigan was
estimated to have ranged from 0.15 to 15 mg/kg body weight over a
230-day period. For this population, dividing the doses over a
lifetime for the average human being would be equivalent to a daily
dose ranging from 6 ng to 0.6 µg/kg body weight per day.
A total intake of 2 ng PBB/kg body weight per day, from known
sources, has been estimated for adults in the general population
and 10 ng/kg body weight per day for infants receiving human milk.
It should be kept in mind that these estimates are based on a very
limited and regional data base.
These calculations assume that a steady state for PBBs would
not be reached over a lifetime and that short-term higher exposure
can be substituted for long-term lower exposures, since these
compounds are extremely poorly metabolized and excreted.
Insufficient information is available for OcBB, NoBB, and DeBB
to calculate a total daily intake that would not result in adverse
effects.
1.2 Conclusions
Most of the PBB congeners found in commercial flame retardants
are lipophilic, persistent, and bioaccumulating. These compounds
are biomagnified in environmental food webs and pose a threat,
especially to organisms in the higher levels of these webs.
Furthermore, some PBB products are precursors to toxic
polybrominated dibenzofurans in combustion processes.
In addition to emissions during manufacture and use, PBB will
enter the environment from the widespread use of flame retardant
products. A considerable part of the PBB produced will ultimately
reach the environment because of the high stability of these
compounds.
PBBs are also found in environmental and human samples from
places far from known point sources. The congener pattern in the
environmental samples does not match those found in the technical
products, which indicates an environmental alteration, possibly a
photochemical debromination.
Very little information is available at present on the extent
of the exposure of the general population to PBBs. However, in the
few instances where measurements were made, trace amounts of PBBs
were identified. At present, this exposure does not give rise to
concern, but further build-up should be avoided. Human data from
the Michigan episode suggest that exposures in Michigan were
several order of magnitude higher than the exposure of the general
population. No definitive health effects that could be correlated
with PBB exposure in the Michigan population have been identified,
though the follow-up period has not been long enough for the
development of cancer. Since PBB levels in adipose tissue and serum
remain high in the Michigan population, their internal exposure
continues. In contrast, toxicity was observed in cattle in
Michigan. This discrepancy is explained by differences in the
extent of the exposure of the cattle.
Occupational exposure has only been examined in two plants in
the USA. It appears that chloracne-like lesions may develop in
workers producing PBB, and hypothyroidism in workers exposed to
DeBB. No studies have been conducted on workers incorporating deca-
or octa-/nona-bromobiphenyl into commercial products.
PBBs are extremely persistent in living organisms and have
been shown to produce chronic toxicity and cancer in animals.
Although the acute toxicity was low, cancer was induced at a dose
of 0.5 mg/kg body weight per day and the no-observed-effect level
was 0.15 mg/kg body weight per day. A number of chronic toxic
effects have been observed in experimental animals at doses of
around 1 mg/kg body weight per day following long-term exposure.
1.3 Recommendations
1.3.1 General
The Task Group is of the opinion that human beings and the
environment should not be exposed to PBBs in view of their high
persistence and bioaccumulation and potential adverse effects at
very low levels after long-term exposure. Therefore, PBBs should no
longer be used commercially.
Because of the limited toxicity data on DeBB and OcBB, their
extreme persistence and their potential break-down in the
environment, and the more toxic persistent compounds formed through
combustion, they should not be used commercially, unless their
safety has been demonstrated.
It is known that observations on the Michigan cohort are still
continuing. Publication of these data is required.
1.3.2 Future research
Future human and environmental PBB monitoring, including
workplace monitoring in the manufacture and user industries, should
be expanded, should be congener specific, and should include
OcBB/NoBB and DeBB. These compounds should be included in
monitoring programmes in progress for other halogenated compounds.
The time trends and geographical distribution of PBB levels in the
environment should continue to be monitored. Release of PBBs into
the environment from waste disposal sites should be surveyed.
Thermolysis experiments simulating conditions of accidental
fires and municipal incineration should be conducted. Additional
research should be continued on the mechanisms of toxicity and
carcinogenicity of PBBs and related compounds. PBBs may serve as
model compounds for such mechanistic research. Purified congeners
should be used in these studies.
The effects of PBBs on reproduction are not well elucidated.
Therefore, well-designed, long-term, reproductive studies at low
doses, using a sensitive species, should be performed.
There is also a need for more information on the
bioavailability and toxicokinetics of OcBB/NoBB, DeBB, and selected
congeners.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1 Identity
2.1.1 Primary constituents
The term "polybrominated biphenyls" or "polybromobiphe nyls"
(PBBs) refers to a group of halogenated hydrocarbons, formed by
substituting hydrogen by bromine in biphenyl (Fig. 1).
Molecular formula C12H(10-x-y)Brx+y
(x and y = 1 to 5)
Molecular (empirical) formulae for PBB components of different
degrees of substitution and their relative molecular masses are
given in Table 1.
Theoretically, there can be 209 different forms (congeners) of
a brominated biphenyl, depending on the number and position of the
bromine (see Table 2).
At present, 101 individual PBB congeners are listed in the
Chemical Abstracts Service (CAS) registry. Because bromobiphe nyls
are produced commercially by the bromination of biphenyl, the
existence of any of the 209 congeners is possible in any commercial
mixture (Aust et al., 1983). Some PBBs exist primarily as
metabolites or accumulation or degradation products of the original
mixture. With increasing advance in analysis techniques, the number
of actually identified PBB compounds is growing.
Table 1. PBBs: molecular formula and relative molecular mass
PBB Formula Relative
molecular mass
Monobromobiphenyl C12H9Br 232.9
Dibromobiphenyl C12H8Br2 311.8
Tribromobiphenyl C12H7Br3 390.7
Tetrabromobiphenyl C12H6Br4 469.6
Pentabromobiphenyl C12H5Br5 548.5
Hexabromobiphenyl C12H4Br6 627.4
Heptabromobiphenyl C12H3Br7 706.3
Octabromobiphenyl C12H2Br8 785.2
Nonabromobiphenyl C12HBr9 864.1
Decabromobiphenyl C12Br10 943.0
Table 2. Multiplicity of PBB isomers and congenersa
Number of
Br Substituent 1 2 3 4 5 6 7 8 9 10
Number of
Isomers 3 12 24 42 46 42 24 12 3 1
a Modified from: Safe (1984).
The synthesis of pure congeners for use as standards is a
prerequisite for advances in chemical analysis, as well as research
into the toxicological and biological effects of PBBs. Some routes
for the synthesis of PBB congeners have been described by Sundström
et al. (1976b), Robertson et al. (1980, 1982a, 1984a), Höfler et al.
(1988), and Kubiczak et al. (1989).
Table 3 gives a list of all 209 possible congeners and their
CAS numbers, if already designated. The CAS names are designated as
follows:
1,1'-Biphenyl, .......... bromo-
e.g., 1,1'-Biphenyl, 2,2',4,4',5,5'-hexabromo- or
2,2',4,4',5,5'-hexabromo-1,1'-biphenyl (BB-153).
2.1.2 Technical products
2.1.2.1 Major trade names
The PBBs produced for commercial use include mixtures mainly
containing hexa-, octa-/nona-, and decabromobiphenyls. Data on past
and present trade names and manufacturers are summarized in Table 4
(for further details see section 3.2.1).
2.1.2.2 Composition of the technical products
Commercial PBB products are mixtures of various brominated
biphenyls. Several structural isomers of each of these brominated
compounds are possible and may be present in the product. All
mixtures are relatively highly brominated, with bromine contents
ranging from about 76% for hexabromobiphenyls to 81-85% for octa- to
decabromobiphenyl mixtures (Brinkman & de Kok, 1980).
Data on the composition of PBB mixtures are given in Table 5.
As shown in Table 5, the analytical results concerning the various
products are rather divergent. It indicates that the exact
composition of the mixtures varies between batches, and also within
each batch according to the sampling and analytical method. It can
be seen that samples of "octabromobiphenyl" often contained a larger
proportion of nona- than of octa-substituted PBBs. In this
monograph, these compounds are also referred to as "octa/nona"
bromobiphenyls.
Information on the isomeric composition of the octa- to deca-
mixtures is scarce. In an analysis of Bromkal 80, three isomers of
octabromobiphenyl were found to be present at 14, 16, and 42%
(Norström et al., 1976). A comparison of the isomeric composition of
an "octabromobiphenyl"-mixture with the FireMaster(R)- mixture has
been given by Moore & Aust (1978). De Kok et al. (1977) analysed
various "octabromobiphenyl"-mixtures and Bromkal 80-9D and discussed
the structures of isomers. Furthermore, two isomeric octa- and
three hexa-bromobiphenyls of a commercial decabromobiphenyl mixture
(RFR) have been reported (de Kok et al., 1977).
Table 3. Systematic numbering of PBB compounds and their CAS numbers
BB-No.a Structure CAS No. BB-No.a Structure CAS No.
Monobromobiphenyls (26264-10-8) 17 2,2',4
18 2,2',5 59080-34-1
1 2 2052-07-7 19 2,2',6
2 3 2113-57-7 20 2,3,3'
3 4 92-66-0 21 2,3,4
22 2,3,4'
Dibromobiphenyls (27479-65-8) 23 2,3,5
24 2,3,6
4 2,2' 13029-09-9 25 2,3',4
5 2,3 115245-06-2 26 2,3',5 59080-35-2
6 2,3' 49602-90-6 27 2,3',6
7 2,4 53592-10-2 28 2,4,4' 6430-90-6
8 2,4 49602-91-7 29 2,4,5 115245-07-3
9 2,5 57422-77-2 30 2,4,6 59080-33-0
10 2,6 59080-32-9 31 2,4',5 59080-36-3
11 3,3' 16400-51-4 32 2,4',6 64258-03-3
12 3,4 60108-72-7 33 2',3,4
13 3,4' 57186-90-0 34 2',3,5
14 3,5 16372-96-6 35 3,3',4
15 4,4' 92-86-4 36 3,3',5
37 3,4,4' 6683-35-8
Tribromobiphenyls (51202-79-0) 38 3,4,5 115245-08-4
39 3,4',5 72416-87-6
16 2,2',3
Tetrabromobiphenyls 40088-45-7 65 2,3,5,6
66 2,3',4,4' 84303-45-7
40 2,2',3,3' 67 2,3',4,5
41 2,2',3,4 68 2,3',4,5'
43 2,2',3,5 69 2,3',4,6
Table 3. cont'd
BB-No.a Structure CAS No. BB-No.a Structure CAS No.
44 2,2',3,5' 70 2,3',4',5 59080-38-5
45 2,2',3,6 71 2,3',4',6
46 2,2',3,6' 72 2,3',5,5'
47 2,2',4,4' 66115-57-9 73 2,3',5',6
48 2,2',4,5 74 2,4,4',5
49 2,2',4,5' 60044-24-8 75 2,4,4',6 64258-02-2
50 2,2',4,6 76 2',3,4,5
51 2,2',4,6' 97038-95-4 77 3,3',4,4' 77102-82-0
52 2,2',5,5' 59080-37-4 78 3,3',4,5
53 2,2',5,6' 60044-25-9 79 3,3',4,5' 97038-98-7
54 2,2',6,6' 97038-96-5 80 3,3',5,5' 16400-50-3
55 2,3,3',4 97038-99-8 81 3,4,4',5 59589-92-3
56 2,3,3',4'
57 2,3,3',5 Pentabromobiphenyls (56307-79-0)
58 2,3,3',5'
59 2,3,3',6 82 2,2',3,3',4
60 2,3,4,4' 83 2,2',3,3',5
61 2,3,4,5 115245-09-5 84 2,2',3,3',6
62 2,3,4,6 115245-10-8 85 2,2',3,4,4'
63 2,3,4',5 86 2,2',3,4,5
64 2,3,4',6 87 2,2',3,4,5'
88 2,2',3,4,6 77910-04-4 111 2,3,3',5,5'
89 2,2',3,4,6' 112 2,3,3',5,6
90 2,2',3,4',5 113 2,3,3',5',6
91 2,2',3,4',6 114 2,3,4,4',5 96551-70-1
92 2,2',3,5,5' 115 2,3,4,4',6
93 2,2',3,5,6 116 2,3,4,5,6 38421-62-4
94 2,2',3,5,6' 117 2,3,4',5,6
95 2,2',3,5',6 88700-05-4 118 2,3',4,4',5 67888-97-5
96 2,2',3,6,6' 119 2,3',4,4',6 86029-64-3
97 2,2',3',4,5 120 2,3',4,5,5' 80407-70-1
98 2,2',3',4,6 121 2,3',4,5',6
Table 3. cont'd
BB-No.a Structure CAS No. BB-No.a Structure CAS No.
99 2,2',4,4',5 81397-99-1 122 2',3,3',4,5
100 2,2',4,4',6 97038-97-6 123 2',3,4,4',5 74114-77-5
101 2,2',4,5,5' 67888-96-4 124 2',3,4,5,5'
102 2,2',4,5,6' 80274-92-6 125 2',3,4,5,6'
103 2,2',4,5',6 59080-39-6 126 3,3',4,4',5 84303-46-8
104 2,2',4,6,6' 97063-75-7 127 3,3',4,5,5' 81902-33-2
105 2,3,3',4,4'
106 2,3,3',4,5 Hexabromobiphenyls (36355-01-8)
107 2,3,3',4',5
108 2,3,3',4,5' 128 2,2',3,3',4,4' 82865-89-2
109 2,3,3',4,6 129 2,2',3,3',4,5
110 2,3,3',4',6 130 2,2',3,3',4,5' 82865-90-5
131 2,2',3,3',4,6 155 2,2',4,4',6,6' 59261-08-4
132 2,2',3,3',4,6' 119264-50-5 156 2,3,3',4,4',5 77607-09-1
133 2,2',3,3',5,5' 55066-76-7 157 2,3,3',4,4',5' 84303-47-9
134 2,2',3,3',5,6 158 2,3,3',4,4',6
135 2,2',3,3',5,6' 119264-51-6 159 2,3,3',4,5,5' 120991-48-2
136 2,2',3,3',6,6' 160 2,3,3',4,5,6
137 2,2',3,4,4',5 81381-52-4 161 2,3,3',4,5',6
138 2,2',3,4,4',5' 67888-98-6 162 2,3,3',4',5,5'
139 2,2'3,4,4',6 163 2,3,3',4',5,6
140 2,2',3,4,4',6 164 2,3,3',4',5',6 82865-91-6
141 2,2',3,4,5,5' 120991-47-1 165 2,3,3',5,5',6
142 2,2',3,4,5,6 166 2,3,4,4',5,6
143 2,2',3,4,5,6' 167 2,3',4,4',5,5' 67888-99-7
144 2,2',3,4,5',6 119264-52-7 168 2,3',4,4',5',6 84303-48-0
145 2,2',3,4,6,6' 169 3,3',4,4',5,5' 60044-26-0
146 2,2',3,4',5,5'
147 2,2',3,4',5,6 Heptabromobiphenyl (35194-78-6)
148 2,2',3,4',5,6'
Table 3. cont'd
BB-No.a Structure CAS No. BB-No.a Structure CAS No.
149 2,2',3,4',5',6 69278-59-7 170 2,2',3,3',4,4',5 69278-60-0
150 2,2',3,4',6,6' 93261-83-7 171 2,2',3,3',4,4',6
151 2,2',3,5,5',6 119264-53-8 172 2,2',3,3',4,5,5' 82865-92-7
152 2,2',3,5,6,6' 173 2,2',3,3',4,5,6
153 2,2',4,4',5,5' 59080-40-9 174 2,2',3,3',4,5,6' 88700-04-3
154 2,2',4,4',5,6' 36402-15-0 175 2,2',3,3',4,5',6
176 2,2',3,3',4,6,6' 195 2,2',3,3',4,4',5,6
177 2,2',3,3',4,5,6' 196 2,2',3,3',4,4',5',6
178 2,2',3,3',5,5',6 119264-54-9 197 2,2',3,3',4,4',6,6' 119264-59-4
179 2,2',3,3',5,6,6' 198 2,2',3,3',4,5,5',6
180 2,2',3,4,4',5,5' 67733-52-2 199 2,2',3,3',4,5,6,6'
181 2,2',3,4,4',5,6 200 2,2',3,3'4,5',6,6' 119264-60-7
182 2,2',3,4,4',5,6' 119264-55-0 201 2,2',3,3',4',5,5',6 69887-11-2
183 2,2',3,4,4',5',6 202 2,2',3,3',5,5',6,6' 59080-41-0
184 2,2',3,4,4',6,6' 119264-56-1 203 2,2',3,4,4',5,5',6
185 2,2',3,4,5,5',6 204 2,2',3,4,4',5,6,6' 119264-61-8
186 2,2',3,4,5,6,6' 119264-57-2 205 2,3,3',4,4',5,5',6
187 2,2',3,4',5,5',6 84303-49-1
188 2,3',3,4',5,6,6' 119264-58-3 Nonabromobiphenyls (27753-52-2)
189 2,3,3',4,4',5,5' 88700-06-5
190 2,3,3',4,4',5,6 79682-25-0 206 2,2',3,3',4,4',5,5',6 69278-62-2
191 2,3,3',4,4',5',6 207 2,2',3,3',4,4',5,6,6' 119264-62-9
192 2,3,3',4,5,5',6 208 2,2',3,3',4,5,5',6,6' 119264-63-0
193 2,3,3',4',5,5',6
Decabromobiphenyl
Octabromobiphenyls (27858-07-7)
209 2,2',3,3',4,4',5,5',6,6' 13654-09-6
194 2,2',3,3',4,4',5,5' 67889-00-3
a The Nos 1-209 correspond to those used by Ballschmiter & Zell (1980) for PCBs (January 1990).
Table 4. Major trade names and manufacturers of technical-grade PBBs and
commercial PBB mixturesa
PBB mixture Manufacturer CAS No.
Hexa-PBBs
FireMaster(R) BP-6 Michigan Chemical Corp. (St. Louis, Mich.) 59536-65-1
FireMaster(R) FF-1b Michigan Chemical Corp. (St. Louis, Mich.) 67774-32-7
Octa/nona-PBBs
Bromkal 80-9D Chemische Fabrik Kalk (Cologne, Germany) 61288-13-9
Technical
octabromobiphenyl White Chemical Corp. (Bayonne, New Jersey)
Octabromobiphenyl
FR 250 13A Dow Chemical Co. (Midland, Mich.)
Deca-PBB
Adine 0102 Ugine Kuhlmann now Atochem (Paris, France) 13654-09-6
Berkflam B 10 Berk (London, United Kingdom)
Flammex B-10 Berk (London, United Kingdom)
Technical
decabromobiphenyl White Chemical Corp. (Bayonne, New Jersey)
HFO 101 Hexcel (Basildon, United Kingdom)
a Adapted from: Brinkman & de Kok (1980).
b A pulverized form of FireMaster BP-6 containing 2% calcium polysilicate
to prevent caking. It was produced in limited quantities as a
development-product in 1971 and 1972.
Most research has been conducted with the hexabromobiphenyl
mixture FireMaster(R), which accounts for most of the manu
factured products and most of the environmental contamination
(Di Carlo et al., 1978). The main constituent of FireMaster(R) is
2,2',4,4',5,5'-hexabromobiphenyl. Its identification was reported by
Andersson et al. (1975), Jacobs et al. (1976), and Sundström et al.
(1976a). The second major component is heptabromobiphenyl containing
bromine at positions 2,2',3,4,4',5,5' (Hass et al., 1978; Moore
et al., 1978c). Accordingly, these two congeners account for about
75% of the mixture (e.g., Dannan et al., 1982d). Data on the
isomeric composition of FireMaster(R) found in the literature are
given in Table 6. The ranges of relative abundances of some
FireMaster(R) constituents are compiled in Table 7. Altogether at
least sixty compounds have been detected in FireMaster(R) (Orti
et al., 1983). About twelve of them are major PBB-components (Aust
et al., 1981), the others belong to the minor components (< 1%).
Table 5. Survey of literature on the composition of PBB mixturesa
PBB mixture (manufacturer) Weight of Weight of different homologus groups Reference
bromine (%)
Br10 Br9 Br8 Br7 Br6 Br5 Br4
"Hexabromobiphenyl"
FM BP-6 (Michigan Chemical) 75 13.8 62.8 10.6 2 de Kok et al.
(1977)c
" [Lot RP-158 (1971)] 12.5 72.5 9 4 Willett & Irving
(1976)
" [Lot 6244A (1974)] 13 77.5 5 4.5 Willett & Irving
(1976)
" 90 10 Norström et al.
(1976)
" 1 18 73 8 de Kok et al.
(1977)
" 33 63 4 Hass et al.
(1978)
" 7.7 74.5 5.6 Robertson et al.
(1984b)
" 24.5 79 6 Krüger (1988)
2,2',4,4',6,6' (RFR) 12 84 1 de Kok et al.
(1977)
2,2',4,4',6,6' (Aldrich) 2 24 70 4 de Kok et al.
(1977)
"Hexabromobiphenyl" (RFR) 25 67 4
(12-25) (60-80) (1-11) (2-5)b de Kok et al.
(1977)
Table 5 (contd).
PBB mixture (manufacturer) Weight of Weight of different homologus groups Reference
bromine (%)
Br10 Br9 Br8 Br7 Br6 Br5 Br4
Octanonabromobiphenyl
Bromkal 80-9D (Kalk) 81-82.5 9 65 1 de Kok et al.
(1977)
Bromkal 80 72 27 1 Norström et al.
(1976)
XN-1902 (Dow Chemical)c 82 6 47 45 2 Norris et al. (1973)
XN-1902 (Dow Chemical)c 2 34 57 7 de Kok et al. (1977)
Lot 102-7-72 (Dow Chemical)c 6 60 33 1 Waritz et al. (1977)
"Octabromobiphenyl" (RFR) 4 54 38 2 de Kok et al. (1977)
2,2',3,3',5,5',6,6' (RFR) 1 28 46 23 2 de Kok et al. (1977)
FR 250 13A (Dow Chemical) 8 49 31 1 Krüger (1988)
Decabromobiphenyl
HFO 101 (Hexcel) 84 96 2 de Kok et al. (1977)
Adine 0102 (Ugine Kuhlmann) 83-85 96 4 de Kok et al. (1977)
Adine 0102 (Ugine Kuhlmann) 96.8 2.9 0.3 Millischer et al.
(1979)
"Decabromobiphenyl" (RFR) 71 11 7 4 4 de Kok et al. (1977)
"DBB": Flammex B 10 (Berk)c 96.8 2.9 0.3 Di Carlo et al
(1978)
a Adapted from: Brinkman & de Kok (1980).
b Range of above readings with the exception of that of Norström et al. (1976), which differs greatly from the others.
c According to de Kok et al. (1977), these have never been marked.
Table 6. Identified PBB congeners in FireMaster(R)
BB No.a Structure % Composition of References
FM BP-6 FF-1
Dibromobiphenyls
4 2,2'- 0.02 Moore et al. (1979a)
Tribromobiphenyls
18 2,2'5- 0.050 Robertson et al. (1984b)
26 2,2',5- 0.024
31 2,4',5- 0.015
37 3,4,4'- 0.021
Tetrabromobiphenyls
49 2,2',4,5'- 0.025
52 2,2',5,5'- 0.052
66 2,3',4,4'- 0.028
70 2,3',4',5- 0.017
77b 3,3',4,4'- < 0.08 Orti et al. (1983)
0.159 Robertson et al. (1984b)
Pentabromobiphenyls
95 2,2',3,5',6- 0.02 Orti et al. (1983)
99 2,2'4,4',5- < 0.08
101 2,2',4,5,5'- 2.69 Robertson et al. (1984b)
4.5 3.7 Aust et al. (1981)
1.54 Orti et al. (1983)
2.6 Krüger (1988)
118 2,3',4,4',5- 2.94 Robertson et al. (1984b)
0.7 Aust et al. (1981)
3.2 Krüger (1988)
0.8 Orti et al. (1983)
126b 3,3',4,4',5- < 0.01
0.079 Robertson et al. (1984b)
Hexabromobiphenyls
132 2,2'.3.3',4,6'- 1 Krüger (1988)
138 2,2',3,4,4',5'- 12.3 Robertson et al. (1984b)
Table 6. cont'd
BB No.a Structure % Composition of References
FM BP-6 FF-1
12 8.6 Aust et al. (1981)
5.23 Orti et al. (1983)
10.6 Krüger (1988)
149 2,2',3,4',5',6- 2.24 Robertson et al. (1984b)
1.4 1.3 Aust et al. (1981)
0.78 Orti et al. (1983)
153 2,2'4,4',5,5'- 53.9 Robertson et al. (1984b)
47.8 47.1 Aust et al. (1981)
55.2 Orti et al. (1983)
58.5 Krüger (1988)
155 2,2',4,4',6,6'- 0.5
156 2,3,3',4,4',5- 0.980 Robertson et al. (1984b)
5.0 Aust et al. (1981)
0.37 Orti et al. (1983)
1.0 Krüger (1988)
157 2,3,3',4,4',5'- 0.05 Orti et al. (1983)
0.526 Robertson et al. (1984b)
0.5 Krüger (1988)
167 2,3',4,4',5,5'- 5.5 3.3 Aust et al. (1981)
3.37 Orti et al. (1983)
< 0.3
7.95 Robertson et al. (1984b)
5.5 Krüger (1988)
169b 3,3',4,4',5,5'- 0.294 Robertson et al. (1984b)
Heptabromobiphenyls
170 2,2',3,3',4,4',5- 0.256
1.1 1.5 Aust et al. (1981)
1.66 Orti et al. (1983)
2.4 Krüger (1988)
180 2,2',3,4,4',5,5'- 6.97 Robertson et al. (1984b)
24.7 Aust et al. (1981)
23.5 Orti et al. (1983) 20.8 Krüger (1988)
172 2,2',3,3',4,5,5'- < 0.30 Orti et al. (1983)
174 2,2',3,3',4,5,6'- 0.24
178 2,2',3,3',5,5',6- 0.3 Krüger (1988)
187 2,2',3,4',5,5',6- 0.392 Robertson et al. (1984b)
1.0 Krüger (1988)
189 2,3,3',4,4',5,5'- 0.51 Orti et al. (1983)
Table 6. cont'd
BB No.a Structure % Composition of References
FM BP-6 FF-1
Octabromobiphenyls
194 2,2',3,3',4,4', 0.9 2.4 Aust et al. (1981)
5,5'-
1.65 Orti et al. (1983)
possible structures for two
minor Br8 peaks:
196 2,2',3,3',4,4', Moore et al. (1980);
5,6'-
201 2,2',3,3',4,5, Orti et al. (1983)
5',6'-
203 2,2',3,4,4',5,
5'6-
a From: Ballschmiter & Zell (1980).
b These coplanar congeners are the most toxic congeners identified in
FireMaster BP-6 (Robertson et al., 1984b).
Table 7. Range of relative abundance of some PBB constituents
of Firemaster(R) FF-1 and BP-6a
Structure No.b BB No.c Abundance (%)
2,2',4',5,5'- 1 101 1.5-4.5
2,3',4,4',5,- 2 118 0.7-4.2
2,2',3,4',5',6- 3 149 0.8-2.2
2,2',4,4',5,5'- 4 153 47.1-59
2,2',3,4,4',5'- 5 138 5.2-12.3
2,3',4,4',5,5'- 6 167 3.3-8.0
2,3,3',4,4',5- 7 168 0.4-5.0
2,2',3,4,4',5,5'- 8 180 7.0-24.7
2,2',3,3',4,4',5- 9 170 0.3-2.4
2,2',3,3',4,4',5,5'- 12 194 0.9-2.4
a For references, see Table 6.
b Congener designation made on the basis of the gas chromatographic
elution sequence of the FireMaster(R) mixture.
c Congener designation according to Ballschmiter & Zall (1980).
Variations are due to differences in batches and analytical
techniques. In many cases, the differing electron capture responses
of the various congeners within the mixture were not taken into
account. Thus, values in Table 7 only give an approximate range of
composition and it is not possible to provide a precise composition
for the material that was introduced into the Michigan environment
(Fries, 1985b).
Both formulations of FireMaster(R) mixture, BP-6 and FF-1
have a similar isomeric composition. However, FireMaster BP-6
contains roughly 10% more of the relatively minor congeners (Dannan
et al., 1982b).
As can be concluded from the composition of the commercial
mixtures (Table 5), the major source of impurity that occurs in PBBs
results from the spread in the degree of bromination. For example,
FireMaster(R) BP-6 has been marketed as a hexabromin ated
biphenyl, but more than one quarter of the product consists of lower
brominated biphenyls because of incomplete bromination reaction
(Neufeld et al., 1977).
However, a producer of decabromobiphenyl has reported that
their material has a degree of purity of more than 98%, the
remaining 2% being nonabromobiphenyl. It is manufactured by a
special proprietary process rendering no brominated by-products
(Neufeld et al., 1977).
It is noteworthy that mixed polybromochlorobiphenyls (PCBs)
have been observed as minor contaminants in FireMaster(R). For
example, monochloropentabromobiphenyl (CAS No. 88703-30-4) was added
to the list of detected impurities (Domino & Domino, 1980; Tondeur
et al., 1984). Such compounds probably result from contamination of
commercial bromine by chlorine (Domino & Domino, 1980).
Polybrominated naphthalenes (PBNs) (Fig. 2) have been
identified as minor components in commercial PBB mixtures (see
Table 8). The isomeric composition of PBNs in FireMaster(R) is
unknown, but studies on this subject have been started (Robertson
et al., 1984a). It is assumed that naphthalene, present as an
impurity in industrial-grade biphenyl, is brominated during the
production of FireMaster(R), and that the presence of numerous
isomers and congeners of PBNs in FireMaster(R) is possible
(Robertson et al., 1984b).
Table 8. Occurrence of polybrominated naphthalenes (PBNs) in FireMaster(R)-mixtures
PBN CAS-Registry FireMaster(R) Concentration Reference
Number mixture
Tetrabromonaphthalene 88703-31-5 BP-6 or FF-1 no information Tondeur et al.
available (1984)
Pentabromonaphthalene 56448-55-6 BP-6 or FF-1 no information Tondeur et al.
available (1984)
FF-1 1 mg/kg O'Keefe (1979)
BP-6 150 mg/kg Hass et al.
(1978)
Hexabromonaphthalene 56480-06-9 BP-6 or FF-1 no information Tondeur et al.
available (1984)
FF-1 25 mg/kg O'Keefe (1979)
BP-6 70 mg/kg Hass et al.
(1978)
It has been shown that synthesis of hexa-bromonaphthalenes by
direct bromination results in a mixture of two isomers (Birnbaum
et al., 1983; Birnbaum & McKinney, 1985). The major isomer,
1,2,3,4,6,7-HBN, can be metabolized and excreted, while the minor
isomer, 2,3,4,5,6,7-HBN, is extremely persistent (Birnbaum &
McKinney, 1985).
Polybrominated benzenes and a possible methylbrominated furan
have also been reported to occur in FireMaster(R) (Brinkman & de
Kok, 1980).
Approximately 20 compounds, other than PBBs, were either
tentatively identified in FireMaster(R) or partially characterized
by Hass et al. (1978).
Polybromodibenzo- p-dioxins and polybromodibenzofurans were
searched for, because of their extreme toxicity and because
chlorinated dibenzofurans had been detected in commercial PCBs
(Nagayama et al., 1976). If present, their concentrations did not
exceed 0.5 mg/kg (Hass et al., 1978, O'Keefe, 1979). Polybromo
dibenzodioxins and polybromodibenzofurans were determined in a
sample of Adine 0102 (decabromobiphenyl). Monobromobenzo difurans
were present at a level of 1 mg/kg (1 ppm), otherwise all other
polybromodibenzodioxins and polybromodibenzofurans were present only
at less than 0.01 mg/kg (Atochem, 1990).
So far, phenoxyphenols and hydroxybiphenyls, which might be
intermediates in the formation of brominated dibenzo- p-dioxins and
brominated dibenzofurans, respectively, have not been identified
(O'Keefe, 1979).
Some impurities in PBBs result from impurities in the original
biphenyl material. According to two major manufacturers, their
biphenyl grade used for bromination contained less than 5 mg/kg and
5000 mg/kg, respectively, of impurities, e.g., toluene, naphthalene,
methylene biphenyl (fluorene), and various methyl biphenyls (Neufeld
et al., 1977).
2.2 Physical and chemical properties
In general, PBBs show an unusual chemical stability and
resistance to breakdown by acids, bases, heat, and reducing and
oxidizing agents (Safe, 1984).
PBBs can be compared chemically to the PCBs. Bromine, however,
is a better leaving group in chemical reactions than chlorine.
Unlike PCBs, the reactivity of PBBs has not been well studied and
documented in the literature (Pomerantz et al., 1978). Like PCBs
their chemical stability is dependent, in part, on the degree of
bromination and the specific substitution patterns (Safe, 1984). All
highly brominated PBB-mixtures are known to degrade rather rapidly
with UV irradiation (Brinkman & de Kok, 1980).
The technical mixtures typically are white, off-white, or beige
powdered solids. Some physical data on commercial PBB mixtures are
given in Table 9. It can be seen that there are discrepancies in the
values for the solubility of commercial PBBs in water (given in
Table 9) as well as those calculated for various PBB congeners
(Table 10). The source and quality of the water is important.
Determinations of water solubility of these very hydrophobic
compounds are also difficult to perform. Adsorption effects on
particles and glass surfaces may influence the results. PBBs were
found to be 200 times more soluble in landfill leachate than in
distilled water (Griffin & Chou, 1981a). In general, it can be said
that PBBs are only slightly soluble in water and that the solubility
decreases with increasing bromination.
For details of thermal decomposition, see section 4.3.2.
2.2.1 Physical and chemical properties of individual congeners
PBBs show a wide range of volatility (Farrell, 1980). Partition
coefficients between water/ n-hexane and water/1-octanol, as well
as aqueous solubilities for some individual PBB congeners are given
in Table 10. Correlations for predicting aqueous solubility and
partition coefficients for PBBs based on molecular structure have
been proposed (Patil, 1991). The solubility of PBBs in n-hexane
decreases rapidly with increasing bromine content (de Kok et al.,
1977).
Data on the melting points and UV absorption of individual PBB
congeners are summarized in Table 11. The main band in these spectra
is caused by pi -> pi* electron transitions, while the k band is
generally attributed to the conjugated biphenyl system with the
contribution of both biphenyl rings. With the k band, the
introduction of bromine atoms in positions meta or para to the
phenyl-phenyl bond induces a shift in kmax towards the visible
region, as is illustrated by 3,3',5,5'-tetra- and 3,3',4,4',5,5'-
hexabromobiphenyl. On the other hand, ortho substitution, which
causes a considerable hindrance for free rotation of the rings and,
thus, a loss in coplanarity, effects a sharp decrease in the
extinction coefficient of the k band (de Kok et al., 1977).
Data on NMR spectra are given by Orti et al. (1983), Robertson
et al. (1984b), and Kubiczak et al. (1989), and on mass spectrometry
(MS) by Erickson et al. (1980), Roboz et al. (1980), Buser (1986),
and Sovocool et al. (1987a,b). The "ortho" effect, observed for PBBs
and PCBs having 2,2'-; 2,2',6- or 2,2',6,6'- halogens can be
combined with GC retention index for isomer specific identifications
by gas chromatography and mass spectrometry (GC/MS) (Sovocool
et al., 1987a).
Table 9. Some physical data on commercial PBB mixturesa
"Hexabromobiphenyl" "Octabromobiphenyl" "Nonabromobiphenyl" "Decabromobiphenyl"
(Firemaster BP-6) (Dow XN 1902) (Bromkal 80-9D)c (Adine 0102)d
Melting point (°C) 72 200-250 220-290 380-386b
360-380
385
Lambda max (nm) 219e 225e 224e 227e
Density (g/cm3) at 2.6 - 3.2 3.2
room temperature
Solubility in water 11f 20-30 < 30
(µg/litre) at 25 °C 30f (pure 2,2', 4,4', 5,5'-)
610f
0.06g (deionized)
0.32g (distilled) insoluble
Solubility in organic
solvents (g/kg
solvent) at 28 °C
petroleum ether 20 18 insoluble in common
acetone 60 organic solvents
carbon tetrachloride 300 10e
chloroform 400
benzene 750 81
toluene 970
dioxane 1150
copra oil (37 °C) 0.8
Table 9 (contd).
"Hexabromobiphenyl" "Octabromobiphenyl" "Nonabromobiphenyl" "Decabromobiphenyl"
(Firemaster BP-6) (Dow XN 1902) (Bromkal 80-9D)c (Adine 0102)d
Vapour pressure (Pa)
25 °C 0.000007h < 0.000006
90 °C 0.01 (temperature not given)
140 °C 1
220 °C 100
Volatility (% weight loss) < 1% at 250 °C 1-2% at 300 °C < 5% at 341 °C
< 10% at 330 °C < 10% at 363 °C
< 50% at 350 °C < 25% at 388 °C
log Pow < 7 (calculated)d 8.6 (calculated)
Decomposition temperature 300-400 °C 435 °C 435 °C 395 °C
> 400° C
a Mumma & Wallace 1975).
b Norris et al. (1973).
c Kerscher (1979); CFK (1982).
d Atochem (1990).
e Brinkman & de Kok (1980).
f Filonow et al. (1976).
g Griffin & Chou (1981a,b).
h Jacobs et al. (1976).
Table 10. Partition coefficients between water and n-hexane (KHW) and 1-octanol
(Kow) and aqueous solubilities (Sw) for some individual PBB congeners (all
aqueous solubility measurements were carried out by the generator method)
Log KHW Log KOW Sw mol per Sw µg/litred
litre x 10-9 (25 °C)
(25 °C)
2-bromobiphenyl 4.59a
3-bromobiphenyl 4.85a
4-bromobiphenyl 4.96a 2800 650
3,5-dibromobiphenyl 5.78c
4,4'-dibromobiphneyl 5.61 5.72 18.4 5.7
2,4,6-tribromobiphenyl 6.21 6.03 41.1 16
3,4',5-tribromobiphenyl 6.42c
2,2',5,5',tetrabromobiphenyl 6.72 6.50 8.6 4
3,3',5,5'-tetrabromobiphenyl 7.42c
2,2',4,5,5'-pentabromobiphenyl 7.10a 0.8b 0.4
2,2',4,4',6,6'-hexabromobiphenyl 7.52 7.20 0.9 0.56
decabromobiphenyl 8.58a
Values from Gobas et al. (1988) with the exception of:
a From: Doucette & Andren (1987).
b From: Doucette & Andren (1988).
c From: Sugiura et al. (1978).
d calculated.
Table 11. Melting points and UV spectral data for some PBB congenersa
UV conditions: solutions in n-hexane; Beckman Acta CIII spectrometer
No.c PBB-isomer Melting point Main band k band
(°C)d lambda Log lambda Log
maximum epsilon maximum epsilon
(nm) (1.mol-1.cm-1) (nm) (1.mol-1.cm-1)
Biphenyl 71 201 4.66 246 4.26
1 2- e 201 4.51 240 3.90
2 3- e 205 4.60 248 4.21
3 4- e 200 4.67 254 4.38
4 2,2'- 81 198 4.64 220-230 e
9 2,5- e 203 4.49 226 4.38
15 4,4'- 164 201 4.64 261 4.43
20 2,4,6- 65-66 213 4.70 220-230 e
21 2,2',5- 78 200 4.66 235-245 e
26 2,3',5- e 213 4.57 e e
31 2,4',5- 78 205 4.60 245-255 e
49 2,2',4,5'- 84 207 4.66 235-245 e
52 2,2',5,5'- 143 204 4.67 235-240 e
80 3,3',5,5'- 188 220 4.76 255 4.18
114b 2,3,4,4',5- 128 222.6 (54.8) 258 e
137b 2,2',3,4,4',5- 124 223.1 (35.4) e e
141b 2,2',3,4,5,5'- 127 223.4 (191) e e
153 2,2',4,4',5,5'- (159-160)f 216 4.66 e e
156b 2,3,3',4,4',5- 178 224.9 (229) 259 e
159b 2,3,3',4,5,5'- 195 226.1 (61.4) 258 e
167 2,3',4,4',5,5'- (165-166)f e e e e
Table 11 (contd).
No.c PBB-isomer Melting point Main band k band
(°C)d lambda Log lambda Log
maximum epsilon maximum epsilon
(nm) (1.mol-1.cm-1) (nm) (1.mol-1.cm-1)
169 3,3',4,4',5,5'- 248 227 4.76 272 4.34
180b 2,2',3,4,4',5,5'- 166(165-166)f 224.1 (62.4) e e
189b 2,3,3',4,4',5,5'- 219 230.7 (102) 265 e
194b 2,2',3,3',4,4',5,5'- 235(232-233)f 223.7 (51.6) e e
202 2,2',3,3',5,5',6,6'- e 224 4.85 e e
206b 2,2',3,3',4,4',5,5',6- 262(263-264)f,g 225.2 (131) e e
Nona-(unidentified) e 225 5.18 e e
Deca- 378 227 5.11 e e
a Adapted from: de Kok et al. (1977), with the exception of the congeners marked with b.
b Congener data, including melting points are taken from Kubiczak et al. (1989). UV measurements: in n-heptane.
c No. according to Ballschmiter & Zell (1980).
d Melting points from Sundström et al. (1976b) but confirmed by de Kok et al. (1977), unless otherwise stated.
e No data available.
f From: Moore & Aust (1978).
2.3 Conversion factors for PBB in air
1 ppm = 26.1 mg/m3 for hexabromobiphenyl at 20 °C and
101.3 kPa.
1 mg/m3 = 0.038 ppm.
2.4 Analytical methods
Analytical methods for the determination of PBBs, which have
been reviewed by de Kok et al. (1977), Pomerantz et al. (1978), and
Fries (1985b), were adapted from established methods for chlorinated
hydrocarbon insecticides and PCBs (AOAC, 1975). The chronological
development of analytical methods for the detection and
quantification of PBB mixtures and congeners is summarized in
Table 12. In the wake of the Michigan disaster, methods were
described for the analysis of: contaminated feed, milk, and milk
products (Fehringer, 1975a,b); animal blood plasma, faeces, milk,
and bile (Willett et al., 1978) and liver and fat (Fawkes et al.,
1982). The methods were developed using tissue from animals fed with
PBBs of known composition. Needham and coworkers developed a method
to determine PBBs in human blood serum (Burse et al., 1980; Needham
et al., 1981) which was thoroughly tested in several laboratories,
but, even here, only the main components of FireMaster(R) were
determined. Similarly, the investigation by Eyster et al. (1983)
into the levels of PBBs in fat, serum, faeces, milk, and placenta
were not isomer specific. Thus, reported values may not reflect the
hazard of the residue because, for example, some congeners are more
toxic than the prominent 2,2',4,4',5,5'-HBB. Most samples of
biological origin have congener distributions that differ from those
of the original material (Fries, 1985b).
Concentrations of PBBs as low as 10 µg/kg in fatty foods
(Fehringer, 1975a), 3 µg/kg in dry feeds (Fehringer, 1975b) and
1 µg/litre in blood serum (Needham et al., 1981) can be detected and
quantified using routine methods. Coefficients of variation become
large as concentrations approach the limits of sensitivity of the
method; thus, values near the limit must be treated with caution
(Fries, 1985b). PBBs adsorb to glass more tenaciously than other
halogenated hydrocarbons, and are not easy to remove by the usual
cleaning methods (Willett et al., 1978). This can lead to erroneous
values, particularly when concentrations in samples are low and
there is a carry over from samples of high concentration. This
problem can be solved by using disposable glassware (Willett et al.,
1978).
Table 12. Analysis of commercial mixtures and individual PBB congeners: A chronological surveya
Sample Solvent Analytical method Detection Detection Comment Reference
limit
FireMaster(R) recrystallization GC FID no data identification of Sundström
BP-6 from ethanol/ given BB 153 and a HpBB as et al.
isopropanol major components (1976a)
PBB congeners no data given GC ECD no data routes of synthesis, Sundström
given melting points, relative et al.
retention times, electron (1976b)
capture responses for
some PBB congeners
Commercial - solubility of HPLC, TLC, MS no data survey of analysis for de Kok
mixtures FR 250 13A PBBs in n-hexane UV, GC given PBBs et al.
(octabromobipheyl) decreases rapidly with 1H- & 13C-NMR (1977)
FireMaster(R) BP-6 increasing bromine
and PBB congeners content; PBBs dissolved
in warm CCl4
Commercial sample hexane GC, 13C-NMR, ECD no data identification of Moore
of 1H-NMR, IR given BB 180 et al.
octabromobiphenyl heptabromobiphenyl (1978)
FireMaster(R) methylene chloride; GC, NMR, MS 0.5 mg/kg contains at least 13 Hass
BP-6 hexane HPLC SIM different PBBs and et al.
bromonaphthalene (no (1978)
bromodibenzofurans or
bromodibenzo-p-dioxins
found)
Table 12 (contd).
Sample Solvent Analytical method Detection Detection Comment Reference
limit
FireMaster(R) hexane GC, NMR MS no data purification and Moore &
FF-1 or BP-6 and given structural characterization Aust
octabromobiphenyl of 6 further PBB congeners (1978)
FireMaster(R) hexane GC ECD 0.03 ng absolute and relative Domino
FF-1 retention times of the 8 et al.
major constituents using (1980a)
tetrabromobiphenyl
as an internal standard
FireMaster(R) hexane GC MS no data mass spectra of major Domino &
FF-1 given PBBs in FireMaster; mixed Domino
poly-bromo and (1980)
chlorobiphenyls detected
FireMaster(R) GC ECD no data comparison of packed and Farrel
BP-6 given capillary columns; solves (1980)
some problems with lower
brominated biphenyls, but
has no great advantages
over packed columns for
more highly substituted
biphenyls
FireMaster(R) no data given GC PED 2.8 mg comparison with ECD; not Mulligan
BP-6 (cf 1.5 ng quite so sensitive, but et al.
ECD) is selective (1980)
Individual PBB toluene GC MS, SIM < 1 ng mono-deca PBB congeners Erickson
congeners et al.
(1980)
Table 12 (contd).
Sample Solvent Analytical method Detection Detection Comment Reference
limit
22 individual hexane GC ECD, micro- 40 pg retention times given Sweetman &
PBBs FireMaster(R) (preceeded coulometric for 23 congeners response Boettner
FF-1 by HPLC) GC-detector increases with degree of (1982)
MS bromination, increased
detection temperature gives
improved sensitivity
FireMaster(R) carbon preparative FID, MS polar and unpolar hexane Needham
FF-1 tetrachloride; HPLC and fractions were also et al.
hexane GC 1H-NMR tested for hyperkeratotic (1982)
activity
FireMaster(R) hexane GC NCI, SIM 0.6 ng evaluation of halogen anion Greaves
BP-6 formation by polybrominated et al.
compounds in NCI-MS; SIM of (1982)
bromine anions has greater
specificity than ECD
FireMaster(R) fractionation by GC ECD, MS no data seven congeners were Dannan
BP-6 preferential given purified et al.
acetone (1982d)
solubilization,
repeated
crystallization,
alumina
adsorption
column
chromatography,
reversed phase
Lipidex-500
Table 12 (contd).
Sample Solvent Analytical method Detection Detection Comment Reference
limit
FireMaster(R) see Needham et al. preparative FID, MS at least 60 components Orti
FF-1 (1982) HPLC, GC, observed; isolated/ et al.
lot FH 7042 GC 1H-NMR determined structure of (1983)
10 minor components of
FireMaster (most are very
polar, later eluting
fractions)
PBB hexane GC helium 230 pg simultaneous monitoring Eckhoff
(unspecified) plasma of 4 atomic emission et al.
atomic wave-lengths; PBB mentioned (1983)
emission
spectrometric
detection
FireMaster(R) no data given GC MS, ECD identity of over 91% of Robertson
BP-6 1H-NMR PBB components in et al.
FireMaster using 22 (1984b)
individual PBB congeners
as standards; identification
of 7 additional PBBs
including 3 very toxic
coplanar PBBs
FireMaster(R) hexane GC PED, rapid multi-element quantification Zerezghi
BP-6 scanning et al.
plasma (1984)
emission
Table 12 (contd).
Sample Solvent Analytical method Detection Detection Comment Reference
limit
FireMaster(R) hexane GC SIM, MS determination of suspected Tondeur
FF-1 toxic impurities et al.
(1984)
PBB photolysis hexane GC FID, ECD, purification of PBB congener Barnhart
mixture MS 2 using charcoal pretreatment et al.
and RPLC (1984)
Benzenes, hexane GC NCI-MS 0.1 pg especially valuable for Buser
biphenyls measuring trace levels in (1986)
dibenzodioxins, biological and environmental
dibenzofurans, samples; must be two Br;
diphenylethers, structural information is
benzofurans, partly lost
phenols
PBB congeners no data given GC MS no data use of 'ortho' effect for Sovocool
given PBB and isomer & Wilson
identification; accurate (1982);
structure assignments Sovocool
without use of multiple GC (1987a)
determinations
Various PBB hexane GC, HPLC FID no data relationship between Höfler
congeners given recorded retention data et al.
from HPLC and GC and (1988)
molecular surface area
Table 12 (contd).
Sample Solvent Analytical method Detection Detection Comment Reference
limit
Nine synthetic products purified GC MS 1 ng synthesis of 2,3,4,5- Kubiczak
PBBs; by alumina/Florisil; substituted PBBs and et al.
FireMaster(R) recrystallization characterization (1989)
FF-1 and BP-6 from methanol or
methylene chloride
Mono- and no data given 1H-NMR, no data no data Anklam
poly-brominated 13C-NMR given given (1989)
biphenyls
a Abbreviations used:
ECD = Pulsed 63Ni electron capture detector. NMR = Nuclear magnetic resonance.
FID = Flame ionization detector. PED = Microwave-induced plasma emission detector.
GC = Gas chromatography. PPINICI = Pulsed positive ion-negative ion chemical ionization.
GPC = Gel permeation chromatography. RPLC = Reverse-phase liquid chromatography.
HPLC = High pressure liquid chromatography. SIM = Selected ion monitoring.
IR = Infrared radiation. TLC = Thin layer chromatograpy.
MS = Mass spectrometry. Unitrex = Universal Trace Residue Extractor.
NAA = Neutron activation analysis. UV = Ultraviolet.
NCI = Negative ion chemical ionization mass
spectrometry.
Recovery of PBBs using established methods is in the range of
80-90% (Fries, 1985b). The solvent system that is used for sample
extraction can affect recovery. Poor recoveries were often found
with hexane but the optimal solvent conditions depend on the source
of the medium sample.
For extraction conditions see Table 13 (environmental samples),
Table 14 (food/feed), Table 15 (biological tissues and fluids (a)
serum/blood (b) adipose and other tissues).
In soil, Griffin & Chou (1981a) found that a polar organic
solvent was important and obtained the best results with
hexane/acetone (9:1).
For serum and blood, the standard extraction method given by
Burse et al. (1980) has been used by most workers.
Extraction of PBBs from adipose and other tissues presents
greater problems. PBBs are readily soluble in fat. They can
therefore be extracted with the fat out of the tissue/sample but,
afterwards, an intensive clean-up procedure for PBBs is necessary.
Various methods, such as adsorption chromatography with Florisil,
gel permeation chromatography, Florisil cartridges (Chiang et al.,
1987), and Unitrex (Head & Burse, 1987) have been proposed.
The sample extraction and clean-up techniques for the
determination of PBBs are similar to those used for PCBs (Krüger
et al., 1988; Jansson et al., 1991). The lipids can be removed from
the extract by gel permeation (Krüger, 1988) or by hydrolysis
(Jansson et al., 1991). Usually PBBs and PCBs are separated from
more polar compounds by adsorption chromatography on silica gel or
Florisil. If the coplanar compounds are to be determined, they have
to be isolated from the major compounds in the extract. This can be
done using activated charcoal, which adsorbs the planar molecules
more strongly than the non-planar. Brominated naphthalenes, dioxins,
and furans will also be separated from the major PBB components in
this step. HPLC methods are now being adopted for these separations
and both charcoal and modified silica gel columns are available for
HPLC separations of coplanar compounds.
Table 13. Determination of PBBs in environmental samplesa
Matrix Extraction Clean up Analytical Detection Detection limit Comment References
method
Soil, grass, benzene/ Florisil GC ECD, FID 0.1 µg/kg BB 153, two PeBB Jacobs
carrots 2-propanol MS dry weight (soil) isomers, three et al.
13C-NMR 10 µg/kg additional HxBB (1976)
wet weight (plant) isomers, two HpBB
isomers detected
Soil leachate benzene/ GC ECD 0.1 µg/kg laboratory experiments Filonow
2-propanol dry weight et al.
(1976)
Soil, plant hexane/ Florisil GC ECD 0.1 µg/kg field and laboratory Jacobs
samples acetone dry weight (soil) experiments; no et al.
TLC ECD 0.3 µg/kg significant (1978)
wet weight (plant) degradation of PBBs
after 1 year
Effluent river hexane/ no data GC ECD 0.1 µg/litre environmental Hesse (1975)
water diethyl given (later 0.01 µg/ samples Hesse &
ether litre) Powers
(1978)
Sediment hexane/ no data GC ECD 100 µg/kg environmental Hesse &
acetone given samples Powers
(1978)
Soil hexane/ no data GC ECD, FID, separation of 30 PBB Stratton &
acetone 9:1 given MS congeners tested Whitlock
optimum conditions (1979)
Table 13 (contd).
Matrix Extraction Clean up Analytical Detection Detection limit Comment References
method
for extraction of
PBBs from soil;
polar organic solvent
important
98 environmental hexane, Florisil GC MS 0.2 µg/kg analysed for hexa-, Stratton
samples Soxhlet hepta-, octa-, nona-, et al.
(fish, sediment, decabromobiphenyls; (1979)
soils, HxBB in 84% of samples
vegetation)
Soil, sediment, hexane Florisil GC MS (SIM) 0.2 µg/kg congeners detected Griffin &
sludge, Chou (1981a)
vegetation
Soil hexane/ Florisil GC FID, ECD degradation of PBBs Hill et al.
acetone 1:1 in soil (1982)
Sewage sludge hexane/ TLC IR, NMR, MS 10 ng/kg no PBBs found Strachan
methanol GC et al.
Soxhlet (1983)
extraction
Plants cut, Florisil GC ECD 0.3 µg/kg no translocation Chou et al.
extracted wet basis in plants (1978)
with hexane/
acetone
Table 13 (contd).
a Abbreviations used:
ECD = Pulsed 63Ni electron capture detector. MS = Mass spectrometry.
FID = Flame ionization detector. NMR = Nuclear magnetic resonance.
GC = Gas chromatography. SIM = Selected ion monitoring.
IR = Infrared radiation. TLC = Thin layer chromatography.
Table 14. Determination of PBBs in food/feeda
Matrix Extraction Clean up Analytical Detection Detection Comment References
method limit
Dairy fat extracted by AOAC GPC, 25% toluene GC ECD 7 µg/kg comparison Fehringer
products (1975) methods in ethyl acetate of methods (1975a)
(methanol/ether)
Florisil/pet ether TLC 0.2 mg/kg
Dry animal finely ground feed Florisil/pet ether GC, TLC ECD 8 µg/kg hexabromo Fehringer
feeds packed into a column 30 µg/kg isomer (1975b)
containing celite, measured
elution with methylene
chloride
Feeds and see Fehringer GC before and ECD 5 µg/kg confirmation Erney
dairy (1975a,b) after UV irradi- of PBB (1975)
products ation to determine residues
background using UV
irradiation
a Abbreviations used:
ECD = Pulsed 63Ni electron capture detector. TLC = Thin layer chromatography.
GC = Gas chromatography. UV = Ultraviolet.
GPC = Gel permeation chromatography.
Table 15. Determination of PBBs in biological tissues and fluidsa
Matrix Extraction Clean up Detection Detection limit Comment References
a) Serum/blood
Human serum methanol-treated serum, Florisil ECD 5 pg analysis based on HxBB Bekesi et al.
extraction with hexane peak (1978)
Human serum methanol-treated serum, Florisil ECD 0.2 µg/litre Wolff et al.
extraction with hexane/ (1978)
ether
Human/rat serum methanol-treated serum, Florisil ECD 0.2 µg/litre PBB homologues as % HxBB Wolff &
extraction with hexane/ peak Aubrey
ether (1978)
methanol-treated serum, Florisil ECD, MS < 1 mg/ml Wolff et al.
extraction with hexane/ (1979a)
ether
Plasma from multiple extraction with Florisil ECD 0.001 µg/litre recovery 96% Willett
PBB-fed cows mixture of diethyl and pet. et al.
ethers (1978)
Human serum methanol-treated serum; Florisil ECD 0.1 µg/litre interlaboratory comparison Burse et al.
extraction with hexane/ (1980)
ether
Table 15 (contd).
Matrix Extraction Clean up Detection Detection limit Comment References
Plasma, white methanol; precipitated Florisil MS-SIM 0.1 µg/mg very exact details with Roboz et al.
cell fraction protein removed; NCI protein review spectra (1980)
erythrocytes extraction with hexane/
ß-lipoprotein ether (1:1)
Human serum methanol; hexane/ silica gel ECD 1 µg/litre Needham
diethylether (1:1) et al.
(1981)
Human serum + methanol precipitated Florisil ECD < 1 µg/litre serum protein precipitated Roboz et al.
protein not removed + MS-NCI with methanol should not (1982)
hexane/diethylether (1:1) be removed from sample
Human serum see Burse et al. (1980) ECD 1 µg/litre Eyster
et al.
(1983)
Blood (in vitro see Roboz et al. (1982) MS- in vitro Roboz et al.
experimental) (PPINCI) (1985a)
Human blood see Roboz et al. (1982) ECD, SIM, 10-35 ng distribution of PBBs Roboz et al.
(model and NCI individual among blood components (1985b)
environmentally serum congener/litre
exposed)
b) Adipose and other tissues
Adipose tissue toluene/ethyl acetate GPC (Bio ECD 0.5 µg/kg major HxBB peak determined Wolff et al.
from exposed (1+3) Beads (1979a)
workers toluene/ethyl
acetate (1+3)
Table 15 (contd).
Matrix Extraction Clean up Detection Detection limit Comment References
Various rat Burse et al. (1980) ECD 10 µg/kg comparison of Miceli &
tissues and concentrations of PBBs Marks
serum in various tissues with (1981)
time
Liver and 1) hexane (liver and 1) Florisil ECD, NAA comparison of extraction Fawkes et al.
perirenal adipose) methods (showed PBB (1982)
adipose tissue extraction with hexane
from dosed rats leads to erratic recoveries
and results) increase in
detection limits over
ECD ( 2 pg FireMaster);
2) chloroform: 2) acidic 1 µg/litre or less of
methanol (liver) alumina hexa congener)
3) methylene chloride
chloroform (adipose)
Human adipose 15% diethyl ether Florisil/GPC ECD GPC clean-up tested (85% MacLeod
tissue in hexane MS recovery); MS free of et al.
serious interference (1982)
from 46 to 500 m/z
Adipose tissue 6% diethyl ether Florisil/GPC MS 1-2 µg/kg HxBB peak Lewis &
from general in hexane Sovocool
population (1982)
Human adipose hexane/diethylether silica gel ECD 1 µg/kg Eyster
tissue, placenta, et al.
cord blood, (1983)
biliary fluid,
faeces
Table 15 (contd).
Matrix Extraction Clean up Detection Detection limit Comment References
Human postmortem Chromaflex ECD 0.5 µg/kg HxBB peak Miceli
tissue adsorption et al.
column with (1985)
5% silica
gel + sodium
sulfate/
hexane
Adipose tissue hexane solid phase ECD 1-14 ng/kg Florisil Chiang et al.
(bovine), spiked Florisil cartridges cartridges to separate (1987)
for model system fat; 116% recovery
c) Milk
Human milk potassium oxalate, ECD 1 µg/kg Eyster et al.
ethanol/diethyl ether; (1983)
hexane
Human milk potassium oxalate, Bio Beads/ MS (NCI, 1 ng/kg separation of coplanar Krüger (1988)
ethanol/diethyl ether Florisil/ SIM) and planar isomers with
activated charcoal
charcoal
d) Biological samples from the environment
Fish, seal freeze, pulverize, Bio Beads/ MS (NCI, 10 ng/kg Krüger (1988)
pet. ether Florisil/ SIM)
activated
charcoal
Table 15 (contd).
Matrix Extraction Clean up Detection Detection limit Comment References
Dolphin fat/ Soxhlet; hexane, GPC; silica MS no data given lowest value given: Kuehl et al.
organ tissue methylene chloride gel 40 µg/kg (1991)
Terrestrial, diethyl ether/hexane hydrolysis MS (NCI) no data given lowest value given: Jansson
freshwater and with 98% 40 ng/kg et al.
marine samples H2SO4/Bio (1991, 1992)
Beads/ silica
gel/activated
charcoal
a Analytical method used was gas chromatography.
Abbreviations used:
ECD = Pulsed 63Ni electron capture detector. NCI = Negative ion chemical ionization mass spectrometry.
GPC = Gel permeation chromatography. PPINICI = Pulsed positive ion-negative ion chemical ionization.
MS = Mass spectrometry. SIM = Selected ion monitoring.
NAA = Neutron activation analysis.
Using negative ion chemical ionization mass spectrometry
(MS-NCI), the bromide ions can be used to detect brominated
compounds with high sensitivity and selectivity. However, using this
detection method (or ECD), interference between congeners of PBB and
polybrominated diphenyl ethers is possible.
The 209 possible PBB congeners have a wide range of volatility,
which causes very difficult separation problems (Farrell, 1980). In
earlier studies, gas chromatography (GC) with packed columns, e.g.,
3% OV-1 on 80/100 mesh Chromosorb W(HP) was used (Fehringer,
1975a,b). Capillary columns enable a good separation with lower
brominated biphenyls but do not have any great advantages over
packed columns for more highly substituted biphenyls (Farrell, 1980;
Orti et al., 1983; Robertson et al., 1984b).
The detection method most frequently used is that of pulsed
63Ni electron capture detection (ECD). In general, retention times
and electron capture responses increase with increasing bromination.
This is a sensitive method, but has some shortcomings. ECD is a
group selective detector that responds to halogens and other
electronegative groups. This places stringent requirements on
chromatographic separation. Moreover, ECD responds differently to
different compounds, depending on the molecular structure. The
response or sensitivity of the ECD depends on the position of the
halogen on the biphenyl nucleus as well as the number of halogens.
This necessitates running a standard for each compound to be
determined (Zerezghi et al., 1984). Sweetman & Boettner (1982)
analysed the structure-sensitivity of PBBs using ECD (see Table 12).
Flame ionisation detection (FID) can only be used for the
analysis of standard substances because of its low specificity
(Krüger, 1988).
A microwave-induced plasma emission detector has been used as a
specific method of detection for bromine (Mulligan et al., 1980;
Zerezghi et al., 1984). However, the method is not sensitive enough
for environmental samples.
Some authors have confirmed their results by GC/ECD
determination before, and after, exposure to UVR. The PBBs present
are photolyzed and, in this way, the background values can be
eliminated (Erney, 1975; Trotter, 1977).
Very often, the presence of PBBs is confirmed using mass
spectrometry (MS) together with gas chromatography. The purity of
the sample can be verified by comparison with known standards.
Negative chemical ionization (NCI) mass spectrometry has a
sensitivity comparable with, and somewhat better than, GC/ECD
analysis. The detection level for hexabromobiphenyl standards is
lower by a factor of 20 to 10-35 ng/ml in comparison with GC/ECD
analyses (Roboz et al., 1982). This relatively new method has also
been used to detect polychlorinated and polybrominated dioxins and
furans (see section 4.3).
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural occurrence
PBBs are not known to occur naturally.
3.2 Man-made sources
3.2.1 Production levels and processes
3.2.1.1 World production figures
1) United States of America
The commercial production of PBBs in the USA commenced in 1970
(Neufeld et al., 1977). Several US producers of commercial
quantities have been identified (Mumma & Wallace, 1975; Neufeld
et al., 1977; Di Carlo et al., 1978; Brinkman & de Kok, 1980).
In 1976, a US firm had a combined production of about 0.45
million kg of PBBs for export to Europe (Anon., 1977).
A list of suppliers of laboratory quantities (with a maximum
production or importation of about 2 kg/year) is presented by Mumma
& Wallace (1975) and Neufeld et al. (1977).
As a result of the Michigan catastrophe of mid-1973, the sole
US manufacturer of hexabromobiphenyl ceased production in November
1974. It is not clear, whether the production of bromine-based fire
retardants was resumed by another US company in 1978 (Brinkman & de
Kok, 1980). Two other companies continued their production of octa-
and deca-PBB until 1977 (Di Carlo et al., 1978). According to the
German "Umweltbundesamt" (UBA, 1989), decabromobiphenyl was produced
in the USA until 1979.
There are repeated statements that all PBBs manufactured in the
USA since 1975-76 have been exported, mainly to Europe, and that
there is no importation of any PBB mixtures into the USA (Brinkman &
de Kok, 1980).
Relevant production data for the period 1970-76 are presented
in Table 16.
Table 16. Commercial production of polybrominated biphenyls in the USA, 1970-76a
Estimated production in thousand kg
Product 1970 1971 1972 1973 1974 1975 1976 1970-76
Hexabromobiphenyl 9.5 84.2 1011 1770 2221 0 0 5369
Octabromobiphenyl 14.1 14.1 14.6 163 48 77.3 366 702
and decabromobiphenylb
Total PBBs 23.6 98.3 1025 1933 2269 77.3 366 6071
a From: Di Carlo et al. (1978).
b Manufacture was continued in 1977, but production figures are not available.
Hexabrominated biphenyl forms the major part (about
5.4 million kg FireMaster(R) BP-6 plus some 68 300 kg
FireMaster(R) FF-1) of the estimated total production of
6.1 million kg (Neufeld et al., 1977). The remaining 0.7 million kg
are accounted for by the higher brominated biphenyls. In 1976, for
example, 0.35 million kg of decabromobiphenyl and 13 600 kg of
octabromobiphenyl were manufactured (Neufeld et al., 1977). No
production figures are available for 1977 (Di Carlo et al., 1978).
2) Japan
According to IARC (1978), PBBs have never been produced in
Japan, but, up to 1978, some were imported.
3) Europe
a) Germany
A German firm produced a mixture of highly brominated PBBs,
called Bromkal 80-9D until mid-1985, when the activities concerning
bromine-based fire retardants were shifted to the USA. No production
figures are available.
b) France
A French firm manufactures a technical-grade decabromobiphenyl,
sold as Adine 0102, production being a few hundred thousand kg/year
(Atochem, 1988). It is marketed in France, Great Britain, Spain and
the Netherlands (Atochem, 1988; UBA, 1989). More than 200 tonnes
decabromobiphenyl/year were used in the Netherlands for
incorporation into polybutylenterephthalate plastics (UBA, 1989).
c) United Kingdom
Two companies are reported to have marketed or produced
technical-grade decabromobiphenyl in the United Kingdom (Brinkman &
de Kok, 1980). In 1977, the production of PBBs was discontinued
(Neufeld et al., 1977).
No production or sales data are available.
d) Netherlands
No domestic producer has been identified. An Israeli company
with two bromine plants in Holland denied the production of PBBs
(Neufeld et al., 1977). However, the amount of decabromobi phenyl
sold annually in the Netherlands was estimated to be of the order of
91 000 kg (Brinkman & de Kok, 1980).
No information is available on production in other parts of the
world.
3.2.1.2 Manufacturing processes
The process of manufacturing PBBs consists of a Friedel-Crafts
type reaction in which biphenyl is reacted with bromine in the
presence of chloride in an organic solvent, using aluminium
chloride, aluminium bromide, or iron as catalyst (Brinkman & de Kok,
1980). In the Atochem decabromobiphenyl manufacturing process,
biphenyl is directly brominated in a large excess of bromine, used
as reactant and solvent in the presence of a Lewis acid catalyst
(aluminium type). Decabromobiphenyl is further purified by
distillation of the excess bromine in the presence of a brominated
solvent (Atochem, 1992).
3.2.1.3 Loss into the environment during normal production
Data are published only for the USA. The following information
refers to reviews by Neufeld et al. (1977) and Di Carlo et al.
(1978).
Losses of PBBs to the environment at sites of its manufacture
can total 51 kg/1000 kg of product. These losses occur through:
1) Emission into the air
In 1977, the maximum air losses as particulate matter at
production sites were estimated to total 1.1 kg of PBBs/1000 kg
manufactured.
(a) Emission to the air from the vents of the hydrogen bromide
recovery system:
Total emission of FireMaster(R) PB-6 was estimated to amount
to 70 mg/1000 kg produced.
(b) Loss of particulate PBB to the atmosphere during centrifugation
(which was carried out to separate the solid reaction products
from the organic solvent).
A New Jersey permit application by Hexcel Corp. plant (1976)
indicated a loss of less than 0.05% of the product.
(c) Loss of dust from drying and pulverizing PBBs to a fine powder
(dust from this operation was removed by a bag type filter).
In 1974, atmospheric levels of PB-6 in the Michigan Chemical
Corp. bagger area were 16-32 mg/m3 during the bagging operation
and 3 mg/m3 after bagging was completed. Lower levels were
detected in other areas of the plant.
(d) Emission of hexabromobiphenyl as a vapour contaminant in
vapour streams leaving scrubbers or equivalent equipment was
calculated to be less than 25 µg/m3 (1 ppb) at ambient
temperature (Neufeld et al., 1977).
2) Losses in waste waters resulting from the quenching and
washing of the PBBs as they are recovered from the reaction mass:
The losses of PBBs to sewers at manufacturing sites were
estimated, in 1977, to be 4.6 µg/kg of product.
- In 1972, samples of the Michigan Chemical Corp. effluent
discharges were found to contain PBB levels of 98-503 µg/litre
(Hesse, 1975);
- The total quantity of PBBs being discharged to the Pine River
was estimated as 0.11 kg daily.
- Unfiltered water from an industrial storm sewer at the Hexcel
Corp. plant contained 92 µg/litre, mainly as decabromobiphenyl
(hexa-, octa-, and nonabromobiphenyls levels were also
measurable).
- Liquid effluents, diluted by canal water, from the White
Chemical Co. plant showed values of up to 31 µg PBBs/litre.
3) Solid losses to landfills resulting from drying, handling,
shipping and transportation.
An estimate of PBB losses as solid waste to landfills was
50 g/kg of product.
According to a report of the Michigan Chemical Corp., their
solid waste included approximately 5% of the BP-6 produced.
4) Losses to the soil
Soil samples from the bagging and loading areas of the Michigan
Chemical corp. contained PBBs at concentrations of 3500 and
2500 mg/kg, respectively.
Losses of other compounds:
The following typical air contaminants released during PBB-
manufacture were reported: hydrogen chloride, bromine, ethylene
dichloride, aluminium chloride, and biphenyls. The total quantity
emitted was stated to be less than 5.5 kg/day.
3.2.1.4 Methods of transport, accidental release, and disposal of
production wastes
Details of present-day labelling and transport regulations are
given in the Health and Safety Guide for PBBs (WHO, 1993).
In 1973, an accidental release of PBBs occurred in Michigan
("Michigan disaster"), when two products manufactured by the
Michigan Chemical Company were inadvertently confused, i.e.,
250-500 kg (Di Carlo et al., 1978) of FireMaster(R), instead of
NutriMaster(R), a magnesium oxide-based cattle feed supplement,
were added to animal feed and distributed to farms within the state.
The compound is believed to have been FireMaster(R) FF-1
(e.g., Fries, 1985b), even if in some publications the name
FireMaster(R) BP-6 is used (e.g., Neufeld et al., 1977; Di Carlo
et al., 1978). This accidental mix up resulted in widespread
contamination by PBBs (see section 5). As a result of this incident,
the production of FireMaster(R) BP-6 by Michigan Chemical Corp.
was stopped in 1974 (Di Carlo et al., 1978). Chronological reports
or reviews of the PBB disaster are given by Carter (1976), Getty
et al. (1977), Kay (1977), Di Carlo et al. (1978), Damstra et al.
(1982), Zabik (1982), and Fries (1985b).
Details of the disposal of manufacturing waste during present
production are not available. In a report by Neufeld et al. (1977),
solids from manufacturing operations were disposed of in landfills.
Waste waters containing small amounts of PBBs were discharged into
the chemical sewer.
3.2.2 Uses
Commercially manufactured PBBs are processed by industrial
users, primarily as flame retardants in polymeric materials. PBBs
were developed for this major application, because: they are able to
meet the flame-resistance performance requirements, they are
economically feasible, and they have little effect on the
flexibility of the base compounds (Mumma & Wallace, 1975).
The process of application is basically one of physical
blending: the PBBs are not functional additives, and on blending
with the dry solid or liquid polymeric material, provide filter-type
flame retardant action with the chemical release of hydrogen bromide
if ignited (Neufeld et al., 1977).
Neufeld et al. (1977) list 34 applications of PBBs found in
patent and technical literature. The majority are related to the use
of the PBBs as flame retardants in polymeric materials, other claims
include self-extinguishing properties and improved wearability and
machinability. Further potential uses of PBBs are: in the synthesis
of biphenyl esters or in a modified Wurtz-Fittig-synthesis; in
light sensitive compositions to act as colour activators; as
relative molecular mass control agents for polybutadiene; as wood
preservatives; as voltage stabilizing agents in electrical
insulation; as functional fluids, such as dielectric media (Neufeld
et al., 1977). In the USA and Canada, hexabromobiphenyl
(FireMaster(R)) was the principal PBB product. It was used as a
fire retardant in three main commercial products:
acrylonitrile-butadiene-styrene (ABS) plastics; coatings and
lacquers; and polyurethane foam (Neufeld et al., 1977).
The types of ABS plastic products in which FireMaster(R) BP-6
was used are compiled in Table 17.
According to Neufeld et al. (1977), the use of FireMaster(R)
BP-6 as a flame retardant in thermoplastic resins was confined to
products that do not come into contact with food or feed and are not
used in fabrics to which humans are exposed.
Although more than 130 companies in the USA used PBBs prior to
1976 (Di Carlo et al., 1978), only a limited number seems to have
been the major users of PBBs. For example, in 1974, the final year
of US production, Borg Warner Corp. (Parkersburg, W.Va.; using
FireMaster(R) in ABS plastics) and Standard T Chemical Co. (Staten
Island, New York; using FireMaster(R) in fire retardant coatings
for industry) consumed over 50% of the total US yearly production
(Mumma & Wallace, 1975; Jamieson, 1977; Neufeld et al., 1977;
Brinkman & de Kok, 1980).
Of the estimated 2200 tonnes hexabromobiphenyl produced in 1974
(IARC, 1978), about 900 tonnes (Mumma & Wallace, 1975; Neufeld
et al., 1977; IARC, 1978) were used in ABS plastic products and
about 34 000 tonnes (Mumma & Wallace, 1975; Neufeld et al., 1977;
IARC, 1978) in cable coatings.
The exact quantity of FireMaster(R) used in polyurethane foam
for automobile upholstery was not published. The two larger
consumers ceased using hexabromobiphenyl (one of these in 1972)
because PBBs did not decompose in the ultimate incineration of
scrapped automobiles (Neufeld et al., 1977).
No current users of hexabromobiphenyl have been identified
(Neufeld et al., 1977; Di Carlo et al., 1978; Brinkman & de Kok,
1980). As regards octa- and decabromobiphenyl, no commercial use was
reported in the USA during 1970-74 (Neufeld et al., 1977). In
Western Europe, the use of higher brominated PBBs seems to be
dominant. The decabromobiphenyl Adine 0102(R) (in the past
manufactured by Ugine Kuhlmann, at present by Atochem) is used as a
flame retardant for thermoplastics and thermosets (e.g., in
polyesters, epoxy resins, polystyrene, ABS, polyolefines, and PVC),
for elastomers (e.g., in PU-elastomers and india rubber) and for
cellulosics (e.g., chip-board). It is applied frequently in
association with antimony trioxide (Sb2O3) (Atochem, 1984a). Its use
in paints and varnishes has also been reported (Brinkman & de Kok,
1980).
Table 17. Uses of FireMaster(R) BP-6 in ABS plastics in the USAa
Industry Approximate % Examples
of total use
Business machines and 48 Typewriter, calculator and microfilm-reader
industrial equipment housings; business machine housings
Electrical 35 Radio and TV parts, thermostats, shaver and
hand-tool housings
Fabricated products 12 Projector housings, movie equipment cases
Transportation 1 Miscellaneous small automotive parts;
electrical-wire connectors, switch
connectors, speaker grills
Miscellaneous 4 Small parts for electrical applications,
motor housings; components for industrial
equipment
a From: Brinkman & de Kok (1980).
Losses of PBBs to the environment from processing plants are
possible, but little information is available about this.
Although decabromobiphenyl and, possibly, other PBBs are still
produced commercially, alternative chemicals have been introduced to
replace them as flame retardants, in particular polybrominated
biphenyl ethers (oxides) (PBBO), e.g., decabromobiphenyl ether
(Adine 505; Bromkal 82-0 DE; Great Lakes DE-83TM and DE 83RTM),
octabromobiphenyl ether (Bromkal 79-8 DE; Great Lakes DE 79), and
pentabromobiphenyl ether (Bromkal 70-5 DE; Great Lakes DE-71TM:
Atochem, 1984b; Great Lakes Chemical Corp., 1986).
Decabromobiphenyl ether (DBBO) for example, appears to be a
much less toxic material than PBBs. However, DBBO is said to have a
tendency to degrade to lower brominated biphenyl oxides. It is
possible that these lower order compounds may pose environmental
problems similar to those of the lower brominated PBBs (Mumma &
Wallace, 1975). In addition, on pyrolysis, PBBOs produce larger
amounts of dioxins and furans than PBBs and so may themselves have
to be replaced by other compounds.
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1 Transport and distribution between media
4.1.1 Air
The commercial PBB-mixtures are solids at room temperature.
Despite their low vapour pressure, air pollution by PBBs can occur
as follows:
PBBs may be released into the atmosphere as vapour or dust
from production and processing plants. Stratton & Whitlock (1979)
found indirect evidence of airborne discharges of PBBs near two out
of three chosen industrial sites in north-eastern New Jersey and
Staten Island, New York, where these materials had been manufactured
or used in product formulations.
Further air contamination may occur during the incineration of
industrial and municipal wastes. Most municipal incinerators are not
very effective in destroying halogenated biphenyls. Like PCBs, PBBs
do not burn readily and incinerating conditions must be carefully
controlled, otherwise these compounds will reenter the environment
in the stack gases (Griffin & Chou, 1981a) or may be transformed to
polybro minated dibenzofurans.
Flameless combustion of the consumer products causes
volatilization of intact PBBs (Benbow & Cullis, 1975).
An appreciable loss of PBBs during the lifetime of PBB-
containing products is unlikely.
Secondary ways of entrance of PBBs into the atmosphere, e.g.,
through evaporation from contaminated soils, are thought to be
negligible, though small losses of PBBs from soil during long-term
(6 months) incubation studies were observed, which were associated
with volatilization rather than sorption or masking (Griffin & Chou,
1981a).
The ability of PBBs to co-distil from landfills or from the
surface layer of water bodies, as reported for PCBs (Kalmaz &
Kalmaz, 1979), has not yet been examined.
By analogy with PCBs, it might be expected that PBBs entering
the atmosphere in the vapour phase would be adsorbed rapidly onto
particles, which would then be deposited by particle sedimentation,
depending on micro- and macrometeorological conditions.
According to Eisenreich et al. (1981) organic compounds having
a vapour pressure > 10-5 kPa should exist almost entirely in
the vapour phase, and those having a vapour pressure > 10-9 kPa
should exist almost entirely in the particulate phase.
PBBs, e.g., hexabromobiphenyl or FireMaster with a vapour
pressure of 6.9 x 10-9 kPa (Jacobs et al., 1976), belong to the
latter. In reality, distribution and atmospheric lifetimes of
organic compounds with a high relative molecular mass depend largely
on the particle concentration and composition in the atmosphere
(Eisenreich et al., 1981). Gas-phase reactions with hydroxyl (OH)
radicals also influence the lifetimes of organic compounds emitted
into the atmosphere. Atkinson et al. (1984) determined rate
constants for the gas-phase reaction of OH radicals with biphenyl
and predicted, from their findings, that the chlorine - and
bromine-substituted biphenyls would have OH radical rate constants
of < 8 x 10-12 cm3/molecule per second at room temperature.
4.1.2 Water
The principal route of entrance of PBBs into aquatic
environments is from industrial waste streams into receiving waters.
Further potential routes (of minor relevance) are atmospheric
deposition and erosion of polluted soils. Groundwater contamination
is possible, if these compounds are leached from landfills (Shah,
1978).
Because compounds like PBB are very poorly soluble, they are
primarily found in sediments of polluted lakes and rivers
(Kimbrough, 1980a). In laboratory experiments, Simmons & Kotz (1982)
determined the "percent adsorption" of PBBs in sediments from sites
at Lake Michigan and the Huron River and concluded from values
ranging from 9 to 32% that the capacity of the sediments for PBB was
small to moderate.
PBBs in water are mainly adsorbed on particulate matter
followed by sedimentation at a rate that depends on several factors,
such as the size and type of the sediment and/or the organic
contents of both the sediment and the overlying water mass. The
relative importance of these parameters is controversial (Simmons &
Kotz, 1982). Laboratory results concerning PCBs (Jensen et al.,
1973) led to the assumption that the kinetics of the sorption
reaction may vary inversely with particle size (because smaller
particles have a larger surface area for surface adsorption).
Leland et al. (1973), Choi & Chen (1976), and Simmons et al. (1980)
have shown that the organic content of the sediment is directly
related to its adsorptive capacity for a specific contaminant.
According to Schwarzenbach & Westall (1981), adsorption of non-polar
compounds is highly correlated with the organic carbon content of
sorbents containing more than 0.1% organic carbon. Simmons & Kotz
(1982) found strong correlations between the adsorptive capacity of
the sediments for PBBs and TOC (total organic carbon) and the %
silt/clay fraction.
Sediments are potential sources as well as sinks for most
chemicals (Simmons & Kotz, 1982). Desorption of a contaminant from
the sediments is favoured where a high concentration of organic
matter exists in the water column (Huang, 1971). The presence of
organic matter may also enhance the partitioning of the contaminant
in the water phase and, thus, facilitate further movement with the
water mass (Hassett & Anderson, 1979). Laboratory studies on the
mode of action that PBBs may take in their movement through the
water column have verified that the total organic content of the
natural water will decrease the adsorption of PBB onto sediment and
therefore keep the PBB in the water phase. For example, comparing
the distilled water versus natural water systems, in river water
with an organic content of 11-12 mg C/litre, the % PBB-adsorption
was decreased by 33-43%; for lake water with an organic content of
3.8 mg/litre, the % PBB-adsorption was reduced by about 12% (Simmons
& Kotz, 1982). Another investigation indicated that the solubilities
of PBBs were directly correlated with the levels of dissolved
organics in the water (Griffin & Chou, 1981a) (see also section
4.1.3).
However, in the natural environment, upon settling out, the
association of the contaminant with the sediment may become the
dominant process in the water/sediment system (Simmons & Kotz,
1982). Transport of PBBs is thought to take place, when mixing or
bioturbation of sediments causes redistribution of the contaminant
in the water column (Simmons & Kotz, 1982), and through transport of
the sediment itself.
4.1.3 Soil
Pollution of soils can originate from point sources such as PBB
plant areas and waste dumps. Very few data are available on the
deposition of PBBs on soil via the atmosphere, sewage sludge from
municipal sewage treatment systems, and the dredging of sludge from
contaminated waters.
Other possible sources are illicit, or improper, disposal of
such chemicals (Kimbrough, 1980a) and incidents. For example, as a
consequence of an incident in 1973, Michigan soils have been
contaminated by manure from PBB-fed animals and by the disposal of
contaminated feed, milk, carcasses, etc. (Getty et al., 1977; Chou
et al., 1978; Damstra et al., 1982; Fries, 1985b). Once PBBs have
been introduced into the soil, they appear to have little tendency
to translocate (Damstra et al., 1982).
The ability of rainfall to carry PBBs through the soil was
tested in a laboratory simulation. Filonow et al. (1976) percolated
water through columns of 4 Michigan soils containing 100 mg
2,2',4,4',5,5'-hexabromobiphenyl/kg. They found a loss of less than
0.6% of the hexabromobiphenyl congener from each soil, even with
leachate quantities equivalent to 20 times the average annual
rainfall in Michigan.
Field investigations also indicated that PBBs were retained in
the top soil. Results of subsequent studies on highly contaminated
farm soils showed that PBBs did not move below the 15 cm level,
except where there was a history of physical mixing of the soil
(Fries, 1985b).
The mobility in soils of a chemical like PBBs will largely be
governed by its solubility in water and its adsorption, or
interaction, with soil particles (Jacobs et al., 1978).
As already mentioned, PBBs have a very low solubility in water.
However, studies with distilled, tap, river, and soil waters showed
that their solubility was markedly influenced by water purity
(Jacobs et al., 1978). Griffin & Chou (1981a) ascertained, under
well defined conditions, the following average solubilities of PBBs:
0.06 µg/litre in distilled water, 0.3 µg/litre in deionized water,
0.5 µg/litre in creek water, 8.9 µg/litre in Du Page leachate, and
16.9 µg/litre in Blackwell leachate.
Hence, PBBs were more than 200 times more soluble in landfill
leachate than in distilled water; the solubilities of PBBs were also
higher in creek water than in distilled water. As shown by the TOC
(total organic carbon) values for the waters, the higher
solubilities of PBBs were directly correlated with the level of
dissolved organic compounds in the waters. The type of dissolved
organic matter may also influence the solubility (Griffin & Chou,
1981a).
PBBs are quite soluble in organic solvents, such as dioxane,
carbon tetrachloride, acetone, and methanol. This could play a major
role in soil environments where leachates from chemical waste
disposal sites are percolating.
The other important factor affecting the migration of PBBs,
i.e., their adsorption by soils, was also studied under laboratory
conditions. The hydrophobic properties of PBBs make them easily
adsorbed from aqueous solutions onto soils. Filonow et al. (1976)
examined the adsorption of purified 2,2',4,4',5,5'-hexabromobi
phenyl (BB153) on four soil types. They found that the adsorption of
2,2',4,4',5,5'-hexabromobiphenyl conformed well to Freundlich
adsorption isotherms, and that 2-19% of the available HBB was
adsorbed. Adsorption of HBB was influenced primarily by the organic
content of the soils. An increase in the organic matter content of
soils enhanced their adsorption capacity.
Neither percentage clay nor pH correlated well with BB153
adsorption. Any effect that the clay contents may have had, was
apparently masked by the effect of the organic contents on
adsorption (Filonow et al., 1976).
Griffin & Chou (1981a,b), using the PBB-mixture FireMaster(R)
BP-6 or 14C-labelled-PBB, also confirmed the strong adsorption of
PBBs on soils and indicated a very high direct correlation between
the total organic carbon content (TOC) of three different soils and
the amounts of PBBs adsorbed. However, they pointed out that, in
soils with a low TOC, the mineral fraction may contribute markedly
to the adsorption capacity.
Furthermore, preferential adsorption of PBB congeners and
isomers was noted, depending on the characteristics of the
adsorbent, e.g., organic content (Griffin & Chou, 1981a), as well as
on the degree and position of bromine substitution (Griffin & Chou,
1980, 1981b).
No measurable adsorption on soils occurred of PBBs from organic
solvents (Griffin & Chou, 1981a).
The results of migration studies were in agreement with the
findings discussed above. The mobility of PBBs in five soils was
measured with several leaching solvents, using a thin-layer
chromatography technique and column leaching studies (Griffin &
Chou, 1981a,b). PBBs remained immobile in the soils when leached
with water or landfill leachate, but were highly mobile when leached
with organic solvents. Mobility was directly proportional to the
solubility in the leaching solvents and inversely proportional to
the soil total organic content.
On the other hand, because PBBs are bound to soil, wherever
contaminated soil moves, whether through wind or water erosion or
animal ingestion and migration, traces of PBBs (if present) can be
expected to be found (Jacobs et al., 1978).
4.1.4 Biota
PBBs are stable and persistent, lipophilic, and only very
slightly soluble in water; they are poorly metabolized, and
therefore accumulate in lipid compartments of biota. Once they have
been released into the environment they will reach the food chain,
where they are concentrated. Fish and wildlife are the most
consistent targets for such contamination, but livestock and humans
may also become contaminated (Kimbrough, 1980a). The precise routes
and transport mechanisms of PBBs travelling through biota have not
been thoroughly investigated as pointed out below.
4.1.4.1 Terrestrial ecosystems
Several studies have been concerned with whether plants in
terrestrial ecosystems would take up, translocate, and introduce
PBBs into the food chain. Jacobs et al. (1976) selected orchard
grass (Dactylus glomerata) as test plants in their greenhouse
studies because of its extensive root mass, and carrots (Daucus
carota), which, according to Iwata et al. (1974), have an
outstanding ability to absorb pesticide residues from the soil. They
did not detect any PBBs in the tops of either species grown in soils
supplied with high levels of PBBs (10 or 100 mg/kg of
FireMaster(R) BP-6). However, they did find traces of PBBs
(20-40 µg/kg) associated with carrot roots. 14C-uptake studies
(autoradiography and GC-analysis) on corn and soybean seedlings
grown in hydroponic solutions and on three root crops (radishes,
carrots, and onions) grown in two different soils, also showed no
translocation of PBBs into plant tops (Chou et al., 1978). In
addition, these authors found that the amount of PBBs associated
with roots depended on plant species and the clay and organic matter
contents of the soil. Roots of carrots contained more PBBs than
those of radish or onion bulbs; all roots had higher levels of PBBs
(50-500 µg/kg tissue) when grown in a high-PBB treatment soil
(100 mg/kg) with lower clay and organic content, than they did
(30-120 ng/g plant tissue) in a soil containing more clay and
organic matter. Furthermore, PBBs seem to be localized on the
surfaces of roots, because a significant portion of 14C-PBBs was
removed, when the roots were dipped in acetone.
Analyses of field samples from plant tissues of corn, alfalfa,
and sudax, grown on Michigan fields with soil PBB levels ranging
from 9 to 371 µg/kg, resulted in no detectable (detection limit:
0.3 µg/kg) PBB (Jacobs et al., 1978). The same was true for washed
radishes from a garden with an estimated PBB concen tration of
500-1000 µg/kg and for corn leaf whorls containing dust from a PBB
contaminated soil (102 µg/kg) (Chou et al., 1978).
However, Stratton & Whitlock (1979), who conducted a field
screening survey near sites of manufacture and use of PBBs, found
high surface contamination of lichens and reeds.
The salt marsh cordgrass (Spartina alterniflora) is reported
to take up, accumulate, and transfer effectively PCB from
contaminated sediments to food chains (Mrozek et al., 1982). No data
are available with regard to PBBs.
So far, except for the surface contamination of roots from
contaminated soils and of foliage via air deposition processes,
plants are generally free of significant amounts of residue. Thus,
vegetation on PBB-contaminated soils is a less likely source of
contamination of animals (Damstra et al., 1982; Fries, 1985a,b).
In contrast, a major route of residue transmission from soils
to animals is the direct ingestion of soil (Fries 1982; 1985a). The
degree of contamination depends on the amount of soil ingested and
the bioavailability of the residues.
Quantitative data on soil ingestion by farm animals are given
by several authors (Healy et al., 1967; Healy, 1968; Fries, 1982;
Fries et al., 1982a,b) and range from 2 to 15% of the intake of dry
matter.
Fries (1985a) determined the bioavailability of soil-borne PBBs
in sheep, under controlled feeding conditions, using diets
containing 5% PBB-contaminated soil, and found 65% PBB absorption
from this diet, which contained 9 µg PBB/kg. Addition of activated
carbon to soil had only little effect on bioavailability of PBB.
The same author recorded PBBs in the fat of beef cows, beef
calves, ewes, and pigs from several farms on which soil-borne PBBs
in confinement areas was the only source of PBBs. It can also be
concluded from these results that the animals consumed soil, and
that soil-borne PBB was bioavailable. As might be expected, pigs
accumulated higher PBB concentrations from a soil environment than
ruminants (Fries, 1985a). Recontamination of soil by animal excreta
(Getty et al., 1977; Fries, 1985a) or carcasses (Shah, 1978) also
occurred.
Recently, PBBs have been detected in European herbivorous
mammals (Swedish reindeers: Jansson et al., 1992; German cows
(milk): Krüger, 1988) (see also sections 5.1.4 and 5.1.6).
Despite the affinity of PBBs for soil, there are no
investigations on the role of the soil fauna in the transfer of
PBBs. Earthworms are of great ecological importance and might be
expected to take up and accumulate PBBs as has been ascertained for
PCBs (Diercxsens et al., 1985) and, thus, introduce them into the
food chain.
4.1.4.2 Aquatic ecosystems
PBBs enter the aquatic food chains via water and food. Bacteria
and plankton play an important role in the accumulation and
translocation of PCBs to higher trophic levels (Kalmaz & Kalmaz,
1979; Lorenz & Neumeier, 1983). According to Falkner & Simonis
(1982), sorption processes probably control uptake and accumulation
of PCBs by phytoplankton, because of its high surface-volume ratio.
These mechanisms could also be valid for PBBs. However, Stratton &
Whitlock (1979) did not find PBBs in algae collected in the vicinity
of industrial sites, where PBB concentrations of sediments ranged
from 20 to 60 µg/kg and where captured fish contained 220-230 µg
PBB/kg (detection limit: not given).
No information on the uptake of PBBs from sediment through
bottom living organisms (e.g., mollusca or oligochaete worms) is
available.
In contrast, several laboratory (Norris et al., 1973; Zitko &
Hutzinger, 1976; Zitko, 1977; Sugiura et al., 1978) and field (Hesse
& Powers, 1978; Stratton & Whitlock, 1979; Jaffe et al., 1985)
studies on fish have been conducted. They confirm PBB uptake from
water and food, with the exception of hepta- and octabromobiphenyl
(Norris et al., 1973; Zitko, 1977), which were not taken up from
water.
Consequently, ingestion of fish is a source of PBB transfer to
mammals and birds. Because of the possible selective accumulation
and metabolism of PBB congeners in prey, it can be expected that
predators will be subjected to a somewhat different PBB congener
composition than that found in the surrounding media (sediment,
water, etc.).
In natural situations, food chains become linked together in
complex food webs, and PBBs are distributed in the corresponding
manner.
PBBs have been detected in other species of wildlife besides
fish, e.g., in ducks living near contaminated waters (Hesse &
Powers, 1978), in a turtle (Stratton & Whitlock, 1979), in the eggs
of waterbirds (Haseltine et al., 1981; Heinz et al., 1983, 1985), in
eagles (Kaiser et al., 1980), and in marine mammals (Jansson et al.,
1987, 1992; Krüger, 1988; Kuehl et al., 1991) (see also section
5.1.6).
4.1.4.3 Accidental contamination of the food chain
A special case of entrance of PBBs into the food chain occurred
accidentally in 1973 in Michigan, when FireMaster(R) FF-1 was
inadvertently substituted for magnesium oxide as a supplement in the
formulation of cattle feed (Damstra et al., 1982). Ten to twenty
bags, 22.8 kg each, of PBBs (Carter, 1976) were mixed into feeds,
that were widely distributed to Michigan farmers.
In addition, feeds not formulated to contain magnesium oxide
also became contaminated (with relatively low concentrations)
because of carryover of PBBs from batch to batch in the mixing
equipment (Dunckel, 1975) and, on farms, through the recycling of
contaminated products (Kay, 1977). Distribution of contaminated
antibiotics, e.g., aureomycin, also contributed to the introduction
of PBBs into farm animals (Di Carlo et al., 1978).
The mixing error was not discovered immediately, and it was
almost a year before analyses indicated that a compound of PBB was
involved in the illness or death of farm animals (Getty et al.,
1977). During this time (IARC, 1978; Zabik, 1982), contaminated
animals and their produce entered the human food supply and the
environment of the state of Michigan. Hundreds of farms were
affected. Altogether, at least 29 800 cattle, 5920 pigs, 1470 sheep,
and 1.5 million chickens had been killed and buried by the end of
1975 (Robertson & Chynoweth, 1975; Carter, 1976), in order to
minimize further human exposure. In addition, at least
785 thousand kg of feed, 8185 kg of cheese, 1197 kg of butter,
15 500 kg of dried milk products, and nearly 5 million eggs were
destroyed (Carter, 1976). The number of animals quarantined or
contaminated below quarantine level was estimated to be several
thousands (Isleib & Whitehead, 1975). Although the Michigan PBB
episode was primarily an incident of feed contamination, it also
resulted in secondary contamination of animals from contaminated
soil (Fries, 1985a).
4.2 Degradation
Compounds like PBBs are very stable to hydrolysis, chemical
oxidation, and thermal decomposition. Degradation by purely abiotic
chemical reactions (excluding photochemical reactions) is therefore
considered an unlikely environmental sink (Pomerantz et al., 1978;
Pearson, 1982).
The persistence of PBBs under actual field conditions is
reported in some publications. Jacobs et al. (1976) detected PBBs in
soils from a field that had received manure from a
FireMaster(R)-contaminated dairy herd 10 months earlier.
Follow-up surveys over a three-year period following the
termination of PBB production showed no significant decline in PBB
levels in sediments from the Pine River (Hesse & Powers, 1978). Soil
samples from the former PBB-manufacturing site in St. Louis,
Michigan, analysed several years (nearly ten years?) after
contamination (during the early 1970s) still contained PBBs.
However, the PBB congener composition differed from that of the
original FireMaster(R) mixture, indicating a partial degradation
of the PBB residue in the soil sample (Hill et al., 1982).
The chemical Inspection and Testing Institute, Japan (1987) has
listed decabromobiphenyl as non-biodegradable.
The most probable degradation mechanisms of PBBs in the
environment, if there is any degradation at all, are
photodecomposition and microbial degradation.
4.2.1 Photolytic degradation
Under laboratory conditions, PBBs were easily degraded by UVR.
The photoreactivity of PBBs has been used to confirm PBB residues
(Erney, 1975; Trotter, 1977). The predominant photochemical reaction
of PBBs in organic solvents was a reductive debromination.
Irradiation of 4-monobromobiphenyl at 300 nm in various polar and
nonpolar solvents led to the formation of biphenyl as the sole
product (Freeman et al., 1991). Earlier studies using lower
brominated PBB congeners (i.e., tetra and lower) reported a
preferential loss of ortho bromines (Bunce et al., 1975; Ruzo
et al., 1976). Irradiation of higher brominated congeners yielded a
series of photoproducts (Table 18), but a stepwise cleavage of
orthobromines did not appear to be preferred to meta or para
debromination (Patterson et al., 1980; Millis & Aust, 1985).
The photoreactivity of 2,2',4,4',5,5'-hexabromobiphenyl, the
main component of FireMaster(R), was consistently found to be
relatively high (Andersson et al., 1975; Ruzo et al., 1976;
Robertson et al., 1983a; Millis & Aust, 1985), and degradation
occurred more rapid than with the hexachloro analogue (Andersson
et al., 1975; Ruzo & Zabik, 1975).
Consistent with the dehalogenation pathway, photodegradation of
the commercial FireMaster(R) mixture led to reduced concentrations
of the more highly substituted PBB congeners (De Kok et al., 1977;
Robertson et al., 1981b, 1983; Epling et al., 1987). Robertson
et al. (1983a) examined changes in the composition of
FireMaster(R) BP-6 during photolysis (300 nm for 2-12 h; solvent:
cyclohexane) by monitoring 25 individual PBB congeners; they also
did not find a preferential loss of ortho bromines. Nevertheless,
the photoproducts of FireMaster(R) did contain increased
concentrations of congeners possessing no ortho bromines (e.g.,
3,4,4'-tri-, 3,3',4,4'-tetra-, 3,3',4,4',5-penta bromobiphenyl).
Moreover, other congeners, known as relatively toxic (e.g.,
2,3',4,4',5-pentabromobiphenyl), were enriched (Robertson et al.,
1983). Biphenyl, the ultimate product of the debromination pathway,
was found only to a small extent after the photolysis of
FireMaster(R) BP-6 (Epling et al., 1987).
Table 18. Photodegradation of higher brominated PBB congeners under laboratory conditions
PBB Irradiation Solvent Initial rate Primary products Remarks References
(duration) of photolysis of photolysis
(nmol/min) identified
2,2',4,5,5'- 254 nm hexane 43.4a 2,3',4',5-tetra ortho-debromination Millis & Aust
penta (up to 100 (minor product) (1985)
min) 2,2',4,5'-tetra meta-debromination
2,2',5,5'-tetra para-debromination
(major product)
(additional production
of a yellow gum)
2,3',4,4',5- 254 nm hexane 50a 2,3',4',5-tetra para-debromination Millis & Aust
penta (up to 90 3,3',4',4'-tetra ortho-debromination (1985)
min)
2,2',4,4',5,5'- 366 nm methanol not specified lower brominated PBBs degradation (90% after 9 Andersson et al.
hexa (main products) min) more rapid than with (1975)
BB 153 methoxy- PBBs (minor the hexachloro analogue
products)
> 300 nm hexane not specified lower brominated PBBs BB 153 was 24.4 times Ruzo et al.
(0.5-2 h) quaterphenyls (< 5%) more reactive than (1976)
4,4'-dibromobiphenyl
2,2',4,4',5,5'- 254 nm hexane 53a 2,2',4,5,5'-penta para-debromination Millis & Aust
hexa (up to 100 (major product) (1985)
min) 2,3',4,4',5-penta ortho-debromination
2,2',4,4',5-penta meta-debromination
Table 18 (contd).
PBB Irradiation Solvent Initial rate Primary products Remarks References
(duration) of photolysis of photolysis
(nmol/min) identified
2,2',4,4',5,5'- 254 nm hexane 53a 2,2',4,5.5'-penta para-debromination Millis & Aust
hexa (up to 100 (major product) (1985)
min) 2,3',4,4',5-penta ortho-debromination
2,2',4,4',5-penta meta-debromination
secondary photoproduct:
3,3',4,4'-tetra
formation of yellow
gum at 25 min
2,2',3,4,4',5,5'- sunlight not not 2,2',4,4',5,5'-hexa meta-debromination Patterson
hepta (390 min) specified specified (major product) et al. (1980)
2,3',4,4',5,5'-hexa ortho-debromination
2,2',3,3',4,4', sunlight not not unidentified hexa- Patterson
5,5'-octa (300 min) specified specified PBB (major product) ortho- and meta- et al. (1980)
2,3',4,4',5,5'-hexa debromination
2,2',3,3',5,5', 300 nm hexane not specified di- to Ruzo et al.
6,6'-octa (0.5-2 h) heptabromobiphenyls, ortho debromination (1976)
e.g., 3,3',5,5'-tetra
a Original PBB concentration = 1.59 mmol/litre.
Technical octabromobiphenyl has been reported to photo degrade
in xylene by reductive debromination with a half-life of 40 h
(Norris et al., 1973).
There were investigations to enhance the photochemical process
aiming at a potential technique for the breakdown and removal of
PBBs from the environment. In laboratory testing, photodegra dation
of PBBs was accelerated in the presence of ethylenediamine and
tertbutylamine (Christensen & Weimer, 1979) and in the presence of
sodium borohydride (Epling et al., 1987).
Epling et al. (1987) obtained high yields of biphenyl during
borohydride enhanced photolysis of FireMaster(R) BP-6 (irradiation
under nitrogen at 254 nm; solvent: 90% acetonitrile/water).
The rates and extent of photolytic reactions of PBBs in the
environment have not been determined in detail. However, the few
field observations available indicate a high persistence of the
original PBBs (Jacobs et al., 1978) or a partial degradation to less
brominated (and often more toxic) photoproducts (Hill et al., 1982).
Jacobs et al. (1978) examined field soil that had received manure
from FireMaster(R)-contaminated cattle, for the first time, 2-3
years earlier. They did not detect any significant changes in the
relative concentrations of the major PBB peaks (Br5, Br6, Br7)
compared with the FireMaster(R) standard. In contrast, soil
samples, obtained from the former FireMaster(R) manufacturing site
in Michigan and analysed several years (approximately 10 years?)
after contamination, contained enhanced concentrations of possible
photodegradation products including 2,3',4,4',5-pentabromobiphenyl,
2,2',4,4',5-pentabromobiphenyl, and two unidentified
tetrabromobiphenyls (Hill et al., 1982).
Considering the diversity of microenvironments, both laboratory
and field data on photo alteration of PBBs are incomplete; there is
a lack of studies on the photochemistry of PBBs in water, or in the
vapour or solid states.
4.2.2 Microbial degradation
In laboratory investigations, mixtures of PBBs appear to be
fairly resistant to microbial degradation. Soil incubation studies
using FireMaster(R) BP-6 (lot no. 6244A) and 14C-PBB
(lot 872-244) showed a little, but not significant, degradation of
the major hexa- and heptabromobiphenyl congeners after 6 months or
1 year; only pentabromobiphenyl was assumed to degrade slowly
(Jacobs et al., 1976, 1978). These results were deduced from
recovery rates of PBBs from soil, 14CO2 production, and the lack of
14C-PBB intermediates.
Soils incubated with photodecomposition products of 14C-hexa
and heptabromobiphenyl caused enhanced, but still minor, degradation
(ca. 3%) as measured by 14CO2 production (Jacobs et al., 1978).
These findings are consistent with observations according to which
degradation of PCBs by bacteria increases with decreasing
chlorination (Kalmaz & Kalmaz, 1979; Fries, 1982).
In further incubation experiments with FireMaster(R) BP-6
(lot no. 6244A) in sterilized and nonsterilized Catlin-soil, Griffin
& Chou (1981a) measured the recoveries of penta-, hexa-, and
heptabromobiphenyls and found that all PBBs persisted for 6 months
with no significant microbial degradation. They observed the same
kind of persistence over a period of 4 weeks in PBB incubations with
mixed cultures of microorganisms (predominantly Alkaligenes
odorans, A. denitrificans, and an unidentified bacterium). This
culture had been isolated previously and was known to degrade
water-soluble PCBs (Clark et al., 1979). No PBB metabolites were
found in the PBB-saturated mineral solution after 4 weeks of
incubation (Griffin & Chou, 1981a).
As with PCBs, the high degree (penta or greater) of halogen
substitution of its major components probably accounts for the lack
of degradation of the FireMaster(R)-mixture (Griffin & Chou,
1981a). Congruently, biodegradation of monobrominated biphenyls has
recently been reported.
A soil isolate, strain S93B1, identified as Pseudomonas
cruciviae, could grow on more than ten biphenyl-related compounds
including o-bromobiphenyl (Takase et al., 1986). O-bromobiphenyl
was converted to o-bromobenzoic acid (Fig. 3) (identified by
IR-spectrum). This is analogous with some PCBs showing chlorinated
benzoates as metabolites (Ballschmiter et al., 1977). In these
experiments, biphenyl-related compounds 0.2-0.5% (w/v) were added as
the sole sources of carbon to the liquid artificial medium.
However, this pathway is also realized under simulated natural
conditions (aquatic environments), as reported by Kong & Sayler
(1983). They used river water as supportive culture medium and
"mixed bacterial cultures" (not identified), which were obtained
from PCB-contaminated river sediments. This mixed bacterial culture
was capable of degrading monohalogenated biphenyls.
The degradation rates of 2-, 3-, and 4-bromobiphenyl, at
30 µg/ml, were 2.3, 4.2, and 1.4 µg/ml per day, respectively, and
were comparable with those of monochlorinated biphenyls. Degradation
occurred when the substrates were supplied as the sole carbon source
or when added in combination with glucose. The major metabolite of
4-bromobiphenyl (para) was 4-bromobenzoate, identified by means of
cochromatography with an authentic compound in HPLC. Two bacterial
strains of the genus Pseudomonas, isolated from a lake sediment by
using p-chlorobiphenyl as a sole carbon source, were capable of
degrading 2-, and 4-bromobiphenyl, but they did not degrade
4,4'-dibromobiphenyl (Sugiura, 1992).
In contrast to several reports indicating that chlorobenzoates
are the principal stable metabolites of PCBs (Furukawa & Matsumara,
1976; Furukawa et al., 1979; Yagi & Sudo, 1980; Reichardt et al.,
1981), 4-bromobenzoate as well as 4-chlorobenzoate appeared
transient. For, when tested with the same bacterial consortium,
4-bromobenzoate at 30 mg/kg was readily degraded at the rate of
4 µg/ml per day (Kong & Sayler, 1983). The terminal decomposition
product is assumed to be CO2 (Kong & Sayler, 1983), i.e.,
4-bromobiphenyl can most likely be completely mineralized by this
bacterial culture. Suflita et al. (1982) also observed degradation
of bromobenzoates. They reported the reductive dehalogenation of
halobenzoates, including 2-, 3-, or 4- bromobenzoate by
microorganisms of lake sediment and sewage sludge. Dehalogenation
required strict anaerobic conditions. The primary degradative event
was loss of the aryl halide without the alteration of the aromatic
ring, the end products were CH4 and CO2. The stable bacterial
consortium enriched from sludge consisted of both chemolithotrophic
and heterotrophic methanogens as well as three, unidentified,
non-motile Gram- negative rods.
Recently, there was a brief report on the reductive
debromination of the FireMaster(R) mixture (rate and extent of
debromination reaction not given) by anaerobic microorganisms eluted
from PCB-contaminated river sediments (Quensen et al., 1990;
abstract only).
4.2.3 Degradation by plants and animals
No degradation of PBBs by plants has been recorded. In contrast
to plants, animals can easily absorb PBBs and, though they have been
found to be very persistent in animals, small amounts of PBB
metabolites have been detected. The main metabolic products were
hydroxy-derivatives and, in some cases, there was evidence of
partially debrominated PBBs (cf. also section 6.3).
The metabolism of crude FireMaster(R) BP-6 by a pig gave a
monohydroxypentabromobiphenyl (Kohli & Safe, 1976). The faeces of
dogs fed FireMaster BP-6 contained a metabolite identified as
6-hydroxy-2,2',4,4',5,5'-hexabromobiphenyl (Gardner et al., 1979).
However, the authors do not exclude microbial metabolism of PBB in
the dog's gut followed by excretion into the faeces. Doses of
2,2',4,4',5,5'-[14C]-hexabromobiphenyl given intravenously or
orally to male rats were not subject to appreciable metabolism
(Matthews et al., 1977). Metabolites were not detected in tissue
extracts. A trace of radioactivity, which may have represented a
PBB-metabolite, was found in bile and faeces, but the quantity was
too small to be isolated and identified.
Some investigations imply that fish may debrominate the more
highly brominated components of PBB-mixtures. Fish (juvenile Salmo
salar), exposed in laboratory studies to FireMaster(R) BP-6 in
water, contained several mono to pentabromobiphenyls that were not
present in BP-6. Several additional pentabromobiphenyls were
detected in fish fed FireMaster(R) BP-6-contaminated food. Fish
fed octabromobiphenyl contaminated food contained unidentified
penta-, hexa-, and heptabromobiphenyls in addition to the
octabromobiphenyls (Zitko, 1977). It was not known whether the
partially debrominated biphenyls were generated by the fish, or by
the associated microflora.
Because the carbon-bromine bond is less stable than the
carbon-chlorine bond, reductive debromination may be a degradative
pathway of bromobiphenyls, and this reaction may have toxicological
consequences not encountered with PCBs (Zitko & Hutzinger, 1976;
Zitko, 1977).
4.2.4 Bioaccumulation
As expected from their high lipophilicity, PBBs show a marked
tendency to accumulate in animals. However, data are available only
on single links of food chains. It has been reported that similar
compounds, e.g., PCBs, which are more widely spread in the
environment, may have bioconcentration factors of 3-4 orders of
magnitude between water and fish, with a further 1-2 orders of
magnitude between whole fish and the fat storage tissues of fish
predators, such as cormorant, heron, and seal (Pearson, 1982).
4.2.4.1 Aquatic organisms
Fish are the only aquatic organisms for which the bioaccumu
lation of PBBs has been investigated intensively. They serve as an
example for the efficiency of such bioaccumulation (Damstra et al.,
1982).
Fathead minnows (Pimephales promelas) caged in a river, where
water levels of PBB (Firemaster(R) BP-6; probably measured as
concentration of the main peak, 2,2',4,4',5,5'-hexabromobiphenyl)
remained consistently at less than 0.1 µg/litre, concentrated these
contaminants in their bodies more than 10 000 fold in two weeks of
exposure (Hesse & Powers, 1978). In laboratory studies, accumulation
coefficients of FireMaster(R) BP-6 and technical octabromobiphenyl
from water (A = concentration in fish, µg/g wet weight/concentration
in water, µg/ml) and from food (B = concentration in fish, µg/g wet
weight/concentration in fish-food, µg/g) were determined.
FireMaster(R) BP-6 reached values of A = 48 (after an exposure of
48 h) and B = 1.0 (in equilibrium) in juvenile Atlantic salmon
(Salmo salar). The main component accumulated was
2,2'4,4',5,5'-hexabromobiphenyl (Zitko, 1977). In contrast,
octabromobiphenyl, as such, was not concentrated from water by
Atlantic salmon (Zitko, 1977) and by rainbow trout (Norris et al.,
1973), but a little uptake (B = 0.023) was observed from suspended
food (Zitko, 1977). Instead of octabromobiphenyl, an unidentified
hexabromobiphenyl was mainly accumulated (A = 1.73; B = 0.114;
Zitko, 1977). In comparison with Aroclor 1254, the accumulation of
FireMaster(R) BP-6 from water was less, but accumulation from food
was a little higher than that of the corresponding PCB mixture (A =
282; B = 0.358; Zitko, 1977).
There are some differences in the accumulation of different
congeners. Zitko & Hutzinger (1976) determined accumulation
coefficients of di-, tri-, and tetrabromobiphenyls in Salmo salar.
The coefficients were calculated on the basis of accumulation from
water after a 48-h exposure, and of the extrapolated equilibrium
levels in fish fed contaminated food. The accumulation coefficients
generally decreased with increasing degree of substitution during
the uptake from water, and increased, when taken up from food. Of
the dibromobiphenyls, the 3,4-isomer accumulated from water much
less than the 2,6- and 2,4-isomer, and did not accumulate from food
(Zitko & Hutzinger, 1976). Sugiura et al. (1978) dealing with the
accumulation of lower substituted halobiphenyls (di-, tri- and
tetra-) in killifish (Oryzias latipes) found that equilibrium
accumulation from water was not reached during a period of 20 days.
Their data, derived from a flow through test using PBB
concentrations of 0.5-50 µg/litre, resulted in bioaccumulation
factors (equilibrium extrapolated) ranging from 340 to 7340. They
also found that accumulation factors were proportional to partition
coefficients (n-octanol/water), when the coefficients were below
106, but not when the coefficients were above 106.
It is obviously important to note the lipid contents of test
animals in bioaccumulation studies. For example, the bioconcen
tration factors of PCB congeners for whole fish tissue were
proportional to the lipid content of the different species, which
can range from 3 to nearly 20% (Sugiura et al., 1979). Gobas et al.
(1989) reported lipid weight-based bioconcentration factors, log
KL ranging from 5.06 to 6.16, for some PBBs (di- to hexa-) in the
guppy (Poecilia reticulata).
4.2.4.2 Terrestrial organisms
Bioaccumulation of PBBs in terrestrial organisms has been
considered only for avian and mammalian species of farm and
laboratory animals. Data were obtained through field observations
(accumulation from soil), evaluation of an accident, and through
controlled feeding studies.
Accumulation of soilborne PBBs has been studied in Michigan
farms that were contaminated accidentally by FireMaster(R) FF-1
(Fries, 1985a). Ratios of PBB concentrations between the fat of farm
animals (cows, sheep, pigs) and soil ranged from 0.10 to 1.86.
Multiparous dairy cows had lower ratios, because of the excretion of
PBB in milk during long-term lactation, and swine had higher ratios,
because they ingest greater amounts of soil than other species
(Fries, 1985a). In another study, PBB (FireMaster(R) FF-1) was
applied to the soil surface for experimental purposes. Sheep grazing
for 180 days on these plots containing 33 mg PBB/m2 (plot 1) and
48 mg/m2 (plot 2) reached average residue levels in body fat of
0.30 and 0.79 µg PBB/g fat (quantified as concen trations of
2,2',4,4',5,5'-hexabromobiphenyl), respectively. Average residue
concentrations in ewes that grazed for 60 days were nearly as great
(Fries & Marrow, 1982). A second trial, conducted 3 years later
after ploughing and reseeding the plots, showed that PBBs were
distributed throughout the top 16 cm of soil with an average
concentration of 0.14 µg 2,2',4,4',5,5'- hexabromobiphenyl/g soil in
plot 2. Sheep grazing here for 136 days had average concentrations
of 0.032 µg PBB/g body fat (Fries & Marrow, 1982).
The accidental ingestion of FireMaster(R) FF-1 by cattle on
Michigan farms, first described by Jackson & Halbert (1974),
resulted in high body burdens of PBBs. There were tissue levels of
2,2',4,4',5,5'-hexabromobiphenyl in the fat of cows of up to
approximately 4000 mg/kg, nearly one year after high exposure
(estimated total dose: 150-400 g of FireMaster(R) FF-1/cow over
14 days). Low exposure from cross contamination produced PBB
concentrations in fat of less than 0.3 µg/g (Fries et al., 1978a,b;
Fries, 1983).
Laboratory data for the accumulation of PBBs from known diets
are given in Table 19 (diets supplemented with FireMaster(R)) and
in Table 20 (diets supplemented with single PBB congeners). PBB
levels in tissues of FireMaster(R)-exposed animals were expressed
as the concentration of the most abundant constituent of the
mixture, namely 2,2',4,4',5,5'-hexabromobiphenyl. Fries et al.
(1976) additionally reported the concentration of a heptabromobi
phenyl component (not the pure isomer). They found 31.4 mg/kg of
this component in the body fat of hens fed diets containing 20 mg
FireMaster(R)/kg feed for 63 days. The fate of minor constituents
of the FireMaster(R) mixture is not evident from the studies
compiled in Table 19.
Generally, accumulation of PBBs in body fat depended on dosage
and duration of exposure. The highest accumulation coefficients
(mg PBB/kg of tissue divided by mg PBB/kg feed) were found in minks
(Table 19). PBB residue levels in the adipose tissue of treated
minks were 60 times the amount in the diet (Aulerich & Ringer,
1979). According to the authors, the high diet-to-fat residue
accumulations in the minks may be due, in part, to the relatively
small subcutaneous fat deposits of the test animals, most of which
were extremely emaciated at the time of death. Technical
octabromobiphenyl was also accumulated from the diet, as shown by
analyses of the bromine contents of the tissues (Norris et al.,
1973; Lee et al., 1975a; Waritz et al., 1977). There was a
dose-related build-up of bromine, predominantly in the fat, as well
as in the liver, of rats fed octabromobiphenyl. For example, after 4
weeks of feeding 1, 10, 100, or 1000 mg octabromobiphenyl/kg feed,
the bromine concentrations in adipose tissue were 2, 12, 120, and
600 times, respectively, greater than those of the controls (Lee
et al., 1975a).
Table 19. Accumulation of PBBs in feeding studies on mammals and birds
a) Feeding of FireMaster(R)
Species FireMaster(R) Dietary Feed intake Feeding Residue level (mg/kg)a Weight References
concentration (g/day) period basis
(mg/kg)
Adipose Liver Others
tissue
Rat (male) BP-6 0.1 20.9c 9 days 0.3 1.5 brain: 0.5 lipid Render et al. (1982)
Rat (male) BP-6 1 23.3b 9 days 1.7 8.3 brain: 1.8 lipid
Rat (male) BP-6 1 not specified 2-3 weeks - 2.7 - dry Babish & Stoewsand
(1977)
Rat (male) BP-6 1 not specified 30 days 7.8 22.3 thymus: 21 lipid Akoso et al. (1982a)
Rat (male) BP-6 10 22.9b 9 days 27 135 brain: 12.3 lipid Render et al. (1982)
Rat (male) BP-6 10 not specified 30 days 61.6 310 kidney: 147 lipid Akoso et al. (1982a)
Rat (male) BP-6 50 not specified 2-3 week - 341 - dry Babish & Stoewsand
(1977)
Rat (male) BP-6 50 26b 10 weeks 864 55 - wet Harris et al. (1978b)
Rat (male) BP-6 100 22b 9 days 251 1213 brain: 103 lipid Render et al. (1982)
Rat (male) BP-6 100 not specified 30 days 1535 2507 thymus:1044 lipid Akoso et al. (1982a)
Rat (male) BP-6 100 27b 10 weeks 3460 107 - wet Harris et al. (1978b)
Rat (male) BP-6 150 26b 10 weeks 3574 295 - wet
Rat (male) BP-6 200 26b 10 weeks 3242 245 - wet
Mouse BP-6 100 not specified 14 days 223 33.2 thymus: 391 wet Corbett et al. (1978a)
(male)
Mouse BP-6 1000 not specified 11 days 39.5 2.5 - wet Corbett et al. (1975)
(male)
Mouse FF-1 5 not specified 3 weeks - 7 thymus: 20 wet Loose et al. (1981)
(male)
Mouse FF-1 5 not specified 6 weeks - 15 thymus: 37.8 wet
(male)
Table 19 (contd).
Species FireMaster(R) Dietary Feed intake Feeding Residue level (mg/kg)a Weight References
concentration (g/day) period basis
(mg/kg)
Adipose Liver Others
tissue
Mouse FF-1 167 not specified 3 weeks - 154 thymus: 109 wet
(male)
Mouse FF-1 167 not specified 6 weeks - 623 thymus: wet
(male) 3088
Sheep BP-6 50 1000 30 days 25 12 heart: 4.3 wet Gutenmann & Lisk
(male) (omental (1975)
fat)
42 (renal
fat)
17
(brisket
fat)
Pig BP-6 20 1880c 4 weeks 0.33 - - wet Ku et al. (1978)
(back fat)
Pig BP-6 20 1880c 16 weeks 64 8.5 muscle: 6.6 wet
(back fat)
42.9
(leaf fat)
Pig BP-6 200 1230c 4 weeks 6.7 - - wet Ku et al. (1978)
(back fat)
Pig BP-6 200 1230c 16 weeks 503 17.2 muscle: wet
18.4
(back fat)
459
(leaf fat)
Table 19 (contd).
Species FireMaster(R) Dietary Feed intake Feeding Residue level (mg/kg)a Weight References
concentration (g/day) period basis
(mg/kg)
Adipose Liver Others
tissue
Mink FF-1 2.5 not specified 136 days 149 - muscle: 7.3 wet Aulerich & Ringer
6.25 172 days - - brain: 66 wet (1979)
15.6 72-93 986 - muscle: 70 wet
days
Japanese not 10 -b 9 weeks - 48 heart: 78 dry Babish et al. (1975a)
quail specified
(male) 20 -b 9 weeks - 374 kidney: 105 dry
100 -b 9 weeks - 642 kidney: 725 dry
Japanese not 10 -b 9 weeks - 99 heart: 48 dry
quail specified
(female) 20 -b 9 weeks - 225 heart: 50 dry
100 -b 9 weeks - 503 kidney: 428 dry
Chicken BP-6 20 not specified 63 days 79.8 - egg: 20 wet Fries et al. (1976)
(White
leghorn
hens)
BP-6 20 -b 4-8 weeks - - egg: 30 wet Cecil & Bitman (1978)
BP-6 64 -b 4-8 weeks - - egg: 100 wet
not 1 106b 5 weeks 0.6 egg: 1.5 wet Ringer & Polin (1977)
specified
not 125 94c 5 weeks - - egg: 209 wet Ringer & Polin (1977)
specified
not 625 28.4c 5 weeks - 80 - wet
specified
Table 19 (contd).
Species FireMaster(R) Dietary Feed intake Feeding Residue level (mg/kg)a Weight References
concentration (g/day) period basis
(mg/kg)
Adipose Liver Others
tissue
Chicken FF-1 0.2 99b 5 weeks (-)d (-)d egg: 0.3 wet Polin & Ringer
(White (1978a,b)
leghorn FF-1 1 106b 5 weeks (-)d (-)d egg: 1.5 wet Polin & Ringer
hens) (1978a,b)
FF-1 5 100b 5 weeks (-)d (-)d egg: 7.4 wet Polin & Ringer
(1978a,b)
FF-1 25 99b 5 weeks (-)d (-)d egg: 43.4 wet Polin & Ringer
(1978a,b)
FF-1 125 94c 5 weeks (-)d (-)d egg: 215 wet Polin & Ringer
(1978a,b)
Chicken FF-1 0.1 35 2 weeks - - carcass: wet Polin & Leavitt (1984)
(White 0.11
leghorn FF-1 1 35 2 weeks - - carcass: wet Polin & Leavitt (1984)
cockerels) 0.87
FF-1 10 -b 28 days - 83.8 - lipid Dharma et al. (1982)
FF-1 100 -b 28 days - 752 - lipid Dharma et al. (1982)
a Measured as the concentration of 2,2',4,4',5,5'-hexabromobiphenyl.
b Values not significantly different from control values.
c Values significantly different from control values.
d Diagrams only, generally, the ratios of tissue PBB: diet PBB averaged 3:1 for adipose tissue, 0.8:1 for liver,
and 1.5:1 for whole egg.
Table 20. Accumulation of PBBs in feeding studies on mammals and birds
b) Feeding of individual PBB congeners
Species Species Dietary Feed intake Feeding Residue level (mg/kg lipid) References
(sex) concentration (g/day) period
(mg/kg) Adipose Liver Others
tissue
2,2',4,4',5,5'- rat 0.1 23.8a 9 days 0.2 1.7 brain: 0.3 Render et al. (1982)
Hexabromobiphenyl (male)
1 26.2b 9 days 3.1 11.4 brain: 1.1
rat 1 not 30 days 16 68.6 kidney: 38.7 Akoso et al. (1982a)
(male) specified
rat 10 25.5b 9 days 31.2 181 brain: 11.5 Render et al. (1982)
(male)
rat 10 not 30 days 149 693 kidney: 373 Akoso et al. (1982a)
(male) specified
rat 100 23.2a 9 days 436 2558 brain: 143 Render et al. (1982)
(male)
rat 100 not 30 days 992 6062 thymus: 3841 Akoso et al. (1982a)
(male) specified
chicken 10 -a 28 days - 105 - Dharma et al. (1982)
(male)
62 -a 28 days - 751 -
Table 20 (contd).
Species Species Dietary Feed intake Feeding Residue level (mg/kg lipid) References
(sex) concentration (g/day) period
(mg/kg) Adipose Liver Others
tissue
2,3',4,4',5,5'- rat 1 not 30 days 9.1 23.5 kidney: 13.9 Akoso et al. (1982a)
Hexabromobiphenyl (male) specified
rat 10 not 30 days 69.1 242 thymus: 211 Akoso et al. (1982a)
(male) specified (1982a)
rat 100 not 30 days 648 4340 thymus: 1639 Akoso et al. (1982a)
(male) specified
chicken 4 -a 28 days - 32.5 - Dharma et al. (1982)
(male)
chicken 10 -a 28 days - 132 - Dharma et al. (1982)
(male)
3,3',4,4',5,5'- rat 0.1 23.6a 9 days 0 3.3 brain: 0 Render et al. (1982)
Hexabromobiphenyl (male)
1 24.7a 9 days 0.4 101 brain: 0
rat 1 24.7b 30 days 0.6 125 thymus: 0 Akoso et al. (1982a)
(male)
rat 10 20.2b 9 days 1.9 - brain: 0 Render et al. (1982)
(male)
rat 10 21.3b 30 days 6.9 448 thymus: 20.4 Akoso et al. (1982a)
(male)
Table 20 (contd).
Species Species Dietary Feed intake Feeding Residue level (mg/kg lipid) References
(sex) concentration (g/day) period
(mg/kg) Adipose Liver Others
tissue
rat 100 13.7b 9 days 22.5 1098 brain: 0 Render et al. (1982)
(male)
a Values not significantly different from control values.
b Values significantly different from control values.
Data on accumulation of technical decabromobiphenyl have not
been found in the literature.
Isomer specific accumulation has been studied for three
hexabromobiphenyl congeners. The residue levels in rats and chickens
fed with 2,2'4,4',5,5'-; 2,3',4,4',5,5'- or 3,3',4,4',5,5'-
hexabromobiphenyl are listed in Table 20. In many cases, the lowest
concentrations in tissues were found with 3,3',4,4',5,5'-
hexabromobiphenyl and the highest, with
2,2',4,4',5,5'-hexabromobiphenyl.
4.3 Ultimate fate following use
4.3.1 Disposal of PBB-contaminated animals and wastes from the
Michigan disaster
Accidental contamination of livestock feed in 1973 by PBBs led
to the destruction of over 30 000 animals in Michigan. As the
toxicity and other physical and chemical properties of PBBs were at
that time not so well known, the State of Michigan decided to locate
an environmentally safe site for the burial of contaminated
carcasses (Shah, 1978). A site in Kalkaska County was chosen and
test drilled in order to determine the long-range protection for
groundwaters in the area. The Kalkaska disposal site received over
10 000 animal carcasses most of which contained PBB levels above
1 mg/kg fat, and close to 20 000 carcasses with PBB levels ranging
from 0.3 to 1 mg/kg. This animal disposal site contains
approximately 45 kg of PBBs in all buried carcasses (Shah, 1978; see
section 5.1.2.3. for groundwater studies).
The Gratiot County landfill near St. Louis became operational
in late 1970, and it was designed only for general municipal solid
waste disposal. According to the Michigan Chemical Corporation
report to the Environmental Protection Agency, PBB wastes were
disposed of in the landfill between 1971 and 1973. Wastes containing
large amounts of PBBs (60-70%) were received in the landfill before
any information about the toxic effects of PBBs on animals was
publicly known (Shah, 1978).
The Forest Waste Disposal site consists of an 11-acre,
abandoned, municipal and industrial waste landfill and 9 surface
impoundments. It is located in Genesee County, Michigan, and is
surrounded by agricultural land and undeveloped woodlands and
wetlands. Forest Waste Disposal conducted landfill operations from
1972 to 1978. PBB-contaminated feed has recently been found in the
landfill. A decontamination programme has been recommended (Anon.,
1988).
The Michigan Chemical Corporation stated that, in their
opinion, PBBs would eventually undergo oxidative/biological
degradation forming carbon dioxide, water, and bromide ion (Cordle
et al., 1978). However, studies on PBBs in soil indicate that they
may remain in soils for many years, because of their resistance to
degradation (Jacobs et al., 1976).
4.3.2 Thermal decomposition of PBBs
There is little information on the pyrolysis of PBBs. The
products of the thermal decomposition of PBBs depend on the
temperature as well as on the amount of oxygen present.
Norris et al. (1973) constructed a special apparatus to measure
the relative amounts of bromine from octabromobiphenyl converted
during combustion, when these materials were used as additives in
thermoplastic resins. An exact temperature is not given. Hydrogen
bromide and bromine were not detected.
Waritz et al. (1977) carried out experiments to determine the
approximate lethal temperature of hexa- and octobromobiphenyl. The
dense clouds of fumes obtained at 350 °C were lethal to rats whereas
those produced at 290 °C were not. The fumes were not analysed.
Earlier experiments by Benbow & Cullis (1975) on the pyrolysis
of decabromobiphenyl pressed together at 160 °C with polystyrene and
polypropylene, respectively, showed that, during flameless
combustion, decabromobiphenyl appeared to be volatilized virtually
unchanged from the polymer, whereas when the polymer burned, the
decabromobiphenyl was converted quantitatively to hydrogen bromide.
In these early experiments, the analytical methods were not so
refined that it was possible to detect furans and dioxins. O'Keefe
(1978) pyrolyzed samples of FireMaster FF-1 at 380-400 °C in open
glass tubes and in tubes sealed after nitrogen flushing. Analysis by
low resolution direct probe mass spectrometry showed the presence of
tetra- and pentabrominated dibenzofurans in extracts of the open
tube pyrolyzed material and trace levels of tetrabromodibenzofuran
in those from PBB pyrolyzed under nitrogen.
Buser et al. (1978) studied the pyrolysis of FireMaster BP-6
with oxygen in sealed tubes. The flame retardant was completely
destroyed at 700 °C, but, at 600 °C, new compounds were formed, one
of which was probably tetrabromodibenzofuran.
The diversity of possible brominated and mixed brominated
furans and their toxicological implications led to further
refinements in analytical methods (Buser, 1986) and to the demand
for, and synthesis of, suitable standard isomers (Mason et al.,
1987a; Sovocool et al., 1987a; Munslow et al., 1989). There are over
5000 halogenated dibenzodioxins and dibenzofurans containing
chlorine and/or bromine, over 400 of which are 2,3,7,8-substituted
tetra-, penta- and hexahalo congeners suspected to be of high
toxicity (Buser 1987). These mixed congeners are of particular
importance with regard to chemical waste burning (Schäfer &
Ballschmiter, 1986).
Investigations into the pyrolysis of FireMaster BP-6 in the
absence of oxygen have shown that small amounts of bromobenzenes and
lower brominated biphenyls are formed (600-900 °C), but no furans
(Thoma et al., 1987a; Thoma & Hutzinger, 1989).
In contrast, the pyrolysis of FireMaster BP-6 in an open quartz
tube (700-900 °C) in the presence of oxygen yielded over 3 mg/kg
(ppm) of di- to heptabrominated dibenzofurans, though the pyrolysis
of pentabromodiphenyl ethers yielded brominated dibenzofurans at
over 300 times this level (Thoma et al., 1987a). In the presence of
polystyrene and polyethylene, higher levels of brominated
(mona-tetra) dibenzofurans (over 8 and 51 mg/kg (ppm), respectively)
were found (Thoma et al., 1987a). Pyrolysis of FireMaster BP-6 with
PVC at 800 °C yielded mixed bromide/chloride biphenyls, the bromine
atoms being substituted by the chlorine. No ring closure to dioxins
and furans occurred (Thoma et al., 1987b).
Decabromobiphenyl was pyrolyzed for 10 min at 800 °C in a
loosely plugged quartz tube. The pyrolysates were extracted with
toluene and after clean-up, analysed using GC/MS. No brominated
dioxins or dibenzofurans were detected (detection limits
0.2-0.8 µg/g). The clean-up was said to be very difficult because of
the formation of a large number of brominated compounds that were
not dioxins or furans. Debromination of decabromobiphenyl appeared
to be the main reaction, but no details were given (Atochem, 1987).
Zacharewski et al. (1988) pyrolyzed samples of FireMaster(R)
BP-6 in open quartz tubes at 800 °C for 10 min. The resulting
products, mainly tetrabromodibenzofurans (1183 µg/g) but also
tribromo-, pentabromo-, hexabromo-, and heptabromodibenzofurans
(187, 584, 107, and 11 µg/g, respectively), were tested for toxicity
(see section 8.12.3.2). Very little is known about the toxicities of
brominated and brominated/chlorinated dioxins and furans, but they
are estimated to be of the same order as those of PCDD and PCDF
(Mason et al., 1987a; Safe, 1987).
Analysis of actual environmental samples has also been carried
out. Monobromo-polychloro substituted benzenes, biphenyls,
dibenzodioxins, and dibenzofurans have been detected in solid
material collected from a chimney of an industrial waste incinerator
(Schäfer & Ballschmiter, 1986). Brominated dibenzo furans with a
very small amount of mixed brominated/chlorinated compounds were
detected in soot from an accidental fire at a bowling alley (Buser,
1986). Schwind et al. (1988; 1989) analysed samples from a municipal
waste incinerator and detected for the first time a complete series
of tetrahalogenated dibenzofurans (Cl4DF, Br1Cl3DF,
Br2Cl2DF, Br3Cl1DF and Br4DF). It is possible that PBCDD/F
could occur during the incineration of flame retardant-treated
plastic material, which produces PBDD and PBDF. These could react
with PVC via the mixed brominated/chlorinated dioxins and furans to
PCDD and PCDF (Schwind et al., 1988).
As with PCB disposal, the destruction of PCB-contaminated waste
should be carefully controlled. For PCBs, a burning temperature
above 1000 °C for 2 seconds is recommended (WHO/EURO, 1987).
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1 Environmental levels
5.1.1 Air
Only one report is available on PBB levels in air. It refers to
air samples taken in the vicinity of three PBB-manufacturing or -
processing plants in the USA (Stratton & Whitlock, 1979). Traces of
hexabromobiphenyl (0.06-0.10 ng/m3) were found at two of the three
industrial sites examined.
Further information on PBB levels in ambient air, e.g., near
municipal incinerators, is lacking.
5.1.2 Water and sediments
5.1.2.1 Surface waters
Surface waters have been monitored in the vicinity of PBB-
producing or -processing industrial sites in the USA and in the
vicinity of the Gratiot County landfill (Michigan, USA), which had
received 122 000 kg of wastes containing 60-70% PBBs between 1971
and 1973. The results are summarized in Table 21.
Depending on the sources, the predominant PBB compounds
detected in surface waters were hexabromobiphenyl and
decabromobiphenyl. However, only Stratton & Whitlock (1979)
determined all PBB homologues from Br1 to Br10, the percentage
composition of some of which is given in Table 22.
5.1.2.2 Sediments
Generally, PBBs reach higher concentrations in sediments (Table
23) than in the associated waters (Table 21).
PBB concentrations in sediments of the Pine River were as high
as 77 mg/kg near the Michigan Chemical Corp. plant. The assays
conducted from July 1974 to April 1975, upstream and downstream of
the plant, showed a decline in sediment PBB content to 6.2 mg/kg,
half a mile downstream, and to 0.1 mg/kg, 24 miles or 29 miles
downstream (Hesse & Powers, 1978).
Table 21. PBB levels in surface waters near sites of manufacture, use, or disposal in the USA
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (µg/litre)
Pine River 1974 8 HxBB 0.01-3.2 Hesse (1975)
(downstream from
the Michigan
Chemical Co.,
St. Louis)
Tittabawassee 1974 2 HxBB < 0.01
Rivera
Canal (called 1977 3 total PBB not detected-46 Stratton & Whitlock (1979);
Platti Kill) in the (MoBB-DeBB) DeCarlo (1979)
vicinity of White
Chemical Co., Bayonne,
New Jersey
Canal (discharging 1977 1 total PBB < 0.2 Stratton & Whitlock (1979)
into Kill van Kull (HxBB-DeBB)
River) in the vicinity
of Standard T Chemical
Co., Staten Island,
New York
Storm sewer, 1977 5 total PBB < 0.2-210 Stratton & Whitlock (1979);
receiving swamp, etc. (HxBB-DeBB) DeCarlo (1979)
in the vicinity of
Hexcel Fine Organics
Sayreville, New Jersey
Table 21 (contd).
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (µg/litre)
Drain waters at 1977 not HxBB 0.1-14 Shah (1978);
or near the margin specified Rosenblatt et al. (1982)
of the Gratiot County
landfill, Michigan
a Note that PBBs were not detected in fish from the Tittabawassee River in 1974 but were detected in 1983 (see Table 30).
Table 22. Percentage of different PBB homologues detected in surface water
samples taken in the vicinity of PBB-producing plantsa
PBB homologues Bayonne, New Jersey Sayreville, New Jersey
(White Chemical Corp.)b (Hexcel Corp.)c
Sample 1 Sample 2 Sample 1 Sample 2
PeBB 1 0 - -
HxBB 4 2 5 < 1
HpBB 2 2 1.6 < 1
OcBB 2 17 1 1
NoBB 15 20 1 2.6
DeBB 76 58 91 96
a From: Stratton & Whitlock (1979).
b Producer of octa- and decabromobiphenyl along with bromobiphenyl ethers.
c Producer of laboratory quantities of various PBBs.
Concentrations measured upstream were all less than the
sensitivity limit of 30 µg/kg with the exception of one sample
collected a quarter of a mile upstream of the plant, which contained
60 µg/kg (Hesse, 1975). This latter analysis was repeated in 1977
(Hesse & Powers, 1978) giving 350 µg/kg (detection limit 100 µg/kg).
Hesse & Powers (1978) compared the PBB levels of Pine River
sediments from the same locations over a period of time after the
termination of FireMaster(R) BP-6 production. The results of the
1976 and 1977 analyses showed that PBB distributions and
concentrations in the sediments had not changed significantly in the
three years after PBB manufacture stopped.
Various PBB homologues were identified again only by Stratton &
Whitlock (1979) who examined aquatic sediments, sludge deposits, and
marsh soils near the sites of manufacture and use of PBBs in New
Jersey and New York (see Table 24).
More recently, sewage sludge has been analysed for PBBs
(Strachan et al., 1983). The authors did not detect any PBBs, PCBs,
or chlorinated hydrocarbon pesticides in the three sludge samples
obtained from sewage treatment plants in three Indiana cities (USA).
However, the detection limit for PCBs and PBBs with the GC-MS system
used was about 10 µg/g, and this apparently is not sensitive enough,
even for PCBs. For example, the amounts of PCBs found in sewage
sludge of German (Lorenz, 1983) and Canadian (Webber et al., 1983)
cities ranged from 1.8 to 2.5 µg/g (dry weight) and from 0.13 to
1.61 µg/g (dry weight), respectively. Values for PBBs have not been
reported in these investigations.
Table 23. PBB levels in sediments and sludge from surface waters near sites of manufacture, use, or disposal in the USA
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (µg/kg dry weight)
Near Michigan 1974/75 19 HxBB < 30-77 000 Hesse (1975)
Chemical Co. 1974 9 < 100-9200 Hesse & Powers (1978)
Pine River 1976 9 < 100-1200
1977 8 < 100-500
Tittibawassee River 1974 2 tr-16 Hesse (1975)
Near White Chemical 1977 3 total PBB < 10-20 Stratton & Whitlock (1979)
Co., Bayonne, New Jersey: (MoBB-DeBB)
Sediments from Platti
Kill Canal and Kill
van Kall River
Sludge from Platti 1 431 000
Kill Canal
Near Standard T Chemical 1977 1 60
Co., Staten Island, New
York Sediment from Kill
van Kull River (at
discharge site)
Near Hexcel Fine 1977 1 total PBB 4600 Stratton & Whitlock (1979)
Organics, Sayreville, (MoBB-DeBB) DeCarlo (1979)
New Jersey
Marsh Soil
Table 23 (contd).
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (µg/kg dry weight)
Gratiot County 1977 not HxBB up to 17 000 Shah (1978)
landfill, Michigan specified Rosenblatt et al. (1982)
Associated sediments
of surface drain waters
Table 24. Concentration of PBB-homologues in aquatic sediment, sludge deposit,
or marsh soil samples taken in the vicinity of PBB-producing or -processing
plantsa (µg/kg dry weight)
PBB Bayonne, New Jersey Staten Island, Sayreville,
(White Chem. Corp.)b New Jersey New Jersey
(Standard T (Hexcel
Chem Corp.)c Corp.)d
Sediment Sludge Sedimente Marsh soile
samples:e
1 + 2 3
MoBB - n.d. 540 n.d. n.d.
DiBB - n.d. 2200 n.d. n.d.
TrBB - n.d. 4300 n.d. n.d.
TeBB - n.d. n.d. n.d. n.d.
PeBB - n.d. 590 n.d. n.d.
HxBB n.d. 10 3800 40 30
HpBB n.d. 10 3300 20 n.d.
OcBB n.d. n.d. 3600 n.d. n.d.
NoBB n.d. n.d. 22 500 n.d. 80
DeBB n.d. n.d. 390 000 n.d. 4500
a From: Stratton & Whitlock (1979).
b Producer of octa- and decabromobiphenyl along with bromobiphenyl ethers.
c Major user of FireMasterR BP-6.
d Producer of laboratory quantities of various PBBs.
e n.d. = Not detected (detection limit = < 10 µg/kg).
Surficial sediments from the St. Lawrence River (USA/Canada)
were analysed for HxBB, but the compound was not detected (estimated
detection limit: 1 ng/g) at the ten stations surveyed (Sloterdijk,
1991).
5.1.2.3 Groundwater
Groundwater monitoring data from the Gratiot County landfill
(Michigan, USA) mentioned above, have shown trace levels of PBBs,
even outside the landfill area (see Table 25). However, so far,
domestic drinking-water wells have not shown any traces of PBBs
(Shah, 1978). Groundwater near the disposal site of PBB-
contaminated animals and other products (see section 4.3.1) in
Kalkaska County (Michigan, USA) is reported not to be contaminated
by PBBs (Shah, 1978).
Table 25. PBB levels in groundwater from Gratiot County landfill, 1977a
Site No. of PBB compound PBB
samples examined concentration
range (µg/litre)
Test wells within 4 HxBB 0.5-26
the landfill site
Observation wells 11 0.1-4.4
outside the landfill
area
Domestic not specified not detected
drinkingwater wells
near the landfill
a From: Shah (1978).
5.1.3 Soil
Data on soil pollution by PBBs are available for areas of
manufacture, use, or disposal of PBBs (Table 26), and for soils from
fields, etc. of the PBB-contaminated Michigan farms (Tables 27 and
28).
Concentrations of PBBs in soils from industrial sites were
highest (more than 2000 mg/kg) in areas around the Michigan Chemical
Company (see Table 26). Although such highly contaminated soils
were removed (Hesse & Powers, 1978), Hill et al. (1982) still found,
some years later, PBB levels up to 2130 mg/kg in soils of the former
manufacturing site. Various PBB homologues from Br4 to Br10 were
present in the industrial soil samples (see Table 27).
Table 26. PBB levels in soils near sites of manufacture, use, or disposal in the USA
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (range) dry weight
Michigan Chemical Co.,
St. Louis, Michigan
bagging area not specified 1 HxBB 3500 mg/kg Hesse (1975);
Hess & Powers (1978)
loading area of not specified 1 HxBB 2500 mg/kg
the plant
"former manufacturing not specified 3 PBB 16-2130 mg/kg Hill et al. (1982)
site" (C12H6Br4-C12H3Br7)
Vicinity of White
Chemical Co.,
Bayonne, New Jersey
150 m east 1977 1 total PBB 4.250 mg/kg Stratton & Whitlock (1979)
150 m west of the 1977 1 (C12H9Br1-C12Br10) 1.135 mg/kg DeCarlo (1979)
plant
not specified not specified PBB 0.75-2.8 mg/kg Di Carlo et al. (1978)
Vicinity of Standard 1977 4 total PBB 10-100 µg/kg Stratton & Whitlock (1979)
T Chemical Co., Staten (MoBB-DeBB)
Island, New York
75 m south west 30
900 m west 10
Table 26 (contd).
Site Date of sampling No. of PBB compound PBB concentration References
samples examined (range) dry weight
1500 m south 10
700 m east (prevailing 100
down-wind direction)
Vicinity of Hexcel 1977 total PBB Stratton & Whitlock (1979);
Fine Organics, (MoBB-DeBB) DeCarlo (1979)
Sayreville, New Jersey
75 m southeast 1 40 µg/kg
Soil in roadside 1 3400 µg/kg
ditch
Gratiot County landfill,
St. Louis, Michigan
Samples inside of the not not "PBB" 12 (16) mg/kg Rosenblatt et al. (1982)
landfill from the specified specified HxBB
uppermost 2.5 cm
(after capping of
the landfill)
Sample somewhat distant "PBB" 61 µg/kg
from the landfill, in (HxBB)
the area of the Michigan
Chemical plant
Table 27. Concentration of PBB homologues detected in soil samples taken in the vicinity of PBB-producing or processing plants
(µg/kg dry weight)
PBB Bayonne, New Jerseya Staten Island, New Yorka Sayreville, New Yorka Michiganb
(White Chemical Corp.)c (Standard T-Chemical Corp.)d (Hexcel Corp.)e (Michigan Chemical Corp.)f
MoBB n.d.g n.d.g n.d.g -
DiBB n.d.g n.d.g n.d.g -
TrBB n.d.g n.d.g n.d.g -
TeBB n.d.g n.d.g n.d.g < 1000-510 000
PeBB n.d.g n.d.-100 n.d.g 4000-60 000
HxBB 15-30 n.d.-10 40-90 12 000-670 000
HpBB 30-110 n.d.-10 n.d.-90 < 1000-190 000
OcBB 90-150 n.d. n.d.-170 -
NoBB 330-2200 n.d. n.d.-440 -
DeBB 530-2100 n.d.-10 n.d.-2600 -
a Data from: Stratton & Whitlock (1979); No. of samples = 2, 4, 2 respectively.
b Data from: Hill et al. (1982); No. of samples = 3.
c Producer of octa- and decabromobiphenyl along with bromobiphenyl ethers.
d Major user of FireMaster(R) BP-6.
e Producer of laboratory quantities of various PBBs.
f Producer of FireMaster(R) BP-6.
g n.d. = Not detected (detection limit = < 10 µg/kg).
Table 28. Composition and concentration of PBBs in soil samples from former
FireMaster(R) manufacturing plant site (St. Louis, Michigan)a
% Composition (concentration in mg/kg)
FireMaster(R)
Compound Lot #5143 Soil 1 Soil 2 Soil 3
Tetrabromobiphenyls < 0.1 23.9 (510) 11.3 (6) (< 1)
Pentabromobiphenyls
2,2',4,5,5'- 3.9 2.8 (60) 9.4 (5) 12.5 (2)
2,2',4,4',5- < 0.1 5.2 (110) (< 1) (< 1)
2,3',4,4',5- 5.7 27.7 (590) 9.4 (5) 12.5 (2)
Hexabromobiphenyls
2,2',4,4',5,5'- 54.9 24.4 (520) 56.6 (30) 62.5 (10)
2,2',3',4,4',5- 10.3 4.7 (100) 7.5 (4) 6.2 (1)
2,3',4,4',5,5'- 5.0 1.9 (40) 5.7 (3) 6.2 (1)
2,3,3',4,4',5- 2.1 0.5 (10) (< 1) (< 1)
Heptabromobiphenyls
2,2',3,4,4',5,5'- 12.8 5.2 (110) (< 1) (< 1)
2,2',3,3',4,4',5- 1.7 3.8 (80) (< 1) (< 1)
(Total PBBs) (2130) (53) (16)
a Adapted from: Hill et al. (1982).
Hill et al. (1982) identified not only PBB homologues, but also
the isomeric composition of PBBs in the soil samples from the
Michigan Chemical Corp. plant (Table 28). Thus, they provided more
exact analytical data and were able to make an interesting
comparison with the original FireMaster(R) mixture; conclusions
could then be drawn on the environmental fate of PBBs (section 4.2).
According to Shah (1978), test samples of the Gratiot County
landfill showed that, in general, the concentrations of PBBs in the
fill increased with depth and were highest at a depth of 3 to 7.6 m
below the top of the refuse.
As a consequence of the Michigan cattle food mixing error, the
soils of the farms involved have been contaminated by PBBs, mainly
through the faeces of the exposed animals. Fries (1985b) calculated
that about 145 kg of PBBs were distributed in this way, and that
most of this was located on 20-25 farms. (The total number of
quarantined farms was over 500; Robertson & Chynoweth, 1975).
Concentrations of PBBs in soil samples from fields that had
received PBB-contaminated manure were as high as 371 µg/kg (dry
weight), whereas levels in samples from manure piles and from dirt
exercise lots were as high as 2000 µg/kg (Jacobs et al., 1978;
Fries, 1985b).
Soil contamination by PBBs can result in PBB accumulation in
animals, when they have direct access to the contaminated soil.
This is most likely to occur when animals are confined to dirt lots
on which manure-containing PBB has been deposited. Crops grown on
PBB-contaminated soils are not considered an important source of PBB
contamination in animals (Fries & Jacobs, 1986).
Soils from industrial sites have, in general, been more heavily
contaminated than Michigan soils.
5.1.4 Feed and food
5.1.4.1 Feed
Contamination of feed by PBBs has been reported only in
connection with the Michigan PBB incident.
In 1973, about 290 kg (Fries, 1985b) - 1000 kg (IARC, 1978) of
FireMaster(R) FF-1 was inadvertently mixed in cattle feeds and
delivered to Michigan farms.
Three feed preparations appeared initially to be involved in
the Michigan episode with PBB levels as follows:
Feed No. 405, 2.4 mg PBB/kg,
Feed No. 410, 1790 mg PBB/kg,
Feed No. 407, 4300 mg PBB/kg
(Cordle et al., 1978).
A concentration as high as 13 500 mg PBB/kg was also cited
(Kay, 1977; Di Carlo et al., 1978; Damstra et al., 1982). Feed of
one highly contaminated farm (Halbert farm) is reported to have
contained 2900 mg PBB/kg (Fries, 1985b).
In 1974, 68% of 1770 feed samples collected in Michigan
contained PBB residues: 60% in the range of trace to 0.99 mg/kg, and
8% over 1 mg/kg. Resampling in 1975 revealed that 6% of 1208 feed
samples were contaminated and that fewer than 0.16% contained more
than 1 mg PBB/kg. In 1976, only 0.3% of 663 samples analysed were
contaminated: no samples contained more than 0.1 mg/kg (Di Carlo
et al., 1978).
PBB residues were not detected in harvested forages grown on
soils with residue levels as high as 0.3 mg/kg (Fries & Jacobs,
1980).
In 1974 and 1975, low-level feed contamination with PBBs was
detected in Indiana and Illinois, which are neighbours of Michigan
(Di Carlo et al., 1978).
5.1.4.2 Food
Again, almost all the data available on PBB residues in food
are derived from the Michigan cattle food contamination incident in
1973.
The extent to which the general population was exposed depended
on where they obtained their milk, dairy products, and eggs, i.e.,
direct from the contaminated farms or from sources where
contaminated products had been mixed with non-contaminated samples.
Table 29 shows examples of some PBB levels in Michigan foods.
Whereas in 1974 milk from some highly contaminated cows contained
PBB concentrations of up to 900 mg/kg fat (Robertson & Chynoweth,
1975), canned milk samples contained concentrations of up to
1.6 mg/kg fat (Cordle et al., 1978). The most highly contaminated
milk (1 to > 100 mg PBB/kg milk fat) originated from a total of 40
herds with different levels of PBBs at the time of detection (Fries,
1985b). In 1975, PBBs were still detected in milk from some herds
(Kay, 1977).
Data on meat can be derived from Table 33, which shows PBB
levels in Michigan farm animals.
Milk contains far less fat than meat (about 4% versus 30%), and
butterfat contains only 40% of the PBB concentration found in the
animal from which it comes (Fries et al., 1978b; Rosenblatt et al.,
1982). Among the dairy products, PBBs are again concentrated in the
high-fat products (Murata et al., 1977; Zabik et al., 1978).
Table 29. Some examples of PBB levels in food (contaminated as a consequence of
the Michigan PBB incident in 1973)
Product Year of PBB concentration References
sampling (mg/kg)
Milka 1974 2.8-270.5h Cordle et al. (1978)
Milkb 1974 44-900h Robertson & Chynoweth (1975)
Milkc 1974 43-56h Jackson & Halbert (1974)
Milkd 1974 up to 595 Kay (1977); IARC (1978)
Milke 1974 1-> 100h Fries (1985b)
Canned milk 1974 1.15-1.62h Cordle et al. (1978)
Dry skimmed milkf 1974 0.75-1.5 Isleib & Whitehead (1975)
Fluid milk 1974 < 0.02-1.15
processors' products
Butter 1974 1-2h Cordle et al. (1978)
Cheese 1974 1.4-15.0h
Milkg 1975 1-13h Kay (1977); IARC (1978)
Eggs 1974 up to 59.7
a = Collected from individual farms.
b = Collected from 21 cows.
c = Collected from 2 cows (having 174 and 200 mg PBBs/kg in body fat,
respectively).
d = Collected from 22 farms.
e = Collected from 28 herds.
f = From one dairy plant.
g = Collected from 16 herds.
h = On a fat basis.
In May 1974, the US Food and Drug Administration (FDA)
established the following enforcement limits for unavoidable
residues of PBBs in foods: 1 mg/kg in the fat of meat, milk, and
dairy products, 0.3 mg/kg in animal feeds, 0.1 mg/kg in eggs. These
enforcement guidelines were reduced in November 1974 to 0.3 mg/kg in
the fat of meat, milk, and dairy products, and 0.5 mg/kg in eggs and
animal feeds. In February 1977, the FDA rejected a petition to lower
the enforcement guideline level to 0.02 mg/kg for all food products
(IARC, 1978). However, according to Fries (1985b), final
legislation, Act 77, lowered the tolerance to 0.02 mg/kg in the body
fat of all cull dairy cows offered for slaughter. (Unlike the
situation under the previous regulations, the finding of a single
animal with a higher than legal body fat level did not lead to
quarantine and the disposal of the whole herd.) As a result of the
rigid quarantine policy, the food levels of PBBs decreased in
Michigan. In 1975, none of 18 milk samples, 3 out of 14 butter
samples, and none of 13 cheese samples exceeded FDA guidelines
(0.3 mg/kg). Also in 1975, 245 of 2040 meat samples were
contaminated with PBBs: 24 contained more than 0.3 mg/kg. None of
the meat specimens collected in 1976 exceeded FDA guidelines: 96% of
1430 samples were contaminated, but only 1 sample contained more
than 0.6 mg/kg of PBBs. A market basket survey of meat in 1976
revealed detectable PBBs in only 1 out of 102 samples in Michigan
(Di Carlo et al., 1978).
Additional information on PBB findings is presented in several
government reports, which are cited by Di Carlo et al. (1978).
According to these reports 29 170 products had been assayed. In
1974, 14 out of 16 milk samples, 4 out of 34 butter samples and 11
out of 23 cheese samples, collected in Michigan, were found to
exceed FDA guidelines for PBBs. Another survey showed that 24.9% of
272 finished product samples, collected from May to October 1974,
were contaminated with PBBs and that 15.8% contained more than
0.3 mg/kg (Di Carlo et al., 1978).
PBBs were also detected in other states in the USA, for example
in beef in Iowa, duck in Wisconsin, chicken in Alabama, Mississippi,
New York, and Texas, and turkey in Indiana: the levels were
extremely low. During 1975 and 1976, PBBs were found in 9 out of 597
food samples outside of Michigan (Di Carlo et al., 1978).
Food contamination, not derived from the Michigan PBB-
incident, becomes evident, when looking at PBB levels in fish (see
Table 30) some of which are used for human consumption. For example,
skinless fillets of carp from the Pine River, captured in the
vicinity of Michigan Chemical Company, contained 1.33 mg PBBs/kg
(wet weight basis) which is approximately equivalent to 30 mg/kg on
a fat weight basis (Hesse & Powers, 1978). This was obviously
greatly in excess of the US FDA tolerance limit for beef, a
tolerance limit for fish has not been established (Hesse & Powers,
1978).
More recent information on "background" PBB levels in food may
be expected in future via a USA data collection programme
(Foodcontam) initiated by the US Food and Drug Administration which
includes PBBs besides other chemicals (Minyard et al., 1989).
Table 30. PBB levels in fish
Year Region Species Type of PBB concentration Weight PBB References
sample (µg/kg) basis examined
1974 Pine River, downstream Carp skinless not detected-1330 wet HxBB Hesse &
from St. Louis (vicinity (Cyprimus carpio) fillets Powers
of Michigan Chemical Co.) (1978)
White sucker 670
Northern pike 540
Bullhead 450-780
1974 Tittabawassee Carp not detected
River (Cyprimus carpio)
Freshwater drum not detected
(Aplodinotus
grunniens
1976 Pine River, downstream Carp 60-750
from St. Louis (vicinity (Cyprimus carpio)
of Michigan Chemical Co.)
Northern pike 180-230
1976 Pine River, downstream Largemouth skinless not detected-740 wet HxBB Hesse &
from St. Louis (vicinity bass fillets Powers
of Michigan Chemical Co.) (1978)
Smallmouth bass 130
Rockbass 320-700
Table 30 (contd).
Year Region Species Type of PBB concentration Weight PBB References
sample (µg/kg) basis examined
1977 Kill van Kull River Killifish whole 220 dry total PBB Stratton &
(vicinity of White Chemical HxBB-DeBB Whitlock
Co., Bayonne, New Jersey); (1979)
Port Johnson
1977 Kill van Kull River Killifish whole 230 dry total PBB
(vicinity of Standarad T HxBB-DeBB
Chemical, Staten Island,
New York); canal at
discharge site
Not Lake Huron Yellow perch 0.3-0.8 Kreis & Rice
specified (Saginaw Bay) (1985)
Saginaw Bay Catfish 21.0
1983 Pine River Hogsucker whole 6000 fat most Jaffe et al.
abundant (1985)
congeners
1983 Chippewa River Carp 5300-15 000
1983 Tittabawassee 140-160
River
1983 Shiawassee River 120
Table 30 (contd).
Year Region Species Type of PBB concentration Weight PBB References
sample (µg/kg) basis examined
1983 Flint River 15-32
1983 Saginaw River 80-200
1983 Saginaw Bay 110-1100
Four samples of cow's milk from Germany have been analysed for
PBBs (Krüger, 1988). Three congeners were detected; BB 153
(0.025-0.053 µg/kg milk fat), BB 180 (0.001-0.007 µg/kg) and BB 187
(0.005-0.014 µg/kg). The other 30 congeners covered by the method
were not detected with detection limits ranging from 0.001 to
0.003 µg/kg milk fat (see Table 33).
The processing and cooking of contaminated food have been found
to have some potential for reducing PBB levels. Spray-drying
appeared to reduce the contents of PBBs in whole milk and skim milk
by 30-36% and 61-69%, respectively (Murata et al., 1977; Zabik
et al., 1978). Pressure cooking of chicken pieces also resulted in a
loss of PBBs, however, part of the PBBs lost were found in the drip
(Zabik et al., 1978).
5.1.5 Other products
Antibiotics used for attending farm animals were also found to
be contaminated: Levels of PBBs in aureomycin, which was distributed
by the Michigan Farm Bureau, were as high as 70 mg/kg (Di Carlo
et al., 1978).
5.1.6 Terrestrial and aquatic organisms
5.1.6.1 Aquatic and terrestrial plants
Only few data on PBB contamination of aquatic and terrestrial
plants are available. Stratton & Whitlock (1979) analysed algae
(e.g., filamentous green algae) from surface waters in the vicinity
of White Chemical (Bayonne, New Jersey) and near Standard T Chemical
Company (Staten Island, New York) for PBBs (MoBB through DeBB). The
two samples did not contain detectable levels of PBBs (detection
limit: 10 µg/kg, dry weight). However, bottom sediments taken in the
same location contained hexa- and heptabromobiphenyl.
Surface contamination was observed on terrestrial vegetation in
the vicinity of PBB facilities (up to 92 mg/kg dry weight; Stratton
& Whitlock, 1979). As Chou et al. (1978) reported, the PBB
contamination of field soils in Michigan (USA) did not result in any
detectable surface contamination of field crops.
5.1.6.2 Animals
a) Wildlife
Most earlier data available on PBB contamination of wildlife
refer to freshwater fish (Table 30) and birds (Tables 31 and 32),
primarily waterfowl in the USA. Recent reports refer to PBB
contamination of fish-eating mammals and birds from marine
environments in the USA (Kuehl et al., 1991) and in Europe (Jansson
et al., 1987, 1992; Krüger, 1988). Residues were found also in
terrestrial mammals (Jansson et al., 1992) and in freshwater and
marine fish in Europe (Krüger, 1988; Jansson et al., 1992).
Table 30 gives PBB levels in fish captured for analysis in
industrialized areas of the USA, at various distances from PBB-
containing or -using facilities. PBBs were detected in several fish
species from all rivers or bays examined. The PBB levels ranged up
to a maximum of 1.33 mg/kg wet weight (approximately equivalent to
30 mg/kg on a fat basis) found in carp from the Pine River near
Michigan Chemical Company (Hesse & Powers, 1978).
No apparent change in PBB concentrations was observed in Pine
River fish between 1974 and 1976 (Hesse & Powers, 1978; see also
Table 30). Although Michigan Chemical Co. had terminated PBB
production in 1974, even in 1983, Jaffe et al. (1985) detected PBB
in fish from the Saginaw River system, with highest concentrations
in fish from Pine and Chippewa Rivers (Table 30). While carp from
Tittabawassee River, to which Pine River joins, did not contain any
detectable PBBs in 1974, PBB-residues were detected (approximately
150 µg/kg on a fat basis) in 1983 (Table 30).
Various PBB homologues were examined in killifish (Oryzias
latipes) from Kill van Kull River near White Chemical Co.
(Bayonne, New Jersey). The main component found was NoBB. In the
vicinity of a FireMaster(R)-using facility (Staten Island, New
York), killifish samples contained only HxBB (Stratton & Whitlock,
1979).
PBB contamination has been reported in wild ducks collected
within two miles of the Michigan Chemical Corporation plant (Table
31), in eggs of waterfowl nesting around Green Bay and other areas
of Lake Michigan and on Lake Michigan island (Table 32), and, in
bald eagles found moribund or dead in 13 US states (Table 31).
Approximately one third of bald eagles examined contained PBB
residues (see Table 31).
Concentrations of PBBs in duck samples with skin left on were
considerably higher than those in skinless samples (see Table 31)
indicating that much of the PBBs is associated with the skin or fat
layer between the skin and muscle (Hesse & Powers, 1978).
Table 31. PBB residues in birds (ducks and bald eagles)
Year Region Species Type of sample No. of PBB concentrationb (mg/kg wet weight) References
samplesa mean range median
1974 Pine River Mallard breast tissue 3 0.25 Hesse & Powers
within two miles (skinless) (1978)
downstream from
St. Louis
Wood duck 0.29
Teal 1.8
1976 Mallard breast tissue:
skinless 3c 0.24
with skin 3c 2.00
Wood duck
4c 0.17
4c 2.70
1977 Wood duck breast tissue:
skinless 4c 0.08
with skin 4c 0.23
1977 Teal breast tissue:
skinless 0c (1) not detected
with skin 0c (1) not detected
Table 31 (contd).
Year Region Species Type of sample No. of PBB concentrationb (mg/kg wet weight) References
samplesa mean range median
13 US states Bald eagle found moribund Kaiser et al.
(Haliaeetus or dead; (1980)
leucocephalus)
carcass 10 0.03-0.27 0.07
(32)d
brain 7 0.03-0.17 0.05
a Number of samples containing residues; median is based on this number. Total number of samples in parentheses.
b PBB values were based on the major hexabromobiphenyl peak (BB 153).
c Paired samples.
d Detection limit: 0.02 mg PBBs/kg.
Table 32. PBB residues in eggs of fish-eating and non-fish-eating waterbirds from Green Bay and Lake Michigan (USA)
PBB concentrationb
Year Collection site Species No. of (mg/kg wet weight) References
eggsa geometric mean range
Fish eater
1975 Green Bay Little gull 1 n.d. Heinz et al.
(Sensila Wildlife Area) (Larus minutus) (1985)
1977 three Lake Michigan islands Red-breasted merganser 114 0.06 n.d.-0.13 Haseltine et al.
off the tip of Door County, (Mergus serrator) (109) (1981)
Wisconsin
1977 islands in north-western Red-breasted merganser Heinz et al.
Lake Michigan (Mergus serrator): (1983)
eggs from the same nests
randomly selected 49 0.05
unhatched 49 0.04
1977 Lake Michigan Herring gull 9 0.18 0.11-0.25 Heinz et
(Gravel Island) (Larus argentatus) (9) al. (1985)
1977 Green Bay Common tern 10 0.06 0.02-0.22 Heinz et al.
(Lone Tree Island) (Sterna hirundo) (10) (1985)
Green Bay (St. Vital Island) Common tern 2 (2) 0.03 0.03-0.04
(Sterna hirundo)
Green Bay (Portage Point) 2 (2) 0.03 0.02-0.06
Green Bay (Cat Island) Double-crested 4 (3) 0.01 n.d.-0.02
cormorant
(Phalocrocorax
auritus)
Table 32 (contd).
PBB concentrationb
Year Collection site Species No. of (mg/kg wet weight) References
eggsa geometric mean range
Lake Michigan (Fish Island) 6 (3) 0.02 n.d.-0.05
Green Bay (Oconto Marsh) Black-crowned night-heron 1 (1) 0.02
(Nycticorax nycticorax)
Green Bay (Oconto Marsh) Green-backed heron 1 n.d.
(Butorides striatus)
Non-fish eater
1977 Three Lake Michigan Mallard 22 n.d. Haseltine
islands off the tip of (Anas platyrhynchos) et al. (1981)
Door County, Wisconsin
1977 Lake Michigan (three Gadwall 4 n.d.
islands off the tip of (Anas strepera)
Door County, Wisconsin)
Black duck (Anas rubripes) 3 n.d.
a Number of collected eggs (in parentheses: number of eggs with quantifiable levels of PBBs).
b PBB values were based on hexabromobiphenyl;
n.d. = No residue of quantifiable level. Level over which quantification was possible: 0.02 mg/kg.
Samples with no detectable residues were calculated in the means as one-half the quantification level.
While the majority of ducks analysed from the Pine River
contained measurable concentrations of PBBs (Table 31), the eggs of
ducks from Lake Michigan islands did not contain detectable PBB
residues (Table 32). In contrast, most eggs of fish-eating
waterbirds from Green Bay and Lake Michigan showed PBB residues
(Table 32). Highest concentrations were detected in herring gull
eggs (0.18 mg/kg wet weight), perhaps reflecting their year round
residence on the Great Lakes (Heinz et al., 1985).
Stratton & Whitlock (1979) analysed a snapping turtle captured
in the vicinity of Hexcel Fine Organics Division (Sayreville, New
Jersey) for hexa- to decabromobiphenyls and found a tissue
concentration of 20 µg hexabromobiphenyl/kg (dry weight).
Di Carlo et al. (1978) reported on PBB contamination of
miscellaneous wildlife, such as deer, rabbits, coyotes, and ravens,
without, however, specifying the sampling locations and the levels
of contamination.
In Europe, 2,2',4,4',5,5'-hexabromobiphenyl (BB 153) was found
in fish from German and Swedish rivers at concentrations ranging
from 0.3 to 0.6 µg/kg lipid (Krüger, 1988; Jansson et al., 1992; see
also Tables 33 and 34). A trout sample from a breeding farm
contained much lower levels of PBBs than the fish samples from the
rivers (Krüger, 1988).
A residue of 22 µg BB 153/kg lipid was observed in pooled
samples of osprey specimens found dead in various parts of Sweden
(Jansson et al., 1992; Table 34).
Swedish reindeers (pooled samples) showed BB 153 levels as low
as 0.04 µg/kg lipid (Jansson et al., 1992; Table 34).
PBBs (as a group) were not found in otters (Lutra canadensis)
from a region relatively remote from industrial sites in north
eastern Alberta (Canada) (Somers et al., 1987).
Fish samples (freshwater and marine species) collected in 1983
from an industrial area of Japan (Osaka) did not contain "PBBs" (not
specified) (Watanabe & Tatsukawa, 1990).
Recently, PBBs have been identified in bottlenose dolphins
(Tursiops truncatus) collected during the 1987/88 mass mortality
event along the Atlantic Coast of the USA. All three animals
(females), analysed for PBBs (tetrabromo- to hexabromobiphenyl
congeners) within a subset of the screening programme for
anthropogenic contaminants, contained PBBs at concentrations ranging
from 14 to 20 ng/g lipid (Kuehl et al., 1991).
Table 33. Average concentrations (µg/kg lipid) of PBB congeners in fish, seals, cows, and human milk samples
Congener River fish Baltic fish North Sea Spitbergen Cow's milk Human milk
(Germany) fish seal (Germany) (Germany)
(No. = 17) (No. = 6) (No. = 11) (No. = 5) (No. = 4) (No. = 25)
BB 103 0.02 0.12 0.10 < 0.02 < 0.02 not analysed
BB 131 + 142/146 0.30 0.62 0.25 0.03 < 0.02 < 0.01
BB 132 0.33 1.25 0.62 0.15 < 0.02 0.05
BB 135 + 144/151 0.69 4.10 1.48 0.46 < 0.02 0.12
BB 147/135 + 144 0.21 0.31 0.25 < 0.02 < 0.02 < 0.01
BB 148/136 0.10 0.13 0.11 < 0.02 < 0.02 < 0.01
BB 149 0.26 0.45 0.53 < 0.02 < 0.02 < 0.01
BB 153 0.60 2.39 1.31 0.81 0.04 1.03
BB 154/151 0.22 0.54 0.37 < 0.02 < 0.02 0.01
BB 155 0.66 2.64 1.11 0.40 < 0.03 0.05
BB 169 < 0.01 15.16 < 0.01 < 0.01 < 0.01 0.05
BB 176 0.03 < 0.01 0.02 < 0.01 < 0.01 < 0.05
BB 178 0.18 0.87 0.36 0.03 < 0.01 0.09
BB 179 0.08 0.04 0.04 < 0.01 < 0.01 < 0.05
BB 180 0.02 < 0.01 0.02 < 0.01 < 0.04 0.02
BB 181 + 174 0.01 0.01 0.01 < 0.01 < 0.01 < 0.05
BB 184 0.05 0.09 0.03 < 0.01 < 0.01 0.01
BB 185 0.03 < 0.01 < 0.01 < 0.01 < 0.01 < 0.05
BB 186 0.30 0.40 0.16 0.01 < 0.01 0.02
BB 187 + 182 0.03 0.05 0.04 0.03 0.01 0.33
BB 188 0.11 0.28 0.11 < 0.01 < 0.01 0.01
BB 192 0.01 < 0.01 < 0.01 < 0.01 < 0.01 n< 0.05
BB 194 0.07 < 0.02 0.04 < 0.02 < 0.02 < 0.05
BB 197 0.11 0.11 0.08 < 0.02 < 0.02 0.04
BB 198 0.27 0.14 0.12 < 0.02 < 0.02 < 0.05
BB 200 + 204 0.41 0.36 0.24 < 0.02 < 0.02 0.02
BB 201 0.09 < 0.02 0.03 < 0.02 < 0.02 < 0.05
Table 33 (contd).
Congener River fish Baltic fish North Sea Spitbergen Cow's milk Human milk
(Germany) fish seal (Germany) (Germany)
(No. = 17) (No. = 6) (No. = 11) (No. = 5) (No. = 4) (No. = 25)
BB 202 0.87 0.42 0.36 < 0.02 < 0.02 0.01
BB 206 0.05 < 0.03 0.04 < 0.03 < 0.03 < 0.01
BB 207 0.06 < 0.03 0.02 < 0.03 < 0.03 < 0.01
BB 208 0.16 0.04 0.04 < 0.03 < 0.03 < 0.01
PBB 6.3 30.5 7.9 1.9 0.05 2.0
From: Krüger (1988).
Table 34. Concentrations (µg/kg lipid) of 2,2',4,4',5,5'-HxBB (BB 153)
in pooled biological samplesa
Species Number of Sampling Concentration
specimens in site of BB 153
the homogenate
Rabbit (Oryctlagus cuniculus) 15 S. Sweden not detected
Moose (Alces alces) 13 not detected
Reindeer (Rangifer tarandus) 31 N. Sweden 0.037
White fish (Coregonus sp.) 35 0.29
Arctic char (Salvelinus alpinus) 15 S. Sweden 0.42
Herring (Clupea harengus) 100 Bothnian Bay 0.092
Herring (Clupea harengus) 60 Baltic Proper 0.16
Herring (Clupea harengus) 100 Skagerrak 0.27
Ringed seal (Pusa hispida) 7 Svalbard 0.42
Grey seal (Halichoerus grypus) 8 Baltic Sea 26
Osprey (Pandion haliaetus) 35 S. Sweden 22
a From: Jansson et al. (1992).
In Europe, PBBs have been detected in seals (Phoca vitulina;
Pusa hispida), guillemots (Uria aalge; U. lomvi), and
white-tailed sea eagles (Haliaeetus albicilla). The concentrations
(estimated by comparison with the technical product FM BP-6) ranged
from 3 to 280 µg/kg lipid (Jansson et al., 1987). The concentrations
of PBBs in comparable samples from the Baltic Ocean were all higher
than concentrations in samples from the Arctic Ocean. The same was
true for polybrominated biphenyl ethers and PCBs (Jansson et al.,
1987).
Concentrations of BB 153 determined in marine fish ranged from
0.2 to 2.4 µg/kg lipid (Krüger, 1988; Jansson et al., 1992; see also
Tables 33 and 34). BB 153 levels of 0.4-26 µg/kg lipid were found in
seals (Krüger, 1988; Jansson et al., 1992; see also Tables 33 and
34).
Detailed isomer-specific PBB analyses were carried out by
Krüger (1988) in fish (several species) from the Baltic and North
Seas and from sections of the Lippe and Rur rivers in North
Rhine-Westphalia, Germany. Seal samples from Spitsbergen (Norway)
were also included in this investigation (Table 33). All samples
contained PBBs. The smallest number of PBB congeners was found in
seals (n = 5) from an area remote from industrial sites. The main
components were different hexabrominated isomers with
2,2',4,4',5,5'-hexabromobiphenyl reaching a mean concentration of
0.8 µg/kg fat. The mean concentrations of several PBB congeners and
isomers (penta- to nonabrominated biphenyls) measured in fish
(n = 35) ranged, mostly, between 0.01 and 2 µg/kg fat. The pattern
of PBB congeners found in fish differed in a characteristic manner,
depending on the different capture sites. While relatively high
amounts of nona- and octabromobiphenyls (besides polybrominated
biphenyl ethers) were present in fish from German rivers (n = 17;
several species), hexabrominated biphenyls were predominant in fish
from the North Sea and the Baltic Sea (n = 17; several species). In
all samples from the Baltic Sea (n = 6),
3,3',4,4',5,5'-hexabromobiphenyl was found in relatively high
concentrations (maximum concentration: 36 µg/kg fat), but it was not
detected in samples from the North Sea and from rivers. The
concentrations of the other hexabrominated biphenyls were mostly
higher in fish from the Baltic Sea than in fish from the North Sea.
b) Farm animals
Farm animals in Michigan were contaminated by PBBs, when
FireMaster(R) FF-1 was accidentally mixed with animal feed in
mid-1973 (see section 4.1). The PBB levels resulting from this event
varied greatly with the extent of exposure. Data reported in the
literature are compiled in Table 35. The extent of contami nation
can be seen from the fact that, during the months following the
event, 172 dairy and beef herds (18 000 animals), 32 swine herds
(3500 animals), 16 sheep flocks (1200 animals), and 92 chicken
flocks (1.5 million birds) were destroyed (Isleib & Whitehead, 1975;
Robertson & Chynoweth, 1975; Mercer et al., 1976). In relation to
these great numbers, the portion of highly contaminated animals was
small (e.g., 40 herds of cattle, as can be derived from
contamination values measured in milk (section 5.1.4.2).
5.2 General population exposure
Apart from data collected after the Michigan disaster, there is
only limited information on exposure of the general public. PBBs
have been detected in humans in the vicinity of manufacturing
premises and in a few sites in the USA and Europe, not directly
connected with PBB contamination.
Table 35. PBB levels in farm animals (derived from the Michigan
cattle food contamination incident in 1973)
Year Animal PBB concentrationa References
(Type of sample) (mg/kg)
1974 Poultryb (tissue) 4600 Kay (1977); IARC (1978)
Not specified Cattle (fat) up to 200 Pearson (1982)
Not specified Aborted calves 120-400 Kay (1977)
1974 Cattlec (body fat) 110-2480 Robertson &
Chynoweth (1975);
Mercer et al. (1976)
1974-75 Cattled (fat) 9-4100 Fries et al. (1978b)
1974 Cattleb (tissue) up to 2700 Kay (1977); IARC (1978)
1974 Cattlej (body fat) 174-200 Jackson & Halbert (1974)
March (1975) Dairy cattlee 1-12 Kay (1977)
1975 Cowsf (tissue-fat) not detected-1.69 Isleib & Whitehead (1975)
1975 Steers and heifersg not detected-2.27
(tissue-fat)
1975 Pigsh (tissue-fat) not detected-0.58
1975-76 Cattlei (male and not detected-0.13 Cook et al. (1978a)
female) (eye fat)
Not specified Cattlek (body fat) not detected-3.8 Mercer et al. (1976)
a PBB values were based on 2,2',4,4',5,5'-hexabromobiphenyl.
b From 22 farm premises.
c 21 highly exposed cows.
d 32 cows from one herd heavily contaminated during September/October
1973, and 9 calves borne to these cows in 1974.
e 16 herds of dairy cattle with a history of feed levels from 1 to 14 mg/kg PBB.
f-h Slaughter house survey during a 3-month period (January-April 1975).
f Number of samples: 216; mean-PBB: 0.018 mg/kg.
g Number of samples: 247; mean-PBB: 0.030 mg/kg.
h Number of samples: 213; mean-PBB: 0.017 mg/kg.
i Cattle of 5 affected herds.
j 2 cows of the Halbert farm.
k Cattle of 12 affected herds.
5.2.1 Quantified data on human exposure
5.2.1.1 Worldwide
For most human populations, direct data on exposure to PBBs
from various sources have never been documented. This is true also
for the possible exposure of the general population from the use of
PBB-containing plastic products, and from fumes, generated in the
combustion of these products inadvertently in fires, or from burning
in dumps (Kay, 1977), and, additionally, from sources such as
PBB-containing landfills or PBB-manufacturing and processing
plants.
5.2.1.2 The Michigan Accident
Widespread human exposure resulting from direct contact with
contaminated feed, and, primarily, from the consumption of PBBs in
meat, eggs, and dairy products has been reported from the state of
Michigan, USA (Kay, 1977; Landrigan, 1980; Fries, 1985b; Table 36).
Many Michigan residents were exposed to PBBs between the onset of
contamination in the autumn of 1973 and the establishment of the
quarantine of affected farm animals in the spring of 1974. There was
considerable variation in both lengths and levels of exposure. At
least 2000 families (primarily farmers and their neighbours)
received the heaviest exposure (Meester & McCoy, 1976; IARC, 1978).
Brilliant et al. (1978) concluded from their results of human
milk analyses, conducted in 1976, that about 8 million of the 9.1
million residents of Michigan have detectable body burdens of PBBs.
Further studies (see Table 37) confirmed this widespread
distribution of PBBs.
The amount of PBBs consumed or absorbed by the various groups
in Michigan cannot be determined accurately (Safe, 1984). However,
there have been some trials to estimate the possible exposure to
PBBs of farm families and other people. The estimates were based on
kinetic data and other observations, e.g., time and level of animal
exposure, residue levels in herds at the time of the contamination,
and serum levels of exposed people.
In this way, Fries et al. (1978a) estimated (assumptions: see
Fig. 4), that the total exposure of an individual in a farm family
consuming its own milk was, for example, 9.8 g over the 230-day
period, during which the contamination was undetected. The
cumulative intake over time is shown in Fig. 4. In addition, the
authors concluded that the most highly exposed people consumed from
5 to 15 g PBBs over a 230-day period via milk. The projected intake
of PBB via the meat of cows slaughtered for home consumption would
have exceeded the projected intake from milk.
Table 36. Approximate distribution of PBBs in the Michigan episodea
Item Amount (kg)
Total released 295
Not fed to livestock 45
Fed to livestock 250
Eliminated in faeces 125
Absorbed by animals 125
In human foods before regulation 94
a Modified from: Fries (1985b).
Application of a pharmacokinetic model (Tuey & Matthews, 1980)
to the mean serum concentrations for residents of quarantined farms
resulted in similar values, e.g., about 170 mg mean total exposure
per individual and 11.7 g highest exposure to PBBs (Fries, 1985b;
Brown & Nixon, 1979) supposed a consump tion of 1-20 g of PBB by
families on the most contaminated farms.
The exposure of an individual in the general population would
have a pattern over time as projected above for the farm family
(Fries et al., 1978a). However, the exposure level would have been
much less, because of dilution in the normal marketing channels (the
mixing of milk from a large number of producers; the use of meat of
cull dairy cattle for hamburger and processed meat products). The
calculations of Fries (1985b) indicate that total exposure was about
9-10 mg for an average male with an average adipose content.
However, the individual with the highest PBB serum concentration was
projected to have had a total exposure of about 800-900 mg.
Table 37. Distribution of serum levels of PBBs, Michigan, 1974a
Quarantined farms Non-quarantined farms
Adults Children Adults Children
Serum PBBs Number (%) Number (%) Number % Number %
(µg/litre)
0 3 3.7 - - 21 28.4 - -
2-19 43 52.4 8 28.6 52 70.3 29 96.7
20-90 19 23.2 10 35.7 1 1.4 1 3.3
100-490 11 13.4 3 10.7 0 0 0 0
500-2260 6 7.3 7 25.0 0 0 0 0
Total 82 100.0 28 100.0 74 100.1 30 100.0
a From: Humphrey & Hayner (1975).
People who bought food primarily from quarantined farms were
thought to have been exposed 10 to 100 times more than the typical
retail store customer (Schwartz & Rae, 1983): ca. 100 mg of PBBs
versus 1-10 mg (Brown & Nixon, 1979).
While many dust and cobweb samples found in the buildings of
some PBB-contaminated farms had very high residue levels, the amount
of PBB residue involved is said not to be sufficient to be an
important contributor to animal residues (Fries & Jacobs, 1980) and,
possibly to human exposure.
5.2.2 Human monitoring methods for PBBs
Usually, suitable human monitoring data, as such, are used to
describe the real exposure to a toxic chemical. As an indicator of
human exposure to PBBs, the presence of PBBs in adipose tissue,
breast-milk, whole blood, serum, red and white blood cells (Bekesi
et al., 1979a,b), and human hair oils (Stratton & Whitlock, 1979)
has been assessed. The most commonly used specimens were serum,
breast-milk, and adipose tissue (see Tables 38-40).
Table 38. Human monitoring data: PBB levels in the Michigan population (USA)
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
1974 82 96.3 serum adults from not 14 not Humphrey &
quarantined farms detected- specified Hayner (1975)
2260
28 100 serum children from 2-2260 35 not
quarantined farms specified
5 100 serum lactating females 3-1068
from quarantined
farms
1976 524 serum Michigan farmers 23.7 2.6 0.2 Wolff et al.
µg/litre (1978a);
Lilis et al.
(1978)
283 serum residents on 0.2-> 1000 33.9 3.9
quarantined farms
153 serum residents of 0.2-50 2.9 1.4
non-quarantined
farms
40 serum consumers of 0.3-1000 56.6 4.2
products
from quarantined
farms
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
28 serum consumers of 0-50 3.4 2.2
products from
non-quarantined
farms
consumers and Wolff et al.
residents: (1978)
quarantined farms:
40 serum females < 18 years 28.0 2.3 0.2
µg/litre
102 serum females > 18 years 18.2 2.5
51 serum males < 18 years 67.7 7.3
129 serum males > 18 years 28.2 4.4
consumers and
residents:
non-quarantined
farms:
37 serum females < 18 years 3.1 1.3
57 serum females > 18 years 1.7 0.9
35 serum males < 18 years 4.8 1.7
51 serum males > 18 years 3.1 2.2
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
1976 485 serum consumers and Chanda et al.
residents: (1982)
quarantined farms:
27 serum 0-5 years 0.2-64.2 10.15 not
specified
137 6-18 years 0.0-962.4 27.22 not
specified
321 > 18 years 0.2-1778.0 24.42
1976 321 serum consumers and Chanda et al.
residents: (1982)
non-quarantined
farms:
18 0-5 years 0.2-37.4 6.42 not
specified
104 6-18 years 0.0-42.6 3.25 not
specified
177 > 18 years 0.0-94.0 3.03 not
specified
1976 serum Michigan children 3.41 not Barr (1980)
specified
143 females 2.72 not
specified
149 males 4.23 not
specified
33 0-4 years 2.75 not
specified
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
77 5-8 years 5.59 not
specified
81 9-12 years 3.18 not
specified
101 13-16 years 2.65 not
specified
1976-77 3639 serum Michigan residents 0-1900 21.2 3.0 1 µg/litre Landrigan
with various et al.
degrees of exposure (1979);
Landrigan
(1980)
1976-77 1750 serum contaminated farm 0-1900 26.9 4.0 1 µg/litre Landrigan
1114 residents farm 0-659 17.1 3.0 et al.
(1979);
216 product recipients 0-1240 43.0 4.5 Landrigan
(1980)
559 chemical workers and 0-111 3.4 2.0
families volunteers
1976-77 52 serum women at the time not 26.2 2.5 1 Landrigan
of delivery detected- µg/litre et al. (1979)
1150
1977 3683 serum Michigan PBB cohort < 1-3150 23.2 4.1 3 not Kreiss et al.
specified (1982)
1888 males 5.8
1795 females 2.8
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
1978 1681 serum Michigan residents Wolff et al.
(1982)
(randomly selected)
1120 68.9 adults 0.2-120.5 1.3 0.6 0.2
µg/litre
461 72.7 children 0.2-37.2 1.8 0.8
232 Upper Peninsula 0.2
Lower Peninsula:
467 Detroit Area 0.5
191 Muskegon Area 1.7
791 remainder of state 0.9
Muskegon County:
54 serum male adults 4.0 2.6 0.2 Wolff et al.
µg/litre (1982)
74 female adults 2.1 1.4
36 male children 4.9 3.4
27 female children 3.8 2.0
1975-80 serum Michigan PBB cohort: Eyster et al.
(1983)
61 pregnant females not 3.5 3 1
detected- µg/litre
1068
56 non-pregnant females not 3.1 2
detected-
873
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
29 male chemical workers 1-1200 25.4 20
83 male farm and other not 5.4 4
workers detected-
1515
1974-75 5 100 milk women from 0.21-92 660 not Humphrey &
quarantined farms specified Hayner (1975)
1976 milk lactating women Brilliant
(fat) (randomly selected et al. (1978)
53 96 from Michigan: not 0.068 0.1 mg/kg
Lower Peninsula detected-
1.2
42 43 Upper Peninsula not
detected-
0.320
1976-77 32 100 milk women at the time of 0.032-93 3.61b 0.225b Landrigan
(fat) delivery (Michigan et al. (1979)
PBB cohort)
1976-78 2986 88.5 milk lactating women not 0.097 0.1 0.06 < 0.05 mg/kg Miller et al.
milk (self-selected) detected-2 (1984)
1975-80 Michigan Eyster et al.
PBB cohort (1983)
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
47 milk pregnant females not 0.312b 0.250b 0.001
(fat) detected- mg/kg
92.7
1974-75 15 100 adipose persons from 0.104-175c Humphrey
quarantined farms & Hayner
(1975)
1975-76 53 adipose quarantined farmers 1.965 Meester &
McCoy
(1976)
29 100 non-quarantined 0.516
farmers
9 100 city residents 0.226
116 fat members of farm 0.58-273.0
families
1977 19 subcutaneous children with known Weil et al.
exposure to PBBs (1981);
fat in utero and/or Schwartz &
through breast milk Rae (1983);
Seagull
(1983)
10 100 "high exposure" 0.116- 4.218
20.960
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
9 100 "low exposure" 0.010- 0.050
0.074
1978 844 97.3 adipose Michigan residents < 0.002- 0.4 0.199 0.002 Wolff et al.
36.7 mg/kg (1982)
(randomly selected) 0.015
87 Upper Peninsula
Lower Peninsula:
255 Detroit Area 0.16
84 Muskegon Area 0.50
418 remainder of state 0.24 0.050
1975-80 32 adipose Michigan PBB-cohort: not 0.330 0.540 0.001 Eyster et al.
lipid pregnant females detected- mg/kg (1983)
174
56 non-pregnant females not 0.00057 0.460
detected-
0.619
29 male chemical 0.4-350 5.29 6.0
workers
83 male farm and other 70-350 1.65 1.05
workers healthy male
Not 7 100 adipose volunteers, aged 0.01-2.72 0.001 Schnare
specified lipid 20-30 years mg/kg et al.
(subcutaneous) (1984)
Table 38 (contd).
Year Number Positive Specimen PBB-concentrationa Detection References
of findings (tissue, Group Range Arithmetic Geometric Median limit
specimens (%) etc.) mean mean
1983 15 100 perirenal autopsy cases from 0.032-1.65 0.475 0.32 0.0005 Miceli
post- the "high" exposure mg/kg et al.
mortem area of Michigan (1985)
adipose (Grand Rapids)
tissue
(wet wt)
a Expressed as the concentration of the major hexabromobiphenyl component (BB 153) in µg/litre serum or
mg/kg milk, or adipose tissue, respectively.
b The sample measuring 93 mg/kg was excluded from statistical analysis.
c Most in the order of 1 mg/kg.
The last one has been preferred for analysis, since depot fat
is the predominant storage site of PBBs (and other persistent
halogenated hydrocarbons), and, therefore, allows an increased
detectability of body burden. For example, had serum PBBs been used
alone as an indicator of exposure in the PBB survey of the general
population of Michigan (Table 38), only 70% of the 839 individuals
would have been considered exposed. When adipose tissue results are
added, an additional 24% indicate exposure, raising the positive
rate to 94%. Even though the limit of detection was an order of
magnitude higher (2.0 µg/litre in adipose tissue vs. 0.2 µg/litre in
serum), the partition ratio of approximately 300:1 made the adipose
limit of detection a more sensitive indicator of exposure (Wolff
et al., 1982; Anderson, 1985).
On the other hand, collection of hair, blood, and breast-milk
samples is simpler and less invasive than adipose tissue biopsy.
Moreover, with some exceptions, significant correlations between
adipose tissue and blood serum or breast-milk PBB levels were found
(section 6.2). Further advantages and limitations of these
techniques are discussed in detail by Anderson (1985) and Fries
(1985b).
It should be noted that levels of PBBs in breast-milk may not
be comparable between studies unless the concentration is adjusted
for fat content, because the fat content of breast-milk varies
widely from woman to woman, and the value increases during feeding
(Rogan et al., 1980).
Although the accurate relationship between observed body levels
of PBBs and individual exposure to PBBs is not clear (Safe, 1984),
PBB concentrations in human tissues can give some idea of the levels
of exposure (Kimbrough, 1980a).
5.2.3 Human monitoring data
In the following subsection, human monitoring data are
presented from contaminated farms in Michigan, from Michigan state,
and from other countries.
Most data available refer to the Michigan PBB incident in
1973-74 (Tables 38 and 39). Because, in this case, the spilling of
PBBs started from farms, the Michigan Department of Public Health
(MDPH) undertook a series of studies on farm families as a high-risk
group in the summer and autumn of 1974.
Serum samples were obtained from 110 persons in the exposed
group (had been working or living in the quarantined farms for six
months or more since the accident) and for 104 persons from the
control group (randomly selected from a list of dairy producers in
the same geographical area, where farms had not been quarantined).
As shown in Tables 37 and 38, serum levels of PBBs were
significantly higher in the people from quarantined farms compared
with those from non-quarantined farms, though low levels were also
observed in the control group (Cordle et al., 1978). In 1976, the
MDPH, together with the Centre for Disease Control, the FDA, NIH,
and EPA, established a cohort of 4545 people in Michigan to be
examined at regular intervals over several decades (Barlow &
Sullivan, 1982) to evaluate the long-term effects of PBB exposure.
Four groups were included (Landrigan, 1980): Quarantined farm
residents, direct recipients of farm produce, chemical workers and
their families, and persons who either volunteered for the study or
who had participated as control subjects in an earlier pilot study
(Humphrey & Hayner, 1975). The first report was published by
Landrigan et al. (1979) followed by several reports on subgroups of
this population (e.g., Kreiss et al., 1982; Eyster et al., 1983).
Study groups of the Mount Sinai School of Medicine have also
conducted comprehensive examinations on similarly categorized
groups, e.g., residents of quarantined farms, residents of
non-quarantined farms, consumers of products directly from
quarantined or non-quarantined farms, and Michigan Chemical Company
workers; residents of the state of Wisconsin were used as a control
group.
It can be seen from Table 38 that nearly 100% of the adipose
samples randomly selected throughout the state had detectable PBB
concentrations. Thus, statewide exposure of Michigan residents to
PBBs can be demonstrated.
Levels of PBBs in serum (Landrigan, 1980; Wolff et al., 1982),
breast-milk (Brilliant et al., 1978; Miller et al., 1984), and
adipose tissue (Wolff et al., 1982) were highest in the area of the
accident (lower peninsula), and lowest in the upper peninsula,
farthest from the source.
Compared with residents of quarantined farms, direct consumers
of products from quarantined farms, and PBB- production workers, the
tissue burdens among the general population of Michigan were 1-3
orders of magnitude lower. Moreover, for example, only 36% of the
general population had serum PBB concentrations greater than
1 µg/litre, compared with 78% among farmers (Anderson et al., 1979;
Wolff et al., 1982).
PBB levels appear to be higher in males than females (Meester &
McCoy, 1976; Landrigan et al., 1979; Landrigan, 1980; Wolff et al.,
1978; 1980; Kreiss et al., 1982; Eyster et al., 1983) and higher in
children (below the age of 10 years) than in adults (Humphrey &
Hayner, 1975; Landrigan et al., 1979; Landrigan, 1980; Barr, 1980;
Wolff et al., 1982).
A later study (Schnare et al., 1984) recorded not only the
concentration of the most abundant congener of the FireMaster(R)-
mixture (2,2',4,4',5,5'-hexabromobiphenyl) but also the concen
trations of other PBB congeners detected in subcutaneous adipose
tissue samples of 7 former participants of the Michigan PBB studies
(Table 39).
Table 39. Range of adipose tissue concentrations of various PBBs in 7 personsa
(mg/kg on a lipid weight basis)b
PBB Rangec (mg/kg)
2,3',4,4',5-penta nd-0.16
2,2',4,4',5,5'-hexa 0.01-2.72
2,2',3,4,4',5'-hexa nd-0.22
2,3',4,4',5,5'-hexa nd-0.09
2,2',3,3',4,4',5-hepta nd-0.26
2,2',3,4,4',5,5'-hepta nd-0.01
a 7 healthy male volunteers, aged 20-30 years, having been exposed to PBBs some
years earlier, as a consequence of the Michigan PBB incident in 1973.
b From: Schnare et al. (1984).
c nd = Not detectable; detection limit = 0.001 mg/kg.
In most cases, PBB concentrations did not appear to be
decreasing significantly over time. Wolff et al. (1979b) did not
find any significant variation in the serum PBB levels of nine dairy
farm residents during 18 month of observation.
Paired serum samples, one collected in 1974 and the other in
1977, were also available for 148 members of the Michigan PBB
cohort. The data indicate that levels were generally stable over the
3-year period with a mean change of 16 µg/litre (Landrigan et al.,
1979). In another study of the Michigan PBB-cohort, the decrements
in median serum levels of PBBs between matched pairs over one -
(1977-78) and two - (1977-79) year intervals were both only 1
µg/litre (Kreiss et al., 1982). No significant change in blood
plasma PBB levels was observed over a 5-month period in 41 residents
of quarantined farms (Humphrey & Hayner, 1975). In contrast, Meester
& McCoy (1976) reported a marked decline over 3 years (1974-76) in
serum levels of PBBs. These authors also found that the average
decrease in PBB concentrations in the fat of 16 individuals was
about 40%, in a period of 6 months. No changes in PBB levels were
seen over an 11-year period (1976-87) in fat samples from a patient
with long-term exposure to PBBs from the early 1970s as a result of
the Michigan PBBs accident. The average fat level of PBBs was
0.8 mg/kg (Sherman, 1991).
In 1981, PBBs were found in 13-21% of serum samples from
4-year-old Michigan children. Their mothers belonged to a group that
was surveyed either with regard to the consumption of Lake Michigan
sport fish (mean PBB level detected in children: 2.4 ng/ml) or with
regard to former exposure to quarantined farm products (mean PBB
level detected in children: 3.0 ng/ml) (Jacobson et al., 1989).
Few human monitoring data are available for the US population
outside of Michigan. They are summarized in Table 40. One study
deals with the population in the vicinity of industrial areas
involved in PBB production or use (Stratton & Whitlock, 1979), the
other with farmers of the state of Wisconsin who were examined as
control group in connection with the Michigan PBB studies (Wolff
et al., 1978).
PBBs were found in all studies, but, because of the limited
data, the significance is unclear. The highest PBB levels were found
in the hair of humans living near PBB industry. Of the nine samples
analysed, five had detectable PBB levels. Both male and female hair
samples contained PBBs (Stratton & Whitlock, 1979).
In contrast to the other surveys, which had regard only to the
major PBBs component (hexabromobiphenyl), Stratton & Whitlock (1979)
identified the different PBB homologues in the extracted oils of the
human hair, collected from barbershops and beauty parlours (Table
41). There were identifiable differences in the composition of PBB
congeners found in hair from the three locations.
The samples with the highest concentrations contained
relatively large amounts of decabromobiphenyl, while the samples
with lower concentrations contained only hexabromobiphenyl (Stratton
& Whitlock, 1979). One sample was different from the others because
it contained dibromobiphenyl (see Table 41). As a result of the
sampling method, it was impossible to ascertain whether the exposure
was related to the workplace or to the ambient environment.
In a report by Lewis & Sovocool (1982), pooled adipose tissue
samples from 202 individuals from nine census regions in the USA
were analysed for HxBB. Although the average concentration was 1-2
µg/kg, it cannot be excluded that this was because of the inclusion
of a few samples with high PBB concentrations.
Table 40. Human monitoring data: PBB levels in the US population (outside of Michigan)
Year No. of % of Specimen PBB PBB Detecion Remarks References
specimens positive tissue group/area concentrationa examined limita
findings range
1977 56 3.6 serum Wisconsin farmers not C12H4Br6 examined as Wolff
a control detected-1.1b et al. (1978)
population
1977 3 33 hair (from males and females, < 100-8100 total PBBs 100 reported as Stratton &
barber- Bayonne New Jersey, µg/kg in oil Whitlock
shops) Vicinity of White (1979)
Chemical
3 100 hair (from males and females, 440-26 600 total PBBs 100 reported as
barber- Staten Island, µg/kg in oil
shops) New York, Vicinity
of Standard T
Chemical Co.
3 33 hair (from males and females, < 100-310 000 total PBBs 100 reported as&
barber- Sayreville New µg/kg in oil
shops) Jersey, Vicinity of
Hexcel Fine
Organics
a (µg/litre or µg/kg).
b PBBs not detected in 54/56 persons. PBBs observed at 1.1 µg/litre in one person, identified as recently
moved from a Michigan farm, and at 0.5 µg/litre in another person.
Table 41. Concentration (range) of different PBB congeners in human hair samples
taken in the vicinity of three industrial sites in the USA, reported as
µg/kg in oila
PBB-congeners Bayonne, New Staten Island, New Sayreville,
Jersey (White York (Standard T New Jersey
Chemical Corp.)b Chemical Comp.)c (Hexcel Corp.)d
MoBB nde nde nde
DiBB nd-8100 nd nd
TrBB nd nd nd
TeBB nd nd nd
PeBB nd nd nd
HxBB nd 440-740 nd-480
HpBB nd nd-890 nd
OcBB nd nd-1100 nd
NoBB nd nd-3600 nd-22 500
DeBB nd nd-20 000 nd-285 000
a Data from: Stratton & Whitlock (1979).
b Having manufactured octa- and decabromobiphenyl along with bromobiphenyl
ethers.
c Major user of FireMaster BP-6.
d Producer of laboratory quantities of various PBBs.
e nd = Not detected (detection limit = 100 µg/kg).
There is very little human monitoring data on PBBs in the
populations of countries other than the USA. Krüger et al. (1988)
reported PBB contamination of breast-milk from European women in a
survey from North Rhine-Westphalia, Germany (Table 33). The milk
samples (n=25) contained a typical pattern of certain PBB congeners.
It included penta- to octabromobiphenyls in concentrations ranging
from 0.002 to 28 µg/kg, based on milk fat. The most abundant
component was 2,2'4,4',5,5'-hexabromobiphenyl (BB 153) followed by a
peak consisting of two heptabromobiphenyl isomers (2,2',3,4',5,5',6-
and 2,2',3,4,4',5,6'-heptabromobiphenyl BB 187 and 182). Differences
in the pattern were only found in the milk given by a Chinese woman
and in that given by a woman having been exposed to several fires in
industry.
Concentrations of BB 153 in human and cow's milk, both
collected from the same region (North Rhine-Westphalia), were
1 µg/kg and 0.03 µg/kg, respectively, measured on a fat basis
(Krüger, 1988).
5.2.4 Subpopulations at special risk
Children are at risk from exposure to PBBs in different ways.
Studies on the Michigan population indicated a significant PBB
transfer to the fetus (Landrigan et al., 1979; Eyster et al., 1983;
Jacobson et al., 1984) and to breast-milk (Brilliant et al., 1978;
Landrigan et al., 1979; Eyster et al., 1983; Jacobson et al., 1984,
1989; Miller et al., 1984). PBB levels to which fetuses and newborn
infants were exposed in the Michigan accident are shown in Table 42.
Because the placenta acts only as a partial barrier to PBBs, a
newborn baby has a body burden, even before breast feeding.
Placental and cord serum levels are much lower than levels in
breast-milk. However, even at low concentrations, intrauterine
exposure may be significant, for several reasons, as pointed out in
detail by Jacobson et al. (1984).
Infants are not only exposed to PBBs through their mothers and
through consumption of contaminated food, but they also through
contact with PBBs from the environment. Young crawling children are
known to ingest accidentally soil or dust to an extent of up to
0.1 g/day.
5.3 Occupational exposure during manufacture, formulation, or use
In general, occupational exposure is to be expected in PBB
manufacturing and processing plants. In Michigan, as a result of the
PBB incident, farmers, and possibly dairymen, elevator, mill
personnel etc. were occupationally exposed (Kay, 1977).
Table 42. PBBb concentrations in maternal serum, adipose lipid, and milk lipid, and in
the cord serum and placenta of Michigan women (Michigan PBB-cohort) at the time of
parturition (1975-80)a
Paired specimen No. Rangec Median Geometric Measure
mean
Maternal serum 61 nd-1068 3 3.5 µg/litre
Placenta nd-370 < 1 - µg/kg
Maternal serum 60 nd-1068 3 3.2 µg/litre
Cord serum nd-104 < 1 - µg/litre
Maternal serum 47 nd-1068 3 3.0 µg/litre
Milk lipid nd-92 667 250 312 µg/kg
Milk lipid 27 52-92 667 384 472 µg/kg
Adipose lipid nd-174 000 522 82 µg/kg
a From: Eyster et al. (1983).
b Concentrations expressed as concentrations of hexabromobiphenyl.
c nd = Not detected (detection limit: 1 µg/litre or kg).
Bialik (1982) reported the following contaminant levels of
decabromobiphenyl measured in 1977 in the manufacturing area of
Hexcel/Fine Organics and Saytech, Inc. (Sayreville; USA):
- Plant air samples: 0.18 and 0.23 mg/m3 8 h TWA (time-weighted
average);
- Wipe tests, unspecified: up to 8 mg/100 cm2; - Wipe tests,
eating Table: 0.1 mg/100 cm2.
At this time, 95% of the plant production consisted of
decabromobiphenyl (18%) and decabromobiphenyl oxide (77%). About
2000 tonnes of decabromobiphenyl were manufactured during 1973-77
(Bialik, 1982).
Employees of chemical plants may be exposed directly to PBBs
(in most cases along with other chemicals) through contact,
inhalation, or ingestion (Wolff et al., 1979a). As an index of
individual exposure, PBB levels in the serum and adipose tissue of
chemical workers have been recorded. The results of several authors
are compiled in Table 43.
Most data refer to the Michigan Chemical Corp., St. Louis
(Michigan), which produced several brominated organic compounds and
manufactured over 5000 tonnes of PBBs, predominantly
hexabromobiphenyl, from 1970 to 1974. Some additional general
exposure from contaminated food can also be included for the workers
of Michigan Chemical.
To summarize, median serum and adipose tissue PBB levels were
higher among chemical workers than among male residents of
quarantined farms.
Non-production workers at the Michigan Chemical plant showed
significantly lower levels than workers involved in PBB production;
for example, median adipose tissue concentrations of PBBs were
2.49 mg/kg and 46.94 mg/kg, respectively.
In another study on workers at a PBB plant in New Jersey, Bahn
et al. (1980b) presented a detailed comparison of serum PBB levels
in various occupational groups. A significantly higher number of PBB
workers had detectable levels of PBBs, compared with other workers
in the study (35.9% compared with 12.2%). Among workers with
detectable PBB levels, the PBB workers had significantly higher
serum levels than workers from neighbourhood industries not using
PBBs.
Although this factory concentrated on manufacturing
decabromobiphenyl and decabromobiphenyl oxide (ether), there was no
positive identification of C12Br10 (Table 44) or C12Br14O
(Bahn et al., 1980b).
No data are available about occupationally exposed women.
Family members of chemical workers have also been found to have
a body burden of PBBs (Landrigan, 1980).
Bekesi et al. (1979b) determined the distribution of PBBs in
the blood compartments of 4 Michigan Chemical plant workers (Table
45) and suggested that the PBB level of the white cell fraction may
be a better indicator for risk potential than the total plasma PBB
concentration.
Table 43. Occupational exposure: PBB levels in chemical workers (USA)
Year Plant Group Sample PBB concentrationa PBB Detection References
(number) range Mean Median examined limita
(geometric
mean)
1975 Michigan workers (8-36 serum 6-85 HxBB Kay (1977)
Chemical Corp. months exposure (7)
(MCC)
(St. Louis,
Michigan)
1976 MCC (St. Louis, employees (55) serum 1.1-1729 123 9.3 HxBB Wolff
Michigan) et al.
(1978,
1979a)
production workers serum 603.9 108.4 HxBB 1 Wolff
(10) et al.
(1979a)
non-production serum 16.5 6.1 HxBB 1
workers (45)
workers (14) serum 1-1530 HxBB < 0.2 Wolff
et al.
(1979b)
1978 workers (14) 1-1363 HxBB < 0.2
(matched pairs)
Table 43 (contd).
Year Plant Group Sample PBB concentrationa PBB Detection References
(number) range Mean Median examined limita
(geometric
mean)
1976-77 MCC (St. Louis, workers and serum not 43.0 4.5 C12H4Br6 1 Landrigan
Michigan) families (216) detected-1240 et al.
(1979)
1975-80 MCC (St. Louis, workers (male) serum 1-2000 (25.4) 20 C12H4Br6 1 Eyster
Michigan) (29) et al.
(1983)
1978 Hexcel/Fine PBB workers serum not MoBB Bahn
Organics and (exposure to PBBs detected-1340 DeBB et al.
Saytech, Inc. (and PBBOs) for at (1980b)
(Sayreville least 6 weeks
New Jersey) between January
1973 and August
1978) (39)
1976 Michigan production workers adipose 5000-581 000 196 490 46 940 HxBB 500 Wolff
(7) tissue et al.
(1979a)
non-production 500-10 000 3880 2490
workers
1975-80 Michigan workers (male) adipose 400-350 000 5290 6000 HxBB 1 Eyster
(29) tissue et al.
(1983)
a In µg/litre or µg/kg.
Table 44. Detectablea serum levels (µg/litre) of PBB homologues in workers
at a plant producing decabromobiphenyl and decabromobiphenyl oxideb
PBB homologue Number of cases Range
C12H9Br 14 0.3-5.5
C12H8Br2 1 6.9
C12H7Br3 1 0.9
C12H6Br4 0 -
C12H5Br5 2 1.6-13.0
C12H4Br6 2 0.4-6.0
C12H3Br7 7 9.0-40.0
C12H2Br8 9 20.0-800.0
C12H Br9 1 500
C12Br10 0 -
Total PBBs 26 0.3-1340
a Excludes cases with "trace", "not confirmed" and "not detectable" levels.
b From: Bahn et al. (1980b).
Despite its significance for toxicological assessment, the
content of minor constituents of FireMaster(R) in the body burden
was rarely investigated. For example, Wolff & Aubrey (1978) examined
other PBB congeners, which are identifiable as peaks by GC/MS
(2 pentabromobiphenyl peaks, and 2 heptabromobiphenyl peaks), in the
serum of Michigan Chemical workers (n = 24) and Michigan dairy
farmers (n = 37), besides the major component (2,2',4,4',5,5'-
hexabromobiphenyl) of FireMaster(R). The relative concentrations,
with respect to the major hexabromobiphenyl peak, of these PBB
components were somewhat different for chemical workers and for
farmers, i.e., the two pentabromobiphenyl values (peak area ratios)
were significantly higher in the serum from chemical workers.
Table 45. Distribution of PBBs in blood compartments of Michigan Chemical Workersa
Polybrominated biphenyls
ng/mg Protein Ratiob
RBC plasma WBC RBC plasma WBC
Michigan Chemical Workers;
not directly involved in 0.07 0.13 3.9 1 : 2 : 56
the production of PBB 0.03 0.23 1.8 1 : 8 : 60
directly involved in 0.67 10.0 57.3 1 : 15 : 86
the production of PBB 0.63 10.2 32.0 1 : 16 : 51
a From: Bekesi et al. (1979b).
b RBC = Red blood cells; WBC = white blood cells.
This variation might be attributed to the different routes
(skin contact, inhalation, direct ingestion versus, primarily,
ingestion of animal foodstuff) and to the different composition
(unchanged versus animal-mediated material) of exposure in chemical
workers versus farmers. Further reasons might be the earlier initial
onset of contamination in workers and slight variations in the
composition (section 2.1.2) of several lots of FireMaster(R) BP-6
(the main product of Michigan Chemical) and FireMaster(R) FF-1,
which caused contamination of livestock feed (Anderson et al.,
1978a; Wolff & Aubrey, 1978; Wolff et al., 1979a).
The change in serum PBB levels over time was investigated in
chemical workers at two facilities. Wolff et al. (1979b) reexamined
serum PBB concentrations (determined as the major hexabromobiphenyl
peak) in 1978 from 14 workers of the Michigan Chemical Corp., who
had also been tested 18 months earlier. They found PBB levels of a
comparable order. In contrast, no subject (n=109) in a study on
chemical workers of Hexcel/Fine Organics and Saytech Inc.
(manufacturing decabromobiphenyl and decabromobiphenyl oxide) showed
any detectable serum level of PBBs (different congeners) in 1981
(Bialik, 1982), which was true, even for the two persons who had
shown high levels of serum PBBs in the previous study of 1978 (Bahn
et al., 1980b; Table 43). However, the results of PBB determination
in the fat of these two cases were positive in 1981. The negative
results of the determination of PBBs in serum were not expected, and
the authors suggested further studies.
6. KINETICS AND METABOLISM
6.1 Absorption
6.1.1 Animal studies
6.1.1.1 Gastrointestinal absorption
Studies have been performed only on the gastrointestinal
absorption of PBBs. Some studies indicate that PBBs are rapidly and
efficiently absorbed, other studies indicate a much lower efficiency
of absorption (see Table 46). No information is available on the
extent of absorption of decabromobiphenyl.
Absorption can be strongly influenced by the vehicle in which
the compound is administered (Birnbaum, 1985). Administration of
hexabromobiphenyl in mineral oil or olive oil solution resulted in
higher absorption than administration in a methyl cellulose
suspension (see Table 46: Rozman et al., 1982). The degree of
halogenation also appeared to influence the absorption of PBB. For
example, less than 10% of 14C-labelled hexabromobiphenyl, but 62%
of a dose of 14C-labelled octabromobiphenyl were eliminated in the
faeces of rats in 24 h, though both compounds had been administered
in corn oil (see Table 46).
The conclusion that more brominated biphenyls are absorbed less
efficiently than less brominated biphenyls can, possibly, be drawn
from other findings. Willett & Durst (1978) observed that, during
feeding of FireMaster(R) BP-6, the relative concentration of
pentabromobiphenyl in the faeces of cows was decreased, and that of
heptabromobiphenyl was elevated compared with the
FireMaster(R)-standard. Similarly, faecal concentrations of
heptabromobiphenyl were enhanced relative to concentrations of
hexabromobiphenyl in the faeces of hens, when FireMaster(R) BP-6
was fed (Fries et al., 1976). However, Polin & Leavitt (1984) found
that the ratio of 3.5 for hexa- to heptabromobiphenyl in the
chemical sample of FireMaster(R) FF-1 shifted to an average ratio
value of 2.5 in the whole carcasses of chickens analysed on days 0,
21, and 42 of withdrawal, inferring a better absorption of hepta-
bromobiphenyl.
Generally, it should be noted that faecal elimination during
the first few days following dosing might be an indicator, but is
not a measure, of lack of absorption, because some absorbed PBB is
eliminated and recycled into the faeces in bile and by diffusion
across intestinal membranes (Rozman et al., 1982; Fries, 1985b).
Table 46. Absorption of PBBs after oral administration
PBB compound Species Vehicle Absorption Methods Comments References
(sex) parametera
[14C-]2,2',4,4',5,5'- rat emulphor-EL 620: 90%, 24 h faeces analysis single dose Matthews
hexabromobiphenyl (male) ethanol: water gut content et al. (1977)
(1 : 1 : 8)
corn oil 90% multiple doses (4)
[14C-] octabromobiphenyl rat (male, corn oil 38%, 24 h faeces analysis single dose Norris et al.
(technical mixture) female) (1973)
[14C-]2,2'4,4',5,5'- rhesus 1% methyl cellulose 40%, 10 days faeces analysis two doses Rozman et al.
hexabromobiphenyl monkey mineral oil 62%, 5 days faeces analysis single dose (1982)
(male) olive oil 66%, 5 days faeces analysis repeated doses (4)
FireMaster(R) BP-6 cow crystalline PBB in 50%, 168 h faeces analysis single dose Willett &
(female) gelatin capsules (7 days) Irving (1976)
calf crystalline PBB in 95%, (9 days) faeces analysis daily feeding
(male) gelatin capsules
a Values based on concentrations of 2,2',4,4',5,5'-hexabromobiphenyl (FireMaster(R) BP-6 sample) or on [14C-]activity.
6.1.1.2 Dermal and inhalation absorption
No quantitative information is available on skin absorption and
intake through inhalation.
6.1.2 Human studies
It is plausible that inhalation and dermal contact are the main
routes of exposure to PBBs for chemical plant workers (Wolff et al.,
1979a), while the main route for Michigan people was the ingestion
of PBBs dissolved in the fat of meat and milk (Di Carlo et al.,
1978). An appropriate model for assessing the latter kind of
absorption is thought to be the rat-corn oil model (Fries, 1985b).
No quantitative data are available on PBB absorption in humans.
6.2 Distribution
6.2.1 Animal studies
6.2.1.1 Levels in organs and blood
As can be seen from Tables 47, 48, and 49, most studies on the
distribution of PBBs have been conducted with the FireMaster(R)
mixture. A few earlier publications refer to technical
octabromobiphenyl. No experimental data are available on tissue
distribution of decabromobiphenyl. When FireMaster(R) was
administered, the distribution process was studied predominantly as
the distribution of 2,2',4,4',5,5'-hexabromobiphenyl, and, with far
less emphasis, on the distribution of the minor components of the
mixture. Little information is available on the distribution of PBB
congeners, when administered individually.
Investigations on rats, mice, cows, sheep, pigs, and avian
species demonstrated that PBBs were distributed widely throughout
the body tissues in all species. Highest (equilibrium)
concentrations on a wet tissue basis were found in adipose tissues,
consistent with the solubility characteristics of PBBs. Adipose
concentrations are usually an order of magnitude higher than those
of most muscle and organ tissues (see Tables 47, 48, 49, and 50).
Much of the variation in concentrations among tissues can be
accounted for by variations in the fat concentrations in these
tissues (Willett & Durst, 1978; Fries et al., 1978b; Fries, 1985b).
Table 47. Distribution of PBBs in mammals after the administration of a single dose of PBBs
PBB Species Administration Time after Tissues, organs, under study - ranked in References
(sex) (dose in mg/kg dosing order of decreasing PBB concentrationsa
body weight) (mg/kg or mg/litre, unless otherwise specified)
FireMaster(R) FF-1 rat oral 1000 10 monthsb adipose tissue (714) > liver (60) > blood Kimbrough et al.
(lot No. 7042) (male) in corn oil (0.94) (1978)
rat 10 monthsb adipose tissue (1202) > liver (37) > blood
(female) (2.9)
FireMaster(R) FF-1 rat oral 80 42 days fat (295) > blood (0.38) Wolff &
(male) in corn oil Selikoff (1979)
FireMaster(R) FF-1 rat oral 500 4 months adipose tissue (1008) > liver (50) > blood Kimbrough et al.
(lot No: 7042) (male) in corn oil (2.1) (1980)
FireMaster(R) FF-1 rat oral 10 24 hb sc fat I (61 500) > sc fat II (38 700) > liver Domino et al.
(lot No: FF-1312-FT) (male) (20 900) > lung (7650) > kidney (7310) > heart (1980b)
(6470) > jejunum (4860) > spleen (3530) >
cerebellum (2990) > grey matter (2850) > white
matter (2750) > testes (2380) > blood (945)
4 weeksb sc fat (19 200) > jejunum (3170) > lung (1240) Domino et al.
> liver (690) > kidney (650) > spleen (520) (1980b)
> heart, testes (both 240) > grey matter
(210) > cerebellum (200) > white matter (170)
> blood (56.9)
FireMaster(R) BP-6 rat intraperitoneal 12 weeks serum (46.80 ng/ml) Miceli &
(male) 10 in corn oil Marks (1981)
Table 47 (contd).
PBB Species Administration Time after Tissues, organs, under study - ranked in References
(sex) (dose in mg/kg dosing order of decreasing PBB concentrationsa
body weight) (mg/kg or mg/litre, unless otherwise specified)
fat (21.90) > adrenal (3.64) > lung (0.98)
> liver (0.59) > pituitary (0.91) > gonad (0.33)
> kidney (0.22) > heart (0.20) > spleen (0.17)
> brain (0.13)
36 weeksb serum (23 ng/ml)
fat (16.62) > adrenal (2.67) > lung (0.51) >
pituitary (0.29) > liver (0.20) > kidney (0.14)
> gonad, brain (both 0.10) > heart (0.08)
> spleen (0.05)
2,2',4,4',5,5'- rat oral 1 in: 1 day muscle (29.9) > adipose (25.5) > skin (17.9) Matthews et al.
[14C]-hexabromobiphenyl (male) Emulphor > liver (9.0) > blood (0.90)c (1977)
EL 600: ethanol:
water (1:1:8)
14C-PBB rat intraperitoneal 28 days ovaries (130) > skin (15.1) > testicles (13.3) McCormack et al.
(male 150 in: peanut > intestine (11.7) > lung (7.3) > liver (4.7) (1979b)
and oil > muscle, heart (1.9) > fat (1.8) > brain (0.9)d
female
pups)
FireMaster(R) BP-6 cow oral 5.95 in: 10 days liver (1.35) > fat (sc: 1.15; perirenal: 1.09; Willett &
(lot No. RP-158) (female) gelatin capsule peri-cardiac: 0.97; intermuscular: 0.81; omental: Irving (1976)
0.78) > brain (pons: 0.27; cortex: 0.08) >
mammary gland (0.25) > kidney (0.12) > heart
(0.11) > lung, muscle (0.08) > ovaries, uterus
(0.06) > plasma, rumen wall (0.04) > bile
(0.02) > synovial fluid (0.01)
Table 47 (contd).
PBB Species Administration Time after Tissues, organs, under study - ranked in References
(sex) (dose in mg/kg dosing order of decreasing PBB concentrationsa
body weight) (mg/kg or mg/litre, unless otherwise specified)
[14C-]octabromobiphenyl rat oral 1 in: 16 days adrenal, adipose, heart, skin > liver, Norris et al.
(technical mixture) (male) corn oil pancreas, spleen (1973)
a Measured as concentration of 2,2',4,4',5,5'-hexabromobiphenyl or [14C-]activity; (in parentheses: values measured - referring
to various measures).
b For additional time points: see original reference.
c Values in average % total PBB dose.
d Values in µg-equivalents/g wet weight.
sc. = Subcutaneous.
Table 48. Studies on the distribution of PBBs in animals following dietary or repeated oral intake
of the FireMaster(R) mixtures or 2,2',4,4',5,5'-[14C]-hexabromobiphenyl
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
FireMaster(R) rat 50 mg/kg day 8 of gestation 0 fat (330) > mammary gland (318) Rickert
BP-6 (pregnant) feed until day 21 of > kidney (30) > skin (22) > liver, et al. (1978)
gestation lung, brain, heart, small
intestine, placenta, uterus (all
< 5)
FireMaster(R) rat 50 mg/kg day 8 of gestation 0 mammary gland (117) > liver (4) Dent et al.
BP-6 (maternal) feed to 14 days (1977b)
postpartum
FireMaster(R) rat 25 mg/kg day 8 of pregnancy 0 fat (74) > mammary > liver McCormack
BP-6 (maternal) feed to 14 days > kidney > lung (6) et al.
postpartum (1979a)
50 mg/kg 0 fat (483) > mammary > kidney
feed > lung (13)
200 mg/kg 0 fat (966) > mammary > kidney
feed > lung (21)
FireMaster(R) rat 100 mg/kg day 8 of pregnancy 0 fat (813) > liver (54) > mammary McCormack &
BP-6 (maternal) feed to 28 days (43) Hook (1982)
postpartum 14 weeks fat (459) > mammary (225) > liver
(after first (12)
and only
Table 48 (contd).
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
litter was
weaned)
> 10 weeks fat (77) > mammary (19) > liver (3)
and after
weaning
their second
litter
2,2'4,4',5,5'- rat 1 mg/kg 4 days 3 days adipose (41.1) > skin > muscle Matthews
hexabromobiphenyl (male) body weight > liver > blood (0.32)b et al. (1977)
per day
FireMaster(R) rat 0.1 mg/kg 9 days 0 liver (1.5) > brain (0.5), Render et al.
BP-6 (Lot 6224A) (male) feed adipose (0.3)c (1982)
1 mg/kg 9 days 0 liver (8.3) > brain (1.8),
feed adipose (1.7)c
10 mg/kg 9 days 0 liver (135) > adipose (27)
feed > brain (12)c
100 mg/kg 9 days 0 liver (1213) > adipose (251)
feed > brain (103)c
FireMaster(R) rat 3 mg/kg 20 days 0 adrenal (93.7) > thyroid (> 20) Allen-
FF-1 (Lot No. (male) body weight > testes (8.7) Rowlands et al.
FF-1312-FT-3) per day (in 1981);
lecithin Castracane
liposomes) et al. (1982)
Table 48 (contd).
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
20 days 5 months adrenal (481) Castracane
(plus dietary et al. (1982)
restriction)
FireMaster(R) mouse 100 mg/kg 14 days 6 h thymus (391) > fat > liver > brain Corbett et al.
BP-6 feed > pancreas > testicles > spleen (1978a)
(2.7)
14 weeks thymus (50) > adrenals = fat >
liver > testicles > spleen > brain
> pancreas (n.d.)
12 weeks perithymic fat (96) > perirenal
fat > adrenal glands > thymus
gland (5.5)
FireMaster(R) mouse 5 mg/kg 3 weeks 0 thymus (20) > lung, liver > spleen Loose et al.
FF-1 feed > serum (< 0.002) (1981)
(lot No. 7042)
8 weeks 0 thymus (24) > liver, lung > spleen
> serum (0.019)
FireMaster(R) mouse 167 mg/kg 3 weeks 0 thymus (109) > liver > lung > Loose et al.
(lot No. 7042) feed spleen > serum (1.22) (1981)
6 weeks 0 thymus (3088) > liver > spleen
> lung > serum (4.75)
Table 48 (contd).
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
8 weeks 0 thymus (2426) > liver > lung
> spleen > serum, (11)
8 weeks 0 thymus (2426) > liver > lung
> spleen > serum (11)
FireMaster(R) cow 50 mg/kg 15 days 15 days renal fat (10) > omental fat Gutenmann &
BP-6 (lactating) feed > brisket fat > liver = thyroid Lisk (1975)
> mammary = chuck muscle > loin
muscle > heart > kidney = brain
> adrenal = spleen (0.4)
FireMaster(R) calf 25 g daily 9 days 0 rumen contents (14257) > feces Willett &
BP-6 (in gelatin > rumen wall > bile > marrow Irving (1976)
(lot 6244 A) capsules) > perirenal fat (441) > kidney
> testes > liver > thymus > heart
> brain, pons > lymph nodes >
tongue > spinal cord > brain,
cortex > plasma > small intestine
> lung > spleen > thyroid >
muscle (25)
FireMaster(R) cow 250 mg daily 60 days 0 fat (25) > liver > glands > nervous Willett &
BP-6 (heifer) (in gelatin > bile > contractiles > plasma Durst (1978)
(lot 6244 A) capsules) > liquids (0.0198)
Table 48 (contd).
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
FireMaster(R) cow environmentally ca. 14 days 9 months perirenal fat (380*) > omental fat Fries et al.
FF-1 contaminated > subcutaneous fat > kidney > liver (1978b)
(Michigan PBB > skeletal muscle > cardiac muscle
incident) > lung > brain (10.5*)
ca. 200-400 g 9-12 months perirenal fat (1224*) > omental fat
(killed in >subcutaneous fat > skeletal muscle
extremis) > liver > cardiac muscle > kidney
> lung > brain (57*)
FireMaster(R) calf 10 mg/kg 4 weeks 0 fat (378) > kidney > liver > muscle Robl et al.
FF-1 (female) body weight (1.26) (1978)
per day in
gelatin
capsules
calf 100 mg/kg 6 weeks 0 fat (6080) > kidney > liver
(male) body weight > muscle (34)
per day
cow 1 158 days 182 days brisket fat (4.5) > bone marrow
> stomach fat > tail fat (3.3)
Table 48 (contd).
PBB Species Exposure Tissues, organs, under study - References
Duration of ranked in order of decreasing
recovery PBB concentrationsa (mg/kg or
Dietary Duration mg/litre wet weight, unless
concentration otherwise specified)
or dose
FireMaster(R) sheep 50 mg/kg 30 days 0 renal fat (42) > omental fat Gutenmann &
BP-6 feed per day > brisket fat > liver > chuck Lisk (1975)
(complete muscle > loin muscle > heart >
ration) thyroid > brain > adrenal > kidney
= spleen (0.9)
FireMaster(R) pig 20 mg/kg 16 weeks 0 back fat (64) > leaf fat > liver Ku et al.
BP-6 feed > muscle > kidney (0.9) (1978)
200 mg/kg 16 weeks 0 back fat (503) > leaf fat > muscle
feed > liver > kidney (13.5)
FireMaster(R) pig 100 mg/kg during 2nd 0 adipose tissue > liver > kidney > Werner &
BP-6 (lactating feed half gestation > braind Sleight (1981)
sow) 200 mg/kg and during
feed lactation
"PBB" Japanese 20 mg/kg 9 weeks 0 liver (374) > kidney > muscle Babish et al.
(ca 75% quail feed > heart > brain (40)e (1975a)
hexabromobiphenyl) male
female 0 liver (225) > heart > kidney >
> muscle > brain (26)e
FireMaster(R) chicken various 5 weeks 0 adipose tissue (3:1) > whole egg Polin &
FF-1 (White concentrations > liver > muscle (0.008:1)f Ringer
Leghorn (1978a)
hens)
Table 48 (contd)
a Measured as concentrations of 2,2',4,4',5,5'-hexabromobiphenyl (in parentheses: values measured - referring to various measures).
b Values in average % total PBB dose.
c Values on a fat basis.
d Concentrations are listed in Table 53.
e Values in mg/kg dry weight.
f Values as ratios of tissue PBBs: diet PBBs.
* = Geometric mean.
Table 49. Studies on distribution of the following continuous exposure to octabromobiphenyl
Species Exposure Duration of Tissues and organs under study, ranked References
Route, Duration recovery in order of decreasing concentrations
concentration (average bromine content; µg/g wet weight)
Rat in diet Lee et al. (1975a)
(male) 0 mg/kg feed (control) 2 weeks liver (3.4) > fat (1.7) > muscle (1.6)
100 mg/kg feed 2 weeks - liver (83) > fat (73) > muscle (14)
1000 mg/kg feed 2 weeks - fat (333) > liver (319) > muscle (77)
100 mg/kg feed 4 weeks 0,2,6 weeks fat > liver > muscle
100 mg/kg feed 4 weeks 18 weeks fat > muscle > liver
Rat inhalation 23 h/day, 7 days Waritz et al.
(OcBB vapour)a per week, 15 weeks (1977)
0 pg/litre air liver (3) > muscle (1.6) > fat (1.5)
(control)
3.5 pg/litre air - liver (4.2) > fat (3.0) > muscle (1.5)
a OcBB = Octabromobiphenyl, Dow, Lot 102-7-72.
Table 50. Tissue: blood ratios of PBBs estimated in a standard 250-g rata
Compartment Ratio
Liver 17:1
Muscle 5:1
Skin 56.5:1
Adipose 340:1
Intestine tissue 1:1
a From: Tuey & Matthews (1980).
However, even when concentrations are expressed on a fat basis
rather than a wet tissue basis, there are some deviations from
uniform concentrations among tissues (Fries, 1985b). PBB
concentrations, for example, were low in nervous tissue, despite its
high lipid content and often disproportionally high in liver,
considering its relatively low lipid content (see Tables 47, 48, and
49; additional information on fat content percentage, e.g., by
Willett & Irving, 1976; Fries et al., 1978a,b; Kimbrough et al.,
1978; Werner & Sleight, 1981).
The ratios between the PBB concentrations of adipose tissue,
blood, and vital organs are different when animals are not at
equilibrium (see also section 6.5) with respect to dosing regimen or
body condition. Usually, concentrations in liver are very high
compared with those in other tissues, immediately after dosing, and
decline relatively as equilibrium concentrations are established
(e.g., Lee et al., 1975a; Matthews et al., 1977; Miceli & Marks,
1981; Fries, 1985b). Generally, this phenomenon is most pronounced
in tissues that have high blood flow rates relative to tissue mass
(Tuey & Matthews, 1980). As an exception, livers of mice, tested in
a small series, appeared to have relatively concentrated the PBB
with passing time (Corbett et al., 1978a).
On the other hand, body weight changes, pregnancy, parturition,
and lactation can affect the concentration relationships until
equilibrium is reestablished (e.g., Rickert et al., 1978; Willett &
Durst, 1978; McCormack & Hook, 1982).
The route of exposure (oral or intravenous administration) had
no effect on the tissue distribution (blood, liver, muscle, adipose,
skin) of 14C-labelled 2,2',4,4',5,5'-hexabromobiphenyl (dose =
1 mg/kg body weight) in rats (Matthews et al., 1977).
Kimbrough et al. (1980) studied the effects of different diets
and of mineral oil on the HxBB concentration in rats that had
received a single oral dose of FireMaster(R) FF-1 (500 mg/kg body
weight, in corn oil). After 3 months of feeding, GC-analysis of
blood, liver, and adipose tissue showed no statistically significant
differences in PBB concentrations among the differently fed groups,
when concentrations were calculated on a lipid weight basis. On a
wet weight basis, however, the PBB concentrations were significantly
increased in the livers of rats on the experimental diets (Teklad-4%
and -20% fibre) and on mineral oil compared with those of rats on
the basal diet (Purina Chow).
In another study, McCormack et al. (1979a) examined the
consequences of simultaneous exposure to PCBs and PBBs in
(lactating) rats, because human populations that have been exposed
to PBBs are also likely to have been exposed to PCBs. The
extrahepatic tissue (kidney, mammary, lung, fat) concentrations of
PCBs and PBBs were similar, regardless of whether the agents were
administered together or alone. Liver, however, contained lower
concentrations of PBBs after treatment with an equal mixture of PCBs
and PBBs than when PBBs were administered alone. (None of the
tissues had higher concentrations of PBBs than PCBs after
concomitant administration. The reasons for this were not clear).
The distribution of PBB (hexa) among blood compartments
(plasma, red cells) has been studied in rats (Domino et al., 1980b).
It was found that plasma levels of 2,2',4,4',5,5'-hexabromobiphenyl
were generally four times greater than red cell levels.
Matthews et al. (1984) reported that 81% of plasma PBB (hexa)
was associated with the total lipoprotein fraction. In another study
(Kraus & Bernstein, 1986), approximately 65% of all radiolabelled
HxBB incubated with human serum in vitro was recovered in the
lipoprotein fraction. Of the HxBB in the lipoprotein fractions, 40%
was recovered in low-density lipoproteins (LDL), 33% in
very-low-density lipoproteins (VLDL), and 23% in high-density
lipoproteins (HDL). Addition of human lipoprotein to a culture
medium influenced the partition of HxBB between adipocytes and
culture medium (Kraus & Bernstein, 1989).
Some data are available on the tissue distribution of the minor
components of FireMaster(R)-mixture (see also section 6.5). Domino
et al. (1980b) analysed the relative percentages of various PBB
congeners (two penta-, three hexa-, and three heptabromobiphenyls)
in several tissues of rats given FireMaster(R) FF-1. From their
list, it was evident that each of the PBB analogues was found in all
tissues examined (liver, lung, testes, fat; blood, brain) but their
partitioning ratios differed. Distribution has been recorded also
after exposure to single PBB congeners, e.g., tetra-, penta-, and
hexa-isomers (Akoso et al., 1982a; Dharma et al., 1982; Domino
et al., 1982; Render et al., 1982; Millis et al., 1985a). In some
cases, it was not clear whether the differences in partitioning
between congeners were real or were caused by analytical problems
(Render et al., 1982).
6.2.1.2 Transfer to offspring
1) Mammals
Placental transfer
PBBs are capable of passing through the placental barrier into
the developing fetuses. This has been demonstrated in mice (Corbett
et al., 1978a; Welsch & Morgan, 1985), rats (Beaudoin, 1977; Rickert
et al., 1978), guinea-pigs (Ecobichon et al., 1983), minks and
ferrets (Bleavins et al., 1981), cows (Detering et al., 1975; Fries
et al., 1978a,b), and pigs (Werner & Sleight, 1981) by administering
the Fire-Master(R)-mixture or individual PBBs, or by using
technical octabromobiphenyl in rats (Aftosmis et al., 1972a; Waritz
et al., 1977).
The studies compiled in Table 51 are rarely intercomparable.
However, it is obvious that PBBs are readily transferred across
placental membranes, the concentrations among fetal tissues being
highest in the liver. The limited data on the distribution of PBBs
in fetal tissues showed often, but not always (Ecobichon et al.,
1983; Welsch & Morgan, 1985), lower PBB residues in fetal than in
maternal tissues (see Table 51). In cows, the average ratio of PBB
concentrations in fetal or calf tissue to PBB concentrations in dam
tissue was 0.36 : 1 for fat and 0.37 : 1 for blood (Fries et al.,
1978a,b). In contrast, the concentration ratio between the fetal and
maternal liver of mice ranged from 3.5:1 to 10:1 (Welsch & Morgan,
1985).
Species-dependent differences in the amounts of PBBs
transferred have been demonstrated for two mustelids, the mink and
the European ferret. PBB levels in the ferret kit were significantly
greater than those in the mink kit (see Table 51: Bleavins et al.,
1981).
Table 51. Placental transfer: PBB concentrations in the fetus and the mother
PBB concentrations
Species Dosing regimena Maternal Whole Fetalb Concentration References
adipose liver others fetus adipose liver others expressed as:c
Mouse FireMaster(R) BP-6; 39.52 2.51 - 0.53 [HxBB] Corbett
(mg/kg) et al. (1975)
1000 mg/kg diet
on days 7-18 of
pregnancy
0 mg/kg (control) 0.04 0.05
Mouse FireMaster(R) BP-6; 112.74 12.02 - 0.95 - 5.86 - [HxBB] Corbett
(mg/kg) et al.
100 mg/kg diet (1978a)
on days 7-18 of
pregnancy
Mouse 2,2',4,4',5,5'- [HxBB] Welsch &
hexabromobiphenyl (mg/kg) Morgan (1985)
(purity: > 99%)
dietary intake
from day 6-15 of
pregnancy; sacrifice
on day 17
placenta:
100 mg/kg feed 9.08 17.26 3.79 3.06 182.88
300 mg/kg feed 17.30 39.84 8.23 4.56 217.48
500 mg/kg feed 69.13 89.47 24.58 17.64 316.79
750 mg/kg feed 95.36 103.70 54.33 18.64 453.12
Table 51 (contd).
PBB concentrations
Species Dosing regimena Maternal Whole Fetalb Concentration References
adipose liver others fetus adipose liver others expressed as:c
Rat FireMaster(R) BP-6 [HxBB] Beaudoin
(mg/kg) (1977)
single oral dose of
800 mg/kg body
weight (in sesame (pooled
oil) at day 12 of samples
pregnancy; killing: 51 267 13 from 4 rats)
24 h later
48 h later 250 248 6
Rat FireMaster(R) BP-6; 330 4.2 - 1.6 0.2 GI tract: [HxBB] Rickert
0.1 (mg/kg) et al. (1978)
50 mg/kg diet from
day 8-21 of
pregnancy
Rat Octabromobiphenyl Waritz
(technical); et al. (1977)
dietary intake
from day 8-15 of
pregnancy; sacrifice
on day 20;
0 mg/kg (control) 1.43 3.56 4.38 [Br]
100 mg/kg 70.4 16.1 7.62 (mg/kg)
1000 mg/kg 326 79.8 21.2
10 000 mg/kg 590 158 30.1
Table 51 (contd).
PBB concentrations
Species Dosing regimena Maternal Whole Fetalb Concentration References
adipose liver others fetus adipose liver others expressed as:c
Mink [14C-]-PBBs (HxBB 0.031 1.622 plasma: 0.002 0 0.005 kidney: % of the Bleavins
and HpBB); iv 0.04 0.003; initial dose et al. (1981)
injection (1 µCi) brain: 0; per g of tissue
in the final intestine: or ml of fluid
trimester of 0.001
gestation; killed
2 h later
Ferret see above 0.124 1.625 plasma: 0.005 0.004 0.013 kidney: see above
0.07 0.010
brain:
0.003
intestine:
0.005
Guinea- FireMaster(R) FF-1; 45 7 kidney: 45 45 kidney: 1 [HxBB] Ecobichon
pig 4.5; (mg/kg) et al. (1983)
single oral dose of lung: 7
50 mg/kg body weight lung: 1.5
at approximately 65
days of gestation;
killed 2 days later
Table 51 (contd).
PBB concentrations
Species Dosing regimena Maternal Whole Fetalb Concentration References
adipose liver others fetus adipose liver others expressed as:c
Pig FireMaster(R) BP-6; Werner &
Sleight (1981)
dietary intake
during 2nd half of
gestation
10 mg/kg feed 0.4 1.0 kidney: [HxBB]
nd; (mg/kg)
brain: nd
100 mg/kg feed 4.9 11.5 kidney:
nd;
brain: nd
200 mg/kg feed 40.3 24.2 kidney: 1.5
brain: 1.8
a HpBB = 2,2',3,4,4',5,5'-heptabromobiphenyl.
b nd = Not detected.
c [HxBB] = Concentration of 2,2',4,4',5,5',-hexabromobiphenyl; [Br] = Concentration of bromide.
Milk transfer
In mammals, the second route of PBB transfer from the mother to
the offspring is nursing. The efficiency of this way has been shown
through determining the PBB content in milk in relation to the body
burden or in relation to exposure levels of contaminated dams, and
through measuring PBB levels in kits that have been exposed to PBBs
only from suckling. The FireMaster(R) mixture was used in all
studies. Mammary transfer of technical octa- or decabromobiphenyl
has not (yet) been assayed.
Most investigations on the PBB contents of milk from
contaminated animals have been conducted on cows (Fries & Marrow,
1975; Willett & Irving, 1976; Robl et al., 1978; Fries et al.,
1978a,b; Willett & Durst, 1978). The ratios of concentrations in
milk fat to body fat in cows no longer receiving PBBs averaged about
0.4 :1 (Willett & Durst, 1978; Fries et al., 1978a,b; see also
Fig. 5). This ratio is much lower than the ratio in humans (see
section 6.2.2).
For other species (guinea-pig, rat, mink, pig) only single data
can be found in the literature. When (lactating) guinea-pigs
received a single oral dose of FireMaster(R) FF-1 (50 mg/kg body
weight) within 6-12 h of parturition, levels of HxBB in breast milk
(and in perirenal adipose tissue) were of the order of 22 µg/g (and
17 µg/g), respectively, 2 days after treatment (Ecobichon et al.,
1983). Rats fed 50 mg FireMaster(R) BP-6/kg in their diet from day
8 of pregnancy until 14 days after delivery showed, on day 14
postpartum, HxBB concentrations of about 51 µg/ml in the milk and
about 483 µg/g wet weight in their body fat (McCormack et al.,
1979a). In the same study, milk transfer of PBBs and PCBs was
compared. Milk usually contained higher concentrations of PCBs than
of PBBs, after simultaneous or separate exposure.
Contrary results were obtained with minks, intraperitoneally
injected with either 3 µCi of 14C-labelled PCB or 3 µCi of 14C-
labelled PBB on the approximate date at which the embryos would have
been implanted (Bleavins et al., 1981). Two weeks postpartum, milk
levels of PBBs were determined to be four times those of PCBs
(0.105% versus 0.025% of the initial maternal dose per gram of
tissue). Werner & Sleight (1981) determined PBB concentrations in
the tissues and milk of sows fed various amounts of FireMaster(R)
BP-6 (Table 53). At the end of lactation (4th week), the adipose
tissue and milk of sows, fed daily with 200 mg PBB/kg feed, had HxBB
concentrations of 194 µg/g tissue (wet weight) and of 22 µg/ml whole
milk, respectively. The authors calculated that, on a body weight
basis, nursing pigs consumed PBBs in concentrations similar to the
concentration given to the sows. Tissue levels of young exposed to
PBBs only via nursing have been determined for rats (Rickert et al.,
1978) and for guinea-pigs (Ecobichon et al., 1983). When pups of
non-treated female rats were nursed by dams fed FireMaster(R) BP-6
(50 mg/kg body weight) on days 1-14 postpartum, hepatic HxBB-
concentrations were on average approximately eight times higher than
those in the dams on day 14 postpartum (Rickert et al., 1978).
When dams of guinea-pigs received a dose of FireMaster(R)
FF-1 on day 1 after delivery, the concentrations of 2,2',4,4',5,5'-
HxBB in the lungs, livers, kidneys, and fat of the pups were similar
to those of the dams for 4-60 days after treatment (Ecobichon
et al., 1983).
Combined placental and milk transfer
Rickert et al. (1978), Bleavins et al. (1981), and Werner &
Sleight (1981) concluded from their studies on rats, minks, and
pigs, respectively, that milk transfer is far more important than
placental transfer; studies on guinea-pigs (Ecobichon et al., 1983)
did not confirm this observation. However, under less controlled
conditions, perinatal exposure (both placental and milk transfer)
occurs and results in a marked body burden in the offspring, as has
been shown in studies on rats (Table 52 and McDaniel & Lucier, 1979)
and pigs (Table 53). From minks, it has been reported that
14-day-old kits of dams that had received a single intraperitoneal
dose of 14C-PBB at an early stage of pregnancy, contained about 3%
of the initial maternal dose (Bleavins et al., 1981). PBB body
burdens in the offspring of rats were still measurable at 328 days
of age and at the end of their life span (see Table 52).
Moreover, a multigeneration study on rats (McCormack et al.,
1981) demonstrated that administration of PBBs to a single
generation resulted in detectable residues in two subsequent
generations (Table 54). The concentrations of PBBs measured in the
tissues of F1-animals were approximately 5-30 times higher than
those in tissues from F2-animals and approximately 50-1000 times
higher than those in tissues from F3-animals (see Table 54).
2) Birds
In birds, eggs are the medium of PBB transfer to the offspring.
The ratio of egg PBB contents to dietary level has been reported to
be 1 : 1 (Fries et al., 1976) and 1.3 - 1.5 : 1 (Babish et al.,
1975a; Ringer & Polin, 1977; Cecil & Bitman, 1978; Polin & Ringer,
1978a) in chickens (White Leghorn hens) and Japanese quail,
respectively. After 63 days of feeding FireMaster(R) BP-6 in the
diet, the PBB level in body fat of White Leghorn hens was about 4
times the level in eggs (Fries et al., 1976).
6.2.2 Human studies
Studies on the distribution of PBBs in humans refer only to
people having been exposed in a direct or indirect way to the
FireMaster(R)-mixture.
As can be seen from a post-mortem study on people from a "high"
exposure area of the State of Michigan (USA), PBBs are distributed
throughout the entire human body (Table 55). Moreover, it was found
that fat and fat-rich tissue had the highest HxBB concentrations.
Perirenal fat had the highest mean concentration (475 ng/g).
Adrenal, atheromatus aorta, and thymus had mean concentrations of
about half that of perirenal fat; all other tissues had mean
concentrations of only one-tenth or less of that of perirenal fat
(Miceli et al., 1985).
Table 52. Tissue concentrations of PBBs in rats following perinatal exposure to PBBs (FireMaster(R)-mixture BP-6 or FF-1)
Dosing regimen to dams Age of Tissue concentrations of PBBsa (mg/kg wet weight) References
offspring
Offspring Dams
50 mg BP-6/kg diet: day 8 of 14 days liver carcass liver Rickert et al.
gestation through day 14 9.5 149.7 4.0 (1978)
postpartum
100 mg PB-6/kg diet: day 8 of liver kidney fat b McCormack et al.
pregnancy through 28 days 28 days 397 96 1693 (1980)
postpartum 328 days 17 11 387
BP-6 (lot 6244 A) in the diet: 28 days lung liver kidney fat b McCormack et al.
day 8 of pregnancy through (1982a)
28 days postpartum:
10 mg/kg 5 18 8 162
100 mg/kg 32 410 109 1693
200 mg FF-1/kg body weight liver: liver: liver Groce &
(in corn oil; by stomach tube): (female) (male) Kimbrough (1984)
day 7 and 14 of pregnancy 2 months 2.4 (218)c 3.0 (280)c 7.8 (542)c
(weaning at day 21 of age) 2 years 0.8 (107)c 0.6 (58)c
a Concentration expressed as the concentrations of 2,2',4,4',5,5'-hexabromobiphenyl.
b See McCormack & Hook (1982) and Table 48.
c Values calculated on a lipid basis.
Table 53. Mean concentrations of PBBs (mg/kg of tissue, wet weight) in tissues of sows and
4-week-old nursing pigs following perinatal exposure to PBBsa
PBBsb Liver Adipose tissue Kidney Brain
(mg/kg feed) Sows Pigs Sows Pigs Sows Pigsc Sows Pigsc
10 1.0 2.4 15.2 14.8 0.6 nd 0.2 nd
100 45.8 30.2 96.3 96.7 2.3 nd 1.7 nd
200 92.6 41.3 194.2 222.5 3.7 4.1 2.7 4.2
a From: Werner & Sleight (1981).
b FireMaster(R) BP-6 fed to the sows during the second half of gestation and during lactation.
c nd = Not detected.
Table 54. Tissue concentrations of PBBs in several generations of rats following perinatal exposure to PBBsa,b,c
Treatment Liver Kidney Lung Thyroid Testis Ovary Fat
Control < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1
F1-10 17.1 ± 3.6 7.5 ± 0.6 5.1 ± 0.8 4.4 ± 1.0 8.2 ± 5.3 24.0 ± 1.6 161.7 ± 24.2
F2-10 0.4 ± 0.1 0.6 ± 0.2 0.9 ± 0.1 0.5 ± 0.1 0.2 ± 0.1 3.0 ± 0.5 6.7 ± 1.9
F1-100 410.2 ± 40.6 108.6 ± 11.2 32.4 ± 2.0 162.6 ± 20.8 -d -d 1693.2 ± 250.4
F2-100 21.8 ± 3.2 7.2 ± 1.3 8.7 ± 1.0 2.7 ± 0.6 1.8 ± 0.11 6.5 ± 2.6 159.5 ± 16.9
F3-100 0.4 ± 0.1 0.8 ± 0.4 0.6 ± 0.1 0.2 ± 0.1 0.3 ± 0.1 0.6 ± 0.1 4.9 ± 0.8
a From: McCormack et al. (1981).
b Rats were fed 0,10, or 100 mg PBBs (FireMaster(R) BP-6)/kg from day 8 of pregnancy until 28 days postpartum at which
time all offspring (F1-10 and F1-100) were weaned on to a control diet, allowed to mature sexually, and bred with
littermates to produce the F2-generation (F2-10 and F2-100). F2-100 littermates were bred to produce F3-100 animals.
c Values are means in mg 2,2',4,4',5,5'-hexabromobiphenyl/kg wet tissue ± SE for at least three animals at 28 days of age.
d Sample not available.
Most of the distribution studies performed with living subjects
used paired samples of serum, adipose tissue (fat biopsy technique,
e.g., Daum et al., 1978), and breast-milk (see Tables 56, 57 and
58). Other tissues or fluids have rarely been analysed for PBB
content, e.g., there is one report on liver biopsy tissue (300 µg
HxBB/kg), fat (1069 µg/kg), bone marrow (3.5 µg/kg) and synovial
fluid (twice the amount present in serum) of a single person
(Meester & McCoy, 1976).
In some early investigations, serum (plasma, resp.) and adipose
tissue levels (Table 56) or serum (plasma, resp.) and breast-milk
levels (Table 57) did not seem to correlate well with each other.
Later studies, performed when continuing exposure had ceased
(Anderson, 1985), did reveal good correlations between serum and
adipose levels (Table 56) and between breast-milk and serum or
adipose tissue levels (Tables 57 and 58). The PBB concentrations
measured are compiled in section 5.2 and 5.3.
Different groups of the population can differ in their ratios.
For example, lowest adipose to serum ratios were found in lactating
and pregnant females (see Table 56). Eyster et al. (1983) found
statistically different ratios for females and male chemical workers
versus farm workers and ot