INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 54
AMMONIA
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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.
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the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
World Health Orgnization
Geneva, 1986
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR AMMONIA
1. SUMMARY
1.1. Properties and analytical methods
1.2. Sources in the environment
1.3. Environmental transport, distribution and transformation
1.4. Environmental levels and human exposure
1.5. Kinetics and metabolism
1.5.1. Uptake and absorption
1.5.2. Distribution
1.5.3. Metabolic transformation
1.5.4. Excretion and turnover
1.5.5. Plant metabolism of ammonia
1.6. Effects on aquatic organisms
1.7. Effects on experimental animals and in vitro test systems
1.7.1. Single exposures
1.7.2. Short-term exposures
1.7.3. Skin and eye irritation; sensitization
1.7.4. Long-term exposure
1.7.5. Reproduction, embryotoxicity, and teratogenicity
1.7.6. Mutagenicity
1.7.7. Carcinogenicity
1.7.8. Mechanisms of toxicity
1.8. Effects on man
1.8.1. Organoleptic effects
1.8.2. Clinical, controlled human studies and accidental
exposure
1.8.3. Endogenous ammonia
1.9. Evaluation of the health risks for man and effects on the
environment
1.10. Conclusions
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Physical and chemical properties of ammonia and ammonium
compounds
2.1.1. Gaseous and anhydrous liquid ammonia
2.1.2. Aqueous solutions
2.1.3. Chemical reactions
2.1.4. Ammonium compounds
2.2. Sampling and analytical methods
2.2.1. Air and water samples
2.2.2. Soil samples
2.2.3. Blood and tissue samples
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Production and use
3.2. Sources releasing ammonia into the air
3.3. Sources discharging ammonia into water
3.3.1. Point sources of ammonia
3.3.2. Non-point sources of ammonia
3.3.3. Comparison between point and non-point sources
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Uptake and transformation in atmosphere
4.2. Transport to the earth's surface
4.2.1. Wet and dry deposition
4.2.2. Contribution to acid rain
4.3. Transformation in surface water
4.4. Uptake and transformation in soils
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Atmospheric levels
5.1.2. Levels in water
5.1.3. Levels in soil
5.1.4. Food
5.1.5. Other products
5.2. General population exposure
5.2.1. Inhalation
5.2.2. Ingestion from water and food
5.2.3. Dermal exposure
5.3. Occupational exposure
5.4. Exposure of farm animals
5.4.1. Oral exposure
5.4.2. Inhalation exposure
6. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
6.1. Microorganisms
6.2. Plants
6.2.1. Terrestrial plants
6.2.2. Aquatic plants
6.2.3. Fresh-water plants
6.2.4. Salt-water plants
6.3. Aquatic invertebrates
6.3.1. Fresh-water invertebrates: acute toxicity
6.3.2. Fresh-water invertebrates: chronic toxicity
6.3.3. Salt-water invertebrates: acute and chronic toxicity
6.4. Fish
6.4.1. Ammonia metabolism in fish
6.4.1.1 Ammonia production and utilization
6.4.1.2 Ammonia excretion
6.4.2. Fish: acute toxicity
6.4.2.1 Salt-water fish
6.4.3. Factors affecting acute toxicity
6.4.3.1 pH
6.4.3.2 Temperature
6.4.3.3 Salinity
6.4.3.4 Dissolved oxygen
6.4.3.5 Carbon dioxide
6.4.3.6 Prior acclimatization to ammonia
6.4.4. Fish: chronic toxicity
6.5. Wild and domesticated animals
6.5.1. Wildlife
6.5.2. Domesticated animals
6.5.2.1 Oral exposure
6.5.2.2 Inhalation exposure
7. KINETICS AND METABOLISM
7.1. Absorption
7.1.1. Respiratory tract
7.1.2. Gastrointestinal tract
7.1.3. Skin and eye
7.2. Distribution
7.2.1. Human studies
7.2.2. Animal studies
7.3. Metabolic transformation
7.4. Reaction with body components
7.5. Elimination and excretion
7.5.1. Expired air
7.5.2. Urine and faeces
7.6. Retention and turnover
7.7. Uptake and metabolism in plants
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
8.1. Single exposures
8.1.1. Inhalation exposure
8.1.2. Oral exposure
8.1.2.1 Effects of metabolic acidosis induced by
ammonium chloride
8.1.2.2 Organ effects following oral
administration
8.1.2.3 Influence of diet on the effects of
ammonia
8.1.3. Dermal exposure
8.1.4. Effects due to parenteral routes of exposure
8.1.4.1 Lethality
8.1.4.2 Central nervous system effects
8.1.4.3 Effects on the heart
8.2. Short-term exposures
8.2.1. Inhalation exposure
8.2.2. Oral exposure
8.2.2.1 Histopathological effects
8.2.2.2 Effects of ammonium as a dietary nitrogen
supplement
8.2.3. Dermal exposure
8.3. Skin and eye irritation; sensitization
8.4. Long-term exposures
8.4.1. Inhalation exposure
8.4.2. Oral exposure
8.5. Reproduction, embryotoxicity, and teratogenicity
8.6. Mutagenicity
8.7. Carcinogenicity
8.8. Factors modifying effects
8.8.1. Synergistic effects
8.8.2. Antagonistic effects
8.9. Mechanisms of toxicity
9. EFFECTS ON MAN
9.1. Organoleptic aspects
9.1.1. Taste
9.1.2. Odour
9.2. Clinical and controlled human studies
9.2.1. Inhalation exposure
9.2.2. Oral exposure
9.2.2.1 Effects of acute oral exposure
9.2.3. Endogenous hyperammonaemia
9.2.3.1 Inborn errors of metabolism
9.2.3.2 Hepatic features
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Atmospheric exposure and effects
10.1.1. General population exposure
10.1.2. Occupational exposure
10.2. Exposure through food and water
10.3. Ocular and dermal exposure
10.4. Accidental exposure
10.5. Evaluation of risks for the environment
10.5.1. The aquatic environment
10.5.2. The terrestrial environment
10.6. Conclusions
10.6.1. General population
10.6.2. Sub-populations at special risk
10.6.3. Occupational exposure
10.6.4. Farm animals
10.6.5. Environment
11. RECOMMENDATIONS
11.1. Research needs
REFERENCES
ANNEX I
REFERENCES TO ANNEX I
ANNEX II
WHO TASK GROUP ON AMMONIA
Members
Professor E.A. Bababunmi, Department of Biochemistry, University of
Ibadan, Ibadan, Nigeria (Chairman)
Dr J.R. Jackson, Albright and Wilson, Ltd., Occupational Health and
Hygiene Service, Warley, United Kingdom (Rapporteur)
Professor I. Kundiev, Research Institute of Labour, Hygiene, and
Occupational Diseases, Saksaganskogo, Kiev, USSR
Dr M. Piscator, Department of Environmental Hygiene, Karolinska
Institute, Stockholm, Sweden
Professor D. Randall, Department of Zoology, University of British
Columbia, Vancouver, British Columbia, Canada
Dr V.R. Rao, Department of Toxicology, Haffkine Institute, Parel,
Bombay, India
Dr J.A.A.R. Schuurkes, Laboratory of Aquatic Ecology, Faculty of
Natural Sciences, Catholic University, Nijmegen, The Netherlands
Dr J.R. Stara, Office of Research and Development, US Environmental
Protection Agency, Cincinnati, Ohio, USA
Dr H. Suzuki, Department of Hygiene, Fukushima Medical College,
Fukushima, Japan
Dr R.V. Thurston, Fisheries Bioassay Laboratory, Montana State
University, Bozeman, Montana, USA
Dr E. Weisenberg, Institute for the Standardization and Control of
Pharmaceuticals, Ministry of Health, Jerusalem, Israel
(Vice-Chairman)
Secretariat
Dr E. Smith, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland (Secretary)
Mrs I.-M. Linquist, Occupational Safety and Health Branch,
International Labour Office, Geneva, Switzerland
Dr C. Xintaras, Office of Occupational Health, World Health
Organization, Geneva, Switzerlanda
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a Attended half day only.
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Every effort is made to present information in the criteria
documents as accurately as possible. In the interest of all users
of the environmental health criteria documents, readers are kindly
requested to communicate any errors that may have occurred to the
Manager of the International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland, in order that they may be
included in corrigenda, which will appear in subsequent volumes.
* * *
A data profile and information on the various limits set by
countries can be obtained from the International Register of
Potentially Toxic Chemicals, Palais des Nations, 1211 Geneva 10,
Switzerland (Telephone No. 988400 - 985850).
Concentrations in this document are expressed in the terms used
in original references.
1 mmol is equivalent to 14 mg ammonia-nitrogen/litre
17 mg NH3/litre
18 mg NH4+/litre
1 mg ammonia-nitrogen is equivalent to 1.21 mg NH3
1.29 mg NH4+
In air, 1 mg/m3 is equal to about 1.42 ppm, depending on the
temperature and pressure.
ENVIRONMENTAL HEALTH CRITERIA FOR AMMONIA
Following the recommendations of the United Nations Conference
on the Human Environment held in Stockholm in 1972, and in response
to a number of resolutions of the World Health Assembly and a
recommendation of the Governing Council of the United Nations
Environment Programme, a programme on the integrated assessment of
the health effects of environmental pollution was initiated in
1973. The programme, known as the WHO Environmental Health
Criteria Programme, has been implemented with the support of the
Environment Fund of the United Nations Environment Programme. In
1980, the Environmental Health Criteria Programme was incorporated
into the International Programme on Chemical Safety (IPCS), a joint
venture of the United Nations Environment Programme, the
International Labour Organisation, and the World Health
Organization. The Programme is responsible for the publication of
a series of criteria documents.
A WHO Task Group on Environmental Health Criteria for Ammonia
was held in Geneva on 8-13 July, 1985. Dr E.M. Smith opened the
meeting on behalf of the Director-General. The Task Group reviewed
and revised the draft criteria document and made an evaluation of
the health risks of exposure to ammonia.
The original draft of this document was prepared by THE UNITED
STATES ENVIRONMENTAL PROTECTION AGENCY ENVIRONMENTAL CRITERIA AND
ASSESSMENT OFFICE under the direction of DR J.F. STARA. Additional
contributions were made by DR J.R. JACKSON, PROFESSOR D. RANDALL,
and DR R.V. THURSTON.
The efforts of these contributors and of all who helped in the
preparation and finalization of the document are gratefully
acknowledged.
* * *
Partial financial support for the publication of this criteria
document was kindly provided by the United States Department of
Health and Human Services, through a contract from the National
Institute of Environmental Health Sciences, Research Triangle Park,
North Carolina, USA - a WHO Collaborating Centre for Environmental
Health Effects.
1. SUMMARY
1.1. Properties and Analytical Methods
Ammonia (NH3) is a colourless acrid-smelling gas at ambient
temperature and pressure. It can be stored and transported as a
liquid at a pressure of 10 atm at 25 °C.
Ammonia dissolves readily in water where it forms, and is in
equilibrium with, ammonium ions (NH4+). The sum of ammonia and
ammonium concentrations is termed "total ammonia" and, because of
the slightly different relative molecular masses, may be expressed
as "total ammonia-nitrogen (NH3-N)". In most waters, NH4+
predominates, but increases in pH or temperature or decreases in
ionic strength may materially increase levels of non-ionized
ammonia.
Ammonia will adsorb on various solids. At concentrations of
between 16 and 27% by volume, it can form explosive mixtures with
air. Catalytic oxygenation is an important reaction in the
manufacture of nitric acid. Ammonia dissolves in dilute acids to
form ionized ammonium salts, which are similar in solubility to
alkali metal salts, and can be crystallized. Some of these salts
are found in nature. Heating solutions or crystals of the salts
yields gaseous ammonia. Ammonia forms chloramines in water
containing hypochlorous acid.
There are difficulties in sampling media for the determination
of ammonia, and in preventing contamination and losses before
analysis. A variety of analytical techniques are available; many
have interactions. For measurements, the flourescent
derivatization technique has advantages.
1.2. Sources in the Environment
Ammonia is present in the environment as a result of natural
processes and industrial activity, including certain types of
intensive farming. Atmospheric ammonia is volatilized from the
earth's surface in quantities of about 108 tonnes/year, mostly from
natural biological activity. Industrial activity may cause local
and regional elevations in emission and atmospheric concentrations.
Surface waters receive ammonia from point sources, such as effluent
from sewage treatment and industrial plants, in quantities
estimated in the USA to be about half a million tonnes annually.
Much more significant quantities arise from non-point sources, such
as atmospheric deposition, the breakdown of vegetation and animal
wastes, applied artificial fertilizers and urban runoff, and these
are significant, even in industrial areas.
1.3. Environmental Transport, Distribution, and Transformation
Ammonia in the environment is a part of the nitrogen cycle. It
volatilizes into the atmosphere where it may undergo a variety of
reactions. Photolytic reactions destroy some of the ammonia and
reactions with sulfur dioxide or ozone produce aerosols, most
importantly of ammonium sulfate or nitrate, which return to the
earth's surface as wet or dry deposition. In surface waters,
ammonium may undergo microbiological nitrification, which yields
hydrogen and utilizes oxygen so that, in certain systems,
acidification and oxygen depletion may result. In one study, one-
third of the acidifying effect of precipitation was attributed to
ammonium deposition. Ammonia may be assimilated by aquatic plants
as a nitrogen source or transferred to sediments or volatilized.
In soil, major sources of ammonia are the aerobic degradation of
organic matter and the application and atmospheric deposition of
synthetic fertilizers. The ammonium cation is adsorbed on
positively charged clay particles and is relatively immobile. Most
ammonium undergoes nitrification; the nitrate ion is mobile and is
removed by leaching, plant root uptake, or denitrification.
1.4. Environmental Levels and Human Exposure
Atmospheric concentrations vary according to underlying land
usage. Urban concentrations are typically in the range of 5 -
25 µg/m3 and rural concentrations, 2 - 6 µg/m3. Areas with
intensive manure production or use may produce concentrations of
100 - 200 µg/m3. Particulate ammonium concentrations above oceans,
remote from land, have been found to be 10 - 115 ng/m3. In most
situations, atmospheric particulate ammonium concentrations are
comparable to gaseous ammonia concentrations.
Surface waters contain concentrations of total ammonia that
vary both regionally and seasonally. In the USA, most surface
waters contain less than 0.18 ng/litre, though those near large
metropolitan areas may contain 0.5 ng/litre, as total ammonia. In
hydrologically isolated acidified small lakes, concentrations may
reach 3 mg NH4+-N/litre, and values near intensive farms of 12 mg
NH4+-N/litre have been recorded. Ground water usually contains low
concentrations of ammonia, because of ammonium adsorption and/or
nitrification; this, and the conversion of ammonia to chloramines
on chlorination, results in low levels of ammonia in most treated
drinking-water.
Ammonia in soil is largely fixed; that in solution is in
dynamic equilibrium with nitrate and is not directly available to
plants. Ammonia occurs in unprocessed foods, but ammonium salts
are added to processed foods. Acceptable Daily Intakes (ADIs),
where specified, relate to the anion. Cigarette smoking and
certain medicines may contribute to intake, in some cases, but the
intake from all sources is small in comparison with endogenous
intestinal ammonia production.
Occupational exposure to low levels of ammonia is common, but,
in certain occupations, work-place concentrations may exceed
100 mg/m3. At such levels, the daily ammonia intake is small in
relation to endogenous production, but it is significant, since
inhaled ammonia enters the systemic circulation.
1.5. Kinetics and Metabolism
1.5.1. Uptake and absorption
At low concentrations, inhaled ammonia dissolves in the mucous
fluid lining the upper respiratory tract and little reaches the
lower airways. Initial retention is about 80% in both the dog and
man, but, in man, it falls to less than 30% in less than 27 min.
In rats, increases in blood-ammonia were measured following short-
term exposure to ammonia at 220 mg/m3 but not at 23 mg/m3. The
increases were less marked with longer exposure. Calculated blood-
ammonia increases with exposure to air containing 18 mg/m3 are
about 10% of fasting levels.
Ammonia is formed in the human intestinal tract by the
biological degradation of nitrogenous matter, including secreted
urea, in quantities of about 4 g/day. Nearly all of this is
absorbed (mainly passively) and is metabolized in the liver on
first passage, so that only small amounts reach the systemic
circulation.
1.5.2. Distribution
Ammonia is normally present in all tissues constituting a
metabolic pool. Its distribution is pH dependent, since NH3
diffuses more easily than NH4+. Oral administration of ammonium
chloride to healthy male and female volunteers at 9 mg/kg body
weight produced transient increases in blood-ammonia in about half
of the subjects. Patients with cirrhosis showed a greater and more
prolonged increase over a higher baseline. This confirms
substantial first pass metabolism in the liver.
Administration of 15N-labelled ammonium compounds to
experimental animals indicated that the initial distribution of 15N
depended on the route of administration and that, after parenteral
administration, more was distributed to organs other than the
liver.
1.5.3. Metabolic transformation
Ammonia is taken up by glutamic acid in many tissues, and this
will take part in a variety of transamination and other reactions,
the nitrogen being incorporated in non-essential amino acids. In
the liver, ammonia is used in the synthesis of protein by the
Krebs-Henseleit cycle.
1.5.4. Excretion and turnover
The principal means of ammonia excretion varies between phyla.
Mammals excrete urea and secrete ammonium in the kidney tubules as
a means of hydrogen ion excretion. Faecal and respiratory
excretion are insignificant. Exhaled air may contain volatilized
ammonia from the microfloral degradation of salivary urea. In man,
on a 70 g protein/day diet, 70% of administered ammonium 15N is
lost in a week; on a 20 g protein/day diet, 35% is lost.
1.5.5. Plant metabolism of ammonia
Ammonia is toxic in plants and cannot be excreted. It is
detoxified by combination with carbon skeletons, and so excess
ammonia may strain carbohydrate metabolism. Some plants have
special means of handling ammonia, enabling them to tolerate it or
use it preferentially.
1.6. Effects on Aquatic Organisms
Concentrations of ammonia that are toxic for aquatic animals
are generally expressed as non-ionized ammonia (NH3), because, in
the environment, NH3 and not the ammonium ion (NH4+) has been
demonstrated to be the principal toxic form of ammonia.
Concentrations of ammonia, acutely toxic for fish, can cause
loss of equilibrium, hyperexcitability, increased breathing,
cardiac output, and oxygen uptake, and, in extreme cases,
convulsions, coma, and death. At lower concentrations, ammonia
produces many effects in fish including a reduction in egg hatching
success, a reduction in growth rate and morphological development,
and pathological changes in the tissue of the gills, liver, and
kidney.
Several factors have been shown to modify acute ammonia
toxicity in fresh water. Some factors alter the concentration
of NH3 in the water by affecting the aqueous ammonia equilibrium,
while other factors affect the toxicity of NH3 itself, either
ameliorating or exacerbating its effects. Factors that have been
shown to affect ammonia toxicity include dissolved oxygen
concentration, temperature, pH, previous acclimatization to
ammonia, fluctuating or intermittent exposures, carbon dioxide
concentration, salinity, and the presence of other toxic
substances. The best studied of these is pH; the acute toxicity
of NH3 has been shown to increase as pH decreases. Data on
temperature effects on acute NH3 toxicity are limited and
variable, but there are indications that NH3 toxicity is greater
at low (< 10 °C) temperatures.
Data concerning concentrations of NH3 that are toxic for fresh-
water phytoplankton and vascular plants, although limited, indicate
that fresh-water plant species are appreciably more tolerant to NH3
than invertebrates or fish.
(a) Fresh-water organisms
Mean 48- and 96-h LC50 values reported for fresh-water
invertebrates and fish ranged from 1.10 to 22.8 mg NH3/litre for
invertebrate species, and from 0.56 to 2.48 mg/litre for fish
species. Mean 96-h LC50 values ranged from 0.56 to 2.37 mg
NH3/litre for salmonid fish and from 0.76 to 2.48 mg/litre for non-
salmonids. In terms of LC50, Percidae and Salmonidae are
considered to be the most sensitive families and walleye and
rainbow trout are the most sensitive species within these families.
For fresh-water organisms, the families most sensitive in terms
of chronic toxicity are Salmonidae and Catostomidae, pink salmon
and white sucker being the most sensitive species within these
families. Limited chronic toxicity data for invertebrates, mostly
cladocerans and one insect species, indicate that they are
generally more tolerant than fish, although the fingernail clam
appears to be as sensitive as salmonids.
(b) Salt-water organisms
Available acute and chronic ammonia toxicity data for salt-
water organisms are very limited. Mean LC50 values for marine
invertebrate species range from 0.94 to 18.3 mg NH3/litre and, for
marine fish species, from 0.32 to 1.31 mg/litre. The prawn,
Macrobrachium rosenbergii, appears to be the most sensitive
invertebrate species tested, and the red drum, the most sensitive
fish species.
1.7. Effects on Experimental Animals and In Vitro Test Systems
1.7.1. Single exposures
There have been many estimates of inhalational toxicity in
which the theoretical relationship between concentration, duration
of exposure, and lethality has been observed. Typical results are
LC50 values in rats ranging from 31 612 mg/m3 for a 10-min exposure
to 11 620 mg/m3 for a 60-min exposure. The corresponding value for
a 2-h exposure was 7600 mg/m3. Exposed mice exhibited avoidance
behaviour at concentrations above 350 mg/m3, and ciliary activity
was arrested above this level in in vitro studies on rabbit
tracheal epithelium. Other effects of exposure include bradypnoea
and bradycardia, changes in various serum-enzyme levels, and
histological changes in the lung. At high concentrations,
convulsions occurred.
There have been a number of studies on the oral toxicity of
various ammonium salts, some of which have been complicated by the
acidity or alkalinity of the preparations used. Median lethal
doses for ammonium sulfamate or sulfate were in the range 3 -
4.5 g/kg body weight in both rats and mice. Ammonium chloride
causes substantial acidosis and has been reported to produce
pulmonary oedema by a different mechanism by gavage, but not by
intraperitoneal injection. There is also evidence that ammonium
ions exert a direct effect on the appetite by their effect on
prepyriform cortical areas. Ammonium chloride, even after
administration for periods of a few days, produces hypertrophy of
the kidney, but the extent to which this results from acidosis, a
solute load, or a direct effect of the ammonium ion is not clear.
Diet and the clinical condition of the liver are important
modulators of ammonia toxicity, and it has been shown that the
administration of ornithine, aspartic acid, or adenosine
triphosphate (ATP) exerts a protective effect against ammonia
toxicity.
No information is available regarding systemic toxicity from
single dermal exposures to ammonia or ammonium compounds.
Symptoms after intravenous injection of ammonium salts are
characterized by immediate hyperventilation and clonic convulsions,
followed by either fatal tonic extensor convulsion or the onset of
coma, in which tonic convulsions and death can occur at any time.
After 30 - 45 min, surviving animals recover rapidly and
completely. After injection, neurological symptoms commenced when
the blood-ammonia concentration doubled above basal values. Brain-
ammonia levels did not increase until blood levels reached 20 times
basal values; at this stage, brain levels suddenly increased to
about 100 mg ammonia-nitrogen/kg wet weight. However, immediate
increases in brain-ammonia after intravenous injection have also
been observed, and it has been suggested that there is no critical
blood-ammonia concentration for diffusion of ammonia through the
blood-brain barrier. Some workers have demonstrated the induction
of ventricular fibrillation of the heart following injections of
ammonium salts.
1.7.2. Short-term exposures
Ninety-day inhalation exposures of rats to 127 mg/m3 and
262 mg/m3 did not produce any, or only minimal, changes. Continuous
exposure to 455 mg/m3 was fatal for 50 out of 51 rats by the 69th
day of exposure. Similar results were obtained in guinea-pigs.
The principal pathological findings were eye irritation, corneal
opacities, and diffuse lung inflammation. Similar results have
been published by a number of authors. Concentration-dependent
increases in susceptibility to infection during ammonia exposure
have been reported. Blood-ammonia levels increased with
inhalational exposure to increasing concentrations of ammonia above
70 mg/m3, for periods of 1 - 7 days.
Studies on the effects of ingestion of ammonium chloride
(10 g/litre drinking-water - about 1 g/kg body weight per day)
and ammonium sulfamate (5 g/kg body weight per day for 6 days
per week) did not show any significant toxic effects. Cyclical
administration of various ammonium salts, at moderate doses, for 3
weeks out of 4 affected the reproductive system of virgin female
rabbits. Ammonium salts have been given as a dietary supplement to
animals on diets deficient in non-essential amino acids, with
resultant increases in weight gain. Ammonium salts can prevent and
reduce the weight loss associated with 10% and 20% reduction of the
crude protein content of the diet of pigs.
There is no information regarding the systemic effects of
short-term dermal exposure.
1.7.3. Skin and eye irritation; sensitization
There is little information on animals to complement the
extensive human experience. In rabbits, ammonia has been shown to
penetrate the cornea rapidly and to cause corneal burns. Ammonium
persulfate is a recognized skin sensitizer in man. No data on
sensitization potential in animal models are available.
1.7.4. Long-term exposure
Inhalation exposure studies did not extend beyond 130 days. A
130-day study demonstrated congestion of parenchymatous organs at
18 weeks, but not at 12 weeks, in guinea-pigs exposed to about
119 mg/m3 for 6 h/day, 5 days/week. Long-term studies have not
been carried out according to modern protocols, and observed
effects have mainly been related to changes in acid-base balance.
1.7.5. Reproduction, embryotoxicity, and teratogenicity
There have not been any formal studies based on modern
protocols, but studies have been undertaken to investigate the
effects of ammonia in hen-houses on the egg-laying performance of
intensively reared poultry. No systematic conclusions could be
drawn.
1.7.6. Mutagenicity
Ammonium sulfate has been reported non-mutagenic in Salmonella
and Saccharomyces test systems, but mutagenic in E. coli at toxic
levels and may affect mutagenic responses to other agents. Various
workers have described effects on Drosophila, which were minimal
or achieved only at toxic levels. There is no evidence that ammonia
is mutagenic in mammals.
1.7.7. Carcinogenicity
There is no evidence that ammonia is carcinogenic, though it
can produce inflammatory lesions of the colon and cellular
proliferation, which could increase susceptibility to malignant
change. There was no evidence that ammonia was responsible for the
increased incidence of tumours with increased dietary protein
intake. Ammonia did not either cause tumours or increase the
spontaneous incidence of tumours in life-time studies on mice.
1.7.8. Mechanisms of toxicity
Although there are a number of hypotheses, there is no
established mechanism for the toxicity of ammonia or ammonium
salts.
1.8. Effects on Man
1.8.1. Organoleptic effects
Ammonia can be tasted in water at levels above about 35
mg/litre. Odour thresholds have been variously reported according
to the definition used and technique of measurement. Most people
can identify ammonia in air at about 35 mg/m3 and can detect it at
about one-tenth of this level.
1.8.2. Clinical, controlled human studies and accidental exposure
Exposure to ammonia in air at a concentration of 280 mg/m3
produced throat irritation; 1200 mg/m3 produced cough; 1700 mg/m3
was life-threatening, and more than 3500 mg/m3 caused a high
mortality. Respiratory symptoms were usually reversible, but
chronic bronchitis has been reported to develop. Volunteers
exposed by oro-nasal mask experienced irritation and increased
minute volumes. Retention of inspired ammonia decreased
progressively to about 24% after about 19 min of exposure. The
blood chemistry remained normal. Respiratory indices were
insignificantly altered at concentrations up to 98 mg/m3 (which was
tolerable). Other studies have demonstrated a high incidence of
symptoms at this level. Irritation occurred at 35 mg/m3, which was
neither discomforting nor painful. Industrial exposure at 88 mg/m3
was described as "definitely irritating".
Ingestion of ammonia solutions has produced caustic burns of
the upper gastrointestinal tract. Ingestion of ammonium chloride
produces metabolic acidosis and diuresis and is administered for
these effects.
1.8.3. Endogenous ammonia
Ammonia plays a key role in nitrogen metabolism, and its level
in the body may be increased as a result, either of in-born errors
of metabolism, or, as a result of impaired liver function. The
role of hyperammonaemia in causing the encephalopathy associated
with the latter is not completely clear, but there is sufficient
evidence to indicate a significant contribution.
1.9. Evaluation of the Health Risks for Man and Effects on the
Environment
Atmospheric exposure of the general population is toxicologically
insignificant. Occupational exposure can give rise to symptoms,
particularly in occupations exposed to decaying organic matter.
Accidental exposure to ammonia in any of its forms produces
irritant or caustic effects.
Exposure to ammonia in the water supply and food is
insignificant in comparison with the nitrogen intake through the
diet which becomes available as metabolic ammonia.
The most significant effects of ammonia are in the aquatic and
terrestrial environments where, as a result of urbanization,
industry, and farming and as a result of deposition to sensitive
environments, significant toxic effects of ammonia may arise.
1.10. Conclusions
Ammonia does not present a direct threat to man except as a
result of accidental exposure, particularly in industry. Farm
animals may be adversely affected when reared intensively in closed
conditions. Localized effects of point-source emissions of ammonia
and of deposition in sensitive environments is a cause of concern.
2. PROPERTIES AND ANALYTICAL METHODS
2.1. Physical and Chemical Properties of Ammonia and Ammonium Compounds
2.1.1. Gaseous and anhydrous liquid ammonia
Ammonia (NH3) is a colourless gas at atmospheric pressure,
which is lighter than air and possesses a strong penetrating odour.
Some of the relevant physical properties of ammonia are summarized
in Table 1.
The vapour pressure of ammonia gas over pure ammonia liquid can
be calculated using the equation (NRC, 1979):
log10P = 9.95028 - 0.003863T - 1473.17/T,
where P = partial pressure in mm Hg, and T = temperature at K.
Ammonia may be liquefied under pressure at about 10 atm and is
stored and transported in this state.
2.1.2. Aqueous solutions
Ammonia dissolves readily in water where it ionizes to form the
ammonium ion.
\
NH3 + H2O ========= NH4+ + OH-
\
The solubility of ammonia in water is influenced by the
atmospheric pressure, temperature, and by dissolved or suspended
materials. Solubility values at moderate concentrations and
temperatures can be obtained from the graphic (Sherwood, 1925) and
tabular (Perry et al., 1963) compilations, and from empirical
formulae (Jones, 1973).
The total ammonia content of water is the sum of non-ionized
(NH3) and ionized (NH4+) species. Ammonia is readily soluble in
aqueous systems (Table 1) and, at the pH of most biological
systems, exists predominantly in the ionized form. At low
concentrations, the molarity of total dissolved ammonia is given by
(Drewes & Hales, 1980):
[NH3] + [NH4+] = H[NH3(gas)] + KbH[NH3(gas)],
where [NH3(gas)] is the molar concentration of gas-phase ammonia,
Kb is the dissociation constant given by:
[NH4+] [OH-]
Kb = ------------ = 1.774 x 10-5 (at 25°C)
[NH3]
and H is a Henry's law constant given by (NRC, 1979):
log10H = 1477.8/T - 1.6937
Table 1. Physical properties of ammoniaa
------------------------------------------------------------------
Properties Values
------------------------------------------------------------------
Boiling point at one atm -33.42 °C
Melting point -77.74 °C
Density (liquid) at -33.35 °C and 1 atm 0.6818 gm/cm2
Density (gas) 0.7714 g/litre
Viscosity at -33 °C 0.254 centipoise
Viscosity at 20 °C 9.821 x 109 poise
Refractive index at 25 °C 1.325
Dielectric constant at 25 °C 16.9
Surface tension at 11 °C 23.38 dyn/cm
Specific conductance at -38 °C 1.97 x 10-7 cm-1
Thermal conductivity at 12 °C 5.51 x 10-5 gcal/cm
Vapour pressure at 25 °C 10 atm
Critical temperature 132.45 °C
Critical pressure 112.3 atm
Critical density 0.2362 g/cm3
Solubility in water, 101 kPa
at 0 °C 895 g/litre
20 °C 529 g/litre
40 °C 316 g/litre
60 °C 168 g/litre
------------------------------------------------------------------
a From: Jones (1973) and Windholz et al., ed. (1976).
The pKa for the ammonia/ammonium equilibrium can be calculated at
all temperatures, T(K), between 0 and 50 °C (273 < T < 323) by
the equation (Emerson et al., 1975):
Ka = [NH3] [H+]/[NH4+],
pKa = 0.09018 + 2729.92/T
Theoretically, the fraction (f) of total ammonia that is non-
ionized depends on both water temperature and pH, according to the
preceding and the following equations (Emerson et al., 1975):
(pKa-pH)
f = 1/[10 + 1]
Thus, in water at 0 °C and a pH of 6, less than 0.01% of the total
ammonia present is in the non-ionized form, whereas, at 30 °C and a
pH of 10, 89% of total ammonia is non-ionized.
The above relationship holds in most fresh waters. However,
the concentration of non-ionized ammonia will be lower at the
higher ionic strengths of very hard fresh waters or saline waters.
Using the appropriate activity coefficients, in sea water of ionic
strength = 0.7, the above relationship can be restated as follows
(API, 1981):
(pKa-pH + 0.221)
f = 1/[10 + 1]
At 25 °C, the pKa can be calculated to be 9.24, from the
equation of Emerson et al. (1975). Therefore, at pH 8, and at a
temperature of 25 °C, the above equation shows that 3.31% of the
total ammonia in sea water exists in the non-ionized form. The
corresponding value in fresh water can be calculated to be 5.38%.
Thus, at this pH and temperature, sea water with an ionic strength
of 0.7 would contain 62% as much non-ionized ammonia as fresh
water.
2.1.3. Chemical reactions
Gaseous ammonia is readily adsorbed on certain solids. The
adsorption characteristics of ammonia on metal surfaces are
important in its synthesis and other catalytic reactions (Cribb,
1964). Because of the adsorption of ammonia on charcoal, acid-
impregnated charcoal masks are used for protection against ammonia
gas.
Ammonia can form explosive mixtures with air at atmospheric
temperature and pressure, if present in concentrations of 16 - 27%
by volume. The products of combustion are mainly nitrogen and
water, but small traces of ammonium nitrate (NH4NO3) and nitrogen
dioxide (NO2) are also formed.
Another important reaction involving the oxidation of ammonia
is its catalytic oxidation to nitric oxide (NO) and nitrous oxide
(N2O) (Miles, 1961; Matasa & Matasa, 1968). This reaction is an
important step in the manufacture of nitric acid.
Under normal atmospheric conditions, ammonia does not undergo
any primary photochemical reactions at wavelengths greater than
290 nm.
When exposed to radicals or other photochemically excited
species, ammonia undergoes secondary decomposition:
NH3 + -OH -> -NH2 + H2O
NH3 + O -> -NH2 + -OH
Some of these reactions may be important in the balance of
atmospheric nitrogen.
Ammonia also undergoes decomposition to nitrogen and hydrogen,
when exposed to an electric discharge (Jones, 1973). It reacts
with sulfur dioxide gas to form ammonium sulfate in the atmosphere
(Kushnir et al., 1970).
Aqueous ammonia can take part in substitution reactions with
organic halide, sulfonate, hydroxyl, and nitro compounds, and, in
the presence of metallic catalysts, it is used to produce amino
acids from keto acids. Ammonia reacts with hypochlorous acid
(HOCl) to form monochloramine, dichloramine, or nitrogen
trichloride (Morris, 1967; Lietzke, 1978). The formation of these
N-chloramines depends on the pH, the relative concentrations of
hypochlorous acid and NH3, the reaction time, and the temperature.
When pH values are greater than 8, and when the molar ratio of HOCl
to NH3 is 1:1 or less, the monochloramine predominates. At higher
Cl2:NH3 ratios or, at lower pH values, dichloramine and
trichloramine are formed. These, and various organic chloramines,
are produced during the chlorination of water containing NH3 or
organic amines. The presence of these chloramines may contribute
to the taste and odour of drinking-water, and to various
associated health problems (Morris, 1978).
2.1.4. Ammonium compounds
Ammonium compounds comprise a large number of salts, many of
which are of industrial importance; ammonium chloride, ammonium
nitrate, and ammonium sulfate are produced on a large scale. With
the exception of metal complexes, the ammonium salts are very
similar in solubility to the salts of the alkali metals, but differ
in that they are completely volatilized on heating or ashing.
Ammonium salts undergo slight hydrolysis in aqueous solution.
Most dissociate at elevated temperatures to give ammonia and the
protonated anion. The physical and chemical properties of ammonium
compounds of environmental importance are discussed below, and some
of their physical properties are summarized in Table 2.
Ammonium chloride [NH4Cl] occurs naturally in volcanic
crevices as a sublimation product. When it sublimes, the
vapour is completely dissociated into hydrogen chloride and
ammonia. Like other ammonium salts of strong acids, the
chloride hydrolyses in aqueous solution to lower the pH of the
solution. The solid tends to lose ammonia during storage. Aqueous
solutions of ammonium chloride have a notable tendency to attack
ferrous metal and other metals and alloys, particularly copper,
bronze, and brass. Ammonium chloride can be oxidized to nitrosyl
chloride and chlorine by strong oxidizing agents, such as nitric
acid.
Ammonium nitrate [NH4NO3] does not occur in nature. It is
soluble in water and liquid ammonia and slightly soluble in
absolute ethyl alcohol, methanol, and acetone. Although ammonium
salts of strong acids generally tend to lose ammonia during
storage, ammonium nitrate can be considered a very stable salt. It
undergoes decomposition at elevated temperatures or under extreme
shock, as in commercial explosives. Ammonium nitrate acts as an
oxidizing agent in many reactions, and, in aqueous solution, it is
reduced by various metals. Solutions of ammonium nitrate attack
metals, particularly copper and its alloys.
Ammonium sulfate [(NH4)2SO4] is found naturally in volcanic
craters. It is soluble in water and insoluble in alcohol and
acetone. The melting point of ammonium sulfate is 230 °C. On
heating in an open system, the compound begins to decompose at
100 °C, yielding ammonium bisulfate (NH4HSO4) that has a melting
point of 146.9 °C.
Ammonium acetate [CH3COONH4] is a deliquescent material that is
highly soluble in cold water and in alcohol. Solubility does not
increase greatly with increasing temperature, at least up to 25 °C.
In aqueous solution at atmospheric pressures, ammonium acetate
readily loses ammonia, especially in alkaline conditions.
Ammonium carbonate [(NH4)2CO3] and ammonium bi-carbonate
[NH4HCO3] have long been known because of their occurrence in
association with animal wastes. Ammonium bicarbonate is the more
readily formed and the more stable. It decomposes below its
melting point (35 °C), dissociating into ammonia, carbon dioxide,
and water. Ammonium bicarbonate reacts with, and dissolves,
calcium sulfate scale. Ammonium carbonate decomposes on exposure
to air with the loss of ammonia and carbon dioxide, becoming white
and powdery and converting into ammonium bicarbonate. Ammonium
carbonate volatilizes at about 60 °C. It dissolves slowly in water
at 20 °C, but decomposes in hot water.
2.2. Sampling and Analytical Methods
2.2.1. Air and water samples
Measurement of ammonia levels in air is difficult. Atmospheric
levels are low, and samples can be contaminated by emissions from
man; thus, the analyst should remain remote from the sampling
device. In addition, air samples are bubbled through acid media to
form an aqueous solution of ammonia, predominately in its ionic
form. The extraction of ammonia is variable and both gaseous
ammonia and that contained in aerosols will be extracted. In some
instances filters are used to remove aerosols from the gas stream
so that only ammonia gas is sampled. There are, however, some
problems with aerosol filters as they may interact with gaseous
ammonia when the aerosol is collected on the filter (NRC 1979).
Table 2. Physical properties of some ammonium compoundsa
-----------------------------------------------------------------------------------------------------------------
Property Ammonium Ammonium Ammonium Ammonium Ammonium Ammonium
chloride nitrate sulfate acetate carbonate bicarbonate
-----------------------------------------------------------------------------------------------------------------
Synonyms ammonium ammonium ammonium ammonium ammonium ammonium bicarbonate;
chloride; nitrate sulfate; acetate carbonate; ammonium hydrogen
sal ammoniac mascagnite monohydrate carbonate
Colour colourless colourless colourless white colourless colourless
Physical state cubic rhombic rhombic crystals, cubic rhombic or monoclinic
(25 °C, 1 atm) crystals crystals crystals hygroscopic crystals crystals
Formula NH4Cl NH4NO3 (NH4)2SO4 CH3COONH4 (NH4)2CO3 x H2O NH4HCO3
Relative 53.49 80.04 132.14 77.08 114.10 79.06
molecular mass
Melting point 340 sublimes 169.6 230 114 58 35
(°C) decomposes decomposes decomposes
Boiling point 520 > 210 decomposes sublimes
(°C) decomposes
Density 1.527 (20 °C) 1.725 (25 °C) 1.769 (50 °C) 1.17 (20 °C) 1.58 (20 °C)
Refractive 1.642 1.533 1.423, 1.555
index, nb20
Solubility in 370 (20 °C) 1920 (20 °C) 754 (20 °C) 1480 (4 °C) 1000 (15 °C) 217 (20 °C)
water
(g/litre)
-----------------------------------------------------------------------------------------------------------------
a From: Dean (1979) and Weast (1979).
Air samples collected by liquid impinger yield aqueous
solutions. Fabric filters used for collecting aerosols may be
extracted with water for analysis. Generally, air and water
samples are analysed using similar techniques, which are summarized
in Table 3.
Various methods for preventing interference can be used, but
distillation at pH 9.5 is often carried out. Care must be taken
with water samples to prevent oxidation, volatilization, or
microbiological assimilation of ammonia. Thus, samples should be
acidified and refrigerated in sealed containers (and may be treated
with reagents) and analysed within 24 h (APHA, 1976; NRC, 1979; US
EPA, 1979b; ASTM, 1980; API, 1981; Analytical Quality Control
(Harmonised Monitoring) Committee, 1982).
2.2.2. Soil samples
Soil samples are usually collected by the grab method. To
inhibit microbial activity during transport and storage, reagents
(e.g., mercury (II) chloride) can be added to the soil (NRC, 1979).
Rapid drying at 55 °C, then sealing the samples in air-tight
containers is a more satisfactory method of preservation for
ammonium determination (NRC, 1979), but even this may not prevent
erroneous results, and samples should be analysed soon after sample
collection (NRC, 1979). Analytical methods for the determination
of ammonia and ammonium in soils have been reviewed by NRC (1979).
2.2.3. Blood and tissue samples
The various techniques used for the determination of ammonia in
blood and tissues ultimately incorporate the ammonia detection
methods described in Table 3, but with various conditions, such as
distillation, aeration, and diffusion to minimize interference
(NRC, 1979). Because of the higher protein concentration in
tissues, determination of ammonia is subject to greater glutamine-
caused error than in body fluids (NRC, 1979).
Table 3. Ammonia detection methods
----------------------------------------------------------------------------------------------------------------------
Medium Particular Method Principle Interferants Sensitivity Reference
application
----------------------------------------------------------------------------------------------------------------------
Air silo air NH3 alkalimetric air is drawn through other acidic or 70 - 700 Elkins (1959);
sulfuric acid until alkaline mg/m3 Leithe (1971)
bromophenol indicator contaminants
changes colour; volume
of air is inversely
proportional to
ammonia concentration
Water high titrimetric NH3 in water is distilled 1 - 25 API (1981)
concentrations off into distilled water mg/litre
which is titrated with
acid to a methyl red/
methylene blue end-point
Air Nesslerization NH3/NH4 in dilute amines, cyanate, 14 - 95 Leithe (1971);
sulfuric or boric acid alcohols, aldehyde, mg/m3 air NIOSH (1977)
is reacted with alkaline ketones, colour,
Water mercuric and potassium turbidity, residual 1 - 25 Stern (1968);
iodide solution (Hg I2 x chlorine mg/litre API (1981)
KI); absorbence at 440 nm water
is compared with a
standard curve; distil-
lation can preceed
analysis
Air low indophenol NH3 in solution is monoalkyl amines, 7 - 7000 Leithe (1971)
concentrations reaction reacted with hypochlorite formaldehyde µg/m3
and phenol (slow-warm
reagents)
Water turbidity, colour 10 - 2000 API (1981)
salt (sea water) µg/litre
Air measurement ammonia measurement of ionization mercury, volatile 14 - 2100 Sloan & Morie
of tobacco electrode potential of NH3 --> amines µg/m3 (1974)
smoke (potentiometric) NH+4
----------------------------------------------------------------------------------------------------------------------
Table 3. (contd.)
----------------------------------------------------------------------------------------------------------------------
Medium Particular Method Principle Interferants Sensitivity Reference
application
----------------------------------------------------------------------------------------------------------------------
Water 0.05 - 1400 API (1981)
mg/litre
Air continuous chemiluminescent air is passed through 3.5 - 3500 Spicer (1977)
measurement high- and low-temperature µg/m3
catalytic converters,
which respectively
measure NOx + NH3 and
NOx; NH3 is obtained by
subtraction
Air tobacco gas chromato- gas chromatography with 7 - 70 Sloan & Morie
smoke graphy thermal conductivity mg/m3 (1974)
detector
Air continuous UV spectro- NH3(gas) exhibits several 0.7 - 7 Leithe (1971)
measurement photometry strong absorption bonds mg/m3
between 190 and 230 nm;
absorption in 10 cm
quartz cells at 204.3 nm
has been used (molecular
extinction coefficient =
2790)
Air continuous Fluorescent 1-phthaldehyde 0.07 µg/m3 Abbas & Tanner
measurement derivatization derivatization upwards (1981)
high technique
sensitivity
----------------------------------------------------------------------------------------------------------------------
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
Ammonia is present in the environment as a result of natural
processes and through the industrial activities of man. It is
generally accepted that, of the ammonia present in the atmosphere,
99% is produced by natural biological processes. Ammonia is
continually released throughout the biosphere by the breakdown or
decomposition of organic waste matter. Thus, any natural or
industrial process that concentrates and makes nitrogen-containing
organic matter available for decomposition represents a potential
source of high local concentrations of ammonia in water, air, and
soil. Industrially-produced ammonia, from non-biological nitrogen,
also represents an environmental source, by release through
agricultural fertilization and industrial emissions. Coal
gasification or liquefaction may provide a major local source of
ammonia. The natural occurrence of ammonia compounds is indicated
in section 2.1.4.
3.1. Production and Use
Ammonia is one of the most widely-used industrial chemicals.
It is ranked fourth in production volume in the USA after sulfuric
acid, lime, and oxygen (Chemical and Engineering News, 1980).
Total production of ammonia-nitrogen in the USA increased from
5.8 x 106 tonnes in 1964 to 11.5 x 106 tonnes in 1974 (Keyes,
1975), and had further increased to 17.6 x 106 tonnes by 1979
(Chemical and Engineering News, 1980). The demand in the USA for
the production of ammonia is projected to reach 25 x 106 tonnes by
1990 (Mai, 1977).
Ammonia is mainly produced industrially by the Haber-Bosch
process in which nitrogen and hydrogen are combined under high
pressure in the presence of a catalyst (Harding, 1959; Matasa &
Matasa, 1968). Prior to the Haber-Bosch process, ammonia was
produced by the hydrolysis of cyanamides or cyanides. A smaller
scale method for ammonia production is regeneration from ammonium
salts by heating with a base. Alkaline earth metal oxides and
hydroxides have been used with the naturally-occurring ammonium
chloride.
Most of the ammonia produced in the USA is consumed as
fertilizers (80%), fibres and plastics (10%), and explosives (5%)
(Chemical and Engineering News, 1980). It is also used in the
production of animal feed (1.5%), pulp and paper (0.6%), and rubber
(0.5%) (Keyes, 1975) and in a variety of other chemical production
processes. Ammonia and ammonium compounds are used as cleaning
fluids, scale-removing agents, and in food as leavening agents,
stabilizers, and for flavouring purposes. A survey by the US Food
and Drug Administration (US FDA) indicated that about 6000 tonnes
of ammonium compounds were used in food in 1970 (FASEB, 1974)
comprising ammonium bicarbonate, 317 tonnes; ammonium carbonate,
24 tonnes; ammonium hydroxide, 535 tonnes; monobasic ammonium
phosphate, 52 tonnes; dibasic ammonium phosphate, 434 tonnes; and
ammonium sulfate, 1468 tonnes. Information for ammonium chloride
was not available. The use of ammonium compounds in food nearly
doubled during the period 1960 - 70.
3.2. Sources Releasing Ammonia into the Air
Ammonia is released into the atmosphere by agricultural, waste-
disposal, and industrial activities. Ammonia global release has
been estimated at 113 - 244 x 106 tonnes ammonia-nitrogen/year
(Söderlund & Svensson, 1976). In the USA, industrial emissions
from ammonia and fertilizer production (anhydrous ammonia, aqueous
ammonia, ammonium nitrate, ammonium phosphates, urea), from
petroleum refineries, coke ovens, and sodium carbonate manufacture,
and loss of anhydrous ammonia during distribution, handling, and
application have been estimated to be approximately 328 x 103
tonnes, annually (NRC, 1979; US EPA, 1981). This figure does not
include volatilization of ammonia after soil applications of
nitrogen fertilizer, which may amount to 5 - 10% of the ammonia and
urea fertilizer applied. These losses were estimated to comprise
another 285 x 103 tonnes, annually (US EPA, 1981).
Combustion processes release ammonia as a by-product in amounts
that are dependent on the substance being burned and the conditions
of combustion. Assuming that 2% of the municipal wastes generated
in the USA are incinerated, about 0.8 x 103 tonnes of ammonia would
be emitted annually from this source. On the other hand, fossil
fuel combustion in the USA is estimated to release 783 x 103
tonnes/year (US EPA, 1981).
On the basis of the number of cattle in the USA and an average
excretion of 31 kg urea per animal per year, it has been estimated
that 3400 x 103 tonnes/year of ammonia are produced by cattle in
the USA (API, 1981). Similar calculations made in the Netherlands
on the basis of the manure production of cattle, pigs, and poultry
give a figure of 114 x 103 tonnes/year (Buysman, 1984). Estimates
of atmospheric emissions from the Netherlands and the USA are shown
in Table 4.
It must be emphasized that substantial uncertainties are
associated with these estimates, which are given for rough
comparison only. Ammonia from sources that cannot be quantified
includes that which volatilizes from livestock wastes or polluted
water, and emissions from the combustion of wood. These sources
must be considered in perspective with natural sources, especially
the microbial fixation of nitrogen and the mineralization of
nitrogenous organic matter. Emissions from these natural sources
far outweigh those from man-made sources, on a global scale;
however, man-made sources can result in locally elevated
atmospheric concentrations.
Table 4. Estimated atmospheric emissions of
ammonia in the USA and the Netherlands
--------------------------------------------------
Source Annual emission
(103 tonnes NH3)
----------------------
USAa the Netherlandsb
--------------------------------------------------
animal manure 3400 114 (1)
fertilizer volatilization 285 6.1 - 10.6
industrial activities 1111 7.6
other sources 0.8 0.5
--------------------------------------------------
a From: US EPA (1981).
b From: Buysman (1984).
The very high contribution to ammonia emission from animal
manure production in the Netherlands is remarkable. More than 80%
of the annually emitted ammonia results from the production of
manure on intensive livestock farms and its use as an agricultural
fertilizer. In all areas with intensive livestock farming, ammonia
emission from animal manure production contributes 90 - 99% to the
total NH3 emission. The number of poultry and pigs used in
livestock farms increased 3 - 5 times between 1950 and 1980, and it
can be expected that the ammonia emission from animal manure
production has increased similarly. In only a few areas does most
of the emitted ammonia result from industrial activities, such as
the production of coke and fertilizers, and the combustion of
fossil fuel.
In Denmark, Belgium, and some parts of the Federal Republic of
Germany and France, animal manure production contributes
significantly to atmospheric emissions of NH3 (Buysman et al.,
1985).
3.3. Sources Discharging Ammonia into Water
Ammonia is released into the aquatic environment from a variety
of man-made point source discharges and from natural and man-made
non-point sources.
3.3.1. Point sources of ammonia
Major man-made point sources discharging ammonia into surface
waters include sewage treatment plants, and plants producing
fertilizers, steel, petroleum, leather, inorganic chemicals,
non-ferrous metals, and ferroalloys, and meat processing plants.
Amounts of ammonia discharged annually by these industries in the
USA were estimated to be nearly 5.6 x 105 tonnes (API, 1981)
(Table 5). These estimates show that the industries examined
contribute < 5% of the total ammonia discharged into surface
waters while publicly owned sewage treatment plants (POTWs)
contribute > 95% of the total. It is important to note that the
POTW figure is based on an estimated actual discharge, while
several of the industrial figures are based on Best Practicable
Control Technology (BPT) guidelines and other industrial data.
An estimate of ammonia discharge by sewage treatment plants was
based on an average ammonia concentration of 15 mg/litre in
secondary treatment waste waters (Metcalf & Eddy, Inc., 1972) and a
total discharge of 104 billion litres per day. However, some
sewage treatment plants discharge waste waters containing much
higher ammonia concentrations. Using data from Mearns (1981), the
US EPA (1981) estimated that the mean effluent concentration of
ammonia from 5 major POTWs in southern California was 107 mg NH3-
N/litre (130 mg NH3/litre).
The iron and steel industries release ammonia, as a by-product
of the conversion of coal to coke, and during blast furnace
operations. The source estimate in Table 5 is based on proposed
BPT effluent control limits and steel production data.
The estimated ammonia contribution from the fertilizer industry
was based on 1978 production figures for ammonia, ammonium nitrate,
urea solutions, and urea solids, and on BPT guideline limits. This
contribution may be underestimated because relatively few of these
producers meet BPT limits and because production is increasing (US
EPA, 1981).
The estimated contribution of ammonia for all other industry
groups in Table 5, except the meat processing and leather
industries, was based on production figures and BPT guideline
limits. The effluents of the meat processing and leather
industries were reported to contain about 40 and 100 mg NH3/litre,
respectively (API, 1981).
3.3.2. Non-point sources of ammonia
Non-point sources of ammonia for surface waters are not as easy
to quantify as point sources. Non-point sources include releases
not discharged by a discrete conveyance. They are variable,
discontinuous, diffuse, and differ according to specific land use.
They may be the result of runoff from urban, agricultural,
silvicultural, or mined lands. Urban runoff may sometimes be
considered a point source, as it is frequently collected and
discharged from drainage systems. Several hydrological models are
available to predict runoff and estimate pollutant loading, but
there is still difficulty with this subject. Major non-point
sources of ammonia for surface waters include fertilizer runoff,
animal feedlots, animal wastes spread on the soil, urban runoff,
and precipitation.
Table 5. Estimates of aquatic emissions of ammoniaa from
point sources in the USA
----------------------------------------------------------
Point source Estimated contribution
(tonnes NH3-N/year)
----------------------------------------------------------
Sewage treatment plants (POTWs) 535 922.3b
Steel industry 12 951.0c
Fertilizer industry 5955.9c
Petroleum industry 2826.1c or 2767.2b
Meat processing industry 1099.3b
Leather industry 687.1b
Inorganic chemicals industry 99.8c
Non-ferrous metals manufacturing 0.9c
Ferroalloy manufacturing industry 0.3c
Total 559 542.7 tonnes/year
----------------------------------------------------------
a Adapted from: API (1981).
b Estimated contribution based on reported or estimated
actual discharge concentrations.
c Estimated contribution based on production data and BPT
guidelines, not actual discharges.
The ammonia content of urban runoff is variable, depending, in
part, on specific land use. In a study of urban runoff, the amount
of ammonia present varied with the seasons of the year. Ammonia
concentrations ranged from 0.18 mg N/litre in the autumn to 1.4 mg
N/litre in the early spring (Kluesener & Lee, 1974). In another
study, Struzewski (1971) reported that ammonia-nitrogen in urban
storm water ranged from 0.1 to 2.5 mg/litre.
The ammonia content of rural runoff originates from natural
and man-made sources, including wastes from wildlife and livestock,
decaying vegetation, fertilizer applications, material originally
present in the soil, and precipitation. Estimating total rural
runoff quantities and ammonia concentrations is extremely complex
and no overall estimates are available. Loehr (1974) reported
that the ammonium-nitrogen concentrations in the drainage from 4
forested watersheds ranged from 0.03 to 0.08 mg/litre. The
ammonium-nitrogen concentrations were 8 - 14% of the nitrate-
nitrogen concentrations.
Precipitation is also a significant non-point source of
ammonia. Concentrations may vary locally, reflecting local
atmospheric sources. The average concentration in rainfall at one
rural location on Long Island, New York (0.18 mg NH3-N/litre) was
less than half those at 2 other Long Island sites closer to the New
York urban area (0.43 and 0.459 mg NH3-N/litre) (Frizzola & Baier,
1975). Among collection sites throughout Wisconsin, ammonia levels
in urban rain samples differed little from those in rural samples
not taken near barnyards (range, 0 - 3 mg NH3-N/litre); however,
values for locations near barnyards were 4 - 5 times higher (range
0 - 3 mg NH3-N/litre) indicating contamination from locally-
generated atmospheric ammonia (Hoeft et al., 1972).
Similar tendencies have been observed in the Netherlands,
though the absolute data are much higher. In agricultural areas
with dense livestock farming, ammonia levels ranging from 2.9 mg
NH4+-N/litre near slurry manured croplands to 5.4 mg NH4+-N/litre
at a distance of 100 m from a poultry farm have been found. In
relatively unaffected areas along the northern coast, the average
value was 1.2 mg NH4+-N/litre, because of the relatively high
background levels of atmospheric ammonia. The average
concentration in wet deposition was 2.4 mg NH4+-N/litre (Schuurkes,
in press).
Watershed studies from pristine forests (Fisher et al., 1968),
rural wood and pasture lands (Taylor et al., 1971), and heavily
fertilized crop lands (Schuman & Burwell, 1974) have all shown that
rainfall nitrogen, including ammonia-nitrogen, accounts for a
substantial proportion (50 - 100%) of nitrogen in surface runoff.
3.3.3. Comparison between point and non-point sources
Little information is available for the accurate comparison of
point and non-point sources of ammonia for surface waters. In one
study, Wilkin & Flemal (1980) examined 3 Illinois river basins to
determine the relative sources of various pollution loadings (by
mass balance accounting) and the possible extent of water quality
improvement by controlling various types of sources. The three
river basins, showed differences in point sources, patterns of land
use (which influences non-point sources), and ammonia-nitrogen
concentrations. The east DuPage basin (42% industrial and urban)
contained 4.73 mg NH3-N/litre, the upper Sangamon basin (19% urban
and industrial), 2.51 NH3-N/litre, and the west DuPage basin (2%
urban and industrial), 0.22 mg NH3-N/litre. The fraction of
ammonia-nitrogen load from undefined (non-point) sources in the
heavily-industrialized east branch DuPage was only 0.54 compared
with 0.84 in the rural upper Sangamon. The authors concluded that
much of the pollution loading appeared to be related to undefined
sources and that further restrictions on point-source contributions
might not result in improved water quality.
These data indicate that, although point sources contribute a
large fraction of ammonia loading to surface waters, the
contribution of undefined non-point sources is also significant.
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
Ammonia in the environment is a part of the total biotic and
abiotic nitrogen balance as represented by the nitrogen cycle. The
processes of the nitrogen cycle consist of nitrogen fixation,
assimilation, ammonification, nitrification, and denitrification.
Nitrogen fixation and ammonification are microbially-mediated
processes that produce ammonium ions from nitrogen gas and organic
nitrogen. Assimilation is the uptake and incorporation of
inorganic nitrogen into organic molecules by microbes and plants.
Nitrification is the microbial oxidation of the ammonium ion to
nitrite (NO2-) and nitrate (NO3-). Denitrification converts
nitrate to nitrogen gas or nitrous oxide.
4.1. Uptake and Transformation in Atmosphere
Ammonia enters the atmosphere as a result of both natural and
artificial processes on the Earth's surface; there is no known
photochemical reaction by which ammonia could be produced in the
atmosphere (NRC, 1979). Atmospheric ammonia undergoes four main
types of reaction, namely aqueous-phase reactions, thermal
reactions, photochemical reactions, and heterogeneous reactions.
In the aqueous-phase reactions, oxidation of aqueous sulfur
dioxide in the presence of ammonia results in the formation of
atmospheric ammonium sulfate aerosols. This process is favoured by
high humidity, high ammonia concentrations, and low temperatures
(NRC, 1979).
Thermal reactions involving anhydrous ammonia and sulfur
dioxide may, via heteromolecular nucleation, also result in the
formation of ammonium sulfate aerosols. Thermal reactions of
ammonia with ozone result in the formation of ammonium nitrate, but
the importance of this mechanism in the production of atmospheric
ammonium nitrate aerosols is not known (NRC, 1979).
Photolytic degradation and reaction with photolytically
produced hydroxyl radicals (-OH) in the troposphere are major
pathways for the removal of atmospheric ammonia. While there is
limited information on the relative importance of these different
reactions, it has been suggested that one-half of the atmospheric
ammonia may be destroyed by the reaction with hydroxyl radicals,
with the balance being destroyed by reaction with soot particles or
by deposition (wet and dry) as particulate ammonium (NRC, 1979).
In addition to the formation of ammonium sulfate and nitrate,
various ammonium surface complexes may be formed by the
heterogeneous reaction of atmospheric ammonia with nitric oxide-
soot surfaces in the atmosphere (NRC, 1979). While these
heterogeneous reactions are significant in combustion reactions,
their importance in the atmosphere at much lower concentrations of
both ammonia and soot particles, is not known (NRC, 1979).
Comparison of the findings of Robinson & Robbins (1971) and
Söderlund & Svensson (1976) on global nitrogen balances for ammonia
reveals differences and it is difficult to evaluate which is the
more accurate.
4.2. Transport to the Earth's Surface
Most of the ammonia entering the atmosphere will be transported
back to the earth by both wet and dry deposition. Wet deposition
includes rainfall, snow, hail, fog, and dew, while dry deposition
mainly concerns gaseous ammonia. In the Netherlands, a comparison
has been made between the total emission and total deposition of
ammonia- and ammonium-nitrogen. Almost 95% of the emitted ammonia
(119 x 103 tonnes/year) is deposited back on the surface (van
Aalst, 1984). In this way, ammonia contributes 60 - 90% of the
nitrogen loading of water and soil, with nitrogen oxides making up
the other part.
4.2.1. Wet and dry deposition
A part of the ammonia in the atmosphere is removed by washout
and rainout. Ammonium sulfate aerosols are produced by aqueous-
phase reactions. Thus, wet deposition of ammonia can be estimated
by measuring ammonium concentrations in precipitation. Annual
average concentrations in wet deposition at locations in 21
European countries vary from 0.12 to 1.74 mg NH4+-N/litre (Fuhrer,
1985). In the Netherlands, the mean annual concentration for the
period 1978 - 82 was 2.4 mg NH4+-N/litre, corresponding to a wet
deposition of 12.2 kg/ha per year. The wet deposition in Norway
ranges from 1.3 kg/ha per year in the centre of the country to
8.6 kg/ha per year in the south (calculated from Overrein et al.,
1980). In the United Kingdom, it varies between 3.2 and 6.0 kg/ha
per year (calculated from Warren Spring Laboratory, 1982).
A comparison has been made of the amounts of dry and wet
deposition of ammonia and ammonium per area in the Netherlands.
The data are summarized in Table 6.
Wet deposition plays only a minor part (1/3) in the total
deposition of NH3 and NH4+. On average, 28.4 kg NH3 + NH4+-N is
deposited per ha per year. However, in rural areas with dense
livestock farming, values may reach up to 50 - 100 kg per year.
Table 6. Dry and wet deposition of NH3 + NH+4
per ha per year in the Netherlandsa
------------------------------------------------
mol/ha per year kg/ha per year
------------------------------------------------
dry deposition 1150 16.2
wet deposition 790 12.2
Total 1940 28.4
------------------------------------------------
a From: Van Aalst (1984).
4.2.2. Contribution to acid rain
Although ammonia is a base and thus increases the pH of rain
water, it contributes to the acidifying action of deposition. In
particular, the conversion of ammonium to nitrate appears to be
important in the acidification of soil and water in carbonate-poor
environments (Roelofs, in press; Schuurkes, in press). This
potentially-acidifying action has been implicated in the acid rain
problem in the Netherlands. On average, NH3 contributes about 32%
of the total deposition of potentially-acidifying substances (Table
7).
Table 7. Average deposition of acid
and acidifying substances (acid eq.,/ha
per year) in the Netherlandsa
---------------------------------------
SO2 NOx NH3
---------------------------------------
Total deposition 2750 1310 1940
(46%) (22%) (32%)
---------------------------------------
a From: The Netherlands Ministry of
Housing, Physical Planning, and
Environment (1984).
4.3. Transformation in Surface Water
Nitrification is important in preventing the persistence or
accumulation of high ammonia levels in waters receiving sewage
effluent or runoff. The overall reaction is:
NH4+ + SO2 ---> 2H+ + NO3- + H2O
It occurs in two steps, involving primarily two bacterial genera,
and forming nitrite as an intermediate.
Nitrosomonas
NH4+ ------------> NO2-
Nitrobacter
NO2- -----------> NO3-
The process depends on many factors, including the amount of
dissolved oxygen, temperature, pH, the microbial population, and
the nitrogen forms present. Nitrification is an oxygen-consuming
process, requiring 2 moles of O2 per mole of NH4+ consumed and
yielding hydrogen ion (NRC, 1979). Nitrification may thus lead to
a depletion of dissolved oxygen and acidification, which may, in
turn, inhibit microbiological nitrification (Knowles et al., 1965;
Schuurkes et al., 1985).
Anthonisen et al. (1976) reported that, at high levels of
total ammonia and a high pH, the resulting concentrations of free
ammonia were toxic to both nitrifying forms, but especially to
nitrobacters, occasionally leading to the accumulation of nitrite.
Other authors (Kholdebarin & Oertli, 1977) have reported that high
pH alone, in the absence of ammonia, can inhibit nitrite oxidation.
At high nitrite levels, formation of free nitrous acid caused
inhibition of nitrosomonad bacteria, resulting in the persistence
of both ammonia and nitrite. However, inhibitory conditions and
persistence of reduced forms are usually transient (Anthonisen et
al., 1976), and reports of high nitrite levels are rare (Ecological
Analysts, Inc., 1981).
Other mechanisms also act to remove ammonia from natural
waters. Ammonia is assimilated by aquatic algae and macrophytes
for use as a nitrogen source. Ammonia in water may be transferred
to sediments by adsorption on particulates, or to the atmosphere by
volatilization at the air-water interface. Both processes have
been described as having measurable effects on ammonia levels in
water; however, the relative significance of each will vary
according to specific environmental conditions (API, 1981).
4.4. Uptake and Transformation in Soils
Ammonia levels in soils are a function of the balance between
natural and man-made activities. As a result of aerobic
degradation processes, ammonia is the first inorganic nitrogenous
compound to be released from organic matter together with amines,
which are rapidly converted to ammonia (Powers et al., 1977).
Other important sources of ammonia in soil are fertilizers
(primarily anhydrous ammonia, ammonium nitrate, and urea, which is
rapidly converted to ammonia), wet and dry deposition, and animal
wastes.
The ammonium cation is relatively immobile in soils, because
it is adsorbed on the negatively-charged clay colloids present
in all soils (Wallingford, 1977). Ammonia may be lost from
soils by volatilization, especially after the application of
ammonia fertilizers (Walsh, 1977), sewage, or manures, and by
uptake of ammonium ions into root systems. However, the most
likely fate of ammonium ions in soils is conversion to nitrate by
nitrification. Nitrate is, in turn, lost from soils by: leaching,
which occurs readily, since it is repulsed by the clay particles;
denitrification, which occurs rapidly within a few days or weeks in
warm, moist soils; and by uptake by the plant root system.
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental Levels
5.1.1. Atmospheric levels
Ammonia is present in the atmosphere in very low
concentrations, which vary with underlying land use. In most
situations, urban atmospheres contain more than non-urban, but
certain rural areas, for example, those characterized by intensive
animal husbandry or use of organic manure, have atmospheric ammonia
levels that exceed urban values. Atmospheric ammonia levels also
show a seasonal variation, the highest levels being attained during
the winter and the lowest during the summer months. In urban
areas, the ammonia levels may increase substantially during
pollution episodes. However, they do not show any circadian
patterns.
Urban and non-urban atmospheric levels of ammonia at some
locations around the world are shown in Tables 8 and 9. It can
be seen that ammonia levels of 4 - 5 µg/m3 and 20 µg/m3 are
typical of non-urban and urban sites, respectively. Levels of
particulate NH4+ ions in the atmosphere above the main oceans
(Atlantic, Pacific, Indian, and Antartic) have been studied; in the
southern hemisphere, remote from terrestrial sources, the NH4+
concentrations were found to be between 10 and 115 ng/m3. The
authors concluded that the oceans are a source of ammonia for the
atmosphere (Servant & Delaporte, 1983).
Atmospheric levels of particulate ammonium at some non-urban
and urban locations around the world are shown in Table 10. It can
be seen that concentrations of 1 µg/m3 and 4 - 5 µg/m3 are typical
for non-urban and urban sites, respectively.
5.1.2. Levels in water
The concentration of ammonia in surface waters varies
regionally and seasonally. Wolaver (1972) studied US Geological
Survey data for total ammonia and reported average concentrations
of < 0.18 mg/litre in most surface waters, and around 0.5 mg/litre
in waters near large metropolitan areas. Analysis of data from the
Water Quality Control Information (STORET) System for the years
1972 - 77 (US EPA, 1979a) showed that, although total ammonia-
nitrogen concentrations in surface waters in the USA tended to be
slightly lower during summer months than during winter months, the
percentage of areas in which non-ionized ammonia concentrations
occasionally exceeded 0.02 mg/litre increased from 11% during
winter to 23% during summer; these percentages were higher when
waters had elevated pH values.
Table 8. Urban and industrial atmospheric levels of ammonia in a
few global locationsa
--------------------------------------------------------------------
Location Year Concentration Reference
(µg/m3)
--------------------------------------------------------------------
Germany, Federal
Republic of
Frankfurt-am-Main pre-1963 8 - 20 Georgii (1963)
Italy
Cagliari - 37 - 280 Spinazzola et
(highest conc. al. (1966)
in the vicinity
of port)
Japan
Tokyo - up to 210 (down- TMRI (1971)
wind from two major
pharmaceutical
plants)
Tokyo 1969 4.8 - 25.8 Okita &
Kanamori (1971)
Tsuruga - up to 6.8 FEPCC (1972)
Netherlands
Bilthoven 1983 5 Van Aalst
(1984)
Delft 1979-81 4.4 Van Aalst
(1984)
USA
Seattle, Washington 1975 0.8 - 77.0 Farber &
Rossano (1975)
St. Louis, Missouri 1972-73 up to 17.5 Breeding et al.
(1976)
Five urban sites - 3 - 60 Hidy (1974)
in California (average 20.0)
Chino-Corona area, 1975 up to 315 Pitts &
California (vicinity of Grosjean (1976)
dairy farm)
USSR
Environment of 1967 190 Saifutdinov
metallurgical plant (1966)
West Berlin - up to 97 Hantzsch &
(average 17.6) Lahmann (1970)
--------------------------------------------------------------------
a Adapted from: NRC (1979). Industrial activities include intensive
farming activities.
Table 9. Non-urban atmospheric levels of ammonia in a few global
locationsa
--------------------------------------------------------------------------
Location Year Concentration Reference
(µg/m3)
--------------------------------------------------------------------------
Harwell, England 1969 up to 5.1 Healy et al. (1970)
(typical level
0.85 - 1.7)
Maritime stations pre-1963 2 - 5 Georgii (1963)
(North Sea, Italian
coast, and Hawaii)
Rural and mountain pre-1963 5 - 8 Georgii (1963)
locations in Switzerland
and the Federal Republic
of Germany
Non-urban locations - 4 - 5 Robinson & Robbins
(1968); McKay (1969)
Rural sites in USA 1971 1.4 - 4.2 Breeding et al. (1973)
Boulder, Colorado, USA 1975 2.0 - 3.1 Axelrod & Greenberg
(1976)
American tropic 1967-68 3.5 - 21.7 Lodge et al. (1974)
(average 10.5)
Non-urban sites in 1972 4.6 - 9.7 Hidy (1974)
California, USA
--------------------------------------------------------------------------
a Adapted from: NRC (1979).
In the Netherlands, enhanced ammonium levels are also present
in waters that are not influenced by surface run-off. In
particular, in hydrologically-isolated acidified small lakes,
concentrations may reach up to 3 mg NH4+-N/litre. In rural areas
with high atmospheric ammonia levels, the loading of these small
lakes with airborne ammonia substances appears to be responsible.
The highest measured value near intensive pig and poultry farms was
12 mg NH4+-N/litre (Leuven & Schuurkes, 1984).
There are few data on the concentrations of ammonia in
drinking-water. This is possibly because of the conversion of most
of the available ammonia to N-chloramines (mono-, di-, and tri-
chloramines) during the chlorination of drinking-water (Morris,
1978), which reduces ammonia concentrations to levels below
analytical detectability. The presence of these N-chloramines may
contribute to the taste, odour, and also the potential health
problems of drinking-water.
Table 10. Urban and non-urban atmospheric levels of particulate
ammonium in some global locationsa
-------------------------------------------------------------------
Location Year Concentration Reference
(µg/m3)
-------------------------------------------------------------------
Non-urban:
England
Harwell - 3 - 4 Healy (1974)
(troposphere) 1971-73 1.3 Reiter et al. (1976)
Germany, Federal
Republic of
Bavaria - 1.0 Georgii & Muller
(lower troposphere) (1974)
USA
28 non-urban sites 1968 0 - 1.2 US EPA (1972)
Point Arguello, - 0.36 Hidy (1974)
California
Goldstone, - 0.76 Hidy (1974)
California
Urban:
Belgium
Ghent 1972 1.3 - 33.0 Demuynck et al.
(severe (1976)
pollution
episode)
Japan
Nagoya 1973-74 2.7 - 4.2 Kadowaki (1976)
Netherlands
Delft 1979-81 4.6 Van Aalst (1984)
Terschelling 1982 2.7 Van Aalst (1984
Houtakker 1983 19 Van Aalst (1984)
Sweden
Rao - 2.2 - 7.2 Brosset et al. (1975)
(aerosol
originating
from England)
United Kingdom
Tees River Valley 1967 up to 33.0 Eggelton (1969)
(severe
pollution
episode)
-------------------------------------------------------------------
Table 10. (contd.)
-------------------------------------------------------------------
Location Year Concentration Reference
(µg/m3)
-------------------------------------------------------------------
USA
Urban areas 1968 0 - 15.1 US EPA (1972)
Five cities 1970-72 0 - 21 Lee & Goranson (1976)
Tuscon, Arizona 1973-74 0 - 6.5 Keesee et al. (1975)
Los Angeles, 1969-70 2.8 - 3.4 Gordon & Bryan (1973)
California
15 urban sites in - average 5.3 Hidy (1974)
California
Riverside, 1975 up to 30.1 Grosjean et al.
California (average 7.6) (1976)
-------------------------------------------------------------------
a Adapted from: NRC (1979).
Ground water is frequently used as drinking-water, without
prior chlorination. Ammonia levels in ground water are usually low
because the adsorption of the ammonium ion on clay minerals, or its
bacterial oxidation to nitrate, limit its mobility in soil (Feth,
1966; Liebhardt et al., 1979). However, nitrogen fertilizers,
livestock wastes, or septic tanks may contribute significant
amounts of ammonia to shallow ground waters, especially those
underlying poorly-drained soils (Gilliam et al., 1974; Rajagopal,
1978). In domestic tap water from Michigan wells averaging 20 m in
depth, mean levels of ammonia-nitrogen were between 0.04 and 0.18
mg/litre; the highest reported single value was 0.57 mg/litre from
a well 12.5 m in depth (Rajagopal, 1978).
In wells drilled for research purposes and not supplying
drinking-water, levels of ammonia-nitrogen in shallow (3 m) wells
beneath wood and crop land usually averaged less than 2 mg/litre
(Gilliam et al., 1974). Levels in shallow (3 - 6 m) ground water
beneath plots spread with poultry manure varied typically between 1
and 15 mg NH3-N/litre (Liebhardt et al., 1979); those in ground
water beneath 29 feedlots averaged 4.5 mg NH3-N/litre and ranged up
to 38 mg/litre (Stewart et al., 1967). Levels in hot springs and
other ground waters have been reported to reach > 1000 mg NH3-
N/litre (Feth, 1966).
The ammonia levels present in the runoff of receiving surface
waters have been measured in various studies. Kluesner & Lee
(1974) found that levels ranged from approximately 0.23 mg
ammonia/litre in the autumn to 1.8 mg ammonia/litre in the early
spring in the urban runoff of Madison, Wisconsin. Struzewski
(1971) reported that ammonia levels in urban storm water ranged
from 0.1 to 3.2 mg/litre.
Only limited data are available on nitrogen pools in the ocean.
Söderlund & Svensson (1976) used values of 5 µg NH3-N/litre for
deep areas and 50 µg NH3-N/litre for near-shore areas and estimated
an ammonia inventory of approximately 9 x 103 µg/litre in coastal
upwelling systems.
Interstitial water in sediments rich in organic matter contain
higher concentrations of ammonia. Sholkovitz (1973) reported
values of 1.4 - 23.8 µg ammonia/litre in the interstitial waters
of the Santa Barbara Basin. The interstitial water of the Long
Island Sound, 2 km off shore, contained concentrations ranging
from 11.2 to 42 µg ammonia/litre (Gold-haber & Kaplan, 1974).
5.1.3. Levels in soil
The quantity of ammonia bound to clay in soil has not been
estimated. The ammonia present in soil is in dynamic equilibrium
with nitrate and other substrates of the nitrogen cycle and is
difficult to measure as its concentration is in constant flux (NRC,
1979).
5.1.4. Food
There is very little ammonia in unprocessed food and in
drinking-water derived from deep ground-water or chlorinated
sources. Various salts of ammonia are added to foods (Annex I).
5.1.5. Other products
Ammonium chloride is a common ingredient in expectorant
cough mixtures and is a component of tobacco smoke (about
40 µg/cigarette) (Sloan & Morie, 1974).
5.2. General Population Exposure
Exposure via inhalation and ingestion must be compared to the
endogenous production of ammonia in the intestinal tract, which is
of the order of several grams per day (section 7.1.2). The
relative importance of the different sources is indicated in Table
11.
5.2.1. Inhalation
Assuming ammonia and ammonium concentrations in non-urban and
urban air are 2 and 6 µg/m3 and 24 and 25 µg/m3, respectively, and
that the amount of air breathed per day by an individual is 20 m3,
the intake of total ammonia through inhalation can be calculated to
be 0.1 - 0.5 mg/day; the amounts exhaled are considerably higher.
The average amount of ammonia inhaled from the smoking of one
cigarette is approximately 42 µg (Sloan & Morie, 1974). Assuming
an individual smokes 20 cigarettes per day, the inhalation of
ammonia through cigarette smoking would be 0.8 mg/day.
5.2.2. Ingestion from water and food
Most drinking-water in the USA is chlorinated, which
effectively eliminates ammonia. However, assuming the direct
consumption of 2 litres per day of untreated surface water, at an
average total ammonia concentration of 0.18 mg/litre (Wolaver,
1972), the average human uptake from this source would be 0.36 mg
per day.
Table 11. Intake of ammonia from
different sources
------------------------------------
Source mg/day
------------------------------------
Endogenous 4000
Exogenous
Ingestion (food and drink) ~18
Inhalation < 1
Cigarette smoking (20/day) < 1
------------------------------------
Although ammonia is a negligible natural constitutent of food,
it is formed in the intestine by deamination of the amino groups of
food proteins. In addition, ammonium compounds are added in small
amounts (< 0.01 - 20 g/kg) to various foods as stabilizers,
leavening agents, flavourings, and for other purposes (FASEB,
1974). Information concerning the usual concentrations of ammonium
salt additives in foods and the estimated total quantities of these
compounds used for this purpose in the USA in 1970 has been used to
estimate the average daily intake of 6 ammonium salt additives
(FASEB, 1974). The estimates for ammonium bicarbonate, carbonate,
hydroxide, monobasic phosphate, dibasic phosphate, and sulfate were
42, 0.3, 7, < 0.1, 6, and 20 mg, respectively. No estimate was
available for ammonium chloride. On this basis, the average daily
ammonia intake from these compounds has been calculated to be
18 mg.
5.2.3. Dermal exposure
Very few data are available concerning levels of dermal
exposure to ammonia or ammonium compounds. Dermal exposure of
human beings mainly occurs through the use of household cleaning
products, accidental spillage, or under occupational conditions.
5.3. Occupational Exposure
Exposure to ammonia or ammonium compounds can occur in certain
occupations involving their production, transportation, and use in
agricultural and farm settings, during fertilizer application, or
as a result of animal waste decomposition.
It is estimated that about half a million workers in the USA,
in a wide variety of occupations, have potential exposure to
ammonia (NIOSH, 1974).
Ammonia is generated as a by-product in a wide variety of
industrial activities, and workplace atmospheric concentrations
are given in Table 12. Municipal waste incineration and gas-fired
industrial incinerators generate concentrations of 20 and 0.4
mg/m3, respectively (NRC, 1979) and shipboard and quayside levels
for natural gas tankers may be about 30 mg/m3 (Avot et al., 1977).
Levels in intensive livestock-rearing buildings are frequently
reported to be up to 30 mg/m3 (Poliak, 1981) or more (Anderson et
al., 1964b; Taiganides & White, 1969; Marschang & Petre, 1971).
Ammonia levels in dairy farms and cattle-fattening facilities in
Romania have been reported to range from 0.7 mg/m3 to 140 mg/m3
(Marchang & Crainiceanu, 1971; Marschang & Petre, 1971).
Maximum daily intake from work-place concentrations such as
these would normally be less than 300 mg/day and this may be
compared with endogenous production (Table 11).
Occupational exposure limits for some countries in the world
are shown in Table 13.
5.4. Exposure of Farm Animals
Farm animals are exposed to ammonia through feed containing
urea or various ammonium salts and to atmospheric ammonia due to
bacterial decomposition and volatilization of ammonia from animal
wastes.
5.4.1. Oral exposure
(a) Non-protein nitrogen additives
Urea and various ammonium salts have been used for several
years as non-protein nitrogen sources in ruminant nutrition. It is
used much more widely for this purpose than the ammonium compounds.
Urea is hydrolysed to ammonia and carbon dioxide by the ruminal
bacteria and, therefore, represents a source of ammonia exposure.
The ammonia released is used by the ruminal microorganisms to
synthesize microbial protein, which is then digested in the small
intestine of the ruminant and used as a source of dietary amino
acids.
(b) Refeeding of livestock wastes
Results of studies on the refeeding of livestock wastes
(Bhattacharya & Taylor, 1975; Arndt et al., 1979; Smith & Wheeler,
1979) have indicated that manure could be of nutritive value,
salvaging some nutrients ordinarily lost (Yeck et al., 1975). The
non-protein nitrogen (e.g., urea, uric acid) present in livestock
wastes is available to ruminants because of microbial conversion in
the rumen. Wastes are of limited value for monogastrics such as
swine.
Table 12. Ammonia levels in some industrial processesa
--------------------------------------------------------
Operation Level (mg/m3)
--------------------------------------------------------
Machinery manufacturing (cleaning) 10.5
Diazo-reproducing machine 5.6
Mildew-proofing 87.5
Electroplating 38.5
Galvanizing, ammonium chloride flux 7 - 61.6
Blueprint machine 7 - 31.5
Printing machine 0.7 - 31.5
Etching 25.2
Refrigeration equipment 6.3 - 25.9
Cementing insoles 5.6 - 19.6
Chemical mixing 42 - 308
Fabric impregnating ND
--------------------------------------------------------
a From: NIOSH (1974).
ND = Not detectable.
5.4.2. Inhalation exposure
(a) Ruminants
Marschang & Crainiceanu (1971) measured the ammonia
concentrations in air (sampled at nose level of animals) in calf
stables at 4 dairy farms in Romania. The ammonia levels ranged
from 0.7 to 140 mg/m3 (1 - 200 ppm). Most of the observed values
greatly exceeded the permissible upper limit of 18.2 mg/m3 (26
ppm). In a second study, Marschang & Petre (1971) measured the
ammonia concentrations in the air of 3 cattle-fattening facilities
in Romania in which the animals were being fed in total
confinement; the capacities of the 3 operations were 3000, 3000,
and 4900 animals. The ammonia concentration ranged from 2 to
1400 mg/m3 (3 to 200 ppm). In general, the ammonia content was
below the admissible upper limit during the summer months but
exceeded it during the winter months, when extremely high
concentrations were observed. These high concentrations were
primarily due to the blocking of the ventilation system, in order
to maintain necessary stall temperatures. The highest value
(1400 mg/m3) was measured when the cleaning mechanism of the
manure canals malfunctioned.
Table 13. Occupational exposure limits (mg/m3)a
-------------------------------------------------
Country Ammonia Ammonium
Ammonia chloride sulfamate
A B A B A B
-------------------------------------------------
Australia 18 10 10
Belgium 18 10 10
Czechoslovakia 40 80
Finland 18
German Democratic 20 10
Republic
Germany, Federal 35 10 15
Republic of
Hungary 20
Italy 20 10
Japan 18
Netherlands 18 10 10
Poland 20
Romania 20 30 5 10 10 15
Sweden 18 36
Switzerland 18 6 10
USA (NIOSH/OSHA) 35 15
(ACGIH) 18 27 10 20 10 20
USSR 20 10
Yugoslavia 35 15
Council of Europe 18 15
-------------------------------------------------
a From: ILO (1970).
Column A represents average values.
Column B is higher quoted limits, which may
variously be ceiling values, short-term exposure
limits, etc.
Note: Occupational exposure levels and limits are derived in
different ways, possibly using different data, and expressed
and applied in accordance with national practices. These
aspects should be taken into account when making comparisons.
(b) Swine
The increased use of confined housing for swine has caused
concern about the purity of the air within the buildings and its
effects on swine growth. Bacterial decomposition of excreta
collected and stored beneath slotted floors in enclosed buildings
produces a number of gases, including ammonia, carbon dioxide,
hydrogen sulfide, and methane (Curtis, 1972). Miner & Hazen (1969)
reported a range of ammonia concentrations of 4.2 - 24.5 mg/m3
(6 - 35 ppm) determined 30 cm above the floor level in a swine-
rearing facility. Levels in solid-floor confinement units were
normally found to be < 35 mg/m3 (< 50 ppm), but they could be
higher during cold months, when ventilation was at a minimum,
particularly when the floor was heated (Taiganides & White, 1969).
The normal ammonia concentration in the air above slotted floors
was reported to be ~7 mg/m3 (~10 ppm), but this was increased by a
factor of 5 - 10 by stirring the stored manure.
(c) Poultry
Poultry are usually exposed to ammonia, together with hydrogen
sulfide, carbon dioxide, and methane, in the air of poultry houses.
These compounds result from bacterial action on poultry wastes
(Ringer, 1971). In cold climates, proper ventilation rates cannot
be maintained in many poultry houses, and gas production in the
manure may build up to toxic levels. Ammonia has been found at
concentrations exceeding 35 mg/m3 (50 ppm) in modern poultry
houses, and at up to 140 mg/m3 (200 ppm) in poorly-ventilated
poultry houses (Anderson et al., 1964b; Valentine, 1964). The
toxic effects in poultry can be prevented through proper management
practices (Lillie, 1970).
6. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
6.1. Microorganisms
Many microorganisms are able to use ammonia as a nitrogen
source for cellular nutrition. Nitrifying organisms derive energy
from the oxidation of ammonia to nitrate. High levels of ammonia
and high pH, which may occur, for example, in waste waters or
fertilized fields, may inhibit nitrification and cause persistance
or accumulation of ammonia and/or nitrite. Improper maintenance of
conditions in waste treatment processes may result in ammonia
overloading and inhibition of the nitrification process, with
consequent ammonia and/or nitrite pollution of receiving surface
waters. Other soil microorganisms may also be inhibited; fungi
reportedly are more sensitive than bacteria. However, these
inhibitory effects are temporary. Aqueous and gaseous ammonia have
been used to control microbial growth in stored fruits, hay, and
grains. Ammonia treatment has proved more effective against fungal
than against bacterial spoilage of food.
The bacterial species Escherichia coli and Bacillus subtilis
were found to be sensitive to ammonium chloride (NH4Cl) (Deal et
al. 1975); exposure to 1100 mg NH3/litre killed 90% of an E. coli
population in 78 min. B. subtilis, an aerobic, spore-forming
bacterium, was destroyed in less than 2 h in a solution of 620 mg
NH3/litre. Anthonisen et al. (1976) and Neufeld et al. (1980)
studied NH3 inhibition of the bacterium Nitrosomonas (which
converts ammonium to nitrite) and the bacterium Nitrobacter (which
converts nitrite to nitrate). The nitrification process was
inhibited by NH3 at a concentration of 10 mg/litre (Neufeld et al.,
1980). Concentrations that inhibited Nitrosomonas (10 - 150
mg/litre) were greater than those that inhibited Nitrobacter
(0.1 - 1.0 mg/litre), and NH3, not NH4+, was reported to be the
inhibiting chemical species (Anthonisen et al. 1976).
Acclimatization of the nitrifying bacteria to NH3, temperature,
and the number of active nitrifying organisms are factors that may
affect the inhibitory concentrations of NH3 in a nitrification
system.
Langowska & Moskal (1974) investigated the inhibitory effects
of NH3 on bacteria during 24-h exposure periods. Ammonifying and
denitrifying bacteria were most resistant to NH3; proteolytic and
nitrifying bacteria were the most sensitive. Concentrations of up
to 170 mg NH3/litre did not adversely affect denitrifying and
ammonifying bacteria; a concentration of 220 mg/litre caused a
reduction in metabolic processes. Proteolytic bacteria were
unaffected at concentrations of 0.8 mg NH3/litre, but were affected
at 13 - 25 mg/litre.
Jones & Hood (1980) conducted studies on 2 species of
Nitrosomonas isolated from 2 wetland environments, one estuarine
and the other fresh water. At 30 °C and pH 8.0, the estuarine
isolate showed peak ammonium oxidation activity at 18 mg NH3/litre;
activity gradually declined to 30% of the peak at 80 mg NH3/litre.
However, the fresh-water isolate was not inhibited by ammonia
concentrations of up to 80 mg NH3/litre.
Application of anhydrous ammonia to soil may strongly affect
soil microorganisms; however, the effect has been attributed more
to alterations in pH than to ammonia toxicity per se. Henis & Chet
(1967) found that ammonia reduced sclerotial germinability of the
fungus Sclerotium rolfsii only when the soil pH rose to 9.8 or
higher. According to Müller & Gruhn (1969), fungi were more
sensitive than bacteria to ammonia application, the fungi
disappearing at pH values above 8. At pH 8.38, bacterial numbers
initially decreased but then increased above control levels, 7 days
after application, with an increased number of protein-decomposing
and nitrifying forms.
Ammonia has been used to control microbial growth in food and
cattle feed. The growth of mould (Penicillium digitatum) on fresh
fruit was inhibited by 70 - 300 mg ammonia/m3 in the air, either