Health and Safety Guide No. 68






    This is a companion volume to Environmental Health Criteria 140:
    Polychlorinated Biphenyls and Terphenyls (Second Edition)

    Published by the World Health Organization for the International
    Programme on Chemical Safety (a collaborative programme of the
    United Nations Environment Programme, the International Labour
    Organisation, and the World Health Organization)

    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

    WHO Library Cataloguing in Publication Data

    Polychlorinated biphenyls, polychlorinated terphenyls
    (PCBs and PCTs) : health and safety guide.

    (Health and safety guide ; no. 68)

    1. Polychlorobiphenyl compounds - poisoning
    2. Polychlorobiphenyl compounds - standards
    3. Polychloroterphenyl compounds - poisoning
    4. Polychloroterphenyl compounds - standards
    5. Environmental exposure      6. Environmental pollutants
    7. Hazardous substances  I. Series

    ISBN 92 4 151068 4          (NLM Classification: QV 633)
    ISSN 0259-7268

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    nature that are not mentioned. Errors and omissions excepted, the
    names of proprietary products are distinguished by initial capital



         1.1. Identity
              1.1.1. Polychlorinated biphenyls - PCBs
              1.1.2. Polychlorinated terphenyls - PCTs
         1.2. Physical and chemical properties
         1.3. Analytical methods
         1.4. Uses

         2.1. Environmental transport, distribution, and transformation
         2.2. Environmental levels and human exposure
         2.3. Kinaetics and metabolism
         2.4. Effects on organisms in the environment
              2.4.1.     Laboratory studies
              2.4.2. Field studies
         2.5. Effects on experimental animals and  in vitro systems
              2.5.1. Single exposure
              2.5.2. Short-term exposure
              2.5.3. Reproduction, embryotoxicity, and teratogenicity
              2.5.4. Mutagenicity
              2.5.5. Carcinogenicity
              2.5.6. Special studies
              2.5.7. Factors modifying toxicity; mode of action
         2.6. Effects in humans

         3.1. Conclusions
              3.1.1. Distribution
              3.1.2. Effects on experimental animals
              3.1.3. Effects on humans
              3.1.4. Effects on the environment
         3.2. Recommendations


         4.1. Main human health hazards, prevention and protection,
              first aid
              4.1.1. Advice to physicians
                  Symptoms of poisoning
                  Medical advice
              4.1.2. Health surveillance advice
         4.2. Explosion and fire hazards
         4.3. Storage
              4.3.1. Leaking containers in store

         4.4. Transport
         4.5. Spillage and disposal
              4.5.1. Spillage
              4.5.2. Disposal

         5.1. Hazards
         5.2. Prevention


         7.1. Previous evaluations by international bodies
         7.2. Exposure limit values
         7.3. Specific restrictions
         7.4. Labelling, packaging, and transport
         7.5. Waste disposal



    The Environmental Health Criteria (EHC) documents produced by the
    International Programme on Chemical Safety include an assessment of
    the effects on the environment and on human health of exposure to a
    chemical or combination of chemicals, or physical or biological
    agents. They also provide guidelines for setting exposure limits.

    The purpose of a Health and Safety Guide is to facilitate the
    application of these guidelines in national chemical safety
    programmes. The first three sections of a Health and Safety Guide
    highlight the relevant technical information in the corresponding
    EHC. Section 4 includes advice on preventive and protective measures
    and emergency action; health workers should be thoroughly familiar
    with the medical information to ensure that they can act efficiently
    in an emergency. Within the Guide is a Summary of Chemical Safety
    Information which should be readily available, and should be clearly
    explained, to all who could come into contact with the chemical. The
    section on regulatory information has been extracted from the legal
    file of the International Register of Potentially Toxic Chemicals
    (IRPTC) and from other United Nations sources.

    The target readership includes occupational health services, those
    in ministries, governmental agencies, industry, and trade unions who
    are involved in the safe use of chemicals and the avoidance of
    environmental health hazards, and those wanting more information on
    this topic. An attempt has been made to use only terms that will be
    familiar to the intended user. However, sections 1 and 2 inevitably
    contain some technical terms. A bibliography has been included for
    readers who require further background information.

    Revision of the information in this Guide will take place in due
    course, and the eventual aim is to use standardized terminology.
    Comments on any difficulties encountered in using the Guide would be
    very helpful and should be addressed to:

    The Director
    International Programme on Chemical Safety
    World Health Organization
    1211 Geneva 27



    1.1 Identity

    1.1.1 Polychlorinated biphenyls - PCBs

     Chemical formula - chemical structure

    The chlorination of biphenyl can lead to the replacement of 1-10
    hydrogen atoms by chlorine.


    The chemical formula can be presented as C12H10-nCln, where  n is
    the number of chlorine atoms in the molecule.

     Chemical composition

    The PCBs are chlorinated hydrocarbons that are manufactured
    commercially by the progressive chlorination of biphenyl in the
    presence of a suitable catalyst (e.g., iron chloride). Depending on
    the reaction conditions, the degree of chlorination can vary between
    21 and 68% (w/w). The yield is always a mixture of different
    compounds and congeners. Thus, a total of 209 different chemical
    components may exist, but only about 130 of these are likely to
    occur in commercial products or mixtures of these compounds.

    Individual PCBs have been synthesized for use as reference samples
    in the identification of gas-liquid chromatographic peaks, for
    toxicological investigations, and in order to study their metabolic
    fate in living organisms.

     Purity and impurities

    Commercial PCBs are sold on the basis of their physical properties,
    not their chemical composition. Different batches may vary somewhat
    in their composition. The impurities known to be present in
    commercial PCBs include chlorinated naphthalenes and small
    quantities of the highly toxic polychlorinated dibenzofurans
    (PCDFs). There are no authenticated reports of the presence of
    polychlorinated dibenzo- p-dioxins (PCDDs) in commercial PCBs.

    Common name:               Polychlorinated biphenyls - PCBs.

    CAS registry number:       1336-36-3

    RTECS registry number:     TQ1350000

    Relative molecular mass:   Depends on degree of chlorination and
                               composition of the mixture.

     Major trade names

    Apirolio (t,c)           Disconon (c)        PCBs
    Areclor (t)              Dk (t,c)            Phenoclor (t,c)
    Aroclor                  Duconol (c)         Polychlorinated biphenyl
    Arubren                  Dykanol (t,c)       Polychlorobiphenyl
    Asbestol (t,c)           EEC-18              Pydraul
    Askarel                  Elemex (t,c)        Pyralene (t,c)
    Bakola 131 (t,c)         Eucarel             Pyranol (t,c)
    Biclor (c)               Fenchlor (t,c)      Pyroclor (t)
    Chlorextol (t)           Hivar (c)           Saf-T-Kuhl (t,c)
    Chlorinated Biphenyl     Hydol (t,c)         Santotherm FR a
    Chlorinated Diphenyl     Inclor              Santovac 1 and 2
    Chlorinol                Interteen (t,c)     Siclonyl (c)
    Chlorobiphenyl           Kanechlor (t,c)     Solvol (t,c)
    Clophen (t,c)            Kennechlor          Sovol
    Chlorphen (t)            Montar              Therminol FR a
    Delor                    Nepolin
    Diaclor (t,c)            No-Flamol (t,c)
    Dialor (c)               PCB

    a  Previous products (FR-series) used as heat transfer fluids
         contained PCBs, but since 1972 current products are different
         series and do not contain PCBs.

    (t) used in transformers.

    (c) used in capacitors.

    1.1.2 Polychlorinated terphenyls - PCTs

     Chemical formula - chemical structure


    The chemical formula can be written as C18H14-nCln, in which  n
    is the number of chlorine atoms, which can range from 1-14.

     Chemical composition

    The theoretically possible number of different PCTs is several
    orders of magnitude greater than the number of PCBs, but in
    practice, as with PCBs, PCTs are sold on the basis of their physical
    properties, which depend on the degree of chlorination, and not
    their chemical composition.

    Common name:               Polychlorinated terphenyls - PCTs.

    CAS registry number:       61788-33-8

    RTECS registry number:     WZ6500000

    Relative molecular mass:   Depends on degree of chlorination and
                               composition of the mixture.

     Main trade names

    PCTs are known by a variety of trade names, some of which are
    similar to those given for PCBs in Section 1.1.1. In the Aroclor
    series, terphenyls are indicated by 54 in the first two places of
    the four digit code. In Japan, the PCTs are coded Kanechlor KC-C.

    1.2 Physical and chemical properties

    Individual, pure congeners of PCB and PCT are colourless, often
    crystalline compounds, but commercial PCBs are mixtures of these
    congeners with a clear, light yellow or dark colour, and range from
    oily liquids to waxy or hard solids. They do not crystallize at low
    temperatures, but turn into solid resins. Because of the chlorine
    atoms in the molecule, the compounds have a fairly high density. In
    practice, PCBs are fire resistant, and have a fairly high
    flash-point (170-380 C). They form vapours that are heavier than
    air, but they do not form an explosive mixture with air. The
    electrical conductivity of PCBs and PCTs is very low, and their
    resistance to thermal breakdown is extremely high. It is on the
    basis of these properties that they are used as cooling liquids in
    electrical equipment. The physical properties of some Aroclors are
    shown in Table 1.

    PCBs are chemically stable under normal conditions. They are very
    resistant to a range of oxidants and other chemicals, and they
    remain chemically unchanged even in the presence of oxygen, or some
    active metals, at high temperatures (up to 170 C), and for
    protracted periods.

    PCBs are practically insoluble in water; however, they dissolve
    easily in hydrocarbons, fats, and other organic compounds, and they
    are readily adsorbed by fatty tissues.

    The partition coefficient (log Kow) values for all 209 PCB
    congeners range from 4.46 to 8.18.

    1.3  Analytical methods

    Only a small number of laboratories in the world have access to, and
    experience of working with, the complicated techniques necessary for
    a reproducible determination of PCBs and PCTs.

    One probable source of error is incomplete extraction and clean-up
    of the PCBs. The method used to quantify the gas-liquid
    chromatographic peaks also gives rise to variation between

    Data on concentrations of PCBs must be interpreted with the greatest
    care. Comparisons can only be made between data from the same
    laboratory, obtained using the same validated technique over a long
    period. Comparisons between data from different laboratories are
    possible in only the very few cases, in which very strict
    interlaboratory checks have been made on the basis of the same
    sampling and analytical techniques. Indications about trends can
    only be obtained when these basic considerations are taken into

    Gas-liquid chromatography (GLC) with packed or capillary columns, is
    generally used for the analysis, and comparison of peak patterns,
    and various PCB standard formulations are used for quantification.
    Different approaches are used for the summing-up of individual

    Analytical methods are discussed in more detail in the WHO/EURO
    (1987) document.

    Individual congeners are identified using GLC, with either hydrogen
    flame ionization detection (HFID) or electron capture detection
    (ECD), and mass spectrometry.

        Table 1. Physical properties of some Aroclors


    Substance   Water         Vapour        Density     Appearance      Henry's Law      Refractive index     Boiling point
    Aroclor     solubility    pressure      g/cm3                       constant                              (distillation
                (mg/litre,    (torr,        (25 C)                     (atm-m3/mol                           range)
                25 C)        25 C)                                    at 25 C)                             (750 torr, C)

    1016        0.42          4.0 x 10-4    1.33        Clear,          2.9 x 10-4       1.6215-1.6135        325-356
                                                        mobile oil                       (at 25 C)

    1221        0.59          6.7 x 10-3    1.15        Clear,          3.5 x 10-3       1.617-1.618          275-320
                                                        mobile oil

    1232        0.45          4.1 x 10-3    1.24        Clear,          unknown          unknown              290-325
                                                        mobile oil

    1242        0.24          4.1 x 10-3    1.35        Clear,          5.2 x 10-4       1.627-1.629          325-366
                                                        mobile oil                       (at 20 C)

    1248        0.054         4.9 x 10-4    1.41        Clear,          28 x 10-3        unknown              340-375
                                                        mobile oil

    1254        0.021         7.7 x 10-5    1.50        Light yellow,   2.0 x 10-3       1.6375-1.6415        365-390
                                                        viscous oil                      (at 25 C)

    1260        0.0027        4.0 x 10-5    1.58        Light yellow,   4.6 x 10-3       unknown              385-420
                                                        sticky resin


    1.4  Uses

    The industrial usefulness of PCBs and PCTs depends on their chemical
    inertness, resistance to heat, non-flammability, low vapour pressure
    (particularly with the higher chlorinated compounds), and high
    dielectric constant.

    The main uses are (or were):

    (a) as dielectrics in transformers and large capacitors (considered
    to be closed systems);

    (b) in heat transfer and hydraulic systems (nominally closed

    (c) in the formulation of lubricating and cutting oils;

    (d) as plasticizers in paints, carbonless copying paper, adhesives,
    sealants, and plastics.

    Both c and d are open-ended applications.


    2.1  Environmental transport, distribution, and transformation

    In the atmosphere, PCBs exist primarily in the vapour phase; the
    tendency to adsorb to particulates increases with the degree of
    chlorination. The virtually universal distribution of PCBs suggests
    that they are transported in air.

    At present, the major source of PCB exposure for the general
    population appears to be as a consequence of the redistribution of
    PCBs previously introduced into the environment. This redistribution
    involves volatilization from soil and water into the atmosphere,
    with subsequent transport in air and removal from the atmosphere
    through wet or dry deposition (of PCBs bound to particulates), and
    then re-volatilization. The concentrations of PCBs in precipitation
    range from 0.001 to 0.25 g/litre. Since the volatilization and
    degradation rates of PCBs vary among the different congeners, this
    redistribution leads to an alteration in the composition of PCB
    mixtures in the environment.

    In water, PCBs are adsorbed to sediments and other organic matter;
    experimental and monitoring data have shown that PCB concentrations
    are higher in sediment and suspended matter than in the associated
    water columns. Strong adsorption to sediment, especially in the case
    of the higher chlorinated PCBs, decreases the rate of
    volatilization. On the basis of their water solubilities and
     n-octanol-water partition coefficients, the lower chlorinated PCB
    congeners will sorb less strongly than the higher chlorinated
    isomers. Although adsorption can immobilize PCBs for relatively long
    periods in the aquatic environment, desorption into the water column
    has been shown to occur by both the abiotic and biotic routes. The
    substantial quantities of PCBs in aquatic sediments therefore act as
    both an environmental sink and a reservoir of PCBs for subsequent
    recycling in the environment. Most of the PCBs in the environment
    are in the aquatic sediment.

    The low solubility of PCBs, and their strong adsorption to soil
    particles, limits leaching in soil; the lower chlorinated PCBs will
    tend to leach more than the highly chlorinated PCBs.

    Degradation of PCBs in the environment depends on the degree of
    chlorination of the biphenyl. In general, the persistence of PCB
    congeners increases as the degree of chlorination increases. In the
    atmosphere, the reaction of PCBs in the vapour phase with hydroxyl
    radicals (which are photochemically formed by sunlight) may be the
    most important transformation process. The estimated half-life of
    this reaction in the atmosphere ranges from about 10 days to 1.5
    years for a monochlorobiphenyl and a heptachlorobiphenyl,

    In the aquatic environment, PCBs are not significantly degraded by
    hydrolysis and oxidation. Photolysis appears to be the only abiotic
    degradation process in water; however, insufficient experimental
    data are available to determine its rate or its importance in the

    Microorganisms degrade mono-, di-, and trichlorinated biphenyls
    relatively rapidly, and tetrachlorobiphenyls slowly, while higher
    chlorinated biphenyls are resistant to biodegradation. The chlorine
    substitution position on the biphenyl ring appears to be important
    in determining the biodegradation rate. PCBs containing chlorine
    atoms in the  para position are preferentially biodegraded. Higher
    chlorinated congeners are biotransformed anaerobically, by reductive
    dechlorination, to lower chlorinated PCBs, which may then be
    biodegradable by aerobic processes.

    Several factors determine the degree of bioaccumulation in adipose
    tissues: duration and level of exposure, chemical structure of the
    compound, and position and pattern of substitution. In general, the
    higher chlorinated congeners are accumulated more readily.

    The bioconcentration factors of various PCBs determined
    experimentally in aquatic species (fish, shrimp, oyster) range from
    200 up to 70 000 or higher. In the open ocean, there is
    bioaccumulation of PCBs in the higher trophic levels, with an
    increased proportion of higher chlorinated biphenyls in the higher
    ranking predators.

    Transfer of PCBs from soil to vegetation takes place mainly through
    adsorption onto the external surfaces of terrestrial plants; little
    translocation takes place.

    2.2  Environmental levels and human exposure

    Because they persist for a long time, and because of other
    physicochemical properties, PCBs are present in the environment all
    over the world.

    PCBs are found in air, all over the world, at concentrations of
    0.002 up to 15 ng/m3. In industrial areas, higher levels of up to
    micrograms/m3 are found. In rain-water and snow, PCBs are found in
    the range of not detectable (<ng/litre) to 250 ng/litre.

    Under workplace conditions, the levels in the air may be much
    higher. In the manufacturing of transformers or capacitors, for
    instance, levels of up to 1000 g/m3 have been observed. In
    emergency situations, concentrations of up to 16 mg/m3 have been
    measured. In the case of fires and/or explosions, the soot may
    contain high levels of PCBs; concentrations of 8000 mg PCBs/kg soot
    have been found. In fires and explosions, PCDFs will also be present

    in the soot. In accidents with transformers in which chlorinated
    benzenes are present in addition to PCBs, polychlorinated dioxins
    (PCDDs) will also be found.

    In these emergency situations, skin contamination with soot is
    possible, and ingestion or inhalation of soot particles may occur
    and result in serious exposures of personnel. However, the exposure
    of the general population through the air will be very low.
    Surface water may be contaminated by PCBs by atmospheric fall-out,
    or by direct emissions from point sources, or waste disposal. Under
    certain conditions, levels of up to 100-500 ng/litre of water have
    been measured. In the water of oceans, levels of 0.05-0.6 ng/litre
    have been found.

    In non-contaminated areas, drinking-water usually contains less than
    1 ng PCBs/litre, but levels up to 5 ng/litre have been reported.
    Soil and sediments normally contain concentrations of PCBs in the
    range of <0.01-2.0 mg/kg. In polluted areas, the levels in soils
    have been much higher, up to 500 mg/kg.

    Over the years, many thousands of samples of different foodstuffs
    have been analysed, in several countries, for contaminants,
    including PCBs. Most samples have been taken from individual food
    items, especially fish and other foods of animal origin, such as
    meat and milk. Food becomes contaminated with PCBs by three main

    a) uptake from the environment by fish, birds, livestock (via
    food-chains), and crops;

    b) migration from packaging materials into food (mainly less than 1
    mg/kg, but in some cases up to 10 mg/kg);

    c) direct contamination of foodstuffs or animal feed as the result
    of an industrial accident.

    For the most important food items that contain PCBs, the following
    concentrations have been found: animal fat, 20-240 g/kg; cow's
    milk, 5-200 g/kg; butter, 30-80 g/kg; fish, 10-500 g/kg, on fat
    basis. Certain fish species (eel) and fish products (fish liver and
    fish oils) contained much higher levels, up to 10 mg PCBs/kg. Levels
    of <10 g/kg were found in vegetables, cereals, fruits, and a
    number of other products. Fish, shellfish, meat, milk, and other
    dairy products are the main foods that give rise to concern as
    regards levels of PCBs. The median levels reported in fish, in
    various countries, are in the order of 100 g/kg (on fat basis);
    however, it appears that the levels of PCBs in fish are slowly

    PCBs accumulate in human adipose tissue and breast milk. The
    concentrations of PCBs in different organs and tissues depend upon
    the lipid content of the organ or tissue, with the exception of the
    brain. The levels of PCB residues in adipose tissue of the general
    population in industrialized countries range from <1 to 5 mg/kg, on
    fat basis.

    The average concentration of total PCBs in human milk is in the
    range of 0.5 to 1.5 mg/kg fat, depending on the donor's place of
    residence, life-style, and the analytical methods used. Women living
    in heavily industrialized urban areas, or with a high fish
    consumption (especially fish from heavily contaminated waters), may
    have higher PCB concentrations in breast milk.

    The composition of most PCB extracts from environmental samples does
    not resemble that of the commercial PCB mixtures. High-resolution
    gas chromatography (GC) analysis shows that the congener
    composition, and relative concentrations of the individual
    components, in adipose tissues and breast milk differ markedly from
    the composition of commercial PCBs. The GC-patterns of PCBs in human
    adipose tissues and breast milk indicate relatively high
    concentrations of mainly the higher chlorinated PCBs, such as,
    2,4,5,3',4'-pentachlorobiphenyl; 2,4,5,2',4',5'-hexa-
    chlorobiphenyl; and 2,3,4,2',4',5'-hexachlorobiphenyl;
    2,3,4,5,2',4',5'-hepta- and 2,3,4,5,2',3',4'-heptachlorobiphenyl. A
    few other PCB congeners are present at much lower concentrations,
    including the most toxic, coplanar PCBs: 3,4,3',4'-tetra-,
    3,4,5,3',4'-penta- and 3,4,5,3',4',5'-hexahlorobiphenyl.

    The daily intake of PCBs by infants from breast milk is of the order
    of 4.2 g/kg body weight (5.2 g/100 kcal consumed) (WHO/EURO,
    1987). The average total quantity of PCBs ingested in breast milk
    during the first 6 months of life is 4.5 mg compared with a
    calculated intake of 357 mg of PCBs over the subsequent life-time
    (0.2 g/kg per day in the diet of a 70-kg person over a 70-year
    life-time). Therefore, the nursing period contributes about 1.3% of
    the life-time intake, which is not large in light of the benefits of
    breast-feeding (WHO/EURO, 1987).

    On the basis of the evaluated background data, the average dietary
    intake of PCBs for adults amounts to a maximum of 100 g/week, or
    approximately 14 g/person per day. For a 70-kg person, this is an
    intake equivalent to a maximum of 0.2 g/kg body weight per day
    (WHO/EURO, 1987).

    2.3  Kinetics and metabolism

    Animal studies have been reported involving mainly oral, inhalation,
    and dermal exposures to both PCB mixtures and individual congeners.
    In general, PCBs appear to be rapidly absorbed, particularly by the
    gastro-intestinal tract after oral exposure. It is clear that
    absorption does occur in humans, but information on the rates of
    absorption of PCBs in humans is limited.

    From the available studies, the data on the distribution of PCBs,
    suggest a biphasic kinetic process with rapid clearance from blood,
    and accumulation in the liver and the adipose tissue of various
    organs. There is also evidence of placental transport, fetal
    accumulation, and distribution to milk. In some studies with humans,
    the skin was a tissue with a high concentration of PCBs but the
    concentration in the brain was lower than would be expected on the
    basis of the lipid content.

    Mobilization of PCBs from fat appears to depend largely on the rates
    of metabolism of the individual PCB congeners. Excretion depends on
    the metabolism of PCBs to more polar compounds, such as phenols,
    conjugates of thiol compounds, and other water-soluble derivatives.
    Metabolic pathways include hydroxylation, conjugation with thiols
    and other water-soluble derivatives, some of which can involve
    reactive intermediates, such as the arene oxides. The rates of
    metabolism have been shown to depend on the PCB structure and
    reflect both the degree and position of the chlorine substituents.
    The polar metabolites of the more highly chlorinated PCBs appear to
    be eliminated primarily in the faeces, but excretion in the urine
    can also be significant. An important elimination route, is via
    (breast) milk. Certain PCB congeners can also be eliminated via the

    The available kinetic studies indicate that there is a wide
    divergence in biological half-life among the individual congeners
    and this can reflect differences in structure-dependent metabolism,
    tissue affinities, and other factors, affecting mobilization from
    storage sites.

    Persistence in tissues is not always correlated with high toxicity
    and differences in toxicity between PCB congeners may be associated
    with specific metabolites and/or their intermediates.

    2.4  Effects on organisms in the environment

    PCBs are universal environmental contaminants and are present
    globally in most environmental compartments, both abiotic and
    biotic. Since many countries have controlled both use and release,
    new input into the environment is on a much smaller scale, compared
    with the past. However, the available evidence suggests that the
    cycling of PCBs is causing a gradual redistribution of some
    congeners towards the marine environment. There is a trend for the
    highest chlorinated congeners to accumulate preferentially. While a
    large proportion of the PCBs is adsorbed onto particulates in
    sediment, it is still bioavailable to organisms and will continue to
    be accumulated in the higher trophic levels.

    2.4.1.  Laboratory studies

    Effects of PCB mixtures on microorganisms are highly variable, with
    some species being adversely affected by a concentration of
    0.1 mg/litre and others being unaffected by 100 mg/litre; effects on
    different species do not vary consistently with the degree of
    chlorination of the mixtures. 

    Almost all of the studies of the effects of PCBs on aquatic
    organisms have involved Aroclor mixtures. Results are extremely
    variable with no consistent relationship between percentage
    chlorination or environmental conditions and toxicity, even with
    closely-related organisms. Over 96 h under static conditions, LC50
    values ranged between 12 g/litre and >10 mg/litre for various
    aquatic invertebrate species and different Aroclor mixtures.
    Flow-through conditions increased the toxicity of the PCBs.
    Generally, the most toxic mixtures were Aroclors in the mid-range of
    chlorination; low and high percentage chlorination mixtures were
    less toxic. This was also true for sublethal effects, such as
    reproduction of  Daphnia. Crustaceans seem to be more susceptible
    to PCBs during moult. In model populations, the community structure
    of estuarine species changed on exposure to Aroclor 1254, with
    amphipods, bryozoans, crabs, and molluscs decreasing in
    representation and annelids, brachyopods, coelenterates, echinoderms
    and nemerines being unaffected. Too few of the groups have been
    included in acute tests to determine whether the result represents
    variation in susceptibility to PCBs or differences in interaction
    between species.

    There is similar variation in the toxicity of PCB mixtures for fish
    with 96-h LC50s varying between 0.008 and >100 mg/litre. Long-term
    tests show that acute exposure, particularly under static
    conditions, considerably underestimates the toxicity of the PCB.
    Rainbow trout were particularly susceptible, with embryo-larval
    stages showing a 22-day LC50 of 0.32 g/litre for Aroclor 1254. The

    no-observed-effect level (NOEL) over 22-days for rainbow trout
    embryo-larval stages was 0.01 g/litre for Aroclors 1016, 1242, and

    Freshwater fathead minnow showed NOELs of 5.4, 0.1, 1.8, and 1.3
    g/litre for Aroclors 1242, 1248, 1254, and 1260, respectively. The
    estuarine sheephead minnow showed NOELs of 3.4 and 0.06 g/litre for
    Aroclors 1016 and 1254, respectively.

    Experimental evidence has confirmed field observations demonstrating
    reproductive impairment in seals fed on fish containing PCBs,
    accumulated in the wild. The effect occurs late in reproduction,
    preventing implantation of the embryo in the uterine wall. 
    In short-term tests, the toxicity of Aroclor for birds increases
    with increasing percentage chlorination; 5-day dietary LC50s ranged
    from 604 to >6000 mg/kg diet. The main reproductive effects in
    birds are reduced hatchability of eggs and embryotoxicity. These
    effects of the PCB continue after dosing has ended, as the hens
    reduce their PCB load via the eggs. There is no evidence that
    Aroclors cause egg-shell thinning directly; effects on the food
    consumption and body weight of hens have an indirect effect on shell
    thickness. Sublethal effects on behaviour and hormone secretion have
    been reported.

    For mink, the acute toxicity of Aroclors decreases with increasing
    percentage chlorination, acute oral LD50s varying between >750 and
    4000 mg/kg body weight; the ferret is less sensitive. Aroclors
    reduce food consumption and, thus, the growth rate of young mink.
    Reproduction in mink is reduced or eliminated by Aroclors, either
    given directly, or as natural contaminants in fish. Aroclors with a
    higher percentage chlorination (notably 1254) have a greater effect.
    The reproductive rate returns to normal after feeding with Aroclor
    is stopped.

    Bats are susceptible to Aroclor released from their fat during

    The majority of laboratory tests on aquatic and terrestrial
    organisms have been carried out using PCB mixtures and it has not
    been possible to identify the specific components of mixtures
    responsible for the effects. Similarly, because tests have been
    conducted under environmentally unrealistic conditions (e.g., beyond
    the solubility of congeners, and, in aquatic tests, without the
    presence of sediment) it is difficult to extrapolate from laboratory
    tests to the field. 

    2.4.2  Field studies

    Results suggesting that PCBs affect fish populations in the field
    are inconclusive. Interpretation of field data on birds is
    difficult, since residues of many different organochlorines are also
    present. Most authors have shown a correlation between
    embryotoxicity and total organochlorine residues. The levels of PCB
    residues correlate best with the effects on embryos, but these
    results cannot be regarded as proof of a field effect of the PCBs.

    There is evidence (confirmed in laboratory studies) that PCBs reduce
    the reproductive capacity of sea mammals. The effect is on
    implantation of the embryo, but PCBs can also lead to physical
    changes in the female reproductive tract.

    It is not possible to extrapolate from the results of acute and
    short-term laboratory tests to effects on populations in the field.
    Uncertainties about which components of the PCB mixtures cause
    effects, the specific congeners present in the environment, and the
    bioavailability of PCB components to organisms, all combine to make
    it difficult to estimate the probable environmental exposure and
    effects. The effects on populatons of sea mammals can be regarded as
    proved, but it is not yet known which component(s) of the PCB
    mixtures are responsible.

    Given the trends towards increased contamination of the marine
    environment, attention should be concentrated on effects on marine
    organisms. There is clear laboratory and field evidence of
    reproductive effects of PCBs on populations of sea mammals in
    heavily polluted areas, and PCB residues and their effects are
    likely to increase in the future. It is less clear whether effects
    will be seen in other organisms, such as birds that feed on marine

    On the evidence of laboratory studies, population and community
    effects on lower organisms, i.e., phytoplankton and zooplankton,
    would be expected to occur. Both the degree and significance of such
    effects are difficult to assess. From currently available
    information, effects on fish populations would not be expected,
    though fish will act as a route of exposure of fish-eating mammals
    and birds.

    Previously reported effects on terrestrial species, fish-eating
    freshwater mammals and migratory bats for example, should be less
    evident as the residues of PCBs are redistributed. Residues in
    terrestrial biota currently show little decline overall, but
    information on changes in congeners is scarce or absent. Levels of
    the higher chlorinated congeners would only be expected to decrease

    2.5  Effects on experimental animals and  in vitro systems

    2.5.1  Single exposure

    The acute toxicity of Aroclors for rats after a single oral exposure
    is generally low. Young animals appear to be more sensitive (LD50,
    1.3-2.5 g/kg body weight) than adults (LD50, 4-11 g/kg body
    weight). The lowest LD50 reported for Aroclor 1254 in adult rats
    was 1.0 g/kg body weight. No sex differences were observed.

    Dermal LD50s in rabbits ranged from >1.26 to <2 g/kg body weight
    for Aroclor 1260 (in corn oil) and from 0.79 to <3.17 g/kg body
    weight for some other undiluted PCB mixtures. Intravenous
    application demonstrated an LD50 of 0.4 g/kg body weight for
    Aroclor 1254 in rats; the LD50, after intraperitoneal injection, in
    the mouse varied from 0.9 to 1.2 g/kg body weight.

    2.5.2  Short-term exposure

    The main targets in mammals with short-term oral exposure to PCB
    mixtures or congeners are the liver, the skin, the immune system,
    and the reproductive system. The rhesus monkey is the most sensitive
    species tested, females being more sensitive than males. Adult
    female rhesus monkeys exposed to a diet containing Aroclor 1248 at a
    level of 2.5 mg/kg diet, or 0.09 mg/kg body weight per day for 6
    months showed an increased mortality rate, growth retardation,
    alopecia, acne, swelling of the Meibomian glands, and possibly
    immunosuppression. Microscopically, enlarged fatty liver with focal
    necrosis, and epithelial hyperplasia and keratinization of hair
    follicles were found. At higher exposure levels, microscopic changes
    have also been observed in other epithelial tissues, such as
    sebaceous and Meibomian glands, gastric mucosa, gall bladder, bile
    duct, nail beds, and ameloblast. Serum levels of total lipid
    triglycerides and cholesterol were decreased. Short-term exposure to
    commercial PCB mixtures induced an increase in the contents and
    concentrations of total lipids, triglycerides, cholesterol, and/or
    phospholipids in the liver. Among the PCB congeners,
    3,4,3',4'-tetrachlorobiphenyl, 3,4,5,3',4',5'-, and 
    2,4,6,2',4',6'-hexachlorobiphenyl were the most potent. Aroclor
    1254, at a dose level of 0.2 mg/kg body weight per day, also showed
    several other effects, such as lymphoreticular lesions, fingernail
    detachment, and gingival effects, but no acne and alopecia. A
    no-observed-effect level (NOEL) for the general toxicity of Aroclor
    1242 of 0.04 mg/kg body weight per day was established in rhesus
    monkeys. Relatively mild effects were shown in suckling rhesus
    monkeys exposed to a much higher dose of Aroclor 1248 of 35 mg/kg
    body weight per day. Effects in the liver have been investigated
    most thoroughly in rats, and include hypertrophy, fatty
    degeneration, proliferation of the endoplasmic reticulum, porphyria,
    adeno-fibrosis, bile duct hyperplasia, cysts, and preneoplastic and

    neoplastic changes. In studies on rats and mice, individual PCB
    congeners caused effects in the liver, spleen, and thymus, the
    planar congeners being most toxic. In monkeys, planar congeners, at
    doses of 1-3 mg/kg diet, induced effects similar in character and
    severity to those seen with Aroclor 1242 at a dose of 100 mg/kg diet
    and with Aroclor 1248 at a dose of 25 mg/kg diet.

    Following dermal exposure of rabbits and mice, PCB mixtures, and
    some congeners, caused effects on the skin and liver similar to
    those found after oral exposure. In rabbits, thymic atrophy, a
    reduction in the germinal centres of the lymph nodes, and leukopenia
    were also observed.

    2.5.3  Reproduction, embryotoxicity, and teratogenicity

    (a) Reproduction and embryotoxicity

    Comprehensive reproduction and teratogenicity studies have not been
    conducted. In a two-generation reproduction study on rats, a NOEL of
    0.32 mg/kg body weight was established for Aroclor 1254 and a NOEL
    of 7.5 mg/kg body weight for Aroclor 1260. However, the lowest
    tested dose (0.06 mg/kg body weight) resulted in increased relative
    liver weights in weanlings.

    In rhesus monkeys exposed to Aroclor 1016, a NOEL of 0.03 mg/kg body
    weight was established on the basis of reproductive parameters.
    However, decreased birth weight was observed at this level and the
    lowest dose tested (0.01 mg/kg body weight) resulted in skin

    In rhesus monkeys, a NOEL of 0.09 mg/kg body weight was established
    for Aroclor 1248 (containing PCDFs) 1 year after exposure ceased.

    (b) Teratogenicity

    Available studies on rats and monkeys did not indicate teratogenic
    effects when animals were dosed orally during organogenesis. A NOEL
    of 50 mg/kg body weight was demonstrated in rats for Aroclor 1254,
    with regard to pup weight, and a lowest-observed-effect level of 2.5
    mg/kg body weight, based on fetotoxicity (lesions in thyroid
    follicular cells), could be assumed.

    In teratogenicity tests of individual congeners on mice, rats, and
    Rhesus monkeys, no NOEL was demonstrated. In Rhesus monkeys, a dose
    of 0.07 mg/kg body weight indicated maternal toxicity

    2.5.4  Mutagenicity

    PCB mixtures did not cause mutation or chromosomal damage in a
    variety of test systems. Chromosome breakage was induced in human
    lymphocytes  in vitro by 3,4,3',4'-tetrachlorobiphenyl. High
    concentrations of PCB mixtures may cause primary DNA damage, as
    indicated by DNA single strand breaks in alkaline elution assays.

    2.5.5  Carcinogenicity

    The interpretation of the available animal data involving commercial
    PCB mixtures is often complicated by lack of information concerning
    the presence or contribution of chlorinated dibenzofuran impurities,
    as well as variations in congener composition.

    A number of long-term carcinogenicity studies have been carried out
    in mice and rats. The PCB mixtures used were Kanechlors 300, 400,
    and 500, Aroclors 1254 and 1260, and Clophens A30 and A60. Except
    for the Clophens, which were reported to be free of polychlorinated
    dibenzo-furans (PCDFs), no data were provided on the purity of the
    PCB mixtures used.

    A significant increase in hepatocellular adenomas and/or carcinomas
    was observed in mice fed with a diet containing Kanechlor 500 and
    Aroclor 1254 at a dose level of approximately 15-25 mg/kg body
    weight. No neoplasms could be detected in mice treated with
    Kanechlors 300 and 400.

    In rats, an increase in hepatocellular adenomas and/or carcinomas
    was noted in the studies on Aroclors 1254 and 1260 and Clophen A30,
    with an exposure period of more than 1 year. The increase in
    occurrence of tumours in animals in these studies was not considered
    to be statistically significant; however, this was the case in two
    other studies. An increase in the incidence of hepatocellular
    (trabecular) carcinomas and adenocarcinomas was demonstrated with
    Aroclor 1260 and Clophen A60, at a dose level of approximately 5
    mg/kg body weight.

    The liver tumours concerned were considered to be non-aggressive
    (benign or weakly malignant, no metastasis) and not life-shortening.
    Adenofibrosis, a pre-neoplastic lesion, and/or neoplastic nodules in
    the liver were reported in some of the studies. In one test with
    Aroclor 1254, dose-related increases in intestinal metaplasia and
    adenocarcinomas of the glandular stomach were demonstrated in the
    rat. There is a substantial body of evidence indicating that PCBs
    increase the incidence of liver carcinogenesis in rodents
    pre-treated with hepatocarcinogens. There is weak evidence that PCB
    mixtures initiate carcinogenesis in rodents. From the genotoxicity
    studies reported, it can be concluded that PCB-mixtures are
    non-genotoxic. These results imply that the association of liver
    tumours with administration of PCBs in rodents is attributable to

    some epigenitic mechanisms involving enforcement of cell
    proliferation in the liver and other manifestations of liver
    toxicity, hence a threshold approach can be followed in the
    evaluation of PCB toxicity. The possibility that PCBs might increase
    carcinogenesis in tissues other than liver in animals pre-exposed to
    various tissue-specific carcinogens needs to be addressed. The
    anticarcinogenic activities of PCBs shown in some studies, where
    PCBs were given to animals during, and prior to, the administration
    of carcinogens, may be related to microsomal enzyme-inducing
    properties of PCBs that result in an increase of detoxication.

    Overall, there is reason to exercise caution in extrapolating to
    humans the available animal data on the carcinogenic potential of

    2.5.6  Special studies

    The lesions induced by exposure to PCB mixtures or individual
    congeners concern the liver, skin, immune system, reproductive
    system, oedema, and disturbances of the gastrointestinal tract and
    thyroid gland.

    PCBs are able to induce various enzymes in the liver. This has been
    demonstrated in rats, mice, guinea-pigs, rabbits, dogs, and monkeys
    for Aroclor 1248, 1254, 1260, and Kanechlor 400 (induction of
    cytochrome P450 and P448). The inducing ability increases with the
    chlorine content of the molecule; it is also dependent on the
    congener composition, where congeners with chlorine in the  para
    and  meta positions induce the P450 enzyme. For AHH (aryl
    hydrocarbon hydroxylase) induction, the position of the chlorine
    seems to be more important than the degree of chlorination.
    Congeners with both  para and at least two  meta positions
    substituted by chlorine are the most potent inducers of AHH.
    Distinct interspecies variations have been demonstrated. The lowest
    NOEL of 0.025 mg/kg body weight was found for Aroclor 1260 in
    Osborn-Mendel rats.

    Effects have been demonstrated on the endocrine system, seen as
    alterations in hormonal receptor-binding and alterations in steroid
    hormone balance. Direct and indirect evidence for a weak estrogenic
    activity of various Aroclors has been observed. Decreased levels of
    gonadal hormones and increased relative testes weights were found in
    rats exposed to 75 mg Aroclor 1242/kg diet for 36 weeks. Decreased
    plasma corticosteroid levels without increased adrenal weight, were
    found in female mice exposed to Aroclor 1254 (25 mg/kg diet) for 3
    weeks. Increased adrenal weight was found in another strain given a
    diet containing 200 mg/kg for 2 weeks.

    PCB mixtures have been shown to have an immunosuppressive effect in
    various animal species. Monkeys and rabbits were the most sensitive
    species. The lowest NOEL in monkeys was 0.1 mg/kg body weight, and
    that in rabbits, 0.18 mg/kg body weight.

    Depressed motor-activity was seen in mice exposed to a single oral
    dose of 500 mg Aroclor (1254/kg body weight). This was probably
    related to inhibition of uptake and release of neurotransmitters.

    PCB mixtures have been found to decrease the levels of vitamins A
    and B1 in the blood and liver of rats. Decreased levels of vitamins
    A, B1, B2, and B6 were seen in rats and mice exposed to PCB

    2.5.7  Factors modifying toxicity; mode of action

    Commercial PCBs produce a spectrum of toxic responses, partly
    resembling those of polychlorinated dibenzodioxins (PCDDs) and
    PCDFs. In addition, the analogous structure-activity relations of
    PCB congeners, with respect to most of their toxic responses and to
    their potency in inducing P448-dependent AHH (aryl hydrocarbon
    hydroxylase), indicate that PCB congeners that are approximate
    stereoisomers of 2,3,7,8,-TCDD are the most active. These findings
    suggest a common mechanism of action based on the affinity of these
    compounds for the cytosolic Ah-receptor protein. Toxic equivalence
    factors relating to 2,3,7,8-TCDD have been proposed for these
    coplanar PCB congeners. The nature of the likely interactions
    between PCBs, PCDFs, and PCDDs has not been investigated adequately.
    As PCBs can stimulate microsomal enzyme activity, they can influence
    the action of other chemicals that undergo microsomal metabolism.
    Other so-called non-planar PCB congeners may cause other more subtle
    toxicities. In addition, PCB congeners, especially the lower
    chlorinated ones, may be metabolized through arene oxide
    intermediates and methylsulfonyl metabolites.

    2.6  Effects in humans

    The toxicological evaluation of PCBs presents many problems. PCBs
    usually occur as mixtures of many congeners, and many of the data on
    the toxicity of the PCBs are based on the testing of such mixtures.
    Some components of the mixtures are more easily degraded in the
    environment than others. Thus, exposure of the general population
    may be to mixtures different from those to which the workers are

    The general population is exposed to PCBs mainly through
    contaminated food (aquatic organisms, meat, and dairy products). In
    most of the industrialized countries, the daily intake of PCBs is of
    the order of some micrograms per person. Such exposure has not been
    associated with disease. Infants are exposed to PCBs through their
    mothers' milk, and their daily intake of PCBs may be some
    micrograms/kg body weight.

    There are great difficulties in assessing the human health effects
    separately for PCBs, PCDFs, or PCDDs, since, quite frequently, PCBs
    contain PCDFs, and occasionally PCDDs have been detected in the
    mixtures involved in certain accidents. Commercial PCBs have been
    shown to be contaminated with PCDFs and, therefore, in many cases it
    is unclear whether effects are attributable to the PCBs or to the
    much more toxic PCDFs. Thus, much of the data that can be retrieved
    from large intoxication episodes in humans, e.g., the Yusho,
    Yu-Cheng, and other intoxications, probably reflect effects of
    exposure to both PCDFs and PCBs.

    The signs of intoxication in the Yusho and Yu-Cheng patients were
    hypersecretion of the Meibomian glands of the eyes, swelling of the
    eyelids, and pigmentation of the nails and mucous membranes,
    occasionally associated with fatigue, nausea, and vomiting. This was
    usually followed by hyperkeratosis and darkening of the skin, with
    follicular enlargement and acneform eruptions. In addition, oedema
    of the arms and legs, liver enlargement and liver disorders, central
    nervous system disturbances, respiratory problems, e.g.,
    bronchitis-like disturbances, and changes in the immune status of
    the patients, were observed. In children of the Yusho and Yu-Cheng
    patients, diminished growth, dark pigmentation of the skin and
    mucous membranes, gingival hyperplasia, xenophthalmic oedematous
    eyes, dentition at birth, abnormal calcification of the skull,
    rocker bottom heel, and a high incidence of low birth weight were
    observed. Whether or not a correlation exists between the exposure
    and the occurrence of malignant neoplasms in these patients cannot
    be definitely concluded, because the number of deaths was too small.
    However, a statistically significant increase was observed in male
    patients, as regards mortality from all neoplasms, and liver and
    lung cancer.

    Under occupational conditions, skin rash has occurred a few hours
    after acute exposure. Furthermore, itching, burning sensations,
    irritation of the conjunctivae, pigmentation of fingers and nails,
    and chloracne were found after exposure to high PCB concentrations.
    Chloracne is one of the most prevalent findings among PCB-exposed
    workers. Besides these dermal signs of intoxication, different
    authors have found liver disturbances, immunosuppressive changes,
    transient irritation of the mucous membranes of the respiratory
    tract, and neurological and unspecific psychological or
    psychosomatic effects, such as headache, dizziness, depression,
    sleep and memory disturbances, nervousness, fatigue, and impotence.

    The overall conclusion is that continuous occupational exposure to
    high PCB and PCDF concentrations may result in effects on the skin
    and liver.

    Two large mortality studies have been carried out with cohorts of
    workers exposed to Aroclor 1254, 1242, and 1016. Increased mortality
    from cancer of the liver and gall bladder was observed in one study
    and from neoplasms and cancer of the gastrointestinal tract in the
    other. None of the available epidemiological studies provide
    conclusive evidence of an association between PCB exposure and
    increased cancer mortality owing to the small number of deaths in
    the exposed populations, the lack of dose relationships, and the
    problems with contaminants in the PCB mixtures.


    3.1  Conclusions

    3.1.1  Distribution

    Because of their physical and chemical properties, PCBs have become
    dispersed globally throughout the environment.

    PCBs are almost universally present in organisms in the environment
    and are readily bioaccumulated. Biomagnification in food-chains has
    also been demonstrated.

    Higher chlorinated congeners accumulate preferentially.

    3.1.2  Effects on experimental animals

    Animal studies suggest that PCBs are immunosuppressive, as assessed
    by alterations in gross measures of immune function (spleen weight,
    thymus weight, or lymphocyte count). NOELs have been estimated in
    monkeys at 100 g/kg body weight for Aroclor 1248 and <100 g/kg
    body weight for Aroclor 1254. Immunosuppression appears to be a
    congener-specific effect.

    Reproductive toxicity is, in general, only seen at doses producing
    systemic toxicity in the mother. Neonates feeding on contaminated
    mother's milk (in monkeys and other animal species used as models)
    appear to be particularly sensitive to PCBs and show reduced growth,
    with other toxic symptoms. The NOEL for Aroclor 1016 in monkeys (on
    the basis of reproductive effects) is 30 g/kg body weight; no NOEL
    could be established for reproductive effects of Aroclor 1248.

    PCBs are not genotoxic and the evidence for any action as tumour
    initiators is inconclusive. PCBs do act as tumour promoters. The
    toxicity of PCB mixtures can be evaluated on a threshold basis.

    3.1.3  Effects on humans

    Exposure of the general population to PCBs is principally through
    food items. Babies are exposed through the mother's milk.

    Two large intoxication episodes in humans have occurred in Japan
    (Yusho) and Taiwan (Yu-Cheng). The main symptoms of the Yusho and
    Yu-Cheng patients have frequently been attributed mainly to the
    contaminants of the PCB mixtures; specifically to PCDFs. The Task
    Group concluded that the symptoms may have been caused by the
    combined exposure to PCBs and PCDFs. Some of the symptoms, and
    principally the chronic respiratory effects, may have been caused
    specifically by the methylsulfone metabolites of certain PCB

    3.1.4  Effects on the environment

    While there have been reports of effects on populations of birds,
    the most important effect of PCBs on organisms in the environment is
    reproductive failure in sea mammals. This has been observed
    principally in semi-enclosed seas and has led to local decreases in
    populations. The prediction that residues of PCBs in the environment
    will gradually be redistributed towards the marine environment
    indicates an increasing hazard for sea mammals in the future.

    3.2  Recommendations

    *    International agreement on analytical procedures to improve the
         comparability of results of monitoring programmes is
         recommended. Development of methods for congener-specific
         analysis should be continued, though the value of analysis
         based on mixtures is recognized.

    *    In order to ensure reliability of analytical data,
         inter-laboratory quality control studies are strongly
         recommended. It is also recommended that an international
         network of technical support and supervision should be
         established to allow developing countries to participate in

    *    Long-term studies using specific congeners and studies on the
         mechanism of action of constituents of PCBs mixtures, with
         special regard to tumour promotion, are recommended to improve
         the precision of risk assessment of PCBs.

    *    Epidemiological studies to improve the assessment of the risk
         to neonates are required, since newborn infants appear to be
         the most vulnerable sector of the general population, because
         of high exposure through milk.

    *    Sensitive and specific biomarkers for some of the more subtle
         aspects of PCB toxicity (such as reproductive, immunological,
         and neural toxicity) should be developed for use in future
         epidemiological studies

    *    PCBs should be disposed of by incineration in properly designed
         and run facilities that can guarantee the constant high
         temperatures (above 1000 C), residence time, and turbulence
         needed to ensure complete breakdown.

    *    Methods to remove PCBs already contained in landfills should be

    *    Worldwide monitoring of PCBs in the environment and in wildlife
         should be encouraged, to monitor the expected redistribution of
         residues already present.

    *    Marine mammals show evidence of reproductive failure as a
         result of PCB contamination. Studies on population size and
         reproductive success of cetaceans should be encouraged,
         together with further research to establish those congeners
         responsible for the effects.


    For a more detailed treatment of prevention and control of
    accidental and environmental exposures to PCBs and PCTs, the reader
    should refer to the WHO/EURO document listed in the Bibliography. A
    detailed description of the human and environmental hazards of PCBs
    is given in EHC 140 (WHO, in preparation).

    4.1  Main human health hazards, prevention and protection, first aid

    PCBs and PCTs are highly chlorinated organic substances. They are
    very persistent and may be hazardous for human beings if incorrectly
    or carelessly handled. It is, therefore, essential that the correct
    precautions are observed during handling, use, and disposal.
    For details see the Summary of Chemical Safety Information in
    section 6.

    4.1.1  Advice to physicians   Symptoms of poisoning

    The acute oral and dermal toxicity is low, but under occupational
    conditions skin rash may occur a few hours after acute exposure.
    Furthermore, itching, burning sensations, irritation of the
    conjunctivae, pigmentation of fingers and nails, and (chlor)acne
    were found after exposure to high PCB concentrations for long
    periods. Massive doses can cause hepatitis, facial oedema, numbness,
    and weakness of the extremities. Chloracne is one of the most
    prevalent findings among workers exposed to PCBs, but may be due to
    the presence of PCDFs in the technical PCB mixtures. In addition to
    these dermal signs of intoxication, liver disturbances,
    immunosuppressive changes, transient irritation of the mucous
    membranes of the respiratory tract, neurological and unspecific
    effects, such as headache, dizziness, depression, sleep and memory
    disturbances, nervousness, fatigue, and impotence, have been
    reported.   Medical advice

    Medical treatment is symptomatic and supportive.

    4.1.2  Health surveillance advice

    A complete medical history and physical examination of workers
    regularly exposed to PCBs should be made annually. Special attention
    should be paid to the skin and to liver function.

    4.2  Explosion and fire hazards

    Fires and explosions involving PCBs have been reported mainly from
    their use in electrical equipment, such as transformers and
    capacitors, but PCBs may also be involved in fires during storage
    and transport. Fires may lead to the formation of highly toxic
    polychlorinated dibenzofurans (PCDFs). In dielectric fluid
    formulations, which also contain various tri- or
    tetra-chlorobenzenes, polychlorinated dibenzo- p-dioxins (PCDDs)
    may be formed upon fire or explosion.

    Fires should be extinguished with alcohol-resistant foam, carbon
    dioxide, or powder. With sufficient burning or external heat, PCBs
    will decompose, emitting very toxic fumes. Fire-fighters should be
    equipped with self-contained breathing apparatus, eye protection,
    and full protective clothing.

    The use of water sprays should be confined to the cooling of
    unaffected stock, thus avoiding the accumulation of polluted run-off
    from the site.

    4.3  Storage

    Products should be stored in well ventilated, locked buildings, out
    of the reach of children and unauthorized personnel. Do not store
    near foodstuffs or animal feed.

    4.3.1  Leaking containers in store

    Take precautions, and use appropriate personal protection (see
    section 6). Empty any product remaining in damaged or leaking
    containers into a clean empty drum, which should then be tightly
    closed and suitably labelled. Sweep up spillage with sawdust, sand,
    or earth (moisten for powders), and dispose of safely.

    4.4  Transport

    Comply with any local requirements regarding the movement of
    hazardous goods. Do not transport in the same compartment as
    foodstuffs. Check that the containers are sound and labels undamaged
    before despatch.

    4.5  Spillage and disposal

    4.5.1  Spillage

    Before dealing with any spillage, precautions should be taken, as
    required, and appropriate personal protection should be used (see
    section 6).

    Prevent material from spreading or contaminating other cargo,
    vegetation, or waterways, by making a barrier of the most suitable
    available material, e.g., earth or sand. Absorb the spilled liquid
    with sawdust, sand, or earth, sweep up and place the contaminated
    material in a closeable container for later transfer to a safe place
    for disposal. Care should be taken to avoid run-off into water

    4.5.2  Disposal

    Dielectric fluids containing PCBs in transformers and capacitors
    should be recovered and sent for destruction.

    Any surplus product, contaminated absorbants, and containers should
    be disposed of in an appropriate way. Waste material should be
    burned in a proper incinerator designed for organochlorine waste
    disposal, with effluent gas-scrubbing. For PCB wastes, incineration
    must be for more than 2 seconds at 1200 C or higher. Cement kilns
    may meet the required temperature/time conditions and may be
    properly constructed for this purpose. If the PCB content of the
    waste is less than 500 mg/kg, any proper waste incinerator can be
    used as long as temperature exceeds 800 C for 0.5 seconds.
    Combustion of PCBs can produce dibenzofurans; PCB dielectric fluids
    also containing tri- or tetrachlorobenzenes can also produce
    dioxins. If proper incineration is not possible, bury in an approved
    dump or landfill where there is no risk of contamination of surface
    or ground water. Decomposition of PCBs is extremely slow.a

    Comply with any local legislation regarding disposal of toxic
    wastes. Puncture and crush containers, to prevent re-use.


    a  For a more complete treatment of the subject, refer to
       WHO/Euro, 1987.


    5.1  Hazards

    PCBs and PCTs are very resistant to degradation and hence very
    persistent in the environment. Because they are very soluble in
    lipids they bioaccumulate, especially in the fatty tissues of all
    living organisms, and biomagnify in the higher trophic levels of the

    Although their acute toxicity is relatively low, bioaccumulation and
    biomagnification may lead to lethal effects, especially at the
    highest trophic levels. Reduced growth and reproduction may affect

    5.2  Prevention

    PCBs and PCTs should be replaced by alternative products wherever

    Industrial discharges occurring during manufacture, formulation, or
    technical applications should not be allowed to pollute the
    environment and should be treated properly.

    Any spillage or unused product should be prevented from spreading to
    vegetation or waterways, and should be treated and disposed of

    In all cases, immediate remedial action is essential.


          This summary should be easily available to all health workers
          concerned with, and users of, PCBs and PCTs.  It should be
          displayed at, or near, entrances to areas where there is
          potential exposure to PCBs and PCTs, and on processing
          equipment and containers. The summary should be translated
          into the appropriate language(s). All persons potentially
          exposed to the chemical should also have the instructions in
          the summary clearly explained.

          Space is available for insertion of the National Occupational
          Exposure Limit, the address and telephone number of the
          National Poison Control Centre, and local trade names.


         Polychlorinated biphenyls (PCBs)                    Polychlorinated terphenyls (PCTs)

         Molecular formula:       C12H10-nCln                Molecular formula:       C18H14-nCln
         CAS registry number:     1336-36-3                  CAS registry number:     61788-33-8
         RTECS registry number:   TQ1350000                  RTECS registry number:   WZ6500000


    Commercial PCBs and PCTs are complex mixtures of many different congeners with various degrees of chlorination. They are
    not produced to a composition specification; the criteria for use are based on physical properties. They are clear, light
    yellow, or dark liquids that may turn into solid resin at low temperatures.

    Their distillation range is in general above 250 C. Their relative molecular mass and density depend on the degree of
    chlorination. They are very fire-resistant, with flash-points above 170 C. Their vapours are heavier than air, but do not
    form explosive mixtures. Their electrical conductivity is very low and their resistance to thermal breakdown extremely
    high. They are practically insoluble in water, easily miscible with most organic solvents, and accumulate in fatty tissues.
    They have high  n-octanol/water partition coefficents.

    They are mainly used as dielectrics in transformers and capacitors, in heat transfer and hydraulic systems, and, to a
    lesser extent, in lubricating and cutting oils, carbonless copying paper, adhesives, sealants, plastics, and as
    plasticizers in paints.

    HAZARDS/SYMPTOMS                     PREVENTION AND PROTECTION                 FIRST AID

    SKIN: May cause irritation           Avoid contact with skin; wear             After contact with skin, wash immediately
    and chloracne                        suitable protective clothing              with plenty of water and soap; immediately
                                         and gloves                                remove all contaminated clothing and
                                                                                   launder before reuse

    EYES: May cause irritation           Avoid contact with eyes; wear             In case of contact with eyes, rinse
                                         eye protection                            immediately with plenty of water and seek
                                                                                   medical advice

    INHALATION: May cause irritation     Adequate ventilation;
                                         do not breathe vapours

    INGESTION: Unlikely occupational     Do not eat, drink, or smoke
    hazard                               during work; wash hands before
                                         eating, drinking, or smoking

    Accidental or intentional                                                      If swallowed, seek medical advice
    ingestion may cause poisoning                                                  immediately and show container or label

    ENVIRONMENT: Bioaccumulates          Strictly avoid environmental
    and biomagnifies                     pollution

    SPILLAGE                                                                       STORAGEFIRE AND EXPLOSION

    Take appropriate personal            Products should be stored in              Extinguish fires with alcohol-resistant
    precautions; prevent liquid from     well ventilated locked buildings;         foam, CO2, or powder; with sufficient
    spreading or contaminating other     keep out of reach of children;            burning or external heat, PCBs and 
    cargo, vegetation, or surface        keep away from food, drink, and           PCTs will decompose, emitting toxic fumes;
    waters and drainage systems,         animal feeding stuffs                     firefighters should be equipped with 
    with a barrier of most suitable                                                self-contained breathing apparatus, eye 
    suitable material, e.g., earth or                                              protection, and full protective clothing;
    sand                                                                           confine the use of water spray to cooling
                                                                                   of unaffected stock, thus avoiding the
    Absorb spilled liquid with saw-                                                accumulation of polluted run-off from the
    dust, sand, or earth; sweep up and                                             site
    place it in a closeable container 
    for later safe disposal; care
    should be taken to avoid run-off
    into water courses


    PCBs and PCTs waste material         National Occupational Exposure            UN No. 2315
    should be burned in a proper         Limit:
    incinerator designed for 
    organochlorine waste disposal;       National Poison Control Centre:
    if this is not possible, bury in 
    an approved dump or landfill         Local trade names:
    where there is no risk of 
    contamination of surface or 
    ground water; comply with any 
    local legislation regarding 
    disposal of toxic wastes


    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file and other United Nations sources. A full reference to the
    original national document from which the information was extracted
    can be obtained from IRPTC. When no effective date appears in the
    IRPTC legal file, the year of the reference from which the data are
    taken is indicated in the table by (r).

    The reader should be aware that regulatory decisions about chemicals
    taken in a certain country can only be fully understood in the
    framework of the legislation of that country. Furthermore, the
    regulations and guidelines of all countries are subject to change
    and should always be verified with the appropriate regulatory
    authorities before application.

    7.1  Previous evaluations by international bodies

    PCBs have been evaluated by IARC in 1978 and 1987 (IARC, 1978, 1987
    (Supplement)). It was concluded that there was sufficient
    experimental evidence to indicate a carcinogenic effect of some PCBs
    in rodents, and that epidemiological data provided suggestive
    evidence of a relationship between exposure to PCBs and the
    development of certain cancers in man. PCBs were classified in group
    2A: the agent is probably carcinogenic for humans. For practical
    purposes, PCBs should be regarded as if they were carcinogenic for
    human beings.

    7.2  Exposure limit values

    Some exposure limit values for PCBs are given in the table on pages


    Exposure limit values


    Medium      Specification     Country          Exposure limit description                 Value               Effective


    AIR         Workplace         Czechoslovakia   Maximum permissible concentration
                                                   - time-weighted average (TWA)              0.5 mg/m3             1985
                                                   - short-term exposure limit (STEL)         1.0 mg/m3

                                  Japan            Maximum permissible concentration
                                                   - time-weighted average (TWA)              0.1 mg/m3 a           1985

                                  Netherlands      Maximum allowable concentration (MAC)
                                                   - time-weighted average (TWA)              0.5 mg/m3             -

                                  Sweden           Occupational exposure limit
                                                   - time-weighted average (TWA)              0.01 mg/m3 a          1985
                                                   - short-term exposure limit (STEL)         0.03 mg/m3

                                  USSR             Maximum permissible concentration
                                                   - time-weighted average (TWA) (vapour)     1.0 mg/m3             1977

                                  United Kingdom   Recommended limit
                                                   - time-weighted average (TWA)              0.5 mg/m3             -
                                                   - short-term exposure limit (STEL)         1.0 mg/m3
                                                     (10-min TWA)


    Medium      Specification     Country          Exposure limit description                 Value               Effective


                                  USA (ACGIH)      Threshold limit value (TLV)
                                                   - time-weighted average (TWA)              0.5 mg/m3             -
                                                   - short-term exposure limit (STEL)         1.0 mg/m3

    FOOD        Animal            Germany,         Maximum residue limit (MRL)                0.008-0.6           1988
                                  Federal            (specified products)                     mg/kg
                                  Republic of

                                  Sweden           Maximum residue limit (MRL) (Specified)    0.05-2 mg/kg        1983

    FOOD        Animal &          France           Maximum residue limit (MRL) (fish)         2 mg/kg             -
                                  Japan            Maximum residue limit (MRL) (Specified)    0.2-3 mg/kg         -

                                  Netherlands      Maximum residue limit (MRL) (Specified)    0.3-1 mg/kg         -

                                  Switzerland      Maximum residue limit (MRL) (Specified)    0.5-2 mg/kg         -

                                  USA              Temporary residue tolerance (Specified)    0.2-3 mg/kg         1981

    FEED                          Japan            Maximum residue limit (MRL) (Specified)    0.05-3 mg/kg        -

                                  Netherlands      Maximum residue limit (MRL) (Specified)    0.3 mg/kg           -

                                  USA              Maximum residue limit (MRL) (Specified)    0.2-2 mg/kg         -

    WATER       Drinking-         EEC              Maximum permissible concentration
                                                   (total PCBs + PCTs)                        0.5 g/litre        1982


    Medium      Specification     Country          Exposure limit description                 Value               Effective


                Environment       Japan            Environment water quality standard         not detectable      1981

                Surface water     USSR             Permissible limit                          0.0 mg/litre        1978
                for fishing

                Effluent          Japan            Effluent standard                          0.003 mg/litre      1981

    GOODS       Packaging         USA              Temporary residue tolerance                10 mg/kg            1983
                material for
                food or feed


    a Skin absorption.

    7.3  Specific restrictions

    Several intergovernmental organizations have been active in
    providing directives or recommendations for regulatory measures to
    control PCBs.

    On 13 February 1973, the Council of the Organisation for Economic
    Cooperation and Development (OECD) adopted a Decision on the
    Protection of the Environment by Control of Polychlorinated
    Biphenyls (C(73)1). The Council decided that PCBs would not be used
    for industrial or commercial purposes, except for five essentially
    closed purposes. These are: dielectric fluids in transformers; large
    power-correcting capacitors; heat-transfer fluids (but only in
    installations that do not process food, feed, pharmaceuticals, or
    veterinary products); hydraulic fluids (but only in mining
    equipment); and in small capacitors (though Member Countries have
    recommended working towards the elimination of this last use). PCBs
    should only be used in the exempted applications where
    non-flammability requirements outweigh the environmental protection
    considerations and where sufficient controls are exercised to
    minimize risk to the environment. The Council also made some
    recommendations concerning the elimination of other uses of PCBs and
    PCB replacements. It also provided for certain administrative and
    engineering control measures for PCBs still in use, and for the
    disposal of PCB wastes. The OECD Council decision provided for an
    exchange of information on PCBs between Member Countries within the
    framework of the OECD Environment Committee and information on PCBs
    was exchanged annually between 1974 and 1980. The information
    exchanged and the experience gained by Member Countries was
    summarized in a report (OECD, 1982). This report indicated that,
    while considerable progress had been made in reducing environmental
    contamination by PCBs, some important problems remained.

    An extensive synopsis of national regulatory measures in a number of
    countries was prepared by the OECD in 1982. Countries have rather
    complex and very different systems to control PCBs in the general
    environment. Most regulations impose usage restrictions and
    prescriptions for transportation and labelling, require notification
    of production and/or importation, and provide rules for the disposal
    of PCB-containing wastes.

    On 13 February 1987, the OECD Council adopted a further
    Decision-Recommendation (C(87)2(final)) on "Further measures for the
    protection of the environment by control of polychlorinated
    biphenyls". With this Decision-Recommendation, the OECD Member
    Countries committed themselves to ban virtually all new uses for
    PCBs, accelerate the phasing out of PCBs from existing uses, control
    PCBs in contaminated products, articles, or equipment, and ensure
    appropriate disposal methods for wastes containing PCBs.

    In the countries of the European Economic Community, the use of PCBs
    and PCTs is prohibited by Directive 85/467/EEC (6th Amendment (PCBs
    and PCTs) Directive 76/769/EEC) but until 30 June 1986 the following
    uses were excepted: (a) closed-system electrical equipment; (b)
    large condensers; (c) small condensers (provided that the PCB has a
    maximum chlorine content of 43% and does not contain more than 3.5%
    of penta- and higher chlorinated biphenyls); (d) heat-transmitting
    fluids in closed-circuit heat-transfer installations; (e) hydraulic
    fluids used in underground mining equipment; (f) primary and
    intermediate products for further processing into other products
    which are not prohibited under the Directive. The use of equipment,
    plant, and fluids referred to in points a to f above that were in
    service on 30 June 1986 shall continue to be authorized until they
    are disposed of or reach the end of their service life. Derogations
    considered to have no deleterious effects on health or the
    environment could be granted after 30 June 1986. These provisions
    apply to PCBs and PCTs (except mono- and dichlorinated biphenyls)
    and preparations with a PCB or PCT content higher than 0.01% by

    Apart from the above restrictions in OECD and EEC countries, several
    other countries have similar, more or less severe restrictions on
    the use of PCBs (and PCTs). In Japan, the manufacture and import of
    all PCBs is prohibited without authorization from the Government. In
    the USA, the manufacture, processing, distribution in commerce and
    use of PCBs is prohibited without Government authorization.

    7.4  Labelling, packaging, and transport

    The United Nations Committee of Experts on the Transportation of
    Dangerous Goods classifies PCBs in:

    Hazard Class 9:      Miscellaneous dangerous substance.

    Packing Group II:    Substances presenting medium danger.

    The European Economic Community legislation requires the labelling
    of PCBs and PCTs as harmful substances using the symbol:

    FIGURE 1

    The label must read:

          Danger of cumulative effects. This material and its container
          must be disposed of in a safe way. It should be stated on the
          label whether the substance is a specific isomer or a mixture
          of isomers.

    7.5  Waste disposal

    The following is an excerpt from the EEC Council Directive

         "EEC Member States shall: (1) prohibit the uncontrolled
         discharge, dumping, and tipping of polychlorinated biphenyls
         (PCBs) and polychlorinated terphenyls (PCTs) as well as
         mixtures, objects, and equipment containing one or both of the
         substances; (2) make compulsory the disposal of such waste; (3)
         ensure that it is disposed of without endangering human health
         or harming the environment; (4) promote the regeneration of PCB
         and PCT; and (5) set up or designate installations which are
         authorized for disposing of such waste.

         "Waste containing or contaminated by polychlorinated biphenyls
         is classified as 'hazardous waste'. Member States shall take
         the necessary measures for the supervision and control, with a
         view to human health and the environment, of the transfrontier
         shipment of hazardous waste both within and if entering and/or
         leaving the community. Where the holder of such waste intends
         to have it shipped into, through or from one to another Member
         State he shall notify the competent authorities through a
         consignment note. He must provide satisfactory information in
         particular on: (1) the source and composition; (2) provisions
         made for routes and insurances; (3) measures to ensure safe
         transport; (4) contractual agreement with the consignee of the
         waste. The hazardous waste must: (a) be properly packed; (b)
         have appropriate labels indicating nature, composition,
         quantity and telephone numbers of persons from whom
         instructions can be obtained; (c) instructions to be followed
         in the event of danger or accident."

    Under proposed EEC Council Directives, combustion gases in
    combustion chambers must be kept at, at least 850 C for 2 seconds,
    and all plant must be fitted with auxiliary burners which come into
    use automatically when combustion chamber gases fall below 850 C.
    These conditions must be met immediately by new plant and by 1994 by
    existing plant (United Kingdom House of Lords paper 17, 1989, HMSO,

    In the USA, PCBs are classified as toxic pollutants and acute
    hazardous wastes, subject to handling, transport, treatment,
    storage, and disposal regulations, and permit and notification
    requirements. An owner or operator of a hazardous waste incinerator
    must achieve 99.9999% destruction and removal efficiency for these
    substances. Effluent limitations and pre-treatment standards are set
    for industries using PCBs. The interim emission standards for
    incinerators are 0.25 mg/m3 (peak value) and 0.15 mg/m3 (peak
    value from liquid PCB incinerators).

    Under the Environmental Contaminants Act, the Canadian Ministry of
    Environment published  "Guidelines for the management of PCB
     wastes". The  Guidelines set out recommended procedures and
    criteria for the safe storage, handling, and disposal of PCB wastes.

    In Italy, an emission standard for PCBs and PCTs of 0.1 mg/m3 for
    urban incinerators has been adopted by the Lombardy Region.

    In Sweden, enterprises producing wastes that contain PCBs are
    required to report the type, content, quantity, and handling of the
    waste to the health authorities. Permission from the authorities is
    required for the transport, handling, and export of such waste

    The Assembly of the Intergovernmental Maritime Consultative
    Organization (IMCO) passed Resolution A 394(x) on 14 November 1977,
    inviting governments to take steps to ensure that the operational
    sea discharge of tank washings from incinerator ships containing
    PCBs is prohibited, except where this is permitted under specific
    regulations or technical guidelines adopted by the contracting

    In 1972, the Final Act of the Intergovernmental Conference on the
    Dumping of Wastes at Sea prohibited the dumping of PCBs at sea. The
    Third Consultative Meeting organized by IMCO in 1978 adopted the
    Amendments to the Convention Annexes which made incineration of
    waste at sea subject to controls under the Convention.

    The Convention on the Prevention of Marine Pollution by Dumping of
    Wastes and other Matter (Oslo, 1972), concerned with the NE
    Atlantic, came into force in 1974. It prohibits the dumping of
    organohalogen (i.e., PCB-inclusive) sources.

    At its sixth meeting (1979), the Interim Baltic Marine Environment
    Protection Commission decided to draft a resolution concerning
    regulation of the use of PCBs and the prevention of discharges


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    See Also:
       Toxicological Abbreviations