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

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    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

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         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


         3.1. 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



         5.1. Production
         5.2. Uses
               5.2.1. Plastics
               5.2.2. Textile/furnishing industry


         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
                Laboratory pyrolysis experiments
                Fire tests and fire accidents


         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





    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




         Every effort has been made to present information in the criteria
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    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 irptc@unep.ch).

                                     * * *

         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

    Environmental Health Criteria



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    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,

    Dr B. Jansson, Institute of Applied Environmental Research, Stockholm
    University, Stockholm, Sweden ( Chairman)

    Dr S.K. Kashyap, National Institute of Occupational Health, Ahmedabad,

    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. Sœderlund, Folkehelsa, National Institute of Public Health,
    Oslo,  Norway ( Rapporteur)

    Dr J. Troitzsch, Fire and Environment Protection Service, Wiesbaden,


    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


    Dr K.W. Jager, International Programme on Chemical Safety, World
    Health Organization ( Secretary)


         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

         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.


    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


         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

         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)
    cyclobuta( cd)pentalene)

    Polychlorinated dibenzo- p-dioxins and          EHC 88 (1989)

    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)

    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

    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


         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

    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

    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

    The Romans used a mixture of alum and vinegar on        About 200 BC

    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

         A glossary of terms concerning flammability and flame retardants
    is given in Annex 1.


         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

         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,

         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

         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

    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

         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).


    3.1  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).

    FIGURE 2

         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

    (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,

    (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 Brœ 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,

         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,

    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,

    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).


         At present, the selection of a suitable flame retardant depends
    on a variety of factors that severely limit the number of acceptable

         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

         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,


    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

    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

         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

                                  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

         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 paraffins                    4 000           4 500            4 300
         Others                                     850             700              900

                        Subtotal                  4 850           5 200            5 200

         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

         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

         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

    *    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.


         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  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

         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.  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


         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,

         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,


         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

    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)


    9.1  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

         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

         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

         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

    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.


    a)   Further studies should be undertaken to elucidate the fate of
         flame retardants in disposal/recycling operations.

    b)   There is a need for further evaluations of flame retardants. 
         Useful criteria for setting priorities are volume of use,
         intrinsic toxic effects on human health and the environment,
         exposure assessments, and persistence and bioaccumulation/
         biomagnification of flame retardants or their breakdown products.


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         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


         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

                       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,

    Table 8.  (contd.)


    Term                    Definition

    Pyrolysis          Irreversible chemical decomposition of a material
                       due to an increase in temperature without

    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

    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


    Flame retardants in commercial use or used formerly


         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
    Kirk-Othmer (1993)                 Kopp (1990)
    Liepins & Pearce (1976)            Pearce & Liepins (1975)
    Sœderlund & 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

         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
    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
    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

    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


    Octabromodiphenyl ether                                    32536-52-0       ABS H                                                 EHC

    Pentabromodiphenyl ether                                   32534-81-9       Textiles, polyurethanes H                             EHC



    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


    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



    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
    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


    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


    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


    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


    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)

    Chlorendic acid                                            115-28-6         Reactive flame retardant for polyester resins,        EHC
                                                                                alkyl paints M                                        185


    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



    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


    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


    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
                                            \       /

    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

    Cyclic phosphonate ester                                   61840-22-0       Polyester fibres; rigid urethane foams L


    Table 9.  (contd.)


    Chemical name                     Chemical structure       CAS registry     Use as flame                                          Remarks
                                                               number           retardant

    Isodecyldiphenyl phosphate                                 29761-21-5       PVC

    O,O-Diethyl-N,N-                                           2781-11-5        Polyurethane foam textiles L



    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)

    Cresyl diphenyl phosphate                                  26444-49-5       PVC, hydraulic fluid, lubricant, food
                                                                                packaging, ABS pc-blends, engineering
                                                                                thermoplastics, rubber phenolics, paints


    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

    Tris(2-ethyl hexyl) phosphate                              78-42-2          PVC, solvents, rubber; paints, polyurethane           EHC

    Trioctyl phosphate                H17C8   O    C8H17       1806-54-8        PVC, solvent paints, rubber, polyurethane
                                           \  "   /


    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

    2-Ethylhexyldiphenyl phosphate                             1241-94-7        Plasticizer in food packaging, hydraulic
                                                                                fluid, PVC H

    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)


    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
    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

    -  Tetrakis(hydroxymethyl)-
    phosphonium chloride-urea-
    melamine condensate

    -  Tetrakis(hydroxymethyl)-
    phosphonium sulfate-urea-

    Phosphonic acid                                            4351-70-6        Polyurethane foam
    derivative                                                                  M

    Bis(5,5-dimethyl-2-                                        4090-51-1        Rayon

    Tris(hydroxymethyl)                     "                                   High impact polystyrene
    phosphine oxide                   HOH2C-P--CH2OH


    Table 9.  (contd.)


    Chemical name                     Chemical structure       CAS registry     Use as flame                                          Remarks
                                                               number           retardant

    Trixylenyl phosphate                                       25155-23-1       PVC,  hydraulic fluids

    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


    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

    Mixture of monomeric                                       64176-42-7       Textiles
    phosphonates and


    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


    Table 9.  (contd.)


    Chemical name                     Chemical structure       CAS registry     Use as flame                                          Remarks
                                                               number           retardant

    Bromine-, chlorine and                                                      Polyurethane foams
    phosphorus-containing                                                       H

    Nitrogen-based and miscellaneous flame retardants

    Melamine                                                                    Polyurethane foams

    Melamine phosphate                                                          Polypropylene

    Melamine cyanurate                                         37640-57-6       Polyamides, polyurethanes,
                                                                                polyolefines, polyester,
                                                                                epoxy resins


    Table 9.  (contd.)


    Chemical name                     Chemical structure       CAS registry     Use as flame                                          Remarks
                                                               number           retardant

    Ferrocene                                                  102-54-5         Additive smoke


    Table 10.  Flame retardants that have been used commercially in the past


    Chemical name                     Chemical structure       CAS registry     Use as flame retardant                                Remarks

    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


    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

    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

    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

    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 

    benzoate                                                                      ABS, polyester, polystyrene


    1,4-Bis(bromomethyl)-tetrabromo                                               Polyolefines



    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


    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

    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



    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


    Table 10.  (contd.)


    Chemical name                     Chemical structure        CAS registry      Use as flame                                          Remarks
                                                                number            retardant

    Hexachlorocyclopenta-                                       51936-55-1        Styrenic polymers


    Dibromochlordene                                            18300-04-4        Styrenic polymers


    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



    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


    Condensate of bis                                                             Cellulosic textiles, cotton and rayon
    phosphonate and alkyl


    Table 10.  (contd.)


    Chemical name                     Chemical structure        CAS registry      Use as flame                                          Remarks
                                                                number            retardant

    Tris(2,4,6-tribromophenyl)                                                    Engineering thermoplastics


    Bis(1,3-dichloro-2-propyl)-                                 61090-89-9        Polyolefins
    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-

    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


    Ethylene-bis[bis                                            33125-86-9        Polyurethane foams


    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.


    US Interagency Testing Commission recommendations on
    brominated flame retardants



    1,2-Dibromo-4-(1,2-dibromomethyl) cyclohexane
    Tetrabromobisphenol A
    Decabromodiphenyl ether
    Pentabromodiphenyl ether
    Octabromodiphenyl ether


    Tetrabromophthalic anhydride
    Dibromoneopentyl glycol
    Ethylene bis(tetrabromophthalimide)
    Ethylene bis(tetrabromonorbornane-2,3-dicarboximide)
    Tribrominated polystyrene
    Ethylene bis(pentabromophenoxide)
    Vinyl bromide
    Ethoxylated tetrabromobisphenol A
    Tetrabromobisphenol A, bis(allyl ether)

    Annex IV (contd).



    Recommended (contd).

    Tribromoneopentyl alcohol
    Tetrabromobisphenol A diacrylate
    Alkanes, C10-16, bromochloro
    2,4-(or 2,6)-Dibromophenol, homopolymer
    Benzene, ethenyl-, homopolymer, brominated


    Bromophenol (Br1, Br2, Br5)
    Bis(dibromopropyl) carbamate
    Bis(2,3-dibromopropyl) phosphite
    Bis(dibromopropyl) phosphite
    Brominated terphenyls
    Dibromopropyl carbamate
    Allyl bis(2,3-dibromopropyl) phosphite
    Bis(dibromopropyl) phosphoryl chloride
    2,3-Dibromo-1-propanol phosphate
    pentabromophenyl allyl ether
    bis(2,3-dibromopropyl) phthalate
    1,2-Ethanediylbis[tris(2-cyanoethyl)phosphonium] dibromide
    Tetrabromophthalic acid, aluminium salt
    Fumaric acid, bis(pentabromophenyl) ester
    tetrabromophthalic acid, dipotassium salt
    Bis(2,4,6-tribromophenyl) fumarate

    Annex IV (contd).



    Deferred (contd)

    Poly(2,6-dibromophenylene oxide)
    Tribromophenyl allyl ether
    3,3',5,5'-Tetrabromobisphenol A diacetate
    3,3',5,5'-Tetrabromobisphenol S
    Tris(dibromophenyl) phosphate
    Dibromopropyl carbamate
    Dibromopropyl carbamate
    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
    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.


    9.1  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'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

         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

    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

    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

    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.


    9.1  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

         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

         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

         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

    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

    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

    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:
       Toxicological Abbreviations
       Flame retardants (EHC 209, 1998)
       Flame retardants (EHC 218, 2000)