UNITED NATIONS ENVIRONMENT PROGRAMME INTERNATIONAL LABOUR ORGANISATION WORLD HEALTH ORGANIZATION INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY ENVIRONMENTAL HEALTH CRITERIA 192 Flame Retardants: A General Introduction This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization. Environmental Health Criteria 192 First draft prepared by Dr G.J. van Esch, Bilthoven, Netherlands Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals. World Health Organization Geneva, 1997 The International Programme on Chemical Safety (IPCS) is a joint venture of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization. The main objective of the IPCS is to carry out and disseminate evaluations of the effects of chemicals on human health and the quality of the environment. Supporting activities include the development of epidemiological, experimental laboratory, and risk-assessment methods that could produce internationally comparable results, and the development of manpower in the field of toxicology. Other activities carried out by the IPCS include the development of know-how for coping with chemical accidents, coordination of laboratory testing and epidemiological studies, and promotion of research on the mechanisms of the biological action of chemicals. WHO Library Cataloguing in Publication Data Flame Retardants: A General Introduction (Environmental health criteria ; 192) 1.Flame retardants - toxicity 2.Occupational exposure 3.Environmental exposure I.Series ISBN 92 4 157192 6 (NLM Classification: WA 250) ISSN 0250-863X The World Health Organization welcomes requests for permission to reproduce or translate its publications, in part or in full. Applications and enquiries should be addressed to the Office of Publications, World Health Organization, Geneva, Switzerland, which will be glad to provide the latest information on any changes made to the text, plans for new editions, and reprints and translations already available. (c) World Health Organization 1997 Publications of the World Health Organization enjoy copyright protection in accordance with the provisions of Protocol 2 of the Universal Copyright Convention. All rights reserved. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters. CONTENTS ENVIRONMENTAL HEALTH CRITERIA FOR FLAME RETARDANTS: A GENERAL INTRODUCTION PREAMBLE GLOSSARY AND ABBREVIATIONS PROLOGUE 1. INTRODUCTION 2. TYPES OF FLAME RETARDANTS 2.1. Inorganic flame retardants 2.1.1. Metal hydroxides 2.1.2. Antimony compounds 2.1.3. Boron compounds 2.1.4. Other metal compounds 2.1.5. Phosphorus compounds 2.1.6. Other inorganic flame retardants 2.2. Halogenated organic flame retardants 2.2.1. Brominated flame retardants 2.2.2. Chlorinated flame retardants 2.3. Organophosphoros flame retardants 2.3.1. Non-halogenated compounds 2.3.2. Halogenated phosphates 2.4. Nitrogen-based flame retardants 3. MECHANISM OF ACTION OF FLAME RETARDANTS 3.1. General aspects 3.1.1. Physical action 3.1.2. Chemical action 3.2. Condensed phase mechanisms 3.3. Gas-phase mechanisms 3.4. Co-additives for use with flame retardants 3.5. Smoke suppressants 3.5.1. Condensed phase 3.5.2. Gas phase 4. PERFORMANCE CRITERIA FOR AND CHOICE OF FLAME RETARDANTS 5. PRODUCTION AND USES OF FLAME RETARDANTS AND FLAME-RETARDED POLYMERS 5.1. Production 5.2. Uses 5.2.1. Plastics 5.2.2. Textile/furnishing industry 6. FORMATION OF TOXIC PRODUCTS ON HEATING OR COMBUSTION OF FLAME-RETARDED PRODUCTS 6.1. Toxic products in general 6.2. Formation of halogenated dibenzofurans and dibenzodioxins 6.3. Exposure to PBDD/PBDF from polymers containing halogenated flame retardants 6.3.1. Exposure from contact or emission from products containing halogenated flame retardants 6.3.2. Workplace exposure studies 6.3.3. Formation of PBDD/PBDF from combustion 18.104.22.168 Laboratory pyrolysis experiments 22.214.171.124 Fire tests and fire accidents 7. OVERVIEW OF EXPOSURE AND HAZARDS TO HUMANS AND THE ENVIRONMENT 7.1. Human exposure 7.1.1. General population 7.1.2. Occupational exposure 7.2. Exposure of the environment 7.3. Hazards to humans 7.4. Hazards to the environment 8. REGULATIONS WITH RESPECT TO FLAME RETARDANTS 9. CONCLUSIONS AND RECOMMENDATIONS FOR THE PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 10. FURTHER RESEARCH REFERENCES ANNEX I: Terminology ANNEX II: Flame retardants in commercial use or used formerly ANNEX III: Fire tests ANNEX IV: US Interagency Testing Commission recommendations on brominated flame retardants CONCLUSIONS ET RECOMMANDATIONS CONCLUSIONES Y RECOMMENDACIONES NOTE TO READERS OF THE CRITERIA MONOGRAPHS Every effort has been made to present information in the criteria monographs as accurately as possible without unduly delaying their publication. In the interest of all users of the Environmental Health Criteria monographs, readers are requested to communicate any errors that may have occurred to the Director of the International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland, in order that they may be included in corrigenda. * * * A detailed data profile and a legal file can be obtained from the International Register of Potentially Toxic Chemicals, Case postale 356, 1219 Châtelaine, Geneva, Switzerland (telephone no. + 41 22 - 9799111, fax no. + 41 22 - 7973460, E-mail email@example.com). * * * This publication was made possible by grant number 5 U01 ES02617- 15 from the National Institute of Environmental Health Sciences, National Institutes of Health, USA, and by financial support from the European Commission. * * * The Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany, provided financial support for this publication. Environmental Health Criteria PREAMBLE Objectives In 1973 the WHO Environmental Health Criteria Programme was initiated with the following objectives: (i) to assess information on the relationship between exposure to environmental pollutants and human health, and to provide guidelines for setting exposure limits; (ii) to identify new or potential pollutants; (iii) to identify gaps in knowledge concerning the health effects of pollutants; (iv) to promote the harmonization of toxicological and epidemiological methods in order to have internationally comparable results. The first Environmental Health Criteria (EHC) monograph, on mercury, was published in 1976 and since that time an ever-increasing number of assessments of chemicals and of physical effects have been produced. In addition, many EHC monographs have been devoted to evaluating toxicological methodology, e.g., for genetic, neurotoxic, teratogenic and nephrotoxic effects. 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It is accepted that the following criteria should initiate the updating of an EHC monograph: new data are available that would substantially change the evaluation; there is public concern for health or environmental effects of the agent because of greater exposure; an appreciable time period has elapsed since the last evaluation. All Participating Institutions are informed, through the EHC progress report, of the authors and institutions proposed for the drafting of the documents. A comprehensive file of all comments received on drafts of each EHC monograph is maintained and is available on request. The Chairpersons of Task Groups are briefed before each meeting on their role and responsibility in ensuring that these rules are followed. WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR FLAME RETARDANTS: A GENERAL INTRODUCTION Members Dr L.A. Albert, Xalapa, Veracruz, Mexico Dr P. Arias, Brussels, Belgium Dr S.A. Assimon, Contaminants Branch, US Food and Drug Administration, Washington, DC, USA Dr H. Hofer, Toxicology, Austrian Research Centre, Seibersdorf, Austria Dr B. Jansson, Institute of Applied Environmental Research, Stockholm University, Stockholm, Sweden ( Chairman) Dr S.K. Kashyap, National Institute of Occupational Health, Ahmedabad, India Dr J. Kielhorn, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany ( Vice-Chairman) Dr R.G. Liteplo, Environmental Health Directorate, Health Canada, Ottawa, Ontario, Canada Mr H. Malcolm, Institute of Terrestrial Ecology, Monks Wood, Huntingdon, United Kingdom Dr E. Sderlund, Folkehelsa, National Institute of Public Health, Oslo, Norway ( Rapporteur) Dr J. Troitzsch, Fire and Environment Protection Service, Wiesbaden, Germany Observers Dr M.L. Hardy, Albermarle Corporation, Baton Rouge, USA Mr T.A. Jay, Applications Laboratory, Great Lakes Chemical (Europe) N.V., Geel, Belgium Dr M. Papez, European Flame Retardants Association, Brussels, Belgium Secretariat Dr K.W. Jager, International Programme on Chemical Safety, World Health Organization ( Secretary) ENVIRONMENTAL HEALTH CRITERIA FOR FLAME RETARDANTS: A GENERAL INTRODUCTION A WHO Task Group on Environmental Health Criteria for Flame Retardants met at the World Health Organization, Geneva, from 4 to 8 December 1995. Dr K.W. Jager, IPCS, welcomed the participants on behalf of Dr M. Mercier, Director of the IPCS, and the three cooperating organizations (UNEP/ILO/WHO). The Task Group reviewed and revised the draft monograph and prepared conclusions and recommendations. The first draft of the monograph was prepared by Dr G.J. van Esch, Bilthoven, the Netherlands. The second draft, incorporating comments received following circulation of the first draft to the IPCS contact points for Environmental Health Criteria monographs, was prepared by the IPCS Secretariat. Dr K.W. Jager and Dr P.G. Jenkins, both of the IPCS Central Unit, were responsible for the scientific content of the monograph and the technical editing, respectively. The efforts of all who helped in the preparation and finalization of the monograph are gratefully acknowledged. ABBREVIATIONS ABS acrylonitrile-butadiene-styrene APP ammonium polyphosphate ATH alumina trihydrate DeBDE decabromodiphenyl ether EPDM ethylene propylene rubber EPS expandable polystyrene FR flame retardant HBCD hexabromocyclododecane HIPS high impact polystyrene HDPE high density polyethylene LDPE low density polyethylene PA polyamides PBDE polybrominated diphenyl ether PBB polybrominated biphenyl PBDD polybrominated dibenzodioxin PBDF polybrominated dibenzofuran PBT polybutylene terephthalate PCDD polychlorinated dibenzodioxin PCDF polychlorinated dibenzofuran PE polyethylene PET polyethylene terephthalate PP polypropylene PVC polyvinyl chloride TBBPA tetrabromobisphenol A TCDD 2,3,7,8-tetrachlorinated dibenzo- p-dioxin TCPP tris(1-chloro-2-propyl)phosphate PROLOGUE The intent of this Environmental Health Criteria (EHC) monograph is to provide a general overview of the nature, mechanism of action, use and production volume of compounds used to improve the flame retardancy of polymeric materials and textiles. The monograph also indicates some of the known health and environmental hazards for certain of the flame retardants that have been assessed by the IPCS. A large number of compounds have been identified as being used as flame retardants. Detailed international assessments of the risks posed to human health and the environment by a number of these substances have been published previously as EHC monographs. In Table 1 are listed the monographs on flame retardants and compounds related to flame retardants that have already been published by IPCS or are in preparation. This monograph is intended to provide a starting point for those interested in obtaining general information on flame-retardant chemicals. More detailed information on use patterns, sources of exposure, and health and environmental risks posed by these substances can be found in the appropriate EHC monograph. Table 1. EHC monographs on chemicals associated with flame-retardant use Substance EHC monograph Mirex (1,1a,2,2,3,3a,4,5,5,5a,5b,6- EHC 44 (1984) dodecachloroocta-hydro-1,3,4-metheno-1H- cyclobuta( cd)pentalene) Polychlorinated dibenzo- p-dioxins and EHC 88 (1989) dibenzofurans Tricresyl phosphate EHC 110 (1990) Triphenyl phosphate EHC 111 (1991) Hexachlorocyclopentadiene EHC 120 (1991) Polychlorinated biphenyls EHC 140 (1992) Polybrominated biphenyls EHC 152 (1994) Brominated diphenyl ethers EHC 162 (1994) Tetrabromobisphenol A and some of its EHC 172 (1995) derivatives Tris(2,3-dibromopropyl) phosphate and EHC 173 (1995) bis(2,3-dibromopropyl) phosphate Chlorendic acid and anhydride EHC 185 (1996) Chlorinated paraffins EHC 181 (1996) Polybrominated dibenzo- p-dioxins and EHC in preparation dibenzofurans Vinylbromide EHC in prepraration Tris(chloropropyl) phosphates EHC in prepraration Tris(2-butoxyethyl) phosphate EHC in prepraration Tris(2-chloroethyl) phosphate EHC in prepraration Tris(2-ethylhexyl) phosphate EHC in prepraration Tetrakis(hydroxymethyl) phosphonium salts EHC in prepraration 1. INTRODUCTION In today's society, there is an unprecedented development in the size and number of buildings, skyscrapers, warehouses and methods of transport. Carpeting, furnishings, equipment, oil and gas for heating all increase the fire load in a building. New technologies, new processes and new applications introduce new fire hazards (e.g., new ignition sources such as welding sparks and short circuits) (Troitzsch, 1990). Modern fire-fighting techniques, equipment and building design have reduced the destruction due to fires. However, a high fuel load in either a residential or a commercial building can offset even the best of building construction (Gann, 1993). Each year, over 3 million fires leading to 29 000 injuries and 4500 deaths are reported in the USA. The direct property losses exceed $8 billion and the total annual cost has been estimated at over $100 billion. Personal losses occur mostly in residences where furniture, wall coverings and clothes are frequently the fuel. Large financial losses occur in commercial structures such as office buildings and warehouses. Fires also occur in aeroplanes, buses and trains (Gann, 1993). To provide additional protection from fires and to increase escape time when a fire occurs, methods to enhance the flame retardance of consumer goods have been developed. Flame retardants are chemicals added to polymeric materials, both natural and synthetic, to enhance flame-retardance properties. Flame-retardant chemicals are most often used to improve the fire performance of low- to-moderate cost commodity polymers. These flame retardants may be physically blended with or chemically bonded to the host polymer. They generally either lower ignition susceptibility or lower flame spread once ignition has occurred. Some polymers are inherently less flammable due to more stable polymeric structures; these are usually higher priced engineering plastics such as polyimides, polybenzimidazoles and polyetherketones (Gann, 1993). Flame-retardant systems for synthetic or organic polymers act in five basic ways: (1) gas dilution; (2) thermal quenching; (3) protective coating; (4) physical dilution; (5) chemical interaction (Pettigrew, 1993); or through a combination of these mechanisms. 1. Inert gas dilution involves using additives that produce large volumes of non-combustible gases on decomposition. These gases dilute the oxygen supply to the flame or dilute the fuel concentration below the flammability limit. Metal hydroxides, metal salts and some nitrogen compounds function in this way. 2. Thermal quenching is the result of endothermic decomposition of the flame retardant. Metal hydroxides, metal salts and nitrogen compounds act to decrease surface temperature and the rate of burning. 3. Some flame retardants form a protective liquid or char barrier. This limits the amount of polymer available to the flame front and/or acts as an insulating layer to reduce the heat transfer from the flame to the polymer. Phosphorus compounds and intumescent systems based on melamine and other nitrogen compounds are examples of this category. 4. Inert fillers (glass fibres and microspheres) and minerals (talc) act as thermal sinks to increase the heat capacity of the polymer or reduce its fuel content. 5. Halogens and some phosphorus flame retardants act by chemical interaction. The flame retardant dissociates into radical species that compete with chain-propagating steps in the combustion process. Chemicals that are used as flame retardants can be inorganic, organic, mineral, halogen-containing or phosphorus-containing. The term flame "retardant" represents a class of use and not a class of chemical structure (Pettigrew, 1993). Preventive flame protection, including the use of flame retardants, has been practised since ancient times. Some examples of early historical developments in flame retardants are shown in Table 2. Table 2. Early historical fire-retardant developmentsa Development Date Alum used to reduce the flammability of wood by the About 450 BC Egyptians The Romans used a mixture of alum and vinegar on About 200 BC wood Mixture of clay and gypsum used to reduce 1638 flammability of theatre curtains Mixture of alum, ferrous sulfate and borax used 1735 on wood and textiles by Wyld in Britain Alum used to reduce flammability of balloons 1783 Gay-Lussac reported a mixture of (NH4)3PO4, 1821 NH4Cl and borax to be effective on linen and hemp Perkin described a flame-retardant treatment for 1912 cotton using a mixture of sodium stannate and ammonium sulfate a From: Hindersinn (1990) The advent of synthetic polymers earlier this century was of special significance, since the water-soluble inorganic salts used up to that time were of little or no utility in these largely hydrophobic materials. Modern developments were, therefore, concentrated on the development of polymer-compatible flame retardants. By the outbreak of the Second World War, flame-proof canvas tentage for outdoor use by the military was produced with a treatment of chlorinated paraffins and an insoluble metal oxide, mostly antimony oxide as a glow inhibitor, together with a binder resin. After the war, non-cellulosic thermoplastic polymers became more and more important as the basic fibres used for flame-retardant applications. A dramatic example of the superiority of the non- cellulosic compounds is provided by the diminished use of cotton fibre in children's sleepwear since the inception of new standards. In 1971, cotton supplied 78% of the fibres used to produce children's sleepwear, whereas in 1973 it supplied less than 10% in the USA (US EPA, 1976). With the increasing use of thermoplastics and thermosets on a large scale for applications in building, transportation, electrical engineering and electronics, new flame-retardant systems were developed. They mainly consist of inorganic and organic compounds based on bromine, chlorine, phosphorus, nitrogen, boron, and metallic oxides and hydroxides. Today, these flame-retardant systems fulfill the multiple flammability requirements developed for the above-mentioned applications. A glossary of terms concerning flammability and flame retardants is given in Annex 1. 2. TYPES OF FLAME RETARDANTS A distinction is made between reactive and additive flame retardants. Reactive flame retardants are reactive components chemically built into a polymer molecule. Additive flame retardants are incorporated into the polymer either prior to, during or (most frequently) following polymerization. There are three main families of flame-retardant chemicals (Troitzsch, 1990; Wolf & Kaul, 1992; Green, 1992; Touval, 1993; Pettigrew, 1993; Weil, 1993). 1. The main inorganic flame retardants are aluminium trihydroxide, magnesium hydroxide, ammonium polyphosphate and red phosphorus. This group represents about 50% by volume of the worldwide flame retardant production. Some of these chemicals are also used as flame retardant synergists, of which antimony trioxide is the most important (OECD, 1994). 2. Halogenated products are based primarily on chlorine and bromine. This group represents about 25% by volume of the worldwide production (OECD, 1994). 3. Organophosphorus products are primarily phosphate esters and represent about 20% by volume of the worldwide production. Products containing phosphorus, chlorine and/or bromine are also important. In addition, nitrogen-based flame retardants are used for a limited number of polymers. Annex II comprises lists of the different flame retardant families commercially used at present (A) and those no more in use (B). 2.1 Inorganic flame retardants Metal hydroxides form the largest class of all flame retardants used commercially today and are employed alone or in combination with other flame retardants to achieve necessary improvements in flame retardancy. Antimony compounds are used as synergistic co-additives in combination with halogen compounds, facilitating the reduction in total flame retardant levels needed to achieve a desired level of flame retardancy. To a limited extent, compounds of other metals also act as synergists with halogen compounds. They may be used alone but are most commonly used with antimony trioxide to enhance other characteristics, for example, smoke reduction or afterglow suppression. Ionic compounds have a very long history as flame retardants for wool- or cellulose-based products. Inorganic phosphorus compounds are primarily used in polyamides and phenolic resins, or as components in intumescent formulations. 2.1.1 Metal hydroxides Metal hydroxides function in both the condensed and gas phases of a fire by absorbing heat and decomposing to release their water of hydration. This process cools both the polymer and the flame and dilutes the flammable gas mixture. The very high concentrations (50 to 80%) required to impart flame retardancy often adversely affect the mechanical properties of the polymer into which they are incorporated. Aluminium hydroxide, also known as alumina trihydrate (ATH) is the largest volume flame retardant in use today. It decomposes when exposed to temperatures over 200°C, which limits the polymers in which it can be incorporated. Magnesium hydroxide is stable to temperatures above 300°C and can be processed into several polymers. 2.1.2 Antimony compounds Antimony trioxide is not a flame retardant per se, but it is used as a synergist. It is utilized in plastics, rubbers, textiles, paper and paints, typically 2-10% by weight, with organochlorine and organobromine compounds to diminish the flammability of a wide range of plastics and textiles (IARC, 1989). Antimony oxides and antimonates must be converted to volatile species. This is usually accomplished by release of halogen acids at fire temperatures. The halogen acids react with the antimony- containing materials to form antimony trihalide and/or antimony halide oxide. These materials act both in the substrate (condensed phase) and in the flame to suppress flame propagation. In the condensed phase, they promote char formation, which acts as a physical barrier to flame and inhibits the volatilization of flammable materials. In the flame, the antimony halides and halide oxides, generated in sufficient volume, provide an inert gas blanket over the substrate, thus excluding oxygen and preventing flame spread. These compounds alter the chemical reactions occurring at fire temperatures in the flame, thus reducing the ease with which oxygen can combine with the volatile products. It is also suggested that antimony oxychloride or trichloride reduces the rate at which the halogen leaves the flame zone, thus increasing the probability of reaction with the reactive species. Antimony trichloride probably evolves heavy vapours which form a layer over the condensed phase, stop oxygen attack and thus choke the flame. It is also assumed that the liquid and solid antimony trichloride particles contained in the gas phase reduce the energy content of the flames by wall or surface effects (Troitzsch, 1990). Other antimony compounds include antimony pentoxide, available primarily as a stable colloid or as a redispersible powder. It is designed primarily for highly specialized applications, although manufacturers suggest it has potential use in fibre and fabric treatment. Sodium antimonate (Na2OSb2O5Ê´H2O) is recommended for formulations in which deep tone colours are required or where antimony trioxide may promote unwanted chemical reactions. 2.1.3 Boron compounds Within the class of boron compounds, by far the most widely used is boric acid. Boric acid (H3BO3) and sodium borate (borax) (Na2B4O7. 10H2O) are the two flame retardants with the longest history, and are used primarily with cellulosic material, e.g., cotton and paper. Both products are effective, but their use is limited to products for which non-durable flame retardancy is acceptable since both are very water-soluble. Zinc borate, however, is water-insoluble and is mostly used in plastics and rubber products. It is used either as a complete or partial replacement for antimony oxide in PVC, nylon, polyolefin, epoxy, EPDM, etc. In most systems, it displays synergism with antimony oxide. Zinc borate can function as a flame retardant, smoke suppressant and anti-arcing agent in condensed phase. Recently, zinc borate has also been used in halogen-free, fire-retardant polymers. 2.1.4 Other metal compounds Molybdenum compounds have been used as flame retardants in cellulosic materials for many years and more recently with other polymers, mainly as smoke suppressants (see section 3.4) (Troitzsch, 1990). They appear to function as condensed-phase flame retardants (Avento & Touval, 1980). Titanium and zirconium compounds are used for textiles, especially wool (Calamari & Harper, 1993). Zinc compounds, such as zinc stannate and zinc hydroxy-stannate, are also used as synergists and as partial replacements for antimony trioxide. 2.1.5 Phosphorus compounds Red phosphorus and ammonium polyphosphate (APP) are used in various plastics. Red phosphorus was first investigated in polyurethane foams and found to be very effective as a flame retardant. It is now used particularly for polyamides and phenolic applications. The flame- retarding effect is due, in all probability, to the oxidation of elemental phosphorus during the combustion process to phosphoric acid or phosphorus pentoxide. The latter acts by the formation of a carbonaceous layer in the condensed phase. The formation of fragments that act by interrupting the radical chain mechanism is also likely. Ammonium polyphosphate is mainly applied in intumescent coatings and paints. Intumescent systems puff up to produce foams. Because of this characteristic they are used to protect materials such as wood and plastics that are combustible and those like steel that lose their strength when exposed to high temperatures. Intumescent agents have been available commercially for many years and are used mainly as fire-protective coatings. They are now used as flame-retardant systems for plastics by incorporating the intumescent components in the polymer matrix, mainly polyolefins, particularly polypropylene (Troitzsch, 1990). 2.1.6 Other inorganic flame retardants Other inorganic flame retardants, including ammonium sulfamate (NH4SONH2) and ammonium bromide (NH4Br), are used primarily with cellulose-based products and in forest fire-fighting (Weil, 1993). 2.2 Halogenated organic flame retardants Halogenated flame retardants can be divided into three classes: aromatic, aliphatic and cycloaliphatic. Bromine and chlorine compounds are the only halogen compounds having commercial significance as flame-retardant chemicals. Fluorine compounds are expensive and, except in special cases, are ineffective because the C-F bond is too strong. Iodine compounds, although effective, are expensive and too unstable to be useful (Cullis, 1987; Pettigrew, 1993). The brominated flame retardants are much more numerous than the chlorinated types because of their higher efficacy (Cullis, 1987). With repect to processability, halogenated flame retardants vary in their thermal stability. In general, aromatic brominated flame retardants are more thermally stable than chlorinated aliphatics, which are more thermally stable than brominated aliphatics. Brominated aromatic compounds can be used in thermoplastics at fairly high temperatures without the use of stabilizers and at very high temperatures with stabilizers. The thermal stability of the chlorinated and brominated aliphatics is such that, with few exceptions, they must be used with thermal stabilizers, such as a tin compound. Halogenated flame retardants are either added to or reacted with the base polymer. Additive flame retardants are those that do not react in the application designated. There are a few compounds that can be used as an additive in one application and as a reactive in another; tetrabromobisphenol A is the most notable example. Reactive flame retardants become a part of the polymer either by becoming a part of the backbone or by grafting onto the backbone. The choice of a reactive flame retardant is more complex than the choice of an additive type. The development of systems based on reactive flame retardants is more expensive for the manufacturer, who in effect has to develop novel co-polymers with the desired chemical, physical and mechanical properties, as well as the appropriate degree of flame retardance (Cullis, 1987; Pettigrew, 1993). Synergists such as antimony oxides are frequently used with halogenated flame retardants. 2.2.1 Brominated flame retardants Bromine-based flame retardants are highly brominated organic compounds with a relative molecular mass ranging from 200 to that of large molecule polymers. They usually contain 50 to 85% (by weight) of bromine (Cullis, 1987). The highest volume brominated flame retardant in use today is tetrabromobisphenol A (TBBPA) (IPCS, 1995a) followed by decabromodiphenyl ether (DeBDE) (IPCS, 1994b). Both of these flame retardants are aromatic compounds. The primary use of TBBPA is as a reactive intermediate in the production of flame-retarded epoxy resins used in printed circuit boards (IPCS, 1995a). A secondary use for TBBPA is as an additive flame retardant in ABS systems. DeBDE is the second largest volume brominated flame retardant and is the largest volume brominated flame retardant used solely as an additive. The greatest use (by volume) of DeBDE is in high-impact polystyrene, which is primarily used to produce television cabinets. Secondary uses include ABS, engineering thermoplastics, polyolefins, thermosets, PVC and elastomers. DeBDE is also widely used in textile applications as the flame retardant in latex-based back coatings (Pettigrew, 1993). Hexabromocyclododecane (HBCD), a major brominated cycloaliphatic flame retardant, is primarily used in polystyrene foam. It is also used to flame-retard textiles. 2.2.2 Chlorinated flame retardants Chlorine-containing flame retardants belong to three chemical groups: aliphatic, cycloaliphatic and aromatic compounds. Chlorinated paraffins are by far the most widely used aliphatic chlorine- containing flame retardants. They have applications in plastics, fabrics, paints and coatings (IPCS, 1996b). Bis(hexachlorocyclopentadieno)cyclo-octane is a flame retardant having unusually good thermal stability for a chlorinated cycloaliphatic. In fact, this compound is comparable in thermal stability to brominated aromatics in some applications. It is used in several polymers, especially polyamides and polyolefins for wire and cable applications. Its principal drawback is the relatively high use levels required, compared to some brominated flame retardants (Pettigrew, 1993). Aromatic chlorinated flame retardants are not used for flame- retarding polymers. 2.3 Organophosphorus flame retardants One of the principal classes of flame retardants used in plastics and textiles is that of phosphorus, phosphorus-nitrogen and phosphorus-halogen compounds. Phosphate esters, with or without halogen, are the predominant phosphorus-based flame retardants in use. For textiles, phosphorus-containing materials are by far the most important class of compounds used to impart durable flame resistance to cellulose. These textile flame retardant finishes usually also contain nitrogen or halogen, or sometimes both (Weil, 1993; Calamari & Harper, 1993). 2.3.1 Non-halogenated compounds Although many phosphorus derivatives have flame-retardant properties, the number of those with commercial importance is limited. Some are additive and some reactive. The major groups of additive organophosphorus compounds are phosphate esters, polyols, phosphonium derivatives and phosphonates. The phosphate esters include trialkyl derivatives such as triethyl or trioctyl phosphate, triaryl derivatives such as triphenyl phosphate and aryl-alkyl derivatives such as 2-ethylhexyl-diphenyl phosphate. The flame retardancy of cellulosic products can be improved through the application of phosphonium salts. The flame-retardant treatments attained by phosphorylation of cellulose in the presence of a nitrogen compound are also of importance (Calamari & Harper, 1993). Plasticizers are mixed into polymers to increase flexibility and workability. The esters formed by reaction of the three functional groups of phosphoric acid with alcohols or phenols are excellent plasticizers. The phosphoric acid esters are also remarkable flame retardants, and for this reason are extensively used in plastics (Liepins & Pearce, 1976). Aryl phosphate plasticizers are used in PVC-based products. They are also used as lubricants for industrial air compressors and gas turbines. Miscellaneous uses of aryl phosphates are as pigment dispersants and peroxide carriers, and as additives in adhesives, lacquer coatings and wood preservatives (Boethling & Cooper, 1985). 2.3.2 Halogenated phosphates In addition to the above types, flame retardants containing both chlorine and phosphorus or bromine and phosphorus are used widely. Halogenated phosphorus flame retardants combine the flame-retardant properties of both the halogen and the phosphorus groups. In addition, the halogens reduce the vapour pressure and water solubility of the flame retardant, thereby contributing to the retention of the flame retardant in the polymer. One of the largest selling members of this group, tris(1-chloro- 2-propyl) phosphate (TCPP) is used in polyurethane foam. Tris(2- chloroethyl) phosphate is used in the manufacture of polyester resins, polyacrylates, polyurethanes and cellulose derivatives. The most widely used bromine- and phosphorus-containing flame retardant used to be tris(2,3-dibromopropyl)phosphate, but it was withdrawn from use in many countries due to carcinogenic properties in animals (Liepins & Pearce, 1976; Green, 1992). 2.4 Nitrogen-based flame retardants Nitrogen-based compounds can be employed in flame-retardant systems or form part of intumescent flame-retardant formulations. Nitrogen-based flame retardants are used primarily in nitrogen- containing polymers such as polyurethanes and polyamides. They are also utilized in PVC and polyolefins and in the formulation of intumescent paint systems (Grabner, 1993). Melamine, melamine cyanurate, other melamine salts and guanidine compounds are currently the most used group of nitrogen-containing flame retardants. Melamine is used as a flame retardant additive for polypropylene and polyethylene. Melamine cyanurate is employed commercially as a flame retardant for polyamides and terephthalates (PET/PBT) and is being developed for use in epoxy and polyurethane resins. Melamine phosphate is also used as a flame retardant for terephthalates (PET/PBT) and is currently being developed for use in epoxy and polyurethane flame retardant formulations. Also in the development stages for use as flame-retardant additives are melamine salts and melamine formaldehyde for their application in thermoset resins (Grabner, 1993). 3. MECHANISM OF ACTION OF FLAME RETARDANTS 3.1 General aspects To understand flame retardants, it is necessary to understand fire. Fire is a gas-phase reaction. Thus, in order for a substance to burn, it must become a gas. In the case of a candle the wax melts and migrates up the wick by capillary action. The wax is pyrolysed to volatile hydrocarbon fragments on the wick's surface at 600-800°C. There is no oxygen at the nucleus of the flame. Some of the hydrocarbon fragments aromatize to soot particles and, in the luminescent region of the flame, react with water and carbon dioxide to form carbon monoxide. Most of the pyrolysis gases are carried to the exterior of the flame and encounter oxygen diffusing inwards. They react exothermically to produce heat, which melts and decomposes more wax, maintaining the combustion reaction. If there is adequate oxygen, the combustion products from the candle are carbon dioxide and water (Anderson & Christy, 1992). Natural and synthetic polymers can ignite on exposure to heat. Ignition occurs either spontaneously or results from an external source such as a spark or flame. If the heat evolved by the flame is sufficient to keep the decomposition rate of the polymer above that required to maintain the evolved combustibles within the flammability limits, then a self-sustaining combustion cycle will be established (Fig. 1). This self-sustaining combustion cycle occurs across both the gas and condensed phases. Fire retardants act to break this cycle by affecting chemical and/or physical processes occurring in one or both of the phases. There are a number of ways in which the self-sustaining combustion cycle can be interrupted. Whatever the method used, the end effect is to reduce the rate of heat transfer to the polymer and thus remove the fuel supply. Troitzsch (1990) described the general physical and chemical mechanisms of flame-retardant action, in both the gas and condensed phases and the behaviour of flame retardants. Fundamentally, four processes are involved in polymer flammability: preheating, decomposition, ignition and combustion/ propagation. Preheating involves heating of the material by means of an external source, which raises the temperature of the material at a rate dependent upon the thermal intensity of the ignition source, the thermal conductivity of the material, the specific heat of the material, and the latent heat of fusion and vaporization of the material. When sufficiently heated, the material begins to degrade, i.e., it loses its original properties as the weakest bonds begin to break. Gaseous combustion products are formed, the rate being dependent upon such factors as intensity of external heat, temperature required for decomposition, and rate of decomposition. The concentration of flammable gases increases until it reaches a level that allows sustained oxidation in the presence of the ignition source. The ignition characteristics of the gas and the availability of oxygen are two important variables in any ignition process. After ignition and removal of the ignition source, combustion becomes self- propagating if sufficient heat is generated and is radiated back to the material to continue the decomposition process. The combustion process is governed by such variables as rate of heat generation, rate of heat transfer to the surface, surface area, and rates of decomposition. Flame retardancy, therefore, can be achieved by eliminating (or improved by retarding) any one of these variables. A flame retardant should inhibit or even suppress the combustion process. Depending on their nature, flame retardants can act chemically and/or physically in the solid, liquid or gas phase. They interfere with combustion during a particular stage of this process, i.e. during heating, decomposition, ignition or flame spread (Troitzsch, 1990). 3.1.1 Physical action There are several ways in which the combustion process can be retarded by physical action (Troitzsch, 1990). (a) By cooling. Endothermic processes triggered by additives cool the substrate to a temperature below that required to sustain the combustion process. (b) By formation of a protective layer (coating). The condensed combustible layer can be shielded from the gaseous phase with a solid or gaseous protective layer. The condensed phase is thus cooled, smaller quantities of pyrolysis gases are evolved, the oxygen necessary for the combustion process is excluded and heat transfer is impeded. (c) By dilution. The incorporation of inert substances (e.g., fillers) and additives that evolve inert gases on decomposition dilutes the fuel in the solid and gaseous phases so that the lower ignition limit of the gas mixture is not exceeded. 3.1.2 Chemical action The most significant chemical reactions interfering with the combustion process take place in the solid and gas phases (Troitzsch, 1990). (a) Reaction in the gas phase. The free radical mechanism of the combustion process which takes place in the gas phase is interrupted by the flame retardant. The exothermic processes are thus stopped, the system cools down, and the supply of flammable gases is reduced and eventually completely suppressed. (b) Reaction in the solid phase. Here two types of reaction can take place. Firstly, breakdown of the polymer can be accelerated by the flame retardant, causing pronounced flow of the polymer and, hence, its withdrawal from the sphere of influence of the flame, which breaks away. Secondly, the flame retardant can cause a layer of carbon to form on the polymer surface. This can occur, for example, through the dehydrating action of the flame retardant generating double bonds in the polymer. These form the carbonaceous layer by cyclizing and cross-linking. Flame retardancy is improved by flame retardants that cause the formation of a surface film of low thermal conductivity and/or high reflectivity, which reduces the rate of heating. It is also improved by flame retardants that might serve as a heat sink by being preferentially decomposed at low temperature. Finally, it is improved by flame retardant coatings that, upon exposure to heat, intumesce into a foamed surface layer with low thermal conductivity properties. A flame retardant can promote transformation of a plastic into char and thus limit production of combustible carbon-containing gases. Simultaneously, the char will decrease thermal conductivity of the surface. Flame retardants can also chemically alter the decomposition products, resulting in a lower concentration of combustible gases. Reduced fuel will result in less heat generation by the flame and may lead to self-extinction. Structural modification of the plastic, or use of an additive flame retardant, might induce decomposition or melting upon exposure to a heat source so that the material shrinks or drips away from the heat source. It is also possible to significantly retard the decomposition process through selection of chemically stable structural components or structural modifications of a polymer. In general, anything that will prevent the formation of a combustible mixture of gases will prevent ignition. However, we may also distinguish those cases in which the flame retardant or the modified polymer unit, upon exposure to a heat source, will form gas mixtures that will react chemically in the gas phase to inhibit ignition. The goal of flame retardance in the combustion and propagation stages is to decrease the rate of heat generated or radiated back to the substrate. Any or all of the above-mentioned mechanisms could function to prevent a self-sustaining flame (Pearce & Liepins, 1975). Flame retardancy occurs both as already stated in the vapour phase (by interfering with oxidation through removal of free radicals) and in the condensed phase (charring or altering thermal degradation processes). Phosphorus acts primarily in the condensed phase by promoting charring, presumably through the formation of phosphoric acid and a decreased release of flammable volatiles. However, some reports indicate that certain organic phosphorus compounds may also work in the gas phase by scavenging free radicals. Antimony (which functions only in the presence of a halogen) is believed to work similarly to phosphorus in the condensed phase and combine with halogens in the gas phase to scavenge free radicals (HÊ and OHÊ) that are necessary for combustion. The role of nitrogen is not completely understood. Nitrogen is known to impart flame retardancy in combination with phosphorus and also by itself, as in polyamides and aminoplasts. Bromine and chlorine act in the gas phase by reacting with free radicals (Ulsamer et al., 1980). The mechanism for imparting durable flame retardance to cellulose is that of increasing the quantity of carbon, or char, formed instead of volatile products of combustion, and flammable tars. Salts that dissociate to form acids or bases upon heating are usually effective flame retardants. Salts of strong acids and weak bases are the most effective compounds. Ammonium and amine salts are generally effective, as are Lewis acids and bases, either by themselves or when formed in combustion. 3.2 Condensed phase mechanisms The role of phosphorus compounds has been extensively studied. In both cellulose and thermoplastics, phosphorus salts of volatile metals and most organophosphorus compounds are known to be effective flame retardants. The formation of char appears to be the key. For example, although triphenyl phosphate, triphenyl phosphite and triphenyl phosphine are all equivalent on a phosphorus basis, the more effective flame retardant compounds act by forming phosphoric acid, which changes the course of the decomposition of cellulose to form carbon and water (US EPA, 1976). The flame-retardant action of phosphorus compounds in cellulose is believed to proceed by way of initial phosphorylation of the cellulose, probably by initially formed phosphoric or polyphosphoric acid. The phosphorylated cellulose then breaks down to water, phosphoric acid and an unsaturated cellulose analogue, and eventually to char by repetition of these steps. Certain nitrogen compounds such as melamines, guanidines, ureas and other amides appear to catalyse the steps forming cellulose phosphate and are found to enhance or synergize the flame-retardant action of phosphorus on cellulose. In polyethylene terephthalate and polymethyl methacrylate the mechanism of action of phosphorus-based flame retardants has been shown to involve both a similar decrease in the amount of combustible volatiles and a similar increase in the amount of residues (aromatic residues and char). The char formed also acts as a physical barrier to heat and gases. In rigid polyurethane foams the action of phosphorus flame retardants also appears to involve char enhancement. In flexible foam the mechanism is less well understood (Weil,1993). 3.3 Gas-phase mechanisms In addition to the condensed-phase mechanism, phosphorus flame retardants can exert gas-phase flame-retardant action. It has been demonstrated that trimethyl phosphate retards the velocity of a methane-oxygen flame with about the same molar efficiency as antimony trioxide (Weil, 1993). The mechanisms of action can differ depending on the type of compound used as a flame retardant. The mechanism affects the generation of products of combustion, some of which are potentially corrosive and toxic. One mechanism of improving the flame retardancy of thermoplastic materials is to lower their melting point. This results in the formation of free radical inhibitors in the flame front and causes the material to recede from the flame without burning. Free radical inhibition involves the reduction of gaseous fuels generated by burning materials. Heating of combustible materials results in the generation of hydrogen, oxygen, and hydroxide and peroxide radicals that are subsequently oxidized with flame. Certain flame retardants act to trap these radicals and thereby prevent their oxidation. Bromine is more effective than chlorine. For example: RBr + HÊ -> HBr + RÊ If the resulting compound R is less readily oxidized than the radical that is removed, the result is reduced flammability. Measurements of the limiting oxygen index of polymers show that, in contrast to the situation with chlorine, the effect of bromine does depend on the gaseous oxidant involved. This suggests that bromine compounds act to some extent by interfering with the flame reactions and it is generally believed that this is probably their principal mode of action, although they can also affect the condensed-phase decomposition of the polymer. Any gas-phase mechanism of flame retardancy by bromine compounds must by definition involve the release of volatile bromine-containing species, which then inhibit the flame reactions. In the case of brominated flame retardants, it is generally assumed that hydrogen bromide is liberated and reacts with the free radicals responsible for the propagation of combustion, replacing them by the relatively unreactive bromine atom. HÊ + Hbr -> H2 + BrÊ OHÊ + Hbr -> H2O + BrÊ The mechanism operating in a particular polymer system will depend on the mode and ease of breakdown of the brominated flame retardant present. Some of these compounds are thermally stable and volatilize when the associated polymer is heated to sufficiently high temperatures. Others decompose to give substantial amounts of either lower molecular weight organic bromine compounds or hydrogen bromide (Cullis, 1987). The presence of chemically bound bromine can also affect the rates and modes of thermal decomposition of organic polymers in the condensed phase. Brominated flame retardants vary considerably in both their volatility and thermal stability. Although some very stable compounds volatilize chemically unchanged, others break down within the polymer or react directly with it in the condensed phase. Hydrogen bromide is often a product and can significantly influence the rate and course of polymer decomposition, although its effect is small in comparison with those which it exerts on polymer combustion as a whole. However, even thermally stable brominated flame retardants can affect the decomposition of polymers in the condensed phase, causing the original polymer breakdown stage to be replaced by two separate stages, both of which involve polymer and additive. Thus, it is clear that hydrogen bromide is not the only bromine-containing compound which affects condensed-phase polymer decomposition and that organic bromine compounds can also markedly change the rate and mode of breakdown of organic polymers (Cullis, 1987). A critical factor governing the effectiveness of brominated flame retardants and indeed their mechanism of action is their thermal stability relative to that of the polymers with which they are associated. The most favourable situation for a flame retardant to be effective will be one in which its decomposition temperature lies 50°C or so below that of the polymer. In general, decomposition at this temperature with the liberation of substantial quantities of hydrogen bromide or elemental bromine is likely to enhance flame- retardant activity. Owing to the relatively low C-Br bond energy, bromine compounds generally breakdown at quite low temperatures (typically 200-300°C). Temperatures in this range overlap well with the decomposition of many common polymers. This is probably a factor determining the superior flame-retardant effectiveness of bromine compounds compared with that of chlorine compounds (Cullis, 1987). 3.4 Co-additives for use with flame retardants Brominated flame retardants are in some cases used on their own, but their effectiveness is increased by a variety of co-additives, so that in practice they are more often used in conjunction with other compounds or with other elements incorporated into them. Thus, for example, the addition of small quantities of organic peroxides to polystyrene greatly reduces the amount of hexabromocyclododecane needed to give a flame-retardant foam; other free radical initiators behave in a similar fashion. These compounds appear to act by promoting depolymerization of the hot polymer, giving a more fluid melt. More heat is therefore required to keep the polymer alight, because there is a greater tendency for the more molten material to drip away from the neighbourhood of the flame (Cullis, 1987; Troitzsch, 1990). The flame-retardant properties of bromine compounds, like those of chlorine compounds, will be considerably enhanced when they are used in conjunction with other hetero-elements, notably phosphorus, antimony and certain other metals. The simultaneous presence of phosphorus in bromine-containing polymer systems usually serves to improve their degree of flame retardance, although, contrary to general opinion, bromine and phosphorus generally exert effects that are largely additive rather than synergistic. Sometimes the two elements are present in the same molecule, e.g., tris(2,3,-dibromopropyl)phosphate. In other systems, however, it is more convenient to use mixtures of a bromine compound and a phosphorus compound so that the ratio of the two elements can be readily adjusted. It has already been pointed out that brominated flame retardants on their own act predominantly in the gas phase. In contrast, phosphorus compounds act mainly in the condensed phase, especially with oxygen-containing polymers. It is therefore of interest to discover whether, when both elements are present together, each continues to act in the usual way or new mechanisms come into operation. However, the evidence here is somewhat conflicting. Studies of the effects of phosphate esters, with or without bromine present, on the combustion of polyesters show that more char is formed when the flame retardant contains bromine, and that most of this bromine remains in the char. This suggests that the bromine-phosphorus compound affects primarily the condensed-phase processes. However, studies of the flammability of rigid polyurethane foams show that the inhibiting effect of tris(2,3-dibromopropyl)- phosphate on combustion depends on the nature of the gaseous oxidant, suggesting that the flame retardant acts here, at least in part, by interfering with reactions in the gas phase. With hydrocarbon polymers, such as polyolefins and polystyrene, the major part of the phosphorus present volatilizes and acts in the gas phase, being apparently converted to simple species, such as phosphorus and phosphorus oxide free radicals. These species can then interfere chemically with the reactions responsible for flame propagation by catalysing the recombination of the active free radicals involved. In such cases, any bromine present simultaneously is presumably converted to species such as Br and HBr, which function in the gas phase in the usual way (Cullis, 1987). Antimony is a much more effective co-additive than phosphorus, generally in the form of its oxide, Sb2O3. On its own this compound has no flame-retardant activity and is therefore almost always used in conjunction with a halogen compound. In general, bromine-antimony mixtures are more effective than the corresponding chlorine-antimony systems. The use of antimony trioxide greatly reduces the high levels normally needed for effective flame retardance of bromine compounds on their own. The principal mode of action is in the gas phase. If bromine and antimony are present simultaneously in a burning organic polymer, the major part of the antimony is volatilized, probably as SbBr3 or SbOBr. These compounds then provide a ready source of hydrogen bromide and they also produce in the middle of the combustion zone a mist of fine particles of solid SbO, which can catalyse the recombination of the free radicals responsible for flame propagation, via the formation of transient species like SbOH. A number of other metal oxides have been investigated as partial or total replacements for antimony trioxide. Their use, however, has a number of disadvantages. The most important point is that volatilization of the bromine occurs at the right stage of the combustion cycle. With zinc oxide, volatilization takes place too early and the bromine has disappeared from the system before it can become effective (Cullis, 1987). It can be concluded that in many, if not most, polymer systems in which bromine and phosphorus are both present, the two elements tend to act independently and therefore additively. The important mode of action of metal oxides as co-additives for brominated flame retardants is to catalyse the breakdown of the bromine compound and therefore the release of volatile bromine compounds into the gas phase. However, metal-bromine compounds may also be formed, and these may have more specific modes of action in inhibiting polymer combustion (Cullis, 1987). 3.5 Smoke suppressants Smoke production is determined by numerous parameters. No comprehensive theory yet exists to describe the formation and constitution of smoke. Smoke suppressants rarely act by influencing just one of the parameters determining smoke generation. Ferrocene, for example, is effective in suppressing smoke by oxidizing soot in the gas phase as well as by pronounced charring of the substrate in the condensed phase. Intumescent systems also contribute to smoke suppression through creation of a protective char. It is extremely difficult to divide these multifunctional effects into primary and subsidiary actions since they are so closely interwoven. At present no uniform theory on the mode of action of smoke suppressants has been established (Troitzsch, 1990). 3.5.1 Condensed phase Smoke suppressants can act physically or chemically in the condensed phase. Additives can act physically in a similar fashion to flame retardants, i.e., by coating (glassy coatings, intumescent foams) or dilution (addition of inert fillers), thus limiting the formation of pyrolysis products and hence of smoke. Chalk (CaCO3), frequently used as a filler, acts in some cases not only physically as a dilutent but also chemically (in PVC, for example) by absorbing hydrogen chloride or by effecting cross-linking so that the smoke density is reduced in various ways. The processes contributing to smoke suppression can be extremely complex. Smoke can be suppressed by the formation of a charred layer on the surface of the substrate, e.g., by the use of organic phosphates in unsaturated polyester resins. In halogen-containing polymers, such as PVC, iron compounds, e.g., iron (III) chloride, cause charring by the formation of strong Lewis acids. Certain compounds such as ferrocene cause condensed-phase oxidation reactions that are visible as a glow. There is pronounced evolution of CO and CO2, so that less aromatic precursors are given off in the gas phase. Compounds such as MoO3 can reduce the formation of benzene during the thermal degradation of PVC, probably via chemisorption reactions in the condensed phase. Relatively stable benzene-MoO3 complexes that suppress smoke development are formed (Troitzsch, 1990). 3.5.2 Gas phase Smoke suppressants can also act chemically and physically in the gas phase. The physical effect takes place mainly by shielding the substrate with heavy gases against thermal attack. They also dilute the smoke gases and reduce smoke density. In principle, two ways of suppressing smoke chemically in the gas phase exist: the elimination of either the soot precursors or the soot itself. Removal of soot precursors occurs by oxidation of the aromatic species with the help of transition metal complexes. Soot can also be destroyed oxidatively by high-energy OH radicals formed by the catalytic action of metal oxides or hydroxides. Smoke suppression can also be achieved by eliminating the ionized nuclei necessary for forming soot with the aid of metal oxides. Finally soot particles can be made to flocculate by certain transition metal oxides (Troitzsch, 1990). 4. PERFORMANCE CRITERIA FOR AND CHOICE OF FLAME RETARDANTS At present, the selection of a suitable flame retardant depends on a variety of factors that severely limit the number of acceptable materials. Many countries require extensive information on human and environmental health effects for new substances before they are allowed to be put on the market. For existing chemicals such data are not always available but several national and international programmes are in the process of gathering this information. For most chemicals, including flame retardants, the following information regarding human and environmental health is essential to understanding a chemical's potential hazards: 1. Data from adequate acute and repeated dose toxicity studies is needed to understand potential health effects. 2. Data on biodegradability and bioaccumulation potential is needed as a first step in understanding a chemical's environmental behaviour and effects. 3. Information on the chemical's possible breakdown and/or combustion products may also be needed. 4. Since flame retardants are often processed into polymers at elevated temperatures, consideration of the stability of the material at the temperature inherent to the polymer processing is needed, as well as on whether or not the material volatilizes at that temperature or during use. 5. Consideration should be given to the need for information on the possible formation of toxic and/or persistent breakdown products during accidental fires or incineration. Successfully achieving the desired improvement in flame retardancy is a necessary precursor to other performance considerations. The basic flammability characteristics of the polymer to be used play a major role in the flame-retardant selection process, as some polymers burn much more readily than others. Flame-retardant selection is also affected by the test method to be used to assess flame retardancy. Some tests can be passed with relatively low levels of many flame retardants, while high levels of very powerful flame retardants are needed to pass other tests. It is not possible to provide a comprehensive review in this monograph, but a short introduction is given in Annex III. There are many performance issues other than flame retardancy that must be considered during the selection of a flame retardant for any use. Just as in applications not needing improved flame retardancy, a long list of processing and performance requirements must be met before a material can be accepted for use. The development of a polymer formulation that meets all of these requirements involves finding the optimum combination of polymer(s), flame retardant(s), synergist(s), stabilizer(s), processing aid(s), and all other additives. This is complex and difficult work requiring a great deal of time, effort and expense. Flame retardants may adversely affect the processing characteristics of polymers. Changes occurring in the viscosity of liquid systems or in the flow of polymers that are melted during processing can cause major problems. Significant alteration of the rate of reaction of thermoset polymers or the speed and degree of crystallization of thermoplastic polymers may result from the use of some flame retardants. The temperatures routinely used to process many polymers severely restrict the number of flame retardants suitable for incorporation. Since flame retardants are frequently used at high levels, they often have a dramatic effect on the basic mechanical properties of polymers in which they are used. Reduction of strength (tensile, compression), rigidity, toughness and/or heat resistance are common problems. When flame retardants are added to polymers their appearance (colour, gloss, transparency) and physical properties (density, hardness, melting and glass transition temperatures, thermal expansion) often change significantly. Electrical properties (resistance, dielectric, tracking) are frequently altered, and aging due to factors such as oxidation, UV radiation, high temperature may be reduced. The chemical properties of a flame retardant are often of great importance in its selection. Resistance to exposure to water, solvents, acids, bases, oils or other substances may be a requirement for use. Issues related to solubility, hydrolysis resistance or reactivity with other formulation components may prevent the use of an otherwise desirable flame retardant. The relationship between cost and performance is an essential consideration in the selection of a flame retardant. All of the above-mentioned issues also apply to textiles. In addition, the durability (resistance to cleaning with water or by other techniques) of the flame retardant system is critical (Jay, 1990). 5. PRODUCTION AND USES OF FLAME RETARDANTS AND FLAME-RETARDED POLYMERS 5.1 Production The worldwide demand for flame-retardant chemicals in 1992 was estimated to be 600 000 tonnes (OECD, 1994). This includes over a hundred different products, which can be classified according to base chemical content as depicted in Table 3. Table 3. Demand for flame retardants according to base chemical content (from: OECD, 1994) Base chemicals Demand (tonnes) Bromine 150 000 Chlorine 60 000 Phosphorus 100 000 Antimony 50 000 Nitrogen 30 000 Aluminium 170 000 Others 50 000 It is difficult to obtain an accurate picture of market volumes of flame retardants as reports from different sources appear to conflict. Table 4 shows USA market volume trends between 1986 and 1991. Table 5 presents the annual consumption of different flame retardants in Japan over the period 1986 - 1994. A comparable table of global use was not available. Table 5 indicates that the consumption of brominated flame retardants and antimony oxide in Japan has more than doubled over this period, compared to the moderate increase in other flame retardants. The market for hydrated aluminium as a flame retardant seems to have decreased in Japan, whereas Table 4 (Gann, 1993) shows that an increase occurred in the USA. Chlorinated paraffins had an estimated world production of 300 000 tonnes/year in 1985 (IPCS, 1996b). Table 4. Flame retardant market volume (from: Gann, 1993) Group 1986 1991 (tonnes) (tonnes) Phosphate esters 20 000 18 000 Halogenated phosphates 13 000 16 000 Chlorinated hydrocarbons 15 000 15 000 Brominated hydrocarbons 28 000 36 000 Brominated bisphenol A 16 000 18 000 Antimony trioxide 22 000 25 000 Borates 8 000 8 000 Aluminium trihydrate 140 000 170 000 Magnesium hydroxide 2 000 3 000 Total 264 000 301 000 5.2 Uses The consumption of flame retardants in plastics and other combustible materials is closely linked to regulations covering fire precautions. The principle regulations relate to the building, transportation, electrical engineering, furnishing and mining sectors (Troitzsch, 1990). A worldwide estimate of the consumption of flame retardants according to materials is not available but the figures for Europe listed in the Table 6 should reflect the market in general. Table 5. Trends in the annual consumption of flame retardants in Japana Type Compound Amount (tonnes) 1986 1990 1994 Brominated Tetrabromobisphenol A (TBBPA) 12 000 23 000 24 000 Decabromobiphenyl ether 3 000 10 000 5 500 Octabromobiphenyl ether 600 1 100 500 Tetrabromobiphenyl ether 1 000 1 000 0 Hexabromocyclododecane 600 700 1 600 Bis(tetrabromophthalimido) ethane - 1 000 2 500 Tribromophenol 100 450 3 500 Bis(tribromophenoxy) ethane 400 400 900 TBBPA polycarbonate oligomer - - 2 500 Brominated polystyrene - - 1 300 TBBPA epoxy oligomer - 3 000 7 000 Others 2 400 - 2 150 Subtotal 20 000 40 650 51 450 Chlorinated Chlorinated paraffins 4 000 4 500 4 300 Others 850 700 900 Subtotal 4 850 5 200 5 200 Phosphoric Halogenated ester 3 000 3 000 3 100 Non-halogenated ester 4 000 4 400 4 400 Others 1 750 1 750 3 310 Subtotal 8 750 9 150 10 810 Table 5. (contd.) Type Compound Amount (tonnes) 1986 1990 1994 Inorganic Antimony oxide 8 300 16 000 17 000 Hydrated aluminium 48 000 37 000 42 000 Others 7 200 8 400 9 000 Subtotal 63 500 61 400 68 000 TOTAL 97 100 116 400 135 460 a Based on the investigation made by Kagaku Kogyo Nippon Co. Ltd. (Japan). (Personal communication from Isao Watanabe, Osaka Prefectural Institute of Public Health, Japan). Table 6. Estimated consumption of flame retardants in western Europe for 1985 and 1992 according to materials (from: Sutker, 1988) Product group Consumption (103 tonnes) 1985 1992 Polystyrene 4.0-4.5 4.5-5.0 ABS 1.0-1.5 1.2-1.8 Polyesters 7.5-8.0 8.5-9.0 Epoxy resins 3.5-4.0 4.0-4.5 Polyolefins 10.0-12.0 11.0-13.0 Polyvinyl chloride) 25.0-27.0 27.0-29.0 Polyurethanes 12.0-13.5 13.5-15.0 Engineering plastics 1.5-1.8 1.7-2.0 Paper and textiles 9.0-10.0 10.0-11.0 Rubber and elastomers 5.0-6.0 6.0-7.0 Other 11.5-11.7 12.6-12.7 Total 90.0-100.0 100.0-110.0 5.2.1 Plastics The plastics industry is the largest consumer of flame retardants, estimated at about 95% for the USA in 1991. About 10% of all plastics contain flame retardants (Wolf & Kaul, 1992). The main applications are in building materials and furnishings (structural elements, roofing films, pipes, foamed plastics for insulation, furniture and wall and floor coverings), transportation (equipment and fittings for aircraft, ships, automobiles and railroad cars), and in the electrical industry (cable housings and components for television sets, office machines, household appliances and lamination of printed circuits). The growth in the flame retardant market reflects the enormous expansion of the plastics industry in recent decades. Between 1988 and 1994, there was a worldwide increase of 20%. Although the USA, western Europe and Japan are still the largest plastic producers (30, 24 and 12% of the market, respectively), other countries showed the largest increases between 1988 and 1994, e.g., South Korea (170%); China (60%); Taiwan (54%) (Anon, 1995). Examples of flame retardants used in various plastics (Wolf & Kaul, 1992) are as follows: PVC: Chlorinated paraffins or phosphate esters, antimony trioxide, aluminium hydroxide Acrylonitrile-butadiene-styrene (ABS): Octabromodiphenyl ether, antimony trioxide Expandable polystyrene: Hexabromocyclododecane High-Impact polystyrene (HIPS): Decabromodiphenyl ether or tetrabromobisphenol A, antimony trioxide Linear polyester: Brominated organics Polypropylene: Tetrabromobisphenol A, bis(2,3-dibromopropyl ether), antimony trioxide Low-density polyethylene (LDPE) films: chlorinated paraffins, antimony trioxide High-density polyethylene (HDPE) and cross-linked polyethylene: Brominated aromatics Polyurethane foams: Organophosphates, brominated organic compounds, alumina trihydrate Polyamides: Brominated aromatic compounds, chlorinated cycloaliphatic compounds, antimony trioxide, red phosphorus, melamine Polycarbonates: Tetrabromobisphenol A, brominated organic oligomers, sulfonate salts Unsaturated polyesters: Chlorinated and brominated organic compounds, antimony trioxide, alumina trihydrate Epoxy resins: Tetrabromobisphenol A 5.2.2 Textile/furnishing industry In contrast to the plastics industry, the textile industry is a much smaller market for flame retardants. However, rather than employing just one flame retardant, the use of a combination of chemicals is usually necessary for textiles. Phosphorus-containing materials are the most important class of compounds to impart durable flame resistance to cellulose (Calamari & Harper, 1993). Flame-retardant finishes containing phosphorus compounds usually also contain nitrogen or bromine, or sometimes both. Another system is based on halogens (usually bromine) in conjunction with nitrogen or antimony. Flame retardants used in furniture/textiles include the following (Anon, 1992; Calamari & Harper, 1993; EFRA, 1995): * organic phosphates such as tri-alkyl or tri-aryl phosphates, tri- chloroalkyl phosphates, dialkyl phosphites, tetrakis(hydroxymethyl)phosphonium chloride (THPC) and related structures; * halogenated compounds such as polybrominated diphenyl ethers (found in over 50% of treated furniture) and chlorinated paraffins (rainproof applications); * inorganic compounds such as antimony trioxide, ammonium bromide, boric acid and aluminium hydrate. Details on the flame-retardant types were reported by Calamari & Harper (1993) and can be found in Annex II. 6. FORMATION OF TOXIC PRODUCTS ON HEATING OR COMBUSTION OF FLAME-RETARDED PRODUCTS Natural or synthetic material that burns produces potentially toxic products. There has been considerable debate on whether addition of organic flame retardants results in the generation of a smoke that is more toxic and may result in adverse health effects on those exposed. There has been concern in particular about the emission of polybrominated dibenzofurans (PBDF) and polybrominated dibenzodioxins (PBDD) during manufacture, use and combustion of brominated flame retardants. 6.1 Toxic products in general Combustion of any organic chemical may generate carbon monoxide (CO), which is a highly toxic non-irritating gas, and a variety of other potentially toxic chemicals. Some of the major toxic products that can be produced by pyrolysis of flame retardants are: CO, CO2, HCl, POX, ammonia vapour, bromofurans, HBr, HCN, NOX and phosphoric acid (Anon, 1992). In general the acute toxicity of fire atmospheres is determined mainly by the amount of CO, the source of which is the amount of generally available flammable material. Most fire victims die in post flash-over fires where the emission of CO is maximized and the emission of HCN and other gases is less. The acute toxic potency of smoke from most materials is lower than that of CO (Hirschler, 1995; Nelson, 1995). Flame retardants significantly decrease the burning rate of the product, reducing heat yields and quantities of toxic gas. In most cases, smoke was not significantly different in room fire tests between flame-retarded and non-flame-retarded products (Babrauskas et al. 1988). Morikawa et al. (1995) reported toxicity studies on gases from full-scale room fires involving fire retardant materials (a variety, but not specified). HCN and CO were the two major toxicants. There was no evidence that the smoke from flame-retarded materials was more toxic to rabbits than the smoke from non-flame-retarded materials. Regarding brominated flame retardants, Cullis (1987) stated that unless suitable metal oxides or metal carbonates are also present, virtually all the bromine is eventually converted to gaseous hydrogen bromide (HBr). This is a corrosive and powerful sensory irritant. In a fire situation however, it is always carbon monoxide (CO) or hydrogen cyanide (HCN), rather than an irritant which causes rapid incapacitation. Owing to its high reactivity, hydrogen bromide is unlikely to reach dangerously high concentrations (Cullis, 1987). 6.2 Formation of halogenated dibenzofurans and dibenzodioxins PBDFs and PBDDs can be formed from polybrominated diphenyl ethers (PBDEs), polybrominated phenols, polybrominated biphenyls (PBBs) and other brominated flame retardants under various laboratory conditions, including heating. Because chlorinated derivatives are preferably formed during pyrolysis, mixed halogen compounds will be predominantly produced if a chlorine source is also available (Buser, 1987a,b). As in the case of PCDD/PCDF, it is the 2,3,7,8-substituted isomers that are toxic. 6.3 Exposure to PBDD/PBDF from polymers containing halogenated flame retardants 6.3.1 Exposure due to contact or emission from products containing halogenated flame retardants Exposure of the general public to PBDD/PBDF impurities in flame- retardant polymers is unlikely to be of significance. The possible exposure to PBDD/PBDF from TV sets and computer monitors flame- retarded with halogenated flame retardants has been discussed in Environmental Health Criteria 162: Brominated diphenyl ethers and is unlikely to be of significance (IPCS, 1994b). 6.3.2 Workplace exposure studies Several studies have been performed to determine whether PBDD/PBDF is present in the fumes emitted during thermal processes, such as the extrusion of resins containing halogenated flame retardants under normal processing conditions at temperatures in the range of 200 to 250°C (IPCS 1994b, 1995a, in preparation). Epidemiological studies of workers engaged in processing polymers with PBDEs have been reported (IPCS, 1994b). Results of PBDD/PBDF workplace monitoring during polymer processing have also been reported (IPCS 1994b, 1995a). PBDD/PBDF personnel and room air levels during processing of PBDEs were < 2 ng/m3 (TCDD equivalent) with the exception of two samples at the extruder head (128 ng/m3, TCDD equivalent) (IPCS, 1994b). Engineering controls were successful in reducing these levels. Workplace control measures should also include appropriate industrial hygiene measures and monitoring of exposure (IPCS, 1994b, 1995a). 6.3.3 Formation of PBDD/PBDF from combustion 126.96.36.199 Laboratory pyrolysis experiments In the late 1980s many pyrolysis experiments (at temperatures of 400-900°C) on brominated flame retardants and flame-retardant systems were performed and the breakdown products measured. Flame retardants or intermediates tested included PBBs, PBDEs, 2,4,6-tribromophenol, pentabromophenol, tetrabromobisphenol A and tetrabromophthalic anhydride (IPCS 1994b, 1995a, in preparation). Pyrolysis of the flame retardants alone, as well as with polymer mixtures, was investigated. As different laboratories carried out the experiments using a variety of testing methods and conditions, a direct comparison of the many experiments is not possible. Details of the pyrolysis experiments involving PBDEs, tetrabromobisphenol A and derivatives, and PBBs are given in the respective EHC monographs (IPCS 1994b, 1995a, in preparation). Although they indicate which flame retardants are likely to form PBDF (and to a lesser extent PBDD) pyrolysis experiments are not generally comparable to actual fire situations. 188.8.131.52 Fire tests and fire accidents Fire tests on televisions have shown smoke and combustion residues containing high levels of PBDD/PBDF. However, levels from actual fire accidents involving televisions revealed much lower levels than those produced under fire test conditions (IPCS, 1994b). Further studies are discussed in the EHC monograph on PBDD/PBDFs (IPCS, in preparation). 7. OVERVIEW OF EXPOSURE AND HAZARDS TO HUMANS AND THE ENVIRONMENT Since flame retardants are a heterogeneous group of diverse chemicals (see chapter 2 and Annex II), the information presented in this section only provides a general overview of possible routes of exposure to chemicals associated with flame-retardant use. This section also provides a brief summary of the hazards to human health and to the environment posed by chemicals connected with flame- retardant use. For detailed information on the extent of exposure and health and environmental effects of individual substances, the appropriate specific EHC monographs should be consulted. The toxicity and ecotoxicity of flame retardants used in the industry of upholstered furniture and related articles has discussed in a report by the European Economic Community (Anon, 1992). 7.1 Human exposure 7.1.1 General population Potential sources of exposure include consumer products, manufacturing and disposal facilities, and environmental media. Factors affecting exposure of the general population include the physical and chemical properties of the product, the extent of manufacturing and emission controls, the use made of the product (surface coating, durability of fabric finishes, incorporation into a polymer, etc.), the end use, and the method of disposal. Potential routes of exposure for the general population include the dermal route (contact with flame-retarded textiles), inhalation and ingestion. 7.1.2 Occupational exposure Occupational exposure may occur during the manufacture, transport, processing and disposal/recycling of flame retardants. Routes of exposure could include inhalation, dermal contact and ingestion. Factors affecting the extent of exposure include industrial hygiene practices, engineering controls, manufacturing processes and the type of product. As with any other industrial chemical, workplace monitoring and good industrial practice can delineate the extent of any exposure. 7.2 Exposure of the environment Environmental exposure may occur as a result of the manufacture, transport, use or waste disposal of flame retardants. Routes of environmental exposure can include water, air and soil. Factors affecting exposure include the physical and chemical properties of the product, emission controls, disposal/recycling methods, volume and biodegradability/persistence. Environmental monitoring can determine the extent of environmental exposure. On the basis of the estimated demand for flame retardants (see Table 3), more than 1 million tonnes of flame-retardant polymers are produced each year. Most flame-retarded products eventually become waste. Municipal waste is generally disposed of via incineration or landfill. Incineration of flame-retarded products can produce various toxic compounds, including halogenated dioxins and furans. The formation of such compounds and their subsequent release to the environment is a function of the operating conditions of the incineration plant and the plant's emission controls. There is a possibility of flame retardants leaching from products disposed of in landfills. However, potential risks arising from landfill processes are also dependent on local management of the whole landfill. The significance of any release of flame retardants from disposal sites has yet to be determined. Some products containing flame retardants, including some plastics, have been identified as suitable for recycling (Lorenz & Bahadir, 1993; Meyer et al., 1993). 7.3 Hazards to humans The hazards to humans associated with some flame retardants have been outlined in the relevant EHC monographs. For example, the use of tris(2,3-dibromopropyl) phosphate and bis(2,3-dibromopropyl) phosphate was banned in 1977 by the US Consumer Product Safety Commission and in several other developed countries for use in children's clothing because of concerns that the chemical might be a human carcinogen and because of the possibility of significant human exposure through contact with treated fabrics (IPCS, 1995b). Delayed neurotoxicity due to tri- ortho-cresyl phosphate (TOCP), one of the tricresyl phosphate isomers, has been observed in humans (IPCS, 1990). Some polybrominated biphenyl (PBB) congeners have been shown to produce chronic toxicity and cancer in experimental animals. However, no definitive human health effects, correlatable with exposure, were found in a population in Michigan, USA, accidentally exposed to PBBs (IPCS, 1994a). 7.4 Hazards to the environment EHC monographs outline the hazards to the environment associated with some flame retardants (see Table 1). Some PBB congeners are persistent and bioaccumulative and may pose a threat especially to higher levels of the food chain (IPCS, 1994a). Hexachloro- cyclopentadiene is highly toxic to aquatic organisms. However, information obtained under environmentally realistic conditions is limited. The potential hazard to the general environment is expected to be low (IPCS, 1991b). Low concentrations of triphenyl phosphate have been detected in environmental samples. Triphenyl phosphate is rapidly degraded in the environment. However, sediment-dwelling organisms near production plants may have been exposed to concentrations high enough to exert toxic effects (IPCS, 1991a). Tricresyl phosphate is also degraded rapidly in the environment, and subsequent environmental concentrations are therefore low. The acute toxicity of tricresyl phosphate to aquatic organisms is low (IPCS, 1990). Persistence of pentabromodiphenyl ether (PeBDE) and lower brominated diphenylethers in the environment suggest that commercial PeBDE should not be used (IPCS, 1994b). Some flame retardants have come under intense environmental scrutiny. US EPA has called for additional testing (US EPA, 1992). The data on environmental levels of short-chain chlorinated paraffins indicate that in areas close to release sources there is a risk to both freshwater and estuarine organisms. Recent data indicate that there is also a potential risk to aquatic invertebrates from intermediate- and long-chain chlorinated paraffin products (IPCS, 1996b). 8. REGULATIONS WITH RESPECT TO FLAME RETARDANTS Several national regulatory bodies have implemented regulations on specific substances associated with flame-retardant applications. In the USA the Interagency Testing Committee (ITC), under the auspices of the Toxic Substances Control Act (TSCA), makes recommendations concerning the need for additional testing on chemicals in the TSCA inventory, including flame retardants. Based on the information published since 1978, the ITC has made initial testing recommendations upon 128 brominated flame retardants (US TSCA, 1992; Walker, 1994; Annex IV). In the European Community, the use of tris(2,3-dibromopropyl) phosphate (EC Directive 76/769/EEC) and tris(1-aziridinyl)phosphine oxide (EC Directive 83/264/EEC) in textiles has been banned. In 1977, the US Consumer Product Safety Commission banned the use of tris(2,3- dibromopropyl)phosphate in children's clothing (IPCS, 1995b). The European Community has also banned the use of PBBs in textiles (EC Directive 83/264/EEC). Several countries have either taken or proposed regulatory actions on PBBs, as outlined in Table 7. Controls on the emissions of dioxins and furans from municipal solid waste incinerators have been implemented in the United Kingdom under the Environmental Protection Act (1990). In Germany, a second modification of the Chemicals Prohibition Ordinance, which was adopted in 1994, imposes limits on 2,3,7,8-substituted chlorinated dioxins and furans and, for the first time, on some 2,3,7,8-substituted brominated dioxins and furans (OECD, 1994). Table 7. Country-specific actions on PBBs either taken or proposeda Country Actions Austria Prohibits the manufacture, placing on the market, import and use of PBBs and products containing these substances. Canada Prohibits the manufacture, use, processing, offer for sale, selling or importation of PBBs for commercial, manufacturing or processing purposes. Denmark Implements EC Directive 89/677 banning the use of PBBs in textiles. Finland PBB may not be used in textile articles intended to come into contact with the skin (in accordance with EC Directive 83/264). France Implements EC Directive concerning PBBs and their use on textiles. Netherlands Proposed resolution would prohibit the storage of PBBs or products or preparations containing these substances or making them available to third parties. (Exports are excluded from the resolution). Norway Ban on PBBs in textiles intended to come into contact with skin, implementation of EC Directives 76/769/EEC, 83/264 and 89/677. Sweden Ban on PBBs in textiles intended to come into contact with skin by implementation of EC Directive 76/769. Switzerland Prohibits manufacture, supply, import and use of PBBs and products containing these substances. Supply and import of capacitors and transformers containing PBBs is forbidden. USA No current production or use. Companies intending to resume manufacture must notify US EPA 90 days in advance for approval. a Adapted from: OECD (1994) 9. CONCLUSIONS AND RECOMMENDATIONS FOR THE PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 9.1 Conclusions Flame retardants are a diverse group of compounds used to improve the flame retardancy of polymers and other materials. A large variety of compounds, from inorganic to complex organic molecules, are used as flame retardants, synergists and smoke suppressants. This overview is focused on organic compounds, which typically contain halogen and/or phosphorus. It is difficult to find accurate figures for the global use of flame retardants but estimates indicate that more than 600 000 tonnes are produced annually. Available data indicate a substantial increase of brominated organic product consumption during the last decade. There are obvious benefits in using flame retardants, as many human lifes and property are saved from fire. At present, knowledge of long-term effects resulting from exposure to flame retardants and their breakdown products is limited. Most people that die in fires are killed by carbon monoxide. The majority of the organic flame retardants are either covalently bound into polymer molecules (reactive) or mixed into the polymer (additive). They can act in several ways, either physically (by cooling, by formation of a protective layer or by dilution of the matrix) or chemically (by reactions in either the gas or the solid phase). A number of factors govern the selection of the type of flame retardant to be used in a specific application. Some of these are the flammability of the matrix, processing and performance requirements, chemical properties and possible hazards to human and environmental health. Exposure of the general population to flame retardants can occur via inhalation, dermal contact and ingestion. Potential sources of exposure are consumer products, manufacturing/disposal facilities and environmental media (including food intake). The same routes are possible for occupational exposure, mainly during production, processing, transportation and disposal/recycling of the flame retardants or the treated products. Occupational exposure to the breakdown products may also occur during fire fighting. As several of the compounds used are lipophilic and persistent, they may bioaccumulate. Some of the compounds have been shown to cause organ damage, genotoxic effects and cancer. There is also concern for occupational health and environmental effects from combustion/pyrolysis products, especially the polyhalogenated dibenzofurans and dibenzo- p-dioxins, from some organic flame retardants. Other breakdown products also need to be taken into account. The properties of a number of flame retardants make them persistent and/or bioaccumulative, and they may therefore pose hazards to the environment. Some of the compounds that have been evaluated so far (polybrominated biphenyls, polybrominated diphenyl ethers and chlorinated paraffins) have been found to belong to this group. Some of these have therefore been recommended to not be used. Several countries have developed regulations affecting the production, use and disposal of flame retardants. Some include restrictions on the use of compounds because of potential toxic effects in humans. Germany has developed rules for the maximum content of some 2,3,7,8-substituted polychlorinated dibenzo- para- dioxins and dibenzofurans in products. The availability of relevant data on flame retardants in the open literature is limited, especially for some existing chemicals produced before regulations for commercialization were strengthened in several countries. IPCS has issued evaluations for some flame retardants and is preparing evaluations for others. 9.2 Recommendations for the protection of human health and the environment a) Information on the content and nature of flame retardants, including impurities in products, should be made available to national authorities. b) More complete information on the volume of flame retardants production and consumption should be made available. c) In view of the increased recycling of flame-retarded products, consideration could be given to harmonized labelling by an international forum. d) Compounds that present a toxic risk to humans and/or the environment should not be used as flame retardants. e) Occupational exposure to flame retardants and their breakdown products should be minimized using appropriate engineering and good industrial hygiene practices. The exposure of people working in these operations should be monitored. f) There is a need for proper assessment of occupational health and environmental effects from combustion or pyrolysis products of flame retardants. g) Emissions to the environment from manufacturing, processing, transportation and disposal/recycling of products containing persistent bioaccumulative compounds should be minimized using best available techniques. The environment in the vicinity of such operations should be monitored for the compounds used. h) The use of flame retardants with properties that make them persistent and bioaccumulative should be avoided. i) The levels of the major persistent bioaccumulating flame retardants should be monitored routinely in environmental matrices (biota and sediments). Some compounds that are no longer produced should likewise be monitored, in order to indicate the long-term influence of such products. 10. 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Geneva, World Health Organization, International Programme on Chemical Safety, 126 pp. IPCS (1992) Environmental health criteria 140: Polychlorinated biphenyls and terphenyls, 2nd ed. Geneva, World Health Organization, International Programme on Chemical Safety, 692 pp. IPCS (1994a) Environmental health criteria 152: Polybrominated biphenyls. Geneva, World Health Organization, International Programme on Chemical Safety, 577 pp. IPCS (1994b) Environmental health criteria 162: Brominated diphenyl ethers. Geneva, World Health Organization, International Programme on Chemical Safety, 347 pp. IPCS (1995a) Environmental health criteria 172: Tetrabromobisphenol-A and derivatives. Geneva, World Health Organization, International Programme on Chemical Safety, 139 pp. IPCS (1995b) Environmental health criteria 173: Tris(2,3- dibromopropyl) phosphate and bis(2,3-dibromopropyl) phosphate. Geneva, World Health Organization, International Programme on Chemical Safety, 129 pp. IPCS (1996a) Environmental health criteria 185: Chlorendic acid and anhydride. Geneva, World Health Organization, International Programme on Chemical Safety. IPCS (1996b) Environmental health criteria 181: Chlorinated paraffins. Geneva, World Health Organization, International Programme on Chemical Safety. IPCS (in preparation) Environmental health criteria: Polybrominated dibenzo-p-dioxins and dibenzofurans. Geneva, World Health Organization, International Programme on Chemical Safety. ISO/IEC Guide (1990) Glossary of fire terms and definitions, 1st ed. Geneva, International Organization for Standardization. Japan Fire Retardant Association (1988) Voluntary rules of the flame retardancy and the toxicological (safety) examination for flame retardant products under the guide-line of the Fire Defence Agency, Fire Retardant Products Approval Commission. Tokyo, Japan Fire Retardant Association. Jay TA (1990) Flame retardants. Presentation to the USSR All-Union Congress on Flame Retardants at Saki, Crimea, USSR, 10 October 1990. Kirk-Othmer (1993) Flame retardants. In: Kirk-Othmer encyclopedia of chemical technology, 4th ed. New York, John Wiley & Sons, vol 10, pp 930-1022. Kopp A (1990) [Discussions on bromine-containing flame-retardants.] Berlin, Germany, Federal Ministry for Environment, Nature Conservation and Nuclear Safety (Document sent to the European Commission, Brussels) (in German) Liepins R & Pearce EM (1976) Chemistry and toxicity of flame retardants for plastics. Environ Health Perspect, 17: 55-63. Lorenz W & Bahadir M (1993) Recycling of flame retardants containing printed circuits: a study of the possible formation of polyhalogenated dibenzodioxins/-furans. Chemosphere, 26(12): 2221-2229. Meyer H, Neupert M, Pump W, & Willenberg B (1993) [Flame retardants determine reusability.] Kunststoffe, 83(4): 253-257 (in German). Morikawa T, Okada T, Kajiwara M, Sato Y, & Tsuda Y (1995) Toxicity of gases from full-scale room fires involving fire retardant contents. J Fire Sci, 13(1): 23-42. Nelson GL (1995) Carbon monoxide and fire toxicity. Handout at the 6th Annual BCC Conference on Flame Retardancy: "Recent Advances in Flame Retardancy of Polymeric Materials, Stamford, Connecticut, May 1995 - 16pp. OECD (1994) Selected brominated flame retardants. Paris, Organisation for Economic Co-operation and Development, Environment Directorate, 152 pp (Risk Reduction Monograph No. 3). Pearce EM & Liepins R (1975) Flame retardants. Environ Health Perspect, 11: 59-69. Pettigrew A (1993) Halogenated flame retardants. In: Kirk-Othmer encyclopedia of chemical technology, 4th ed. New York, John Wiley & Sons, vol 10, pp 954-976. Soderlung E & Dybing E (1982) [Flame-retardant toxicology: A literature survey.] Oslo, National Institute for Public Health (Unpublished report ) (in Norwegian). Sutker BJ (1988) Flame retardants. In: Ullmann's encyclopedia of industrial chemistry, 5th ed. Weinheim, Germany, VCH Verlag, vol A11, pp 123-140. Teuerstein A (1990) Brominated FRS, production and uses (Summary). Data from Eurobrom BV. In: Workshop on Brominated Aromatic Flame Retardants. Proceedings of a Workshop held at Skoloster, Sweden, 24-26 October 1989. Solna, Swedish National Chemicals Inspectorate, pp 49-52. Touval I (1993) Antimony and other inorganic flame retardants. In: Kirk-Othmer encyclopedia of chemical technology, 4th ed. New York, John Wiley & Sons, vol 10, pp 936-954. Troitzsch JH (1990) International plastics flammability handbook: Principles, regulations, testing and approval, 2nd ed. Münich, Germany, Hanser Publishers. Ullmann (1988) Ullmann's encyclopedia of industrial chemistry: Volumes A11 et A26, 5th ed. Weinheim, Germany, VCH Verlag. Ulsamer AG, Osterberg RE, & McLauglin J Jr (1980) Flame-retardant chemicals in textiles. Clin Toxicol, 17(1): 101-131. US EPA (1976) A study of flame retardants for textiles. Washington, DC, US Environmental Protection Agency (EPA-560/1-76-001; NTIS PB-251-44). US EPA (1989) Twenty-fifth report of the Interagency Testing Committee to the administrator. Fed Reg, 54(237): 51114-51130. US EPA (1992) Aryl phosphate base stocks: Proposed test rule and reporting requirements. Fed Reg, 57(12): 2136-2158. Walker JD (1994) Testing decisions of the TSCA Interagency Testing Committee for Brominated Flame Retardants: A review of decisions and health and safety data. Presented at the Meeting of the Fire Retardant Chemicals Association, Williamsburg, Virginia, 9-12 October 1994. Washington, DC, US Environmental Protection Agency. Weil ED (1993) Phosphorus flame retardants. In: Kirk-Othmer encyclopedia of chemical technology, 4th ed. New York, John Wiley and Sons, vol 10, pp 976-998. Wolf R & Kaul BL (1992) Plastics, additives. In: Ullmann's encyclopedia of industrial chemistry, ed. Weinheim, Gemany, VCH Verlag, vol A20, pp 459-507. ANNEX I TERMINOLOGY There is no clear definition for many of the terms used to describe fire, flammability and flame retardants. As a result, some confusion has been created by the interchangeable use of terms such as fire retardant, flame retardant, flame-proof and fire-proof. The meaning of these and other terms is often clear only in the context. Therefore, many efforts have been undertaken, at an international level, to harmonize definitions and terms related to fire, including fire protection and flame retardants. The definitions compiled in Table 8 have been taken from the ISO/IEC Guide (1990) and other sources (e.g., Troitzsch, 1990). Other terms, which mostly concern mostly textile flame retardancy, are defined below (US EPA, 1976, Kirk-Othmer, 1993): Fireproof textile This term applies only to those fabrics that undergo virtually no change when exposed to a flame. Flame-retardant textile The term flame-retardant textile refers to any fabric that will not support combustion after the source of ignition is removed. It is synonymous with the term fire-resistant textile. The textile is expected to char or melt. The term covers all treatments short of fire-proofing. Durability Durability refers to the ability of a flame-retardant textile to withstand washing/cleaning, chlorine bleaching, weathering and sun exposure. A durable treatment is any chemical process which imparts flame-retardant properties to textiles and textile products that will last for at least 50 launderings and dry cleaning for the life of the fabric. A semi-durable treatment will resist water but not withstand dry cleaning or more than 10 to 15 launderings. A non-durable treatment is readily removed by water or perspiration and requires replacement after each exposure of the textile to water. The definition of durability must be related to the conditions of use of the textile and the product. Table 8. Definitions of terms connected with fire Term Definition Afterflame Persistence of flaming of a material after the ignition source has been removed Afterglow Persistence of glowing of a material after cessation of flaming or, if no flaming occurs, after the ignition source has been removed Burn To undergo combustion Burning All the physical and/or chemical changes that behaviour take place when a material or product is exposed to a specified ignition source Char Carbonaceous residue resulting from pyrolysis or incomplete combustion Combustible Capable of burning Combustion Exothermic reaction of a substance with an oxidizer, generally accompanied by flames and/or glowing and/or emission of smoke Fire a) A process of combustion characterized by the emission of heat accompanied by smoke and/or flame b) Rapid combustion spreading uncontrolled in time and space Fire All the physical and/or chemical changes behaviour that take place when a material, product and/or structure is exposed to an uncontrolled fire Fire The total gaseous, particulate or effluent aerosol effluent from combustion or pyrolysis Fire The ability of an element of building resistance construction to fulfil for a stated period of time the required load-bearing function, integrity and/or thermal insulation specified in the standard fire-resistance test (see ISO 834) Flame Zone of combustion in the gaseous phase from which light is emitted Table 8. (contd.) Term Definition Flame The property of a material either retardance inherent or by virtue of a substance added or a treatment applied to suppress, significantly reduce or delay the propagation of flame Flame A substance added or a treatment applied retardant to a material in order to suppress, significantly reduce or delay the combustion of the material Flame spread Propagation of a flame front Flame spread Distance travelled by a flame front rate during its propagation per unit time under specified test conditions Flammability Ability of a material or product to burn with a flame under specified test conditions Flammable Capable of burning with a flame under specified test conditions Flash over The rapid transition to a state of total surface involvement in a fire of combustible materials within an enclosure Fully The state of total involvement of developed fire combustible materials in a fire Glowing Combustion of a material in the solid combustion phase without flame but with emission of light from the combustion zone Heat release The calorific energy released per unit rate time by a material during combustion under specified test conditions Ignition Minimum temperature of a material at temperature which sustained combustion can be initiated under specified test conditions Melting Phenomena accompanying the softening of behaviour a material under the influence of heat (including shrinking, dripping, burning of molten material, etc.) Table 8. (contd.) Term Definition Pyrolysis Irreversible chemical decomposition of a material due to an increase in temperature without oxidation Reaction The response of a material under to fire specified test conditions in contributing by its own decomposition to a fire to which it is exposed Smoke A visible suspension of solid and/or liquid particles in gases resulting from combustion or pyrolysis Smoke The reduction in luminous intensity due obscuration to passage through smoke Smouldering The slow combustion of a material without light being visible and generally evidenced by an increase in temperature and/or by smoke Soot Finely divided particles, mainly carbon, produced and/or deposited during the incomplete combustion of organic materials ANNEX II Flame retardants in commercial use or used formerly Introduction Tables 9 and 10 have been compiled on the basis of all the information on flame retardants available to the IPCS and from the following sources: Arias (1992) BFR/CEM Working Group (1989) Boethling & Cooper (1985) Dynamac Corporation (1982) EFRA (1995) Flick (1986) Hutzinger et al. (1976) IARC (1975, 1978, 1979, 1986a,b, 1987, 1989, 1990) IRPTC (1987) Japan Fire Retardant Association (1988) Kirk-Othmer (1993) Kopp (1990) Liepins & Pearce (1976) Pearce & Liepins (1975) Sderlund & Dybing (1982) Teuerstein (1990) Troitzsch (1990) Ulsamer et al. (1980) Ullmann (1988) US EPA (1989) US TSCA (1992) More than 175 flame retardants, or groups of them are tabulated in these two tables. On just 17 of them the database was adequate for preparing a hazard and risk evaluation for man and the environment, and Environmental Health Criteria (EHC) monographs have been, or are being prepared, on these. For the others the hazard to man and the environment has not been evaluated internationally. Most of these substances also have other major uses. In addition, some chemicals used as intermediates in the production of flame retardants have beeen listed. It is likely that these lists are not exhaustive, and that new chemical structures are being developed as flame retardants. Table 9 lists flame retardants in commercial use today and some intermediates, while Table 10 lists flame retardants that have been used in the past. The tables list the chemical name, the chemical structure, the CAS registry number and the uses as flame retardants. The "Use" column also contains information on the global production volume of those compounds that are currently being produced commercially (estimated for the IPCS Task Group by P. Arias, 1995). The international evaluation status of the substances is indicated in the column "Remarks". The following abbreviations are used in this table: EHC An Environmental Health Criteria monograph on the chemical has been published. If no EHC number is given, the document is still in preparation. IARC The International Agency for Research on Cancer of WHO in Lyon has evaluated the carcinogenicity. H High production volume (> 5000 tons per year) M Moderate production volume (1000-5000 tons per year) L Low production volume (<1000 tons per year or in the developmental stage) Table 9. Flame retardants being used commercially today Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Inorganic flame retardants Potassium fluorotitanate K2TiF6 16919-27-0 Wool Potassium fluorozirconate K2ZrF6 16923-95-8 Wool Aluminium hydroxide Al(OH)3 21645-51-2 Rubber compounds, PVC, polyolefins, thermosets H Antimony pentoxide Sb2O5 1314-60-9 Additive type flame-retardant synergist M Antimony trioxide Sb2O3 1309-64-4 Additive type flame-retardant synergist H IARC (1989) Zinc oxide ZnO 1314-13-2 Additive type flame-retardant synergist polyamides, rubber M Boric acid H3BO3 11113-50-1 Wool, cellulosic, textiles H Sodium borate (borax) Na2B4O7.10H2O 1303-96-4 Flame retardant and synergist H Zinc borate 3ZnO.2B2O3. 1332-07-6 Synergist and smoke supressant M Ammonium sulfamate NH4SO3NH2 7773-06-0 Cellulosic and textiles Ammonium orthophosphate (NH4)3PO4 10124-31-9 Cellulosic and textiles Ammonium carbamate phosphate Textiles Di-ammonium phosphate (NH4)2HP04 7783-28-0 Textiles Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Ammonium polyphosphate 68333-79-9 Cellulosics and mastics, paints, polyolefins H Huntite- Mg3Ca(CO3)4 - 19569-21-2 Thermoplastics, coatings H hydromagnesite Mg5(CO3)4Ê(OH)2Ê4H2O 12411-64-2 Smoke supressant M 12125-28-9 Ammonium octamolybdate (NH4)4Mo8O26 Magnesium hydroxide Mg(OH)2 1309-42-8 Thermoplastics, thermosets, rubbers H Ammonium bromide NH4 Br 12124-97-9 Cellulosics H Barium metaborate BaB2O4ÊxH2O 14701-59-2 Flame retardant additive, synergist M Molybdenum trioxide MoO3 1313-27-5 Smoke suppressant L Ammonium sulfate (NH4)2 SO4 7783-20-2 Cellulosic textiles Ammonium chloride NH4Cl 12125-02-9 Cellulosics Zinc hydroxystannate ZnSn(OH)6 12027-96-2 Smoke suppressant and flame-retardant synergist L Red phosphorus P 7723-14-0 Polyamides, phenolics, engineering thermoplastics M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Sodium tungstate Na2WO4.2H2O 13472-45-2 Textiles Sodium antimonate NaSbO3 15432-85-6 Flame-retardant additive, synergist Brominated flame retardants Decabromobiphenyl 13654-09-6 ABS, polystyrene M EHC 152 IARC (1986b) Decabromodiphenyl ethane 61262-53-1 Additive flame retardant for thermoplastics such as high impact polystyrene, ABS polypropylene, polyamide and polyester/ cotton M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Decabromodiphenyl ether 1163-19-5 Polystyrene, polyesters, polyamides, textiles EHC 162 H IARC (1990) Octabromodiphenyl ether 32536-52-0 ABS H EHC 162 Pentabromodiphenyl ether 32534-81-9 Textiles, polyurethanes H EHC 162 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrabromobis phenol A 79-94-7 Intermediates for epoxy resins, polyester EHC (30496-13-0) resins, polycarbonate resins, unsaturated 172 polyesters. ABS, phenolic resins H Tetrabromobisphenol 21850-44-2 Polyolefin resins M EHC A-bis-(2,3-dibromopropylether) 172 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrabromobisphenol 4162-45-2 Unsaturated and linear polyesters; intermediates; EHC A-bis-(2-hydroxyethylether) epoxy thermoset resins: polyurethanes. 172 Reactive flame retardant M Tetrabromobisphenol 25327-89-3 EPS, foamed polystyrene M EHC A-bis-(allylether) 172 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrabromobisphenol 37853-61-5 Expandable polystyrene L EHC A-dimethylether 172 Tetrabromobisphenol 32844-27-2 Reactive and active flame retardants; EHC A diglycidyl-ether epoxy 71342-77-3 polyethylenes, polypropylenes, polystyrenes, 172 oligomer carbonate oligomer ABS, polyamides, linear polyester, polycarbonate, epoxide resins, unsaturated polyester, phenolic resins H Tetrabromobisphenol S 39635-79-5 Intermediate for flame-retardant production L Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Ethylene-bistetrabromophthalimide Polyethylene, polypropylene M Dibromoneopentylglycol CH2OH 3296-90-0 Unsaturated polyesters; rigid polyurethane (1,3-propanediol, BrH2C--|--CH2Br foams; intermediates; elastomers H 2,2-bis(bromomethyl)) CH2OH Tribromoneopentylalcohol CH2Br 36483-57-5 Substantially used as reactive flame retardant BrH2C--|--CH2OH Rigid and flexible polyurethane foam; CH2Br intermediates for flame retardants M Vinylbromide H2C=CHBr 593-60-2 Monomeric reactive flame retardant. EHC Modacrylic fibers M IARC (1986a) Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tribromophenyl allylether 3278-89-5 (EPS) Expandable polystyrene L (Poly)pentabromobenzyl acrylate 59447-55-1 Polyamide; PBT; PET; ABS; polypropylene; (polymer) Polystyrene and others - polyamides, 59447-57-3 polyesters, polycarbonates M Pentabromotoluene 87-83-2 Unsaturated polyesters; polyethylene; polypropylenes; polystyrene; SBR-latex, textiles, rubbers. ABS M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 2,3-Dibromo-2-butene-1,4-diol 3234-02-4 Intermediate for the production of flame retardants M (Poly)bromophenols: 615-58-7 Epoxy resins; phenolic resins; intermediates 2,4-Dibromophenol 118-79-6 polyester resins; polyolefins H 2,4,6-Tribromophenol 608-71-9 Pentabromophenol Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 1,2-Bis(2,4,6- 37853-59-1 Additive flame retardant for thermoplastics tribromophenoxy)ethane ABS polymer systems. High impact polystyrene L 1,1-(1,2-ethanediylbis(oxy), bis 2,4,6-tribromo-benzene Tetrabromophthalic acid Na salt 25357-79-3 Additive flame retardant. Unsaturated polyesters and rigid polyurethane foams. Reactive intermediates for polyols: esters; imides; paper; textiles; epoxides L Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrabromophthalic acid diol 20566-35-2 Wool, leather and polyurethane foams M [2-Hydroxypropyl-oxy-2- (2-hydroxyethyl)- ethyltetrabromophthalate] Tetrabromophthalic anhydride 632-79-1 Reactive flame retardant. Unsaturated poly esters and rigid polyurethane foams. Reactive intermediates for polyols; esters; imides; paper; textiles; epoxides H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant N,N'-Ethylene-bis-(tetrabromophthalimide) 32588-76-4 High impact polystyrene; polyethylene; polypropylene; thermoplastic polyesters; polyamide; EPDM; rubbers; polycarbonate; ethylene co-polymers; ionomer resins; textiles M 1,3-Butadiene homopolymer brominated 68441-46-3 Elastomers L Bis(tribromophenoxy)ethane Polystyrene, polycarbonate, coatings M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetradecabromodi 58965-66-5 Engineering thermoplastics M phenoxybenzene Poly(2,6-dibromophenylene oxide) 69882-11-7 For crystalline polymer polyamide, thermoplastic polyester resins, polystyrenes, polyamides, polycarbonate, ABS M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Poly-tribromostyrene 57137-10-7 Polyethylene, linear polyester, epoxide resins, Brominated polystyrene unsaturated polyester resin, polyamides, ABS M Polydibromostyrene 31780-26-4 Styrenic polymers, engineering plastics M Hexabromocyclododecane 25637-99-4 Expandable polystyrene; latex; textiles; adhesives; (1,2,5,6,9,10-HBCD) also coatings; foamed and high-impact polysytrene; 3194-55-6 unsaturated polyesters H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 1,2-Dibromo-4(1,2 dibromomethyl) 3322-93-8 Expandable polystyrene L cyclohexane Ethylene-bis(5,6-dibromonorbornane-2, 41291-34-3 Polypropylene M 3-dicarboximide 52907-07-0 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Dibromostyrene grafted PP 171091-06-8 Polyolefins 1,3,5-tris(2,3-dibromo-propoxy)- 52434-59-0 Polypropylene L 2,4,6-triazine Diester of tetrabromophthalic acid 20566-35-2 PVC, rubber, thermoplastics, PUR, coatings H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Chlorinated flame retardants Chlorinated paraffins CxH(2x+2-y) Cly 63449-39-8 High and low density polyethylene; high EHC 181 (at least 20 impact polystyrene; PVC, unsaturated polyester IARC other CAS resins; polypropylene, rubber, textiles H (1990) numbers) Chlorendic acid 115-28-6 Reactive flame retardant for polyester resins, EHC alkyl paints M 185 IARC (1990) Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Chlorendic anhydride 115-17-5 Reactive flame retardant, used as flame EHC retardant for unsaturated polyester, 185 epoxides, alkyl paints, epoxy hardener M Dodecachlorodimethano- 13560-89-9 Polyamides, polystyrene M dibenzocyclo-octane Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Hexachlorocyclopentadiene 77-47-4 Intermediate for production of flame EHC retardants H 120 Tetrachlorophthalic anhydride - TCPA 117-08-8 Unsaturated polyester resins. Alkyds. M Bromo-chlorinated paraffins CxH(2x+2-y-z) BryClz 61090-89-9 Textile fabrics, PVC, Polyurethane L 68527-01-5 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 2,2',6,6-Tetrachlorobisphenol A 79-95-8 Expoxy intermediate L Tetrachlorophthalic anhydride 117-08-8 Intermediate, unsaturated polyesters, alkyds M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Organophosphorus flame retardants Dimethylphosphono- 20120-33-6 Cotton; cotton/polyester; rayon H N-hydroxymethyl-3-propionamide Tris(2-butoxyethyl) phosphate 78-51-3 Additive flame retardant and EHC plasticizer in plastics and synthetic rubbers M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Isopropylphenyl diphenyl phosphate 68937-41-7 Plasticizer; hydraulic fluid; lubricant and in engineering thermoplastics H Tricresyl phosphate 1330-78-5 Solvent; additive for pressure lubricants EHC and hydraulic systems, cutting oils, 110 transmission fluids, PVC H Triphenylphosphate 115-86-6 PVC, phenolics resins; phenylene-oxide-based EHC resins H 111 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Dimethyl-methyl- O 756-79-6 Unsaturated polyesters; paints and coatings: phosphonate (DMMP) H3C " CH3 urethane rigid foam M \ / O-P--O | CH3 Resorcinol 57583-54-7 Engeneering thermoplastics dipheny-lphosphate H Diethyl-ethyl- H5C2 O C2H5 78-38-6 Unsaturated polyesters; paints and coatings: phosphonate \ " / urethane rigid foam L (DEEP) O-P--O | C2H5 Cyclic phosphonate ester 61840-22-0 Polyester fibres; rigid urethane foams L (including: 42595-45-9 41203-81-0 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Isodecyldiphenyl phosphate 29761-21-5 PVC H O,O-Diethyl-N,N- 2781-11-5 Polyurethane foam textiles L bis(2-hydroxyethyl) aminomethyl phosphonate Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Dimethyl- Cellulosic fabrics 3-(hydroxymethylamino)-3- H oxopropyl phosphonate Dimethyl phosphonate H3C O CH3 868-85-9 Flame retardant to cotton textile IARC \ " / and polyamide paints (1990) O-P--O | H Cresyl diphenyl phosphate 26444-49-5 PVC, hydraulic fluid, lubricant, food packaging, ABS pc-blends, engineering thermoplastics, rubber phenolics, paints H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Octyl diphenyl phosphate 115-88-8 PVC, rubber, paints, coatings H Tris(2-ethyl hexyl) phosphate 78-42-2 PVC, solvents, rubber; paints, polyurethane EHC M Trioctyl phosphate H17C8 O C8H17 1806-54-8 PVC, solvent paints, rubber, polyurethane \ " / O-P--O | O \ C8H17 Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Triethyl phosphate H5C2 O C2H5 78-40-0 PVC, polyester resins, polyurethane \ " / M O-P--O | O \ C2H5 2-Ethylhexyldiphenyl phosphate 1241-94-7 Plasticizer in food packaging, hydraulic fluid, PVC H CH2OH Tetrakis (hydroxymethyl)- | Reactive flame retardant for cotton; EHC phosphonium HOH2C-P+--CH2OH X- rayon and other cellulosic materials as IARC salts (THP salts): | well as polyester fabrics (1990) CH2OH Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Acetate 7580-37-2 Chloride H Acetate-phosphate (3:1) 55818-96-7 Sulfate H Acetate phosphate (1:1) 62588-94-7 Others L Bromide 5940-69-2 6-Carboxycellulose salt 73082-49-2 Cellulose carboxymethyl ether 73083-23-5 Chloride 124-64-1 Ethanedioate 52221-67-7 Formate 25151-36-4 Hydroxybutanedioate 39734-92-4 2-Hydroxypropionate 39686-78-7 Iodide 69248-12-0 1-Naphthalenesulfonate 79481-21-3 2-Naphthalenesulfonate 79481-22-4 Oxalate (1:1) 53211-22-6 Oxalate (2:1) 52221-67-7 Phosphate 22031-17-0 Sulfate 55566-30-8 Tetraphenylborate- 15652-65-0 tetraacetate p-Toluenesulfonate 75019-90-8 n addition the following complex condensates are used: Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant - Tetrakis (hydroxymethyl) phosphonium sulfate-urea precondensate - Tetrakis(hydroxymethyl)- phosphonium chloride-urea- melamine condensate - Tetrakis(hydroxymethyl)- phosphonium sulfate-urea- N-hydroxymethyl-dimethyl- phosphonopropionamide precondensate Phosphonic acid 4351-70-6 Polyurethane foam derivative M Bis(5,5-dimethyl-2- 4090-51-1 Rayon thiono-1,3,2- dioxaphosphorinamyl) oxide O Tris(hydroxymethyl) " High impact polystyrene phosphine oxide HOH2C-P--CH2OH " CH2OH Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Trixylenyl phosphate 25155-23-1 PVC, hydraulic fluids M Tris(isopropy-lphenyl) 68937-41-7 PVC, engineering phosphate thermoplastics H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Halogenated organophosphorus flame retardants Tris(1,3-dichloro- 13674-87-8 Additive flame retardant in polyurethane EHC 2-propyl) phosphate and styrene-butadiene rubber; synthetic fibres H Tris(2-chloroethyl) 115-96-8 Polyester resins, polyurethanes, cellulose EHC phosphate derivatives, PVC H IARC (1990) Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris(2-chloroethyl) 28205-79-0 Polyurethane EHC phosphate polymer M Tris(2-chloro-1-propyl) 6145-73-9 Polyurethane foam EHC phosphate H Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris(1-chloro-2-propyl) 13674-84-5 Polyurethane foam, polyesters foams EHC phosphate H Bis(2-chloroethyl) vinyl 115-98-0 Cotton; rayon, polyolefins; phosphate intermediate L Mixture of monomeric 64176-42-7 Textiles chloroethyl phosphonates and high-boiling phosphonates Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 2,4-Dibromophenyl 49690-63-3 Engineering thermoplastics phosphate L Tris(tribromoneopentyl) Thermoplastics phosphate L Chlorinated brominated 35-37% Br, 8-9% 125997-20-8 Polyurethane foams, phosphate ester Cl, 6-8% P thermosets, coating (Firemaster 836) and M (HP-36) Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Bromine-, chlorine and Polyurethane foams phosphorus-containing H polyol Nitrogen-based and miscellaneous flame retardants Melamine Polyurethane foams H Melamine phosphate Polypropylene L Melamine cyanurate 37640-57-6 Polyamides, polyurethanes, polyolefines, polyester, epoxy resins M Table 9. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Ferrocene 102-54-5 Additive smoke suppressant L Table 10. Flame retardants that have been used commercially in the past Chemical name Chemical structure CAS registry Use as flame retardant Remarks number Inorganic flame retardants Sodium stannate Na2SnO3 12058-66-1 Textiles Sodium aluminate NaAlO2 1302-42-7 Textiles Sodium silicate Na2SiO3Ê9H2O 1344-09-8 Textiles Sodium bisulfate NaHSO4Ê2O 7631-90-5 Textiles Ammonium borate NH4BO3 12007-58-8 Textiles Ammonium iodide NH4I 12027-06-4 Textiles Zinc chloride ZnCl2 7646-85-7 Non-durable finish, textiles Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Calcium chloride CaCl2Ê6H2O 10043-52-4 Non-durable finish, textiles Magnesium chloride MgCl2 7786-30-3 Non-durable finish, textiles Brominated flame retardants Dibromopropylacrylate 19660-16-3 Acrylic fibres Tetrabromodipenta-erythritol 109678-33-3 Polyester Polyurethane Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Pentabromoethylbenzene 85-22-3 Textiles; adhesives; polyurethane foam. Thermoset polyester resins, coatings. Additive for unsaturated polyesters Tetrabromoxylene 23488-38-2 Additive for styrene thermoplastics and polyolefines and textiles Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 2,4,6-Tribromophenoxy- 35109-60-5 Extrusion grade of PP 2,3-dibromopropane Hexabromobenzene 87-82-1 Paper, electric goods, polyamides, PES fibres, PP and PBT Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Hexabromobiphenyl 59536-65-1 Thermoplastic polymers EHC 152 67774-32-7 IARC (1986b) Octabromobiphenyl 61288-13-9 Thermoplastic polymers EHC 152 Hexabromodiphenyl ether 61262-53-1 Variety of resins (high thermal stability). EHC 36483-60-0 Polystyrene, ABS polycarbonate, unsaturated 162 polyester Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrabromobisphenol A-bis- 66710-97-2 High thermal stability (2-ethylether acrylate) Pentabromochlorocyclo-hexane 87-84-3 Polystyrene foam and polypropylene Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris(2,3-dibromopropyl) phosphate 126-72-7 Polyesters, urea and melamine resins, textiles EHC 173 IARC (1979, 1987) Bis(2,3-dibromopropyl) phosphate 66519-18-4 K salt EHC 173 and salts 64864-08-0 Na salt 36711-31-6 Mg salt 5412-25-9 H (base) 34432-82-1 Ammonium salt Tetrabromo-2,3-dimethylbutane 00-00-0 EPS Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 2,4,6-Tribromoaniline 147-82-0 Reactive flame retardant 1-Pentabromophenoxy-2-propene 3555-11-1 Synergist 2,4-dibromophenylglycidyl ether 20217-01-0 Reactive flame retardant Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Trichloromethyl ABS, polystyrene, polyester tetrabromobenzene Pentabromophenyl benzoate ABS, polyester, polystyrene 1,4-Bis(bromomethyl)-tetrabromo Polyolefines benzene Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Bis-(2,3-dibromo-1-propyl) 7415-86-3 Polyesters, alkyl phthalate Hexabromocyclohexane 1837-91-8 Styrene foams Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 5,6-dibromohexahydro-2-phenyl- 40703-79-5 Styrenic polymers 4,7-methano-1H-isoindole- 1,3(2H)-dione Chlorinated flame retardants Dimethyl chlorendate Reactive flame retardant for polyester resins, alkyl paints Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Dibutyl chlorendate 1770-80-5 Reactive flame retardant for polyester resins, alkyl paints 1,2,3,4,6,7,8,9.10,10,11, 31107-44-5 Cross-linked polyethylene, polyolefins, 11-Dodecachloro-1,4,4a,5a,6, polystyrene 9,9a,9b-octahydro-1,4:6,9- dimethanodibenzofuran Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant 1,1a,2,2,3,3a,4,5,5,5a,5b, 2385-85-5 Plastics, rubber, paints, paper, and electrical EHC 6-Dodecachloro- goods No. 44 octahydro- (Mirex) 1,3,4-metheno-1H- IARC cyclobuta(cd)pentalene (1979) Polychlorinated biphenyls 1336-36-3 Fire-resistant liquid in closed-system EHC hydraulic fluids polystyrene, polyolefines No. 140 IARC (1978, 1987) Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Hexachlorocyclopenta- 51936-55-1 Styrenic polymers dienyl-dibromocyclooctane Dibromochlordene 18300-04-4 Styrenic polymers [4,7-Methano-1H-indene, 1,2-dibromo-4,5,6,7,8,8- hexachloro-2,3,3a,4,7,7a- hexahydro] Organophosphorus flame retardants Trimethylphosphoramide Cotton, rayon Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris(1-aziridinyl)phosphine 545-55-1 Cotton fabrics, polyester fibres IARC (1975, oxide 1987) Cyanamide-phosphoric acid H2NCN + H3PO4f Finishes Halogenated organophosphorus flame retardants Ethylene bis[tris 10310-38-0 Additive for thermoplastics, textiles (2-yanoethyl)phosphonium] bromide Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tetrakis(2-chloroethyl) 33125-86-9 Plastics ethylene diphosphate Tris(2,3-dichloro-1-propyl) 78-43-3 Additive flame retardant in plastics, plasticizer EHC phosphate Condensate of bis Cellulosic textiles, cotton and rayon (betachloroethyl) phosphonate and alkyl phosphonate Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris(2,4,6-tribromophenyl) Engineering thermoplastics phosphate Bis(1,3-dichloro-2-propyl)- 61090-89-9 Polyolefins (3-chloro-2,2- dibromomethylpropyl) phosphate Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Chlorinated phosphonic acid Polyurethane foam ester condensate with tris- dibromo-propyl-iso-cyanurate Tris(dichloropropyl) phosphite 6749-73-1 Textiles Bis[bis(2-chloroethoxy)-phosphinyl] Textiles isopropylchloro-ethyl phosphate Table 10. (contd.) Chemical name Chemical structure CAS registry Use as flame Remarks number retardant Tris-(2-chloroethyl)- 140-08-9 Textiles, hydraulic fluids phosphite Ethylene-bis[bis 33125-86-9 Polyurethane foams (2-chloroethyl)phosphate] Nitrogen-based flame retardants Pyrophosphate dimelamine salts 70776-17-9 Polyurethane, polyester ANNEX III Fire tests Fire tests are usually carried out to comply with specific regulations or voluntary agreements. They can be classified into three groups (Troitzsch, 1990; Arias, 1992; OECD, 1994): (a) Tests reflecting single events in a fire. For historical reasons, many different national fire tests now exist, particularly for building products. These may not necessarily correlate well. Within the European Union, efforts are being made to harmonize testing. (b) Tests addressing flammability. These tests are mainly used with respect to transportation and electrical/electronic products. They are mostly used internationally. (c) Screening tests. These are used to screen materials during product development or for quality control. ANNEX IV US Interagency Testing Commission recommendations on brominated flame retardants Chemical Designateda 1,2-Epoxy-3-bromopropane 2,4,6-Tribromoaniline 1,2-Dibromo-4-(1,2-dibromomethyl) cyclohexane Pentabromoethylbenzene Tetrabromobisphenol A Decabromodiphenyl ether Hexabromocyclododecane Pentabromodiphenyl ether Octabromodiphenyl ether 1,2-Bis(2,4,6-tribromophenoxy)ethane Recommendedb 2,4,6-Tribromophenol Tetrabromophthalic anhydride Dibromoneopentyl glycol Ethylene bis(tetrabromophthalimide) Ethylene bis(tetrabromonorbornane-2,3-dicarboximide) Tribrominated polystyrene Ethylene bis(pentabromophenoxide) Bromochloromethane 3,4',5-Tribromosalicylanilide 2,3,4,5,6-Pentabromotoluene 1,2,3,4,5-Pentabromo-6-chlorocyclohexane 2,3-Dibromopropanol Vinyl bromide 2,4-Dibromophenol Ethoxylated tetrabromobisphenol A Tetrabromobisphenol A, bis(allyl ether) Annex IV (contd). Chemical Recommended (contd). Tetrabromodichlorocyclohexane Tribromotrichlorocyclohexane Tribromoneopentyl alcohol Tetrabromobisphenol A diacrylate Alkanes, C10-16, bromochloro 2,4-(or 2,6)-Dibromophenol, homopolymer Benzene, ethenyl-, homopolymer, brominated DeferredC Polybromobiphenyl Tetrabromo-o-chlorotoluene Bromophenol (Br1, Br2, Br5) Bis(dibromopropyl) carbamate Bis(2,3-dibromopropyl) phosphite Bis(dibromopropyl) phosphite Tetrabromochlorotoluene Brominated terphenyls Dibromopropyl carbamate Allyl bis(2,3-dibromopropyl) phosphite Bis(dibromopropyl) phosphoryl chloride 2,3-Dibromo-1-propanol phosphate Pentabromophenol 3,3-Bis(bromomethyl)oxetane (bromomethyl)oxirane pentabromophenyl allyl ether 2,6-Dibromo-4-[1-(3-bromo-4-hydroxyphenyl)-1-methylethyl]phenol bis(2,3-dibromopropyl) phthalate 1,2-Ethanediylbis[tris(2-cyanoethyl)phosphonium] dibromide (bromoethyl)oxirane Decabromobiphenyl Tetrabromophthalic acid, aluminium salt Fumaric acid, bis(pentabromophenyl) ester 1,2-Dibromo-4,5,6,7,8,8-hexachloro-2,3,3a,4,7,7a-hexahydro-4,7 -methano-1H-indene tetrabromophthalic acid, dipotassium salt 2-(2,4,6-Tribromophenoxy)ethanol Bis(2,4,6-tribromophenyl) fumarate Annex IV (contd). Chemical Deferred (contd) Tribromophenol Dibromoethane Poly(2,6-dibromophenylene oxide) Tribromophenyl allyl ether Nonabromobiphenyl Octabromobiphenyl Bromophenol 3,3',5,5'-Tetrabromobisphenol A diacetate 3,3',5,5'-Tetrabromobisphenol S Tris(dibromophenyl) phosphate Dibromopropyl carbamate 2,3,4,6-Tetrabromo-5-methylphenol 2-(Pentabromophenoxy)ethanol Dibromopropyl carbamate 3,9-Bis[3-bromo-2,2-bis(bromomethyl)propoxy]- 2,2-Bis(bromomethyl)-3-chloropropyl phosphoric acid Tribromophenyl allyl ether Decabrominated diphenoxyethane 2,4,6-Tribromophenol carbonate pentabromophenol, aluminium salt 3,4,5,6-Tetrabromo-1,2-benzenedicarboxylic acid, magnesium salt 2-Butenedioic acid (z), bis(pentabromophenyl) ester Pentabromo[2-(tetrabromophenoxy)ethoxy]benzene Pentabromo[2-(tetrabromochlorophenoxy)ethoxy]benzene 1,3,5-Tribromo-2-(2-bromoethoxy)benzene Brominated and chlorinated benzene Bis[3-bromo-2-(bromomethyl)-2-(hydroxymethyl) propyl]hexanoate Adapted from Walker (1994) and from a Memorandum dated 22 October 1992 entitled Actions on Brominated Flame Retardants; Toxic Substances Control Act, Interagency Testing Committee (ITC), US Environmental Protection Agency, Washington DC a ITC designated chemical to US EPA for a decision about testing. b ITC required additional information for further recommendation. c Consideration for testing by ITC. 9. CONCLUSIONS ET RECOMMANDATIONS POUR LA PROTECTION DE LA SANTE HUMAINE ET DE L'ENVIRONNEMENT 9.1 Conclusions Les retardateurs de flamme sont un groupe de composés très divers qu'on utilise pour retarder l'inflammation des polymères et autres matériaux. On utilise une grande variété de composés, des substances minérales aux molécules organiques complexes, comme retardateurs de flamme, synergisants et inhibiteurs de fumée. Les considérations générales qui suivent portent essentiellement sur des composés organiques caractérisés par la présence d'halogènes ou de phosphore. Il est difficile de se faire une idée exacte de l'utilisation des retardateurs de flammes au niveau mondial, mais selon les estimations, ce sont plus de 600 000 tonnes qui sont produites chaque année. Les données dont on dispose indiquent qu'au cours de la dernière décennie, les dérivés organiques bromés ont vu leur production s'accroître de façon substantielle. L'utilisation de retardateurs de flamme présente des avantages évidents puisqu'ils permettent de sauver nombre de vies humaines et de biens matériels. A l'heure actuelle, on ne connaît pas très bien les effets à long terme pouvant résulter d'une exposition à ces composés et à leurs produits de décomposition. La plupart des personnes qui décèdent lors d'incendies sont victimes de l'oxyde de carbone. La majorité des retardateurs de flamme organiques sont fixés soit par une liaison covalente aux molécules de polymères (réactifs) , soit incorporés aux polymères (additifs). Ils peuvent agir de plusieurs manières, soit physiquement (par refroidissement, par formation d'une couche protectrice ou par dilution de la matrice) ou chimiquement (par des réactions dans la phase gazeuse ou solide). Un certain nombre de facteurs président au choix de tel ou tel type de retardateurs de flamme à utiliser pour une application donnée. Il peut s'agir notamment de l'inflammabilité de la matrice, de certaines exigences de fabrication ou de comportement, des propriétés chimiques et des risques éventuels pour la santé de l'homme et pour l'environnement. L'exposition de la population générale à ces composés se produit par la voie respiratoire, le contact cutané ou l'ingestion. Cette exposition peut avoir lieu lors de l'utilisation des produits de consommation, en cas de présence sur les lieux de fabrication ou d'élimination ou encore par l'intermédiaire des différents compartiments du milieu (y compris par l'absorption de nourriture). Ces mêmes voies d'exposition se retrouvent en cas d'exposition professionnelle, principalement lors de la production, de la transformation, du transport, de l'élimination ou du recyclage des retardateurs de flamme ou des produits traités avec ces composés. Il peut également y avoir exposition professionnelle aux produits de décomposition lors de la lutte contre les incendies. Comme plusieurs de ces composés sont lipophiles et persistants, ils peuvent subir une bioaccumulation. On a montré que certains d'entre eux pouvaient entraîner des lésions au niveau de certains organes, des effets génotoxiques et des cancers. On se préoccupe également de l'exposition professionnelle aux produits de combustion et de pyrolyse, en particulier les dibenzofuranes polyhalogénés et les dibenzo-p-dioxines contenus dans certains retardateurs de flamme organiques, ainsi d'ailleurs que des effets que ces produits peuvent exercer sur l'environnement. Il existe également d'autres produits de décomposition dont il faut tenir compte. Les retardateurs de flamme ont des propriétés qui les rendent persistants ou enclins à la bioaccumulation , donc dangereux pour l'environnement. Certains des composés qui ont été évalués jusqu'ici (polybromobiphényles, éthers diphényliques polybromés et paraffines chlorées) se sont révélés appartenir à ce groupe. L'usage de certains de ces produits est donc déconseillé. Plusieurs pays ont promulgué une réglementation relative à la production, à l'utilisation et à l'élimination des retardateurs de flamme. Certaines de ces réglementations prévoient des restrictions à l'utilisation de ces composés en raison de leurs effets toxiques potentiels pour l'homme. En Allemagne, la réglementation fixe la teneur maximale en dibenzo-para-dioxines et en dibenzofuranes polychlorés substitués en position 2,3,7,8. Il y a peu de données intéressantes sur les retardateurs de flamme dans les publications non soumises à restriction, en particulier en ce qui concerne un certain nombre de produits chimiques produits avant que la réglementation concernant leur commercialisation n'ait été renforcée dans un certain nombre de pays. Le PISC a déjà évalué un certain nombre de retardateurs de flamme et les évaluations concernant d'autres produits de ce type seront publiées ultérieurement. 9.2 Recommandations pour la protection de la santé humaine et de l'environnement a) Les autorités nationales doivent avoir communication de données sur la teneur et la nature des retardateurs de flamme, et notamment sur les impuretés qu'ils peuvent contenir. b) On doit avoir accès à une information plus complète sur l'ampleur de la production et de la consommation des retardateurs de flamme. c) Etant donné que les produits contenant des retardateurs de flamme sont de plus en plus souvent recyclés, il faudrait faire harmoniser l'étiquetage par une commission internationale. d) Les composés qui présentent un risque toxique pour l'homme ou pour l'environnement ne doivent pas être utilisés comme retardateurs de flamme. e) Il convient de réduire au minimum l'exposition professionnelle aux retardateurs de flamme et à leurs produits de décomposition en ayant recours à des techniques appropriées et en respectant les règles de l'hygiène industrielle. Il convient en outre de surveiller l'exposition des personnes qui sont exposées professionnellement. f) Il y a nécessité d'une bonne évaluation des effets que les produits de combustion et de pyrolyse des retardateurs de flamme peuvent exercer sur l'environnement ou sur les personnes exposées de par leur profession. g) Les émissions dans l'environnement qui résultent de la fabrication, de la transformation, du transport , de l'élimination ou du recyclage de produits contenant des composés persistants ayant tendance à s'accumuler dans les tissus biologiques doivent être réduites au minimum par le recours aux meilleures techniques disponibles. Il convient de surveiller la présence des composés utilisés dans l'environnement immédiat des sites où il est procédé à ces opérations. h) Il convient d'éviter d'utiliser des retardateurs de flamme dont les propriétés sont telles qu'ils persistent dans l'environnement et s'accumulent dans les tissus biologiques. i) Il faut surveiller systématiquement la concentration, dans certaines matrices environnementales (biotes et sédiments), des principaux retardateurs de flamme persistants et susceptibles de bioaccumulation. La même surveillance doit s'exercer sur certains composés qui ne sont plus produits afin de voir quelle peut être l'influence à long terme de ces substances. 9. CONCLUSIONES Y RECOMENDACIONES PARA La PROTECCIN DE LA SALUD HUMANA Y EL MEDIO AMBIENTE 9.1 Conclusiones Los pirorretardadores son un grupo variado de compuestos utilizados para mejorar la pirorretardancia de polímeros y otro material. Hay una amplia variedad de compuestos, desde inorgánicos hasta complejas moléculas orgánicas, que se utilizan como pirorretardadores, sinergistas y supresores del humo. El presente resumen se refiere a los compuestos orgánicos, que normalmente contienen un halógeno y/o fósforo. Es difícil encontrar cifras precisas sobre el uso de los pirorretardadores a nivel mundial, pero se estima que se producen más de 600 000 toneladas anuales. Los datos disponibles indican un aumento sustancial del consumo de productos orgánicos bromados durante el último decenio. La utilización de los pirorretardadores tiene beneficios evidentes, ya que éstos permiten salvar muchas vidas humanas y bienes materiales del fuego. En la actualidad disponemos de conocimientos limitados sobre los efectos a largo plazo de la exposición a los pirorretardadores y productos de la descomposición de éstos. La mayor parte de las muertes ocurridas en los incendios están causadas por el monóxido de carbono. La mayor parte de los pirorretardadores orgánicos se hallan combinados mediante enlace covalente en moléculas de polímeros (por reacción) o mezclados en el polímero (por adición). Pueden actuar de varias maneras, ya sea físicamente (por enfriamiento, por formación de una capa protectora o por dilución de la matriz) o químicamente (por reacciones en el gas o en la fase sólida). La selección del tipo de pirorretardador que se ha de utilizar en una aplicación específica se basa en varios factores. Algunos de ellos son la inflamabilidad de la matriz, requisitos de elaboración y rendimiento, propiedades químicas y riesgos posibles para la salud humana y el medio ambiente. La población en general puede verse expuesta a los pirorretardadores por inhalación, contacto dérmico o ingestión. Las fuentes potenciales de exposición son productos de consumo, instalaciones de fabricación/eliminación y diversos medios ambientales (inclusive los alimentos que se ingieren). La exposición ocupacional puede tener las mismas vías, principalmente durante la producción, la elaboración, el transporte y la eliminación/reciclado de los pirorretardadores o los productos tratados con ellos. También puede haber exposición ocupacional a los productos de descomposición durante la extinción de incendios. Varios de los compuestos utilizados son lipofílicos y persistentes, por lo que son bioacumulables. Se ha observado que algunos de los compuestos ocasionan lesiones orgánicas, efectos genotóxicos y cáncer. Los productos de la combustión/pirólisis, especialmente dibenzofuranos polihalogenados y dibenzo- p-dioxinas, de algunos pirorretardadores orgánicos son motivo de preocupación en lo concerniente a la salud ocupacional y los efectos ambientales. También es preciso tener en cuenta otros productos de la descomposición. Cierto número de pirorretardadores tienen propiedades que los hacen persistentes y/o bioacumulativos, por lo que pueden constituir un riesgo para el medio ambiente. Algunos de los compuestos que se han evaluado hasta hoy (bifenilos polibromados, difenil éteres polibromados y parafinas cloradas) pertenecen a este grupo. Por lo tanto, se ha recomendado la no utilización de algunos de ellos. Varios países han establecido reglamentaciones que afecta a la producción, la utilización y la eliminación de los pirorretardadores. Algunas comprenden restricciones sobre la utilización de compuestos en razón de sus efectos tóxicos potenciales en el ser humano. Alemania ha establecido normas aplicables al contenido máximo de algunos dibenzofuranos y dibenzo- para-dioxinas 2,3,7,8-policloradas y en los productos. En la bibliografía abierta son limitados los datos pertinentes que pueden encontrarse sobre los pirorretardadores, especialmente sobre algunas sustancias químicas existentes producidas antes de que en varios países se reforzara la reglamentación aplicable a la comercialización. El IPCS ha emitido evaluaciones sobre algunos pirorretardadores y está preparando evaluaciones de otros. 9.2 Recomendaciones para la protección de la salud humana y del medio ambiente a) Debe ponerse a disposición de las autoridades nacionales la información sobre el contenido y la naturaleza de los pirorretardadores, inclusive sobre las impurezas presentes en los productos. b) Debe ponerse a disposición información más completa sobre el volumen de la producción y el consumo de pirorretardadores. c) En vista del creciente reciclado de productos pirorretardados, debe considerarse la posibilidad de que un foro internacional armonice el etiquetado. d) Los compuestos que conlleven un riesgo de toxicidad para el ser humano y/o el medio ambiente no deben utilizarse como pirorretardadores. e) La exposición ocupacional a los pirorretardadores y los productos de la descomposición de éstos debe reducirse al mínimo mediante una ingeniería apropiada y buenas prácticas de higiene industrial. Debe vigilarse la exposición de las personas que trabajan en esas actividades. f) Es necesario que se haga una evaluación apropiada de los efectos de los productos de la combustión o la pirólisis de los pirorretardadores en la salud ocupacional y el medio ambiente. g) Las emisiones en el medio ambiente resultantes de la fabricación, la elaboración, el transporte y la eliminación/ reciclado de los productos que contengan compuestos bioacumulativos persistentes en el medio ambiente debe reducirse al mínimo mediante la utilización de las mejores técnicas disponibles. El medio ambiente próximo a los lugares donde se realizan dichas operaciones debe vigilarse para detectar la presencia de los compuestos utilizados. h) Debe evitarse la utilización de pirorretardadores con propiedades que los hagan persistentes y bioacumulativos. i) Deben vigilarse sistemáticamente en las matrices ambientales (biota y sedimentos) los niveles de los principales pirorretardadores bioacumulativos persistentes. Algunos compuestos que han dejado de producirse deben someterse igualmente a vigilancia para determinar la influencia a largo plazo de dichos productos.
See Also: Flame retardants (EHC 218, 2000)