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    IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
    Health and Safety Guide No. 107

    HEXACHLOROBENZENE
    HEALTH AND SAFETY GUIDE






    UNITED NATIONS ENVIRONMENT PROGRAMME

    INTERNATIONAL LABOUR ORGANISATION

    WORLD HEALTH ORGANIZATION




    WORLD HEALTH ORGANIZATION, GENEVA 1998

    IPCS

    Health and Safety Guide No. 107


    HEXACHLOROBENZENE
    HEALTH AND SAFETY GUIDE

    This is a companion volume to
    Environmental Health Criteria 195: Hexachlorobenzene

    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) and produced within the framework
    of the Inter-Organization Programme for the Sound Management of
    Chemicals

    WORLD HEALTH ORGANIZATION, GENEVA 1998

    This is a companion volume to Environmental Health Criteria 195:
    Hexachlorobenzene

    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) and produced within the framework
    of the Inter-Organization Programme for the Sound Management of Chemicals.

    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

    Health and safety guide for hexachlorobenzene

    (Health and safety guide ; no. 107)

    1.Hexachlorobenezene - toxicity  2.Environmental exposure
    3.Guidelines             I.International Programme on Chemical Safety
    II.Series

    ISBN 92 4 151107 9          (NLM Classification: QV 633)
    ISSN 0259-7268

    The World Health Organization welcomes requests for permission to
    reproduce or translate its publications, in part or in full. 
    Applications and enquiries should be addressed to the Office of
    Publications, World Health Organization, Geneva, Switzerland, which
    will be glad to provide the latest information on any changes made to
    the text, plans for new editions, and reprints and translations
    already available.

    (c) World Health Organization 1998

    Publications of the World Health Organization enjoy copyright
    protection in accordance with the provisions of Protocol 2 of the
    Universal Copyright Convention.  All rights reserved.

    The designations employed and the presentation of the material in this
    publication do not imply the expression of any opinion whatsoever on
    the part of the Secretariat of the World Health Organization
    concerning the legal status of any country, territory, city or area or
    of its authorities, or concerning the delimitation of its frontiers or
    boundaries.

    The mention of specific companies or of certain manufacturers'
    products does not imply that they are endorsed or recommended by the
    World Health Organization in preference to others of a similar nature
    that are not mentioned.  Errors and omissions excepted, the names of
    proprietary products are distinguished by initial capital letters.

    CONTENTS

    INTRODUCTION

    1. PRODUCT IDENTITY AND USES

         1.1. Identity
         1.2. Physical and chemical properties
         1.3. Analytical methods
         1.4. Uses

    2. SUMMARY AND EVALUATION

         2.1. Exposure
         2.2. Environmental fate
         2.3. Kinetics and metabolism
         2.4. Effects on animals and  in vitro test systems
         2.6. Effects on humans
         2.7. Effects on organisms in the environment

    3. CONCLUSIONS

         3.1. Human health
         3.2. Environment

    4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION

         4.1. Human health hazards, prevention and protection, first aid
         4.2. Advice to physicians
               4.2.1. Decontamination
               4.2.2. Prevention of absorption after oral exposure
               4.2.3. Treatment
         4.3. Health surveillance advice
         4.4. Explosion and fire hazards, prevention
               4.4.1. Explosion and fire hazards
               4.4.2. Prevention
               4.4.3. Fire-extinguishing agents
         4.5. Storage
         4.6. Transport
         4.7. Spillage

    5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    6. SUMMARY OF CHEMICAL SAFETY INFORMATION

    7. CURRENT REGULATIONS, GUIDELINES AND STANDARDS

         7.1. Occupational exposure limit
         7.2. Specific restrictions
         7.3. Labelling, packaging and transport
         7.4. Waste disposal

    BIBLIOGRAPHY
    

    INTRODUCTION

    The Environmental Health Criteria (EHC) monographs 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
    Switzerland

    THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING
    POINT TO A COMPREHENSIVE HEALTH AND SAFETY PROGRAMME

    1.  PRODUCT IDENTITY AND USES

    1.1  Identity

    CAS/IUPAC name           Hexachlorobenzene (HCB)

    Chemical formula         C6C16

    Chemical Structure

    CHEMICAL STRUCTURE 1

    Common synonyms          perchlorobenzene, pentachlorophenyl chloride,
                             phenyl perchloryl

    CAS registry number      118-74-1

    RTECS number             DA 2975 000

    UN transport number      2729

    Conversion factors       1 ppm = 11.8 mg/m3
                             1 mg/m3 = 0.08 ppm

    1.2  Physical and chemical properties

         At ambient temperature, HCB is a white crystalline solid. 
    Technical grade HCB is available as a wettable powder, liquid or
    dust.  It is virtually insoluble in water, but is soluble in ether,
    benzene, chloroform and hot ethanol. HCB has a high octanol/water
    partition coefficient, low vapour pressure and low flammability.  
    Some physical and chemical properties of hexachlorobenzene (HCB) are
    listed in Table 1.  Technical grade HCB contains up to 2% impurities,
    about half of which is pentachlorobenzene, the remainder including
    hepta- and octa-chlorodibenzofurans, octachlorodibenzo- p-dioxin, and
    decachlorobiphenyl.

    Table 1.  Some physical and chemical properties of hexachlorobenzene
                                                                        

         Property                                     Value
                                                                        

         Relative molecular mass                      284.79
         Melting point (C)                           230
         Boiling point (C)                           322 (sublimes)
         Vapour pressure (Pa at 25 C)                0.0023
         Water solubility (mg/litre at 25 C)         0.005
         Log octanol/water partition coefficient      5.5
                                                                        

    1.3  Analytical methods

         Analysis of HCB in environmental media and biological materials
    generally involves extraction of the sample into organic solvents,
    often followed by a clean-up step to remove potential interference by
    other organo-chlorine compounds.  Organic extracts are analysed by gas
    chromatography/ mass spectrometry (GC/MS) or gas chromatography with
    electron capture detection (GC/ECD).  Using an electron capture
    detector, limits of  detection of 0.1 g/m3 in air, 0.05 g/g in
    water, and 33 pg/g in breast milk have been reported.

    1.4  Uses

         Historically, HCB had many uses in industry and agriculture.  The
    major agricultural application for HCB was as a seed dressing for
    crops such as wheat, barley, oats and rye to prevent fungal disease. 
    The use of HCB in such applications was discontinued in many countries
    in the 1970s owing to concerns about adverse effects on the
    environment and human health.  However, HCB continued to be used for
    this purpose in some countries as late as 1985.  The present situation
    is not clear.

         Other previous commercial applications of HCB include the
    production of munitions, as a fluxing agent in the manufacture of
    aluminium, a wood-preserving agent, in the manufacture of graphite
    anodes, and in the rubber industry.  It is likely that many of these
    applications have been discontinued, although no information to verify
    this fact could be found.

         Worldwide production of HCB was estimated to be
    10 000 tonnes/year for the period 1978-1981.  An estimated 300 tonnes
    was produced in the USA in 1973.  HCB was produced in the European
    Community at 8000 tonnes/year in 1978, and a company in Spain produced
    an estimated 150 tonnes of HCB annually.  Approximately 1500 tonnes of
    HCB are manufactured annually in Germany for the production of the
    rubber auxiliary PCTP, but that production was to have been

    discontinued in 1993. No other recent data on levels of production
    have been reported.  However, production of HCB has probably declined
    as a result of restrictions on its uses starting in the 1970s.
    Considerable amounts of HCB are also produced as a by-product in the
    manufacture of chlorinated solvents and chlorinated pesticides.

    2.  SUMMARY AND EVALUATION

    2.1  Exposure

         The major source of human exposure to HCB is as a contaminant in
    food.  Very low levels of HCB are found in drinking-water and ambient
    air. It is estimated that the total average daily intake of HCB in the
    general population varies between 0.0004 and 0.003 g/kg body weight. 
    Owing to elimination of HCB in breast milk, intakes in nursing infants
    are estimated to range from < 0.018 to 5.1 g/kg body weight per day.

         Inappropriate manufacturing and waste management practices may
    expose nearby populations to higher HCB concentrations than the
    general population. Exposure to HCB may be elevated in some indigenous
    subsistence populations consuming food species near the top of the
    food chain.

         Workers in some industries may be exposed to higher levels of HCB
    than the general population, particularly those involved in the
    manufacture of chlorinated solvents and in the manufacture and
    application of chlorinated pesticides contaminated with HCB.

    2.2  Environmental fate

         HCB is widely distributed in the environment by virtue of its
    chemical stability and mobility (subject to long-range aerial
    transport). Slow photo-degradation of airborne HCB occurs with a
    half-life of 80 days, and slow microbial degradation of HCB does take
    place (half-life of several years).  It is a bioaccumulative
    substance, and biomagnification of HCB through the food chain has been
    reported.

    2.3  Kinetics and metabolism

         There is a lack of toxicokinetic information for humans. HCB is
    readily absorbed by the oral route but only poorly through the skin in
    experimental animals, and it undergoes limited metabolism to
    pentachlorophenol, tetra-chlorohydroquinone and pentachlorothiophenol,
    which are excreted in the urine.  Elimination half-lives for HCB range
    from about one month in rats and rabbits to two or three years in
    monkeys. In animals and humans HCB accumulates in lipid-rich tissues
    such as adipose, adrenal cortex, bone marrow, skin and some endocrine
    tissues.  It can be transferred to offspring both by placental
    transfer and via breast milk.

    2.4  Effects on animals and in vitro test systems

         The toxicity of HCB after a single oral dose to experimental
    animals is low; LD50 values between 1000 and 10 000 mg/kg body weight
    have been reported.  Reported LC50 values for inhalation exposures
    range from 1600 mg/kg body weight in the cat to 4000 mg/kg body weight
    in the mouse.  Lethal doses elicit convulsions, tremors, weakness,
    ataxia, paralysis, and pathological changes in several organs.

         In experimental animals, HCB is not a skin or eye irritant and
    did not sensitize the guinea-pig.

         The effects of short-term repeated exposure to HCB are primarily
    hepatotoxic and neurological.  The pathway for the synthesis of haem
    appears to be a major target of HCB toxicity.  Porphyria has been
    reported in rats after short-term and long-term exposures between 2.5
    and 15 mg HCB/kg body weight per day.  Excretion of coproporphyrins
    was increased in pigs that ingested 0.5 mg HCB/kg body weight per day. 
    Repeated exposure to HCB can also affect a wide range of organ
    systems, but such effects occur less frequently and usually at higher
    doses than porphyria. HCB is a mixed cyto-chrome P-450-inducing
    compound and is known to bind to the Ah receptor.

         Other non-neoplastic effects of HCB exposure include
    reproductive, developmental and immunological.  Oral exposure of
    monkeys for 90 days to 0.1 mg HCB/kg body weight per day affected the
    ultrastructure of the surface germinal epithelium and the primordial
    germ cells.  Male reproductive effects were observed in monkeys at
    much higher doses (between 30 and 221 mg HCB/kg body weight per day). 
    The offspring of mink with chronic exposure to about 0.16 mg HCB/kg
    body weight per day had reduced birth weights and increased mortality
    before weaning.  Neurobehavioural development of rat pups was affected
    by  in utero exposure to HCB at oral maternal doses of 0.64 to
    2.5 mg/kg body weight per day.  HCB adversely affects the immune
    system in rats, mice and monkeys.  In mice immunosuppression was noted
    with an oral dose of 0.6 mg HCB/kg body weight per day for 3 to 18
    weeks.  When exposed  in utero and through nursing to maternal doses
    of 0.5 and 5 mg HCB/kg body weight per day, mice showed severe
    depression of the delayed-type hypersensitivity response to a contact
    allergen.  In rats immuno-stimulating effects were seen at oral doses
    of about 0.2 mg HCB/kg body weight per day.

         In long-term studies, mild histopathological changes and enzyme
    induction occurred in the liver in several studies in rats at dose
    levels between 0.25 and 0.6 mg HCB/kg body weight per day; the
    no-observed-effect levels (NOELs) in these studies were 0.05 to
    0.07 mg HCB/kg body weight per day.  Calcium homoeostasis and bone
    morphometry were affected in subchronic studies in rats at 0.7 mg
    HCB/kg body weight per day, but not at 0.07 mg/kg body weight per day.

         In summary, with respect to non-neoplastic effects of HCB after
    repeated exposures, a wide range of effects in several species of
    animals, with similar lowest-observed-effect levels (LOELs) and NOELs
    for a number of end-points, have been reported.  These effects include
    hepatotoxicity in pigs and rats, calcium metabolism in rats, ovarian
    histopathology in monkeys, immune function in rats and mice and
    neurotoxicity in mink and rats.  The range over which the various
    effects have been observed is quite narrow; the lowest LOELs range
    from 0.1 to 0.7 mg/kg body weight per day, while the lowest NOELs
    range from 0.05 to 0.07 mg/kg body weight per day.

         HCB has little capability to directly induce gene mutation,
    chromo-somal damage and DNA repair.  It exhibited weak mutagenic
    activity in a small number of the available studies on bacteria and
    yeast, although it should be noted that each of these studies had
    limitations.  There is also some evidence of low-level binding to DNA
     in vitro and  in vivo, but at levels that were all below those
    expected for genotoxic carcinogens.

         Based on the induction of a variety of tumours in hamsters, rats
    and mice exposed by ingestion, there is sufficient evidence that HCB
    is carcinogenic in experimental animals.  In a two-generation study in
    rats where animals were exposed to a combination of  in utero, 
    lactational and direct oral ingestion from food for 130 weeks
     post-utero, there were increased incidences of neoplastic nodules
    and adrenal phaeochromocytomas in females and of parathyroid adenomas
    in males at the highest average daily doses (1.5 mg HCB/kg body weight
    per day in males and 1.9 mg/kg body weight per day in females).

         The available evidence indicates that HCB has little or no
    genotoxic activity, and is therefore unlikely to be a direct-acting
    (genotoxic) carcinogen. However, tumours, some of which were
    malignant, have been induced in multiple species, at multiple sites,
    and in some instances at doses that were not overtly toxic in other
    respects and are within an order of magnitude of doses causing more
    subtle toxicological effects from chronic or subchronic exposure. 
    Although there is some evidence to suggest that HCB may cause cancer
    by indirect mechanisms, the evidence is not definitive at this time
    and does not address all tumour sites.

    2.5  Effects on humans

         Available data on the effects of HCB in humans are limited
    principally to those concerning people exposed in an accidental
    poisoning incident that occurred in Turkey between 1955 and 1959. 
    More than 600 cases of porphyria cutanea tarda (PCT) were observed,
    and infants of exposed mothers experienced cutaneous lesions, clinical
    symptoms and high mortality.  It has been estimated that victims were
    exposed to 50-200 mg HCB/day for an undetermined, but extended, period

    of time. However, the basis for this estimate was not provided,
    making exposure calculations unreliable for this population.  In this
    incident, disturbances in porphyrin metabolism, dermatological
    lesions, hyperpigmentation, hypertrichosis, enlarged liver,
    enlargement of the thyroid gland and lymph nodes, and (in roughly half
    the cases) osteoporosis or arthritis were observed, primarily in
    children.  Breast-fed infants of mothers exposed to HCB in this
    incident developed a disorder called "pembe yara" ("pink sore"), and
    most died within a year.  There is also some limited evidence that PCT
    occurs in humans exposed to relatively high levels of HCB in the
    workplace or in the general environment.

         Studies of the carcinogenicity of HCB in humans are limited to
    two small epidemiological studies of cancer incidence in populations
    with poorly characterized exposures to HCB as well as to numerous
    other chemicals.  No excesses of neoplasms have been reported in
    long-term follow-up studies of the people with porphyria in the
    incident in Turkey, but only a small fraction of the population was
    followed up, and these studies were not designed specifically to
    assess neoplastic end-points.

         The available data on humans are inadequate to serve as a basis
    for assessment of effects from exposure to HCB.  The development of
    health-based guidance values for the daily intake of HCB is based upon
    the evaluation of studies in animals.

    2.6  Effects on organisms in the environment

         HCB is widely distributed in the environment, by virtue of its
    mobility and resistance to degradation, although slow photodegradation
    in air (half-life of around 80 days) and microbial degradation
    (half-life of several years) do occur.  It has been detected in air,
    water, sediment, soil and biota from around the world.  HCB is a
    bioaccumulative substance (bioconcentration factors range from 375 to
    > 35 000), and biomagnification of HCB through the food chain has
    been reported.

         In studies of the acute toxicity of HCB to aquatic organisms,
    exposure to concentrations in the range of 1 to 17 g/litre reduced
    production of chlorophyll in algae and reproduction in ciliate
    protozoa.  In longer-term studies, the growth of sensitive freshwater
    algae and protozoa was affected by a concentration of 1 g/litre,
    while concentrations of approximately 3 g/litre caused mortality in
    amphipods and liver necrosis in largemouth bass.  The concentration of
    HCB in surface water around the world is much lower than these effect
    levels (3 to 5 orders of magnitude lower), except in a few extremely
    contaminated locales.

         Injection studies in eggs have shown that tissue levels of
    1500 ng/g wet weight (lowest dose tested) reduced embryo weights

    in herring gulls. No studies were available to establish a
    no-observed-adverse-effect level (NOAEL).  For many bird species,
    reduced embryo weights are associated with lower survival of chicks. 
    This effect level is within an order of magnitude of the levels
    measured in the eggs of sea birds and raptors from a number of
    locations from around the world, suggesting that present levels of HCB
    in certain locations may harm embryos of bird species.

         Experimental studies on mink indicate that they are sensitive to
    the toxic effects of HCB.  Long-term ingestion of diets containing
    1000 ng HCB/g (the lowest dose tested) increased mortality and
    decreased birth weights of offspring exposed  in utero and via
    lactation, as well as altered levels of neurotransmitters in the
    hypothalamus of dams and their offspring.  No studies were available
    to establish a NOAEL.  This dietary effect level is only a few times
    higher than the concentrations of HCB measured in various species of
    fish from a number of industrialized locations from around the world,
    suggesting that present levels of HCB in fish species from certain
    locations may adversely affect mink and perhaps other fish-eating
    mammals.

    3.  CONCLUSIONS

    3.1  Human health

         Exposure of the general population to HCB occurs by consumption
    of food. Levels in drinking-water and ambient air are very low.

         The total average daily intake of HCB in the general population
    varies between 0.0004 and 0.003 g HCB/kg body weight per day. 
    Intakes of nursing infants are estimated to range from <0.018 to
    5.1 g/kg body weight per day.

         Animal studies have shown that HCB causes cancer and affects a
    wide range of organ systems, including the liver, lungs, kidneys,
    thyroid, reproductive tissues, nervous and immune systems.

         Clinical toxicity, including porphyria cutanea tarda in children
    and adults, and mortality in nursing infants, has been observed in
    humans with high accidental exposures.

         Available data on the effects of HCB exposure in experimental
    animals are sufficient to develop guidance values for daily exposure
    to HCB based on non-neoplastic and neoplastic effects.

         For non-neoplastic effects, based on the lowest reported
    no-observed-effect level (0.05 mg HCB/kg body weight per day) for
    primarily hepatic effects observed at higher doses in studies on pigs
    and rats exposed by the oral route, and incorporating an uncertainty
    factor of 300 (x 10 for interspecies variation, x 10 for intraspecies
    variation, and x 3 for severity of effect), a tolerable daily intake
    of 0.17 g/kg body weight per day has been derived.

         The approach for neoplastic effects is based on the Tumorigenic
    Dose5 (TD5), i.e., the intake associated with a 5% excess incidence
    of tumours in experimental studies on animals. Based on the results of
    the two-generation carcinogenicity bioassay in rats, and using the
    multi-stage model, the TD5 value is 0.81 mg/kg body weight per day
    for neoplastic nodules of the liver in females. Based on consideration
    of the insufficient mechanistic data, an uncertainty factor of 5000
    was used to develop a health-based guidance value of 0.16 g/kg body
    weight per day.

    3.2  Environment

         HCB is a persistent chemical, which bioaccumulates due to its
    lipid solubility and resistance to breakdown.

         The number of experimental studies on which an environmental risk
    assessment can be made is small.  Levels of HCB in surface waters are
    generally several orders of magnitude lower than those expected to

    present a hazard to aquatic organisms, except in a few extremely
    contaminated localities. However, HCB concentrations in the eggs of
    sea birds and raptors from a number of locations from around the world
    approach those associated with reduced embryo weights in herring gulls
    (1500 ng/g), suggesting that it has the potential to harm embryos of
    sensitive bird species.  Similarly, levels of HCB in fish at a number
    of sites worldwide are within an order of magnitude of the dietary
    level of 1000 ng/g associated with reduced birth weights and increased
    mortality of weaning in mink.  This suggests that HCB has the
    potential to adversely affect mink and perhaps other fish-eating
    mammals.

    4.  HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY
        RESPONSE

    4.1  Human health hazards, prevention and protection, first aid

         The human health hazards associated with exposure to HCB,
    preventive and protective measures, and first aid measures are
    indicated in the Summary of Chemical Safety Information in Section 6.

         HCB is harmful by dust inhalation or if swallowed.  Occupational
    exposure to HCB and dietary intake of contaminated food or water are
    the chief circumstances where intoxication occur.

         HCB may cause a slight irritation to eyes, skin and mucous
    membranes.  Inhalation results in irritation of the respiratory tract.

         The central nervous system toxicity is low.  Ingestion of large
    amounts of HCB may cause headache, dizziness, nausea, vomiting,
    numbness of hands and arms, apprehension, partial paralysis of
    extremities, coma and seizures.

         Prolonged periods of ingestion may cause porphyria cutanea tarda,
    where blistering and epidermolysis of the unusually light-sensitive
    skin occurs (Hayes & Laws, 1991).  Pigmented scars, contractures,
    alopecia, hirsutism, arthritis, osteomyelitis, anorexia, weight loss
    and muscle atrophy can be features of the syndrome.  Hepatomegaly and
    thyroid enlargement have been observed.  The mortality can be as high
    as 10%.  Long-term sequelae are hyperpigmentation, hirsutism, scarring
    of hands and face, fragile skin, enlarged liver and persistent active
    porphyria.

         Infants may develop the syndrome of "pink sore" when exposed to
    HCB-contaminated breast milk and transplacental transfer.  It carries
    a high mortality (95%).  Diarrhoea, fever, papules on the back of
    hands, infiltration of the lungs, subcutaneous abscesses, severe
    hypochromic anaemia and leukocytosis occur.

         HCB is carcinogenic in animals and causes hepatomas,
    hepatocellular carcinomas, bile duct adenomas, parathyroid adenomas,
    phaeochromocytomas and renal cell adenomas.  No excess cancer was
    reported in two follow-up studies of affected humans.

    4.2  Advice to physicians

    4.2.1  Decontamination

         In cases of exposure after inhalation, the victim should be moved
    to fresh air.  Contaminated clothing and shoes should be removed and
    isolated at the site.  Eyes or skin should be flushed with running

    water for at least 15 min after exposure.  Skin, including hair and
    nails, should be washed vigorously.  Leather absorbs pesticides and
    hence should not be worn.

    4.2.2  Prevention of absorption after oral exposure

         Emesis is not recommended.  Gastric lavage may be indicated if it
    can be performed soon after ingestion.  The airways must be protected
    at all times.  Activated charcoal should be administered.  A saline
    cathartic given orally may reduce absorption.  Oils should not be
    given by mouth as this tends to increase intestinal absorption of the
    lipophilic chemical.

    4.2.3  Treatment

         This is mainly symptomatic and supportive.  Chelating agents such
    as sodium-calcium-EDTA may enhance excretion of porphyrins in the
    urine.  The faecal excretion might be increased by oral administration
    of cholestyramine. Avoidance of sunlight reduces the development of
    photo-sensitive skin eruptions. Haemodialysis, haemoperfusion or
    exchange trans-fusion have not been shown to be effective.

         Inhalation exposure might make assisted ventilation and
    administration of humidified oxygen necessary.  When HCB is heated to
    decomposition, the toxic fumes produced may result in pulmonary
    oedema.

    4.3  Health surveillance advice

         Where exposure to pure HCB is possible, preplacement and regular
    medical examinations should be performed.

    4.4  Explosion and fire hazards, prevention

    4.4.1  Explosion and fire hazards

         There is a slight fire potential when HCB is exposed to heat or
    flame. Fire may produce irritating or poisonous gases.

    4.4.2  Prevention

         HCB should be kept away from open flames and there should be no
    smoking.

    4.4.3  Fire-extinguishing agents

         Fires involving HCB may be extinguished with dry chemical, CO2,
    Halon, water spray or standard foam.

    4.5  Storage

         HCB must be stored separate from food and feedstuffs, in a cool,
    dry place.

    4.6  Transport

         HCB may be shipped via air, rail, road or water in containers
    bearing the label "Keep away from food".

    4.7  Spillage

         Small spills of HCB may be taken up with sand or other
    non-combustible material and placed into containers for later disposal
    as indicated by local and national regulations.  Large spills should
    first be dyked far ahead of the spill, dampened to avoid dust, and
    then transferred to suitable containers.  An appropriate respirator
    with adequate eye protection should be worn for these operations.

    5.  HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

         HCB is released to the environment as a by-product from the
    manufacture of chlorinated solvents, chlorinated aromatics and
    pesticides, and in emissions from incinerators and other industrial
    processes.  It is subject to long-range transport and thus may be
    deposited far from known sources.  Therefore, HCB can be found
    worldwide in measurable concentrations in various media to which
    humans and other organisms may be exposed.

         HCB is a persistent substance widely dispersed throughout the
    environment.  It accumulates in aquatic sediments and is subject to
    biomagnification.  This suggests that benthic biota and those of
    higher tropic levels (e.g., predatory birds and fish-eating mammals)
    are the most likely to be exposed to higher concentrations of HCB and
    to be at greater risk from adverse effects on reproduction and
    development and cancer.

    6.  SUMMARY OF CHEMICAL SAFETY INFORMATION

         The material in this section is adopted from the IPCS
    International Chemical Safety Card number 895.  This card should be
    easily available to all health workers concerned with, and users of,
    hexachlorobenzene.  It should be displayed at, or near, entrances to
    areas where there is potential exposure to hexachlorobenzene and on
    processing equipment with containers.  The card should be translated
    into the appropriate language(s).  All persons potentially exposed to
    the chemical should also have the instructions on the chemical safety
    card clearly explained.

        SUMMARY OF CHEMICAL SAFETY INFORMATION
                                                                                                                                                 

                                                        HEXACHLOROBENZENE
                                                        C6Cl6
                                                                                                                                                 

    PHYSICAL PROPERTIES                                                                            OTHER CHARACTERISTICS
                                                                                                                                                 

    Boiling point (C)                                  323-326                                    Hexachlorobenzene is a colourless to white
    Melting point (C)                                  231                                        solid in various forms.  The substance
    Relative density (water =1)                         2.04                                       decomposes on heating producing toxic
    Solubility in water                                 None                                       fumes; it reacts violently with dimethyl
    Vapour pressure (kPa at 114 C)                     0.133                                      formamide above 65C.
    Vapour pressure (Pa at 20 C)                       0.1
    Relative vapour density (air = 1)                   9.8
    Flash point (C)                                    242
    Octanol/water partition coefficient (low Pow)       6.2
                                                                                                                                                 

    HAZARDS/SYMPTOMS                                    PREVENTION AND PROTECTION                  FIRST AID
                                                                                                                                                 

    SKIN: may cause slight irritation and be absorbed   Protective gloves and clothing             Remove contaminated clothing. Rinse and
                                                                                                   then wash skin with water and soap.  Refer
                                                                                                   for medical attention.  Wear protective
                                                                                                   gloves when administering first aid.

    EYES: slight irritation                             Face shield or eye protection in           First rinse with plenty of water for
                                                        combination with breathing protection      at least 15 min (remove contact lenses
                                                                                                   if easily possible), then take to a doctor.
                                                                                                                                                 

    SUMMARY OF CHEMICAL SAFETY INFORMATION (con't)
                                                                                                                                                 

    HAZARDS/SYMPTOMS                                    PREVENTION AND PROTECTION                  FIRST AID
                                                                                                                                                 

    INHALATION                                          Local exhaust or breathing protection      Fresh air and rest.  If patient is not
                                                                                                   breathing, give artificial respiration;
                                                                                                   if breathing is difficult, give oxygen.
                                                                                                   Refer for medical attention.

    INGESTION                                           Do not eat, drink or smoke during work.    Rinse mouth. If victim is conscious,
                                                                                                   use gastric lavage to clean out stomach
                                                                                                   followed by saline catharsis.  If
                                                                                                   unconscious or having convulsions, do
                                                                                                   nothing except keep victim warm.  Refer for
                                                                                                   medical attention.
                                                                                                                                                 

    SPILLAGE                                            STORAGE                                    FIRE AND EXPLOSION
                                                                                                                                                 

    Sweep spilled substance into containers.            Separated from food and feedstuffs         Hexachlorobenzene is slightly combustible;
    Carefully collect remainder, then remove to         Cool, dry environment                      avoid heat or open flames.  Fires involving
    safe place. Do NOT let this chemical enter                                                     hexachlorobenzene may be extinguished with
    the environment                                                                                dry chemical, CO2, Halon, water spray or
                                                                                                   standard foam.
                                                                                                                                                 

    PACKAGING AND LABELLING                                                                        
                                                                                                                                                 

    May be shipped via air, rail, road and
    water in containers bearing the label
    "Keep away from food"                                                                          
                                                                                                                                                 
        7.  CURRENT REGULATIONS, GUIDELINES AND STANDARDS

    7.1  Occupational exposure limits

         Examples of occupational exposure limit values are given in
    Table 2. Some guidance values and standards for HCB in other
    environmental media are given in Table 3.

    Table 2.  Representative occupational exposure values for
              hexachlorobenzene
                                                                        

    Country                  Exposure limit valuea      Effective dateb
                                   (mg/m3)
                                                                        

    Czech Republic                  1 (TWA)                  1991R

    Commonwealth of                 0.9 (STEL)               1991R
     Independent States
     (former USSR)

    USA (ACGIH)                     0.25 (TWA)               1994
                                                                        

    a    TWA = time-weighted average (8 or 10 h shift);
         STEL = short-term exposure limit (15 min) not to be
         exceeded at any time during a shift.

    b    R = effective date of ILO publication.


    Table 3.  Guidelines and standards for non-occupational exposure
                                                                        

    Country/organization        Environmental medium       Value
                                                                        

    Canada                      surface water              6.5 ng/litre

    USA                         drinking-water             1 g/litre

    WHO                         drinking-water             1 g/litre
                                                                        

    7.2  Specific restrictions

         HCB is banned in Austria, Czech Republic, the European Union,
    Hungary, Liechtenstein, Panama, Switzerland, Turkey and the former
    USSR. It is severely restricted or has been voluntarily withdrawn in
    Argentina, New Zealand, Norway and Sweden.

    7.3  Labelling, packaging and transport

         HCB may be shipped via air, rail, road or water in containers
    bearing the label "Keep away from food".  Internationally, HCB is
    classed as a poisonous (toxic) substance (UN number 2729 and packing
    group III, i.e., low risk of poisoning).

    7.4  Waste disposal

         Disposal methods are incineration, deep-well injection and
    landfill as required by local and national regulations.  Incineration
    is most effective at 1300 C for 0.25 seconds.

    BIBLIOGRAPHY

    BUA (German Chemical Society-Advisory Committee on Existing Chemicals
    of Environmental Relevance) (1994) Hexachlorobenzene. Stuttgart,
    S. Hirzel Wissenschaftliche Verlagsgesellschaft, 257 pp (BUA
    Report 119).

    Canadian Environmental Protection Act (CEPA) (1993) Priority
    substances list assessment report on hexachlorobenzene, Ottawa,
    Canada, Government of Canada, 52 pp.

    Hayes WJ & Laws ER (1991) Handbook of pesticides toxicology. New York,
    London, Academic Press, vol. III, pp 1422-1433.

    IARC (1985) In: Morris CR & Cabral JRP ed. Hexachlorobenzene:
    Proceedings of an international symposium. Lyon, International Agency
    for Research on Cancer, 691 pp (IARC Scientific Publications No. 77).

    IPCS  (1997) Environmental Health Criteria 195: Hexachlorobenzene.
    Geneva, World Health Organization, International Programme on Chemical
    Safety.

    IRPTC (1993) Legal File. Geneva, United Nations Environment Programme, 
    International Register of Potentially Toxic Chemicals.

    Mackay D, Shiu WY, & Ma KC  (1992) Illustrated handbook of
    physical-chemical properties and environmental fate for organic
    chemicals - Vol. 1: Monoaromatic hydrocarbons, chlorobenzenes and
    PCBs.  Chelsea, Michigan, Lewis Publishers.





    See Also:
       Toxicological Abbreviations
       Hexachlorobenzene (EHC 195, 1997)
       Hexachlorobenzene (ICSC)
       Hexachlorobenzene (PIM 256)
       Hexachlorobenzene (FAO/PL:1969/M/17/1)
       Hexachlorobenzene (WHO Pesticide Residues Series 4)
       Hexachlorobenzene  (IARC Summary & Evaluation, Supplement7, 1987)
       Hexachlorobenzene  (IARC Summary & Evaluation, Volume 20, 1979)
       Hexachlorobenzene  (IARC Summary & Evaluation, Volume 79, 2001)