INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 156
HEXACHLOROBUTADIENE
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.
First draft prepared by Dr. T. Vermeire,
National Institute of Public Health and
Environmental Protection, Bilthoven,
The Netherlands
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
World Health Orgnization
Geneva, 1994
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carried out by the IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
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of the biological action of chemicals.
WHO Library Cataloguing in Publication Data
Hexachlorobutadiene.
(Environmental health criteria: 156)
1. Butadienes - toxicity 2. Environmental exposure
I.Series
ISBN 92 4 157126 X (NLM Classification QV 305.H7)
ISSN 0250-863X
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR HEXACHLOROBUTADIENE
1. SUMMARY
1.1. Identity, physical and chemical properties,
analytical methods
1.2. Sources of human and environmental exposure
1.3. Environmental transport, distribution and
transformation
1.4. Environmental levels and human exposure
1.5. Kinetics and metabolism
1.6. Effects on organisms in the environment
1.7. Effects on experimental animals and
in vitro test systems
1.7.1. General toxicity
1.7.2. Reproduction, embryotoxicity and
teratogenicity
1.7.3. Genotoxicity and carcinogenicity
1.7.4. Mechanisms of toxicity
1.8. Effects on humans
1.9. Evaluation of human health risks and
effects on the environment
1.9.1. Evaluation of human health risks
1.9.2. Evaluation of effects on the
environment
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Conversion factors
2.4. Analytical methods
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Anthropogenic sources
3.2.1. Production levels and processes
3.2.2. Uses
3.2.3. Waste disposal
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1. Transport and distribution between media
4.2. Abiotic degradation
4.2.1. Photolysis
4.2.2. Photooxidation
4.2.3. Hydrolysis
4.3. Biodegradation
4.4. Bioaccumulation
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water
5.1.3. Soil and sediment
5.1.4. Biota
5.2. General population exposure
5.3. Occupational exposure
6. KINETICS AND METABOLISM
6.1. Absorption and distribution
6.2. Metabolism
6.2.1. In vitro studies
6.2.2. In vivo studies
6.3. Reaction with body components
6.4. Excretion
7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
7.1. Aquatic organisms
7.1.1. Short-term toxicity
7.1.2. Long-term toxicity
7.2. Terrestrial organisms
7.2.1. Short-term toxicity
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
8.1. Single exposure
8.1.1. Inhalation exposure
8.1.1.1 Mortality
8.1.1.2 Systemic effects
8.1.2. Oral exposure
8.1.2.1 Mortality
8.1.2.2 Systemic effects
8.1.3. Dermal exposure
8.1.3.1 Mortality
8.1.3.2 Systemic effects
8.1.4. Other routes of exposure
8.2. Short-term exposure
8.2.1. Inhalation exposure
8.2.2. Oral exposure
8.2.2.1 Rats
8.2.2.2 Mice
8.3. Long-term exposure
8.4. Skin and eye irritation; sensitization
8.4.1. Irritation
8.4.2. Sensitization
8.5. Reproduction, embryotoxicity and
teratogenicity
8.5.1. Reproduction
8.5.2. Embryotoxicity and teratogenicity
8.6. Mutagenicity and related end-points
8.6.1. In vitro effects
8.6.2. In vivo effects
8.7. Carcinogenicity/long-term toxicity
8.7.1. Inhalation exposure
8.7.2. Oral exposure
8.7.3. Dermal exposure
8.7.4. Exposure by other routes
8.8. Other special studies
8.8.1. Effects on the nervous system
8.8.2. Effects on the liver
8.8.2.1 Acute effects
8.8.2.2 Short-term effects
8.8.3. Effects on the kidneys
8.8.3.1 Acute effects
8.8.3.2 Short- and long-term effects
8.9. Factors modifying toxicity; toxicity of
metabolites
8.9.1. Factors modifying toxicity
8.9.1.1 Surgery
8.9.1.2 Inhibitors and inducers of
mixed-function oxidases (MFO)
8.9.1.3 Inhibitors of gamma-glutamyltrans-
peptidase (EC 2.3.2.2)
8.9.1.4 Inhibitors of cysteine conjugate
ß-lyase
8.9.1.5 Inhibitors of organic anion
transport
8.9.1.6 Non-protein sylfhydryl scavengers
8.9.2. Toxicity of metabolites
8.9.2.1 In vitro studies
8.9.2.2 In vivo studies
8.10. Mechanisms of toxicity - mode of action
8.10.1. Mechanisms of toxicity
8.10.2. Mode of action
9. EFFECTS ON HUMANS
9.1. General population exposure
9.2. Occupational exposure
9.3. In vitro metabolism studies
9.4. Extrapolation of NOAEL from animals to
humans
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Evaluation of human health risks
10.1.1. Hazard identification
10.1.2. Exposure
10.1.3. Hazard evaluation
10.2. Evaluation of effects on the environment
10.2.1. Hazard identification
10.2.2. Exposure
10.2.3. Hazard evaluation
11. FURTHER RESEARCH
12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
RESUME
RESUMEN
WHO TASK GROUP MEETING ON ENVIRONMENTAL HEALTH CRITERIA FOR
HEXACHLOROBUTADIENE
Members
Dr T.M. Crisp, Reproductive and Development Toxicology Branch, Human
Health Assessment Group, Office of Health and Environmental
Assessment, Environmental Protection Agency, Washington, DC, USA
(Joint Rapporteur)
Professor W. Dekant, Toxicology Institute, Würzburg University,
Würzburg, Germany
Dr I.V. German, Ukrainian Institute for Ecohygiene and Toxicology of
Chemicals, Kiev, Ukraine
Dr B. Gilbert, Fundaçao Oswaldo Cruz, Ministry of Health,
Manguinhos, Rio de Janeiro, Brazil (Joint Rapporteur)
Ms E. Kuempel, Document Development Branch, National Institute for
Occupational Safety and Health, Robert A. Taft Laboratories,
Cincinnati, Ohio, USA
Dr E.A. Lock, Biochemical Toxicology Section, Imperial Chemical
Industries, Central Toxicological Laboratory, Alderly Park,
Macclesfield, Cheshire, United Kingdom
Professor M.H. Noweir, Industrial Engineering Department, College of
Engineering, King Abdul Aziz University, Jeddah, Saudi Arabia
(Chairman)
Dr A. Smith, Toxicology Unit, Health and Safety Executive, Bootle,
Merseyside, United Kingdom
Secretariat
Professor F. Valic, IPCS Consultant, World Health Organization,
Geneva, Switzerland, also Vice-Rector, University of Zagreb,
Zagreb, Croatia (Responsible Officer and Secretary)
Dr T. Vermeire, National Institute of Public Health and
Environmental Protection, Toxicology Advisory Centre, Bilthoven,
The Netherlands
NOTE TO READERS OF THE CRITERIA MONOGRAPHS
Every effort has been made to present information in the
criteria monographs as accurately as possible without unduly
delaying their publication. In the interest of all users of the
Environmental Health Criteria monographs, readers are kindly
requested to communicate any errors that may have occurred to the
Director of the International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland, in order that they may be
included in corrigenda.
* * *
A detailed data profile and a legal file can be obtained from
the International Register of Potentially Toxic Chemicals, Case
postale 356, 1219 Châtelaine, Geneva, Switzerland (Telephone No.
9799111).
* * *
This publication was made possible by grant number 5 U01
ES02617-14 from the National Institute of Environmental Health
Sciences, National Institutes of Health, USA.
ENVIRONMENTAL HEALTH CRITERIA FOR HEXACHLOROBUTADIENE
A Task Group on Environmental Health Criteria for
Hexachlorobutadiene met at the Institute of Hygiene and
Epidemiology, Brussels, Belgium, from 10 to 15 December 1992. Dr C.
Vleminckx welcomed the participants on behalf of the host
institution and Professor F. Valic opened the meeting on behalf of
the three cooperating organizations of the IPCS (UNEP/ILO/WHO). The
Task Group reviewed and revised the draft monograph and made an
evaluation of the risks for human health and the environment from
exposure to hexachlorobutadiene.
The first draft of this monograph was prepared by Dr T.
Vermeire, National Institute of Public Health and Environmental
Protection, Bilthoven, The Netherlands.
Professor F. Valic was responsible for the overall scientific
content of the monograph and for the organization of the meeting,
and Dr P.G. Jenkins, IPCS, for the technical editing of the
monograph.
The efforts of all who helped in the preparation and
finalization of the monograph are gratefully acknowledged.
ABBREVIATIONS
ACPB 1-( N-acetylcystein- S-yl)-1,2,3,4,4-pentachloro-1,3-
butadiene
BCTB 1,4-(bis-cystein- S-yl)-1,2,3,4-tetrachloro-1,3-
butadiene BGTB 1,4-(bis-glutathion- S-yl)-1,2,3,4-
tetrachloro-1,3-butadiene
CMTPB 1-carboxymethylthio-1,2,3,4,4-pentachloro-1,3-
butadiene
CPB 1-(cystein- S-yl)-1,2,3,4,4-pentachloro-1,3-butadiene
GPB 1-(glutathion- S-yl)-1,2,3,4,4-pentachloro-1,3-
butadiene
GSH reduced glutathione
HCBD hexachlorobutadiene
ip intraperitoneal
iv intravenous
MTPB 1-methylthio-1,2,3,4,4-pentachloro-1,3-butadiene
NIOSH National Institute of Occupational Safety and Health
NOAEL no-observed-adverse-effect level
OECD Organisation for Economic Co-operation and Development
PATPB 1-(pyruvic acid thiol)-1,2,3,4,4-pentachloro-1,3-
butadiene
PBSA 1,2,3,4,4-pentachloro-1,3-butadienyl sulfenic acid
TBA 2,3,4,4-tetrachloro-1,3-butenoic acid
TPA 12- o-tetradecanoylphorbol-13-acetate
TPB 1-thiol-1,2,3,4,4-pentachloro-1,3-butadiene
UDS unscheduled DNA synthesis
1. SUMMARY
1.1 Identity, physical and chemical properties, analytical methods
Hexachlorobutadiene is a non-flammable, incombustible, clear,
oily and colourless liquid at ordinary temperature and pressure. It
is poorly soluble in water but miscible with ether and ethanol.
The substance can be detected and determined quantitatively by
gas chromatographic methods. The detection limits are 0.03 µg/m3
in air, 0.001 µg/litre in water, 0.7 µg/kg wet weight in soil or
sediment, and 0.02 µg/litre in blood. A level of 0.47 µg/kg wet
weight has been determined in tissue.
1.2 Sources of human and environmental exposure
Hexachlorobutadiene is not reported to occur as a natural
product. It is chiefly produced as a by-product of the manufacture
of chlorinated hydrocarbons where it occurs in the heavy fractions
(Hex-waste). The world annual production of the compound in heavy
fractions was estimated in 1982 to be 10 000 tonnes.
Hexachlorobutadiene can be used for recovery of
chlorine-containing gas in chlorine plants and as a wash liquor for
removing certain volatile organic compounds from gas streams. It has
further been used as a fluid in gyroscopes, as heat transfer,
transformer, insulating and hydraulic fluids, as a solvent for
elastomers, and as an intermediate and fumigant.
1.3 Environmental transport, distribution and transformation
The main pathways of entry into the environment are emissions
from waste and dispersive use. Intercompartmental transport will
chiefly occur by volatilization, adsorption to particulate matter,
and subsequent deposition or sedimentation. Hexachlorobutadiene does
not migrate rapidly in soil and accumulates in sediment. In water,
it is considered persistent unless there is high turbulence.
Hydrolysis does not occur. The substance seems to be readily
biodegradable aerobically, though biodegradability has not been
investigated thoroughly. Hexachlorobutadiene photolyses on surfaces.
In addition to deposition, reaction with hydroxyl radicals is
assumed to be an important sink of hexachlorobutadiene in the
troposphere, and the estimated atmospheric half-life is up to 2.3
years. The substance has a high bioaccumulating potential as has
been confirmed by both laboratory and field observations. Average
steady-state bioconcentration factors of 5800 and 17 000, based on
wet weight, have been determined experimentally in rainbow trout.
Biomagnification has not been observed either in the laboratory or
in the field.
1.4 Environmental levels and human exposure
Hexachlorobutadiene has been measured in urban air: in all
cases levels were below 0.5 µg/m3. Concentrations in remote areas
are less than 1 pg/m3. In lake and river water in Europe
concentrations of up to 2 µg/litre have been recorded, but mean
levels are usually below 100 ng/litre. In the Great Lakes area of
Canada, much lower levels (around 1 ng/litre) were measured. Bottom
sediment levels here can be as high as 120 µg/kg dry weight. Older
sediment layers from around 1960 contained higher concen-trations
(up to 550 µg/kg wet weight). The sediment concentration was
demonstrated to increase with particle size in the sediment.
Concentrations of hexachlorobutadiene in aquatic organisms,
birds and mammals indicate bioaccumulation but not biomagnification.
In polluted waters, levels of over 1000 µg/kg wet weight have been
measured in several species and 120 mg/kg (lipid base) in one
species. Present levels generally remain below 100 µg/kg wet weight
away from industrial outflows.
The compound has been detected in human urine, blood and
tissues. Certain food items containing a high lipid fraction have
been found to contain up to about 40 µg/kg and, in one case, over
1000 µg/kg.
One study reported occupational exposures of 1.6-12.2 mg/m3
and urine levels of up to 20 mg/litre.
1.5 Kinetics and metabolism
Hexachlorobutadiene is rapidly absorbed following oral
administration to experimental animals, but the rate of absorption
following inhalation or dermal exposure has not been investigated.
In rats and mice, the compound distributes mainly to the liver,
kidneys and adipose tissue. It is rapidly excreted. Binding to liver
and kidney protein and nucleic acids has been demonstrated.
The biotransformation of the compound in experimental animals
appears to be a saturable process. This process proceeds mainly
through a glutathione-mediated pathway in which hexachlorobutadiene
is initially converted to S-glutathione conjugates. These
conjugates can be metabolized further, especially in the
brush-border membrane of renal tubular cells, to a reactive sulfur
metabolite, which probably accounts for the observed nephrotoxicity,
genotoxicity and carcinogenicity.
1.6 Effects on organisms in the environment
Hexachlorobutadiene is moderately to very toxic to aquatic
organisms. Fish species and crustaceans were found to be the most
sensitive, 96-h LC50 values ranging from 0.032 to 1.2 and 0.09 to
approximately 1.7 mg/litre for crustaceans and fish, respectively.
The kidney was demonstrated to be an important target organ in fish.
Based on several long-term tests with algae and fish species, a
no-observed-effect level (NOEL) of 0.003 mg/litre was established;
this classifies the compound as very toxic to aquatic species.
End-points investigated include general toxicity, neurotoxicity,
biochemistry, haematology, pathology, and reproductive parameters.
In one 28-day early-lifestage test with fathead minnows,
reproduction was unaffected at concentrations of up to
0.017 mg/litre, whereas increased mortality and a decreased body
weight were observed at 0.013 and 0.017 mg/litre. The NOEL was
0.0065 mg/litre.
Only one reliable test with terrestrial organisms has been
described. In a 90-day test with Japanese quail, receiving a diet
containing the compound at concentrations from 0.3 to 30 mg/kg diet,
the survival of chicks was decreased at 10 mg/kg diet only.
1.7 Effects on experimental animals and in vitro test systems
1.7.1 General toxicity
Hexachlorobutadiene is slightly to moderately toxic to adult
rats, moderately toxic to male weanling rats, and highly toxic to
female weanling rats following a single oral dose. The major target
organs are the kidney and, to a much lesser extent, the liver.
Based on animal data, the vapour of hexachlorobutadiene is
irritating to mucous membranes and the liquid is corrosive. The
substance should be regarded as a sensitizing agent.
In the kidneys of rats, mice and rabbits, hexachlorobutadiene
causes a dose-dependent necrosis of the renal proximal tubules.
Adult male rats are less sensitive to renal toxicity than adult
females or young males. Young mice are more susceptible than adults,
no sex difference being apparent. In adult female rats the lowest
single intraperitoneal dose at which renal necrosis was observed was
25 mg/kg body weight, and in adult male and female mice it was
6.3 mg/kg body weight. Biochemical changes and distinct functional
alterations in the kidneys occurred at doses similar to or higher
than those at which necrosis occurred.
In six short-term oral tests, two reproductive studies and one
long-term diet study with rats, the kidney was also the major target
organ. Dose-related effects included a decreased relative kidney
weight and tubular epithelial degeneration. The no-observed-
adverse-effect level (NOAEL) for renal toxicity in rats in a 2-year
study was 0.2 mg/kg body weight per day. In mice the NOAEL in a
13-week study was 0.2 mg/kg body weight per day. In both species,
adult females were more susceptible than adult males.
In one short-term inhalation test (6 h/day for 12 days),
similar effects on the kidneys were observed with a nominal vapour
concentration of 267 mg/m3, at which concentration respiratory
difficulties and cortical degeneration in the adrenal glands were
also observed.
1.7.2 Reproduction, embryotoxicity and teratogenicity
Two reproduction diet studies in rats at doses up to 20 and
75 mg/kg body weight per day, respectively, revealed reduced birth
weight and neonatal weight gain at maternally toxic doses of 20 and
7.5 mg/kg body weight, respectively. The highly toxic dose of
75 mg/kg body weight per day was sufficient to prevent conception
and uterine implantation. Skeletal abnormalities were not observed.
In two teratogenicity tests, where rats were exposed either to
hexachlorobutadiene vapour at concentrations between 21 and
160 mg/m3 for 6 h/day (from days 6 to 20 of pregnancy) or
intraperitoneally to 10 mg/kg body weight per day (from days 1 to 15
of pregnancy), fetuses demonstrated developmental toxicity,
including reduced birth weight, delay in heart development and
dilated ureters, but no gross malformations. The retarded
development was observed at levels which were also toxic to the
dams.
1.7.3 Genotoxicity and carcinogenicity
Hexachlorobutadiene induces gene mutations in the Ames
Salmonella test under special conditions favouring the formation of
glutathione conjugation products. It induced chromosomal aberrations
in one in vivo study but not in two in vitro studies. In one in
vitro test the frequency of sister chromatid exchanges was
increased in Chinese hamster ovary cells. High mutagenic potency by
sulfur metabolites of hexachlorobutadiene was reported. In in vitro
studies, the compound induced unscheduled DNA synthesis in Syrian
hamster embryo fibroblast cultures but not in rat hepatocyte
cultures. It induced unscheduled DNA synthesis in rats in vivo,
but did not induce sex-linked recessive lethal mutations in
Drosophila melanogaster.
In the only long-term (2 years) study, in which rats received a
diet containing hexachlorobutadiene at doses of 0.2, 2 or 20 mg/kg
body weight per day, an increased incidence of renal tubular
neoplasms was observed only at the highest dose level.
1.7.4 Mechanisms of toxicity
The nephrotoxicity, mutagenicity and carcinogenicity of
hexachlorobutadiene is dependent on the biosynthesis of the toxic
sulfur conjugate 1-(glutathion- S-yl)-1,2,3,4,4-pentachloro-
1,3-butadiene (GPB). This conjugate is mainly synthesised in the
liver and is further metabolized in the bile, gut and kidneys to
1-(cystein- S-yl)-1,2,3,4,4-pentachloro-1,3-butadiene (CPB). The
activation of CPB, dependent on cysteine conjugate ß-lyase, to a
reactive thioketene in the proximal tubular cells finally results in
covalent binding to cellular macromolecules.
1.8 Effects on humans
No pathogenic effects in the general population have been
described.
There have been two reports of disorders among agricultural
workers using hexachlorobutadiene as a fumigant, but they were also
exposed to other substances. An increased frequency of chromosomal
aberrations was found in the lymphocytes of peripheral blood of
workers engaged in the production of hexachlorobutadiene and
reported to be exposed to concentrations of 1.6-12.2 mg/m3.
1.9 Evaluation of human health risks and effects on the environment
1.9.1 Evaluation of human health risks
As there have been very few human studies, the evaluation is
mainly based on studies in experimental animals. However, limited
human in vitro data suggest that the metabolism of
hexachlorobutadiene in humans is similar to that observed in
animals.
Hexachlorobutadiene vapour is considered to be irritating to
the mucous membranes of humans, and the liquid is corrosive. The
compound should also be regarded a sensitizing agent.
The main target organs for toxicity are the kidney and, to a
much lesser extent, the liver. On the basis of short- and long-term
oral studies in rats and mice, the NOAEL is 0.2 mg/kg body weight
per day. In one short-term inhalation study in rats (12 days,
6 h/day), the NOAEL was 53 mg/m3.
Reduced birth weight and neonatal weight gain was observed only
at maternally toxic doses, as was developmental toxicity.
Hexachlorobutadiene has been found to induce gene mutations,
chromosomal aberrations, increased sister chromatid exchanges and
unscheduled DNA synthesis, although some studies have reported
negative results. There is limited evidence for the genotoxicity of
hexachlorobutadiene in animals, and insufficient evidence in humans.
Long-term oral administration of hexachlorobutadiene to rats
was found to induce an increased frequency of renal tubular
neoplasms, but only at a high dose level causing marked
nephrotoxicity. There is limited evidence for carcinogenicity in
animals and insufficient evidence in humans.
On the basis of the NOAEL for mice or rats of 0.2 mg/kg body
weight per day, a NOAEL of 0.03-0.05 mg/kg body weight per day has
been estimated for humans. There is a margin of safety of 150
between the estimated NOAEL and the estimated maximum total daily
intake assuming absorption of the compound via contaminated
drinking-water and food of high lipid content.
1.9.2 Evaluation of effects on the environment
Hexachlorobutadiene is moderately to highly toxic to aquatic
organisms; crustaceans and fish are the most sensitive species. An
environmental concern level of 0.1 µg/litre has been established. It
is estimated that the maximum predicted environmental concentration
away from point sources is twice the extrapolated environmental
concern level and, consequently, aquatic organisms may be at risk in
polluted surface waters. Adverse effects on benthic organisms cannot
be excluded.
Considering the toxicity of hexachlorobutadiene to mammals,
consumption of benthic or aquatic organisms by other species may
cause concern.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL
METHODS
2.1 Identity
Chemical formula: C4Cl6
Chemical structure:
Common name: hexachlorobutadiene
Common synonyms: 1,3-hexachlorobutadiene, 1,1,2,3,4,4-
hexachloro-1,3-butadiene, perchloro-
butadiene
Common trade names: C-46, Dolen-pur, GP40-66: 120, UN2279
Common abbreviation: HCBD
CAS registry number: 87-68-3
RTECS registry number: EJ 0700000
Relative molecular mass: 260.8
2.2 Physical and chemical properties
Hexachlorobutadiene is a non-flammable, incombustible, clear,
colourless and oily liquid at ordinary temperature and pressure. Its
odour is described as turpentine-like. The odour threshold for the
compound in air is reported to be 12 mg/m3 (Ruth, 1986). In water
an odour threshold of 0.006 mg/litre has been reported (US EPA,
1980). The compound is poorly soluble in water but is miscible with
ether and ethanol.
Hexachlorobutadiene is very stable to acid and alkali in the
absence of an appropriate solvent and has no tendency to polymerize
even under high pressure. It reacts with chlorine under severe
reaction conditions, often with cleavage of the carbon skeleton
(Ullmann, 1986).
Some physical and chemical data on hexachlorobutadiene are
presented in Table 1.
Table 1. Some physical and chemical properties of
hexachlorobutadienea
Physical state liquid
Colour clear, colourless
Melting point -18 °C
Boiling point 212 °C at 101.3 kPa
Water solubility 3.2 mg/litre at 25 °Cb
Log n-octanol-water partition
coefficient (Kow) 4.78b, 4.90c
Density 1.68 g/cm3 at 20 °C
Relative vapour density 9.0
Vapour pressure 20 Pa (0.15 mmHg) at 20 °Cd
Autoignition temperature 610 °C
a Unless otherwise stated, the data are selected from secondary
sources.
b Experimentally derived by Banerjee et al. (1980)
c Experimentally derived by Chiou (1985)
d McConnell et al. (1975)
2.3 Conversion factors
1 ppm = 10.67 mg/m3 air at 25 °C and 101.3 kPa (760 mmHg)
1 mg/m3 air = 0.094 ppm.
2.4 Analytical methods
A summary of relevant methods of sampling and gas
chromatographic analysis is presented in Table 2.
The analytical method for air, reported by Dillon (1979) and
Boyd et al. (1981) has been approved by NIOSH and was published in
the NIOSH Manual of Analytical Methods (NIOSH, 1979, 1990).
Table 2. Sampling, preparation and analysis of hexachlorobutadiene
Medium Sampling method Analytical method Detection limit Sample size Comments Reference
Air adsorption on Chromosorb gas chromatography 360 litre developed for personal Mann et al.
101; extraction by hexane with electron capture sampling in industry (1974)
detection
Air adsorption on Amberlite gas chromatography 10 µg/m3 3 litre suitable for personal Boyd et al.
XAD-2; extraction by with electron capture and area monitoring; (1981); Dillon
hexane detection validation range (1979)
10-2000 µg/m3
Air adsorption on Tenax-GC; gas chromatography 11 µg/m3 2 litre suitable for Melcher &
purging of water vapour, with flame ionization continuous area Caldecourt
oxygen, etc., by nitrogen; detection monitoring (1980)
desorption by heating
Air adsorption on Tenax-GC; gas chromatography 0.03 µg/m3 a developed for the Krost et al.
desorption by heating (capillary column) analysis of ambient (1982); Pellizari
under a helium flow; with mass air (1982); Barkley
cryofocussing spectro-metric et al. (1980)
detection
Water extraction by hexane; gas chromatography 0.05 µg/litre 16 litre developed for the Oliver & Nicol
concentration; drying with (capillary column) analysis of surface (1982)
Na2SO4; clean-up by silica with electron water
gel chromatography capture detection
Table 2 (contd).
Medium Sampling method Analytical method Detection limit Sample size Comments Reference
Water extraction by gas chromatography 0.0014 µg/litre 0.8-1 litre US EPA Method Lopez-Avila
dichloro-methane-acetone; with electron capture 8120 et al. (1989)
drying; concentration detection
by N2 stream
Water extraction by gas chromatography 0.001 µg/litre 12 litre developed for Zogorski (1984)
dichloro-methane; with electron capture monitoring of
drying; concentration detection domestic and process
waters
Water extraction by gas chromatography 0.34 µg/litre 1 litre US EPA Method 612; US EPA (1984a)
dichloro-methane; with electron capture developed for the
drying; concentration detection analysis of municipal
and exchange to and industrial
hexane; clean-up by discharges
fluorisil chromatography
Water extraction by gas chromatography 0.9 µg/litre 1 litre US EPA Method 625; US EPA (1984b)
dichloro-methane at pH developed for the
>11, then at pH <2; analysis of municipal
drying; concentration and industrial
discharges
Water purging by helium; gas chromatography 0.4 µg/litre 0.1 litre developed for the Otson & Chan
trapping; desorption by (capillary column) analysis of volatile (1987);
heating with mass organics in waters Eichelberger
spectro-metric et al. (1990)
detection
Table 2 (contd).
Medium Sampling method Analytical method Detection limit Sample size Comments Reference
Soil, extraction by gas chromatography 0.7 µg/kg Laseter et
sediment acetone-benzene with electron capture wet weight al. (1976)
detection
Soil add water; adjust to pH gas chromatography developed for Kiang & Grob
>12; extraction by (capillary column) screening of soil (1986)
dichloromethane; with flame ionization for priority
centrifugation; drying; and mass pollutants
concentration spectro-metric
detection
Sediment add water; adjust to pH gas chromatography developed for Lopez-Avila et
> 11; extraction by (capillary column) screening of al. (1983)
dichloromethane; with flame/electron sediment for
centrifugation; drying; capture/mass priority pollutants
concentration; spectro-metric
clean-up by silica detection
gel chromatography
Sediment extraction by gas chromatography 13 µg/kga 10-15 g dry Oliver & Nicol
hexane-acetone; removal (capillary column) weight (1982)
of acetone by with electron capture
water extraction; drying; detection
concentration; clean-up
by silica gel
chromatography and
agitation with mercury
Table 2 (contd).
Medium Sampling method Analytical method Detection limit Sample size Comments Reference
Biota homogenization; filtration; gas chromatography 0.7 µg/kg method applied to Laseter et
separation; extraction by with electron capture analysis of fish al. (1976)
hexane; clean-up by detection
fluorisil chromatography
Biota grind and mix edible gas chromatography 0.005 mg/kg 25 g (eggs) wet weight Yurawecz et
tissue; extraction; with electron capture wet weight 50 g (fish) wet weight al. (1976)
clean-up by fluorisil detection or 0.04 3 g (milk fat)
chromatography mg/kg fat 100 g (vegetables)
wet weight
Biota grinding with Na2SO4; gas chomatography 0.47 µg/kga 15 g method applied to Oliver &
Nicol
extraction by (capillary column) analysis of fish (1982)
hexane-acetone; with electron capture
back-extraction of acetone detection
by water; concentration;
clean-up by silica
gel chromatography
Biota extraction by gas chromatography 1 µg/kg 2 g method applied to Mes et al.
benzene-acetone; with electron capture wet weighta analysis of (1982; 1985;
filtration; concentration; detection chlorinated 1986)
redissolution in hexane; hydrocarbon residues
clean-up including in human adipose
fluorisil-silicic tissue and human milk
acid chromatography
Table 2 (contd).
Medium Sampling method Analytical method Detection limit Sample size Comments Reference
Biota extraction by hexane gas chromatography 0.0182 µg/litre 100 mg method applied to Kastl & Hermann
containing an internal with electron capture whole (rat) blood (1983)
standard; centrifugation; detection analysis
direct injection
a lowest reported level measured
The method was validated for the concentration range of
10-2000µg/m3 in 3 litre air samples. The lowest detectable
quantity for this method was reported to be 20 ng, the desorption
efficiency 98%, and the relative standard deviation 9%. Melcher &
Caldecourt (1980) described a gas chromatographic method for the
direct determination of organic compounds in air using a collection
precolumn from which the compounds are directly injected into the
analytical column by rapid heating of the precolumn. The method was
reported to be suitable for the analysis of aqueous samples by
purging the precolumn following injection of the sample
(0.01-0.2 cm3). The analytical method developed for volatile
halogenated compounds by Krost et al. (1982) was applied by
Pellizari (1982) and Barkley et al. (1980). Barkley et al.
(1980) also described the analysis of volatile halogenated compounds
in water, blood and urine using a modification of this method: the
substances are recovered from water by heating and from biological
matrices by heating and purging and are subsequently trapped on a
Tenax column.
A spectrophotometric method for the determination of
hexachlorobutadiene in blood and urine has been reported. The method
involves extraction by heptane and determination by either UV
spectroscopy or colorimetry after derivatization with pyridine.
Reported detection limits were 0.05 mg/litre for the UV method and
5 mg/litre for the colorimetric method (Gauntley et al., 1975).
Interference by other chlorinated hydrocarbons can be expected.
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural occurrence
Hexachlorobutadiene has not been reported to occur as a natural
product.
3.2 Anthropogenic sources
3.2.1 Production levels and processes
The available data are in general of poor quality and not
up-to-date. Commercial production of hexachlorobutadiene was
reported to occur in Germany and Austria (SRI, 1984). In the USA,
commercial production was apparently terminated around 1970 (Mumma &
Lawless, 1975). The compound was and is chiefly produced as
by-product of the manufacture of chlorinated hydrocarbons, often in
association with hexachlorobenzene. In the USA, the manufacture of
tetrachloroethene, trichloroethene and carbon tetrachloride
accounted in 1972 for over 99% of this production of
hexachlorobutadiene in heavy fractions, the so-called Hex-waste, and
amounted to 3310-6580 tonnes (Brown et al., 1975; Mumma & Lawless,
1975; Yurawecz et al., 1976; see also section 3.2.3). It was also
reported to be a by-product of the manufacture of vinyl chloride,
allyl chloride and epichlorohydrin by chlorinolysis processes (Kusz
et al., 1984). Hexachlorobutadiene has been identified in the
effluents of sewage treatment plants (section 5.2) and as a
by-product of the pyrolysis of trichloro-ethene (Yasuhara & Morita,
1990) and plastics (Singh et al., 1982). The annual world
production of hexachlorobutadiene in heavy fractions was estimated
in 1982 to be 10 000 tonnes (Hutzinger, 1982). No data have been
found regarding the amount of hexachlorobutadiene, if any, which is
now recovered from this waste.
Apart from the possible commercial production of
hexachloro-butadiene by recovery from Hex-waste, three pathways for
chemical synthesis are known: the chlorination and
dehydro-chlorination of hexachlorobutene; the chlorination of
polychlorobutanes; and the catalytic chlorination of butadiene
(Mumma & Lawless, 1975; CESARS, 1981). There is no evidence,
however, that the latter reactions have ever been used commercially.
The fraction of hexachlorobutadiene released to the environment
during its industrial life cycle (not defined) has been estimated to
be between 1 and 3% (SRI, 1984). The fraction of hexachlorobutadiene
lost to the environment during its production at a tetrachloroethene
manufacturing plant in the USA was estimated to be 1.5% (Brown
et al., 1975). Using a simple model describing the troposphere,
the global annual emission rate was calculated to be 3000 tonnes of
hexachlorobutadiene based on air sampling data of 1985 (Class &
Ballschmiter, 1987; see also section 4.2.2).
3.2.2 Uses
Hexachlorobutadiene can be used for the recovery of "snift",
which is chlorine-containing gas in chlorine plants, and as a wash
liquor for removing volatile organic compounds from gas streams. It
can be used as a fluid in gyroscopes, as heat transfer, transformer,
insulating and hydraulic fluids, and as solvent for elastomers. It
can be an intermediate in the manufacture of lubricants and rubber
compounds. In the ex-USSR, the substance was reported to find
widespread application as a fumigant for treating Phylloxera on
grapes, and 600-800 tonnes was used for this purpose in 1975 (Brown
et al., 1975; Mumma & Lawless, 1975).
3.2.3 Waste disposal
Hex-waste containing hexachlorobutadiene may be destroyed by
incineration, placed in landfill, or simply stored. Another
procedure involves recycling the compound by catalytic chlorination
and subsequent high temperature chlorinolysis to carbon
tetrachloride and tetrachloroethene (Markovec & Magee, 1984).
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1 Transport and distribution between media
The main pathways for entry of hexachlorobutadiene into the
environment are its emission via industrial waste (section 3.2.3)
and following dispersive use (section 3.2.2). The compound may enter
surface and ground water, soil and air. In view of its physical
properties, intercompartmental transport of hexachloro-butadiene is
expected to occur by volatilization and adsorption to suspended
particulate matter.
Considering the vapour pressure of the compound, i.e. 20 Pa at
20 °C (McConnell et al., 1975), transfer across soil-air
boundaries may be significant. Depending on the soil type,
adsorption will hinder this transport (see below). In a field study
in the ex-USSR, concentrations of hexachlorobutadiene in air above a
vineyard were found to be 0.08 and 0.003 mg/m3 at 1 day and 3
months, respectively, following a spring application of 250 kg/ha.
The method of analysis was not reported. Volatilization of the
compound from light soils was more rapid than from heavy soils
(Litvinov & Gorenshtein, 1982).
The Henry coefficient of hexachlorobutadiene is 0.43 (1040
Pa.m3.mol-1) at 25 °C (Shen, 1982) and 0.3 at 22 °C Hellmann,
1987a). These values are comparable to those of other chlorinated
aliphatic alkenes. They indicate possible transfer of the compound
across water-air boundaries leading to a wide distribution, with
aerial transport playing a major role (McConnell et al., 1975). In
a model experiment, hexachlorobutadiene was allowed to evaporate
from a 20-mg/litre aqueous-methanolic solution, containing 10%
methanol, in a porcelain basin with slow magnetic stirring at 22 °C.
UV spectrophotometry recorded a 25% loss within 28 min. It was shown
that methanol decreased the disappearance time. For the transfer of
this and other model results to flowing waters, a reduction factor
of 30 was proposed for the rate of evaporation on the basis of
limited data for two compounds (Hellmann, 1987a).
In a model experiment, UV spectrophotometric analysis of
solutions of hexachlorobutadiene in deionized water to which
1 g/litre of clay mineral (Fuller's earth) was added revealed a
clay-water partition coefficient of 500 litre/kg, showing limited
adsorption to pure clay minerals comparable to that of other
chlorinated alkenes (Hellmann, 1987b). Based on the log
octanol-water partition coefficient (log Kow) of 4.78-4.90
(Table 1), hexa-chlorobutadiene is expected to adsorb strongly to
organic matter. The organic carbon-water partition coefficient
(Koc) can be estimated to be 25 120 litre/kg on the basis of a log
Kow of 4.8 using the semi-empirical equation of Karickhoff (1981).
Oliver & Charlton (1984) determined a Koc value of 158 500
litre/kg on the basis of sediment and water concentrations in the
Niagara River, USA. Partition coefficients of approximately
200-260 litre/kg were found for two unspecified types of soil in
model experiments employing gas chromatographic analysis of
solutions of hexa-chlorobutadiene in water (Leeuwangh et al.,
1975; Laseter et al., 1976). In field experiments conducted along
the Mississippi river in the USA in 1974-1975, some water samples
were found to contain 1.0-1.5 µg/litre, whereas levee soil samples
at the same sites contained 62-1001 µg/kg dry weight. At a more
polluted site near a Hex-waste landfill, water samples contained
0.04-4.6 µg/litre and mud samples 270-2370 µg/kg dry weight. These
studies show that soil-water partition coefficients can range over 2
to 4 orders of magnitude assuming equilibrium (Laseter et al.,
1976). It can be concluded that the compound does not migrate
rapidly in soils and will accumulate in sediment. It should be noted
that the micro-particles onto which hexachlorobutadiene is absorbed
may themselves migrate in the sub-surface resulting in facilitated
transport. The degree of adsorption to soil is highly dependent on
the content of organic matter and is less pronounced in sandy soils.
On the basis of data for Dutch surface waters, the half-lives
of hexachlorobutadiene were estimated to be 3-30 days in rivers and
30-300 days in lakes and ground water. This suggests that
turbulence, and therefore increased aerobic biodegradation,
volatilization and adsorption, account for the shorter half-lives in
river water, that the compound is difficult to degrade both
biologically and chemically (see below), and that, overall, the
compound is persistent in water (Zoeteman et al., 1980).
4.2 Abiotic degradation
4.2.1 Photolysis
Hexachlorobutadiene absorbs light within the solar spectrum.
Irradiation of a solution of hexachlorobutadiene in benzene at
254 nm for 15 min resulted in the formation of numerous products
having a relative molecular mass greater than that of
hexachloro-butadiene itself (Laseter et al., 1976). The extent of
mineralization of the compound adsorbed to silica gel and exposed to
oxygen was examined following irradiation with ultraviolet light
filtered by quartz (wavelength < 290 nm) or by pyrex (simulating
tropospheric UV with a wavelength > 290 nm). After 6 days, 50-90%
mineralization to hydrogen chloride and/or chlorine, and carbon
dioxide was observed (Gb et al., 1977). These experiments indicate
that hexachlorobutadiene present as a virtual monolayer on silica
gel undergoes quite rapid photolysis.
4.2.2 Photooxidation
Using a steady-state mathematical model for the troposphere
(describing it as 2 boxes one north one south of the equator) and on
the basis of gas chromatographic analysis of air samples from sites
far away from anthropogenic sources, the tropospheric lifetime of
hexachlorobutadiene was estimated to be 2.3 years for the northern
hemisphere and 0.8 years for the southern hemisphere. It was assumed
that the reaction with hydroxyl radicals in the troposphere is the
main sink for hexachloro-butadiene, by analogy with other
halocarbons. The calculated lifetimes at -8 °C correspond to a
pseudo-first order rate constant of (2 ± 1) x 10-14
cm3.molecules-1.sec-1 at estimated hydroxyl radical
concentrations of 7 x 105 molecules.cm-3 for the northern
hemisphere and 17 x 105 for the southern hemisphere (Class &
Ballschmiter, 1987). Experimentally, a half-life of 1 week was
determined when hexachlorobutadiene was exposed to air in flasks
outdoors. This relatively short disappearance time was possibly due
to heterogeneous reactions on the vessel walls, as suggested by the
authors of the report. Hydrogen chloride was found to be the main
degradation product after exposure of samples to xenon arc
radiations (wavelength > 290 nm) (Pearson & McConnell, 1975).
4.2.3 Hydrolysis
Hexachlorobutadiene is highly resistant to chemical degradation
by strong acids and alkalis in the absence of appropriate solvents,
although it is readily degraded by ethanolic alkali (Roedig &
Bernemann, 1956). Based on the measured hydrolysis rate of the
compound in a 1:1 acetone-water mixture, a half-life of over 1800 h
was calculated (Hermens et al., 1985).
4.3 Biodegradation
Hexachlorobutadiene, at concentrations of 5 or 10 mg/litre, was
completely degraded by adapted aerobic microorganisms within 7 days
in a static-culture flask screening procedure at 25 °C, as shown by
gas chromatography and by determination of total and dissolved
organic carbon. The inoculum was taken from settled domestic waste
water (Tabak et al., 1981). Approximately 70% adsorption to sludge
and 10% degradation was found to occur within 8 days in a pilot
low-loaded biological sewage treatment plant (Schröder, 1987).
Anaerobic degradation of hexachlorobutadiene at 100 mg/litre
was not observed in 48-h batch assays at 37 °C using an inoculum
from a laboratory digester (Johnson & Young, 1983).
4.4 Bioaccumulation
Considering the low water solubility of 3.2 mg/litre and the
high log Kow of 4.78-4.90 (Table 1), a strong bioaccumulating
potential would be expected. Both laboratory and field data support
this prediction. In flow-through laboratory tests with algae,
crustaceans, molluscs and fish in fresh or marine waters,
bioconcentration factors (on a wet weight basis) were between 71 and
17 000. The results appear to be highly dependent on the exposure
period and there is great variability between organisms (Leeuwangh
et al., 1975; Pearson & McConnell, 1975; Laseter et al., 1976;
Oliver & Niimi, 1983). Steady state was clearly demonstrated to be
reached in only one of these tests. Oliver & Niimi (1983) exposed
rainbow trout (Salmo gairdnerii) to aqueous solutions of
hexachlorobutadiene at 0.10 and 3.4 ng/litre and found average
bioconcentration factors of 5800 and 17 000, steady states having
been reached after 69 and 7 days, respectively. When Oligochaete
worms were exposed via spiked Lake Ontario sediments to a pore water
concentration of 32 ng/litre in a flow-through system, steady state
was reached within 4 to 11 days and the average bioconcentration
factor was 29 000, based on dry weight of which about 8% is lipid
(Oliver, 1987). Biomagnifi-cation, the concentrating of a substance
through a food chain, was not observed for hexachlorobutadiene in
two limited laboratory experiments with fish fed contaminated food
(Pearson & McConnell, 1975; Laseter et al., 1976).
The bioaccumulation factors found in plankton, crustaceans,
molluscs, insects and fish in surface waters are comparable to those
observed in the laboratory: available bioaccumulation factors based
on wet weight range between 33 and 11 700 (Goldbach et al., 1976;
Laseter et al., 1976). No biomagnification was observed when
levels in fish were compared with those of detritus and several
invertebrates (Goldbach et al., 1976). The latter was confirmed by
a trophodynamic analysis in the Lake Ontario ecosystem (Oliver &
Niimi, 1988).
Limited bioaccumulation of hexachlorobutadiene was observed in
the fat of rats following exposure for 4 to 12 weeks to a mixture of
this compound and 1,2,3,4-tetrachlorobenzene, hexachloroben-zene,
1,3,5-trichlorobenzene, o-dichlorobenzene and
gamma-hexa-chlorocyclohexane in food (each compound at 2 or 4 mg/kg
body weight per day). Fat concentrations of up to 8 mg/kg were
observed at the higher dose rates (Jacobs et al., 1974).
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1 Environmental levels
5.1.1 Air
Concentrations of hexachlorobutadiene measured in air at
different locations are summarized in Table 3.
5.1.2 Water
Concentrations of hexachlorobutadiene measured in water at
different locations are summarized in Table 4.
5.1.3 Soil and sediment
Concentrations of hexachlorobutadiene measured in soil and
sediment at different locations are summarized in Table 5.
5.1.4 Biota
Concentrations of hexachlorobutadiene measured in aquatic
organisms, birds and mammals are summarized in Table 6.
5.2 General population exposure
Levels of hexachlorobutadiene encountered in the food and
drinking-water of the general population are summarized in Table 7.
Hexachlorobutadiene was not detected in the urine or blood of
nine individuals living near Old Love Canal, USA, whereas trace
levels were found in the breath of one of them (Barkley et al.,
1980). In another investigation the compound could not be detected
in the blood of 36 Love Canal area residents (Bristol et al.,
1982). Hexachlorobutadiene was found at levels of 0.8-4 µg/kg wet
weight (fat) and 1.2-13.7 µg/kg wet weight (liver) in postmortem
tissues from 6 out of 8 United Kingdom residents in 1970 (McConnell
et al., 1975). In the adipose tissue of accident victims in Canada
(1976), levels of 1 to 8 µg/kg wet weight were measured in 128 out
of 135 samples (Mes et al., 1982, 1985). In Canada (1982),
hexachlorobutadiene could not be detected in any of 210 samples of
breast milk (Mes et al., 1986).
When 15 samples of hazardous waste from incineration facilities
in the USA were analysed, 4 sites were found to contain
hexa-chlorobutadiene, but the levels were reported to be below
10 mg/kg (Demarini et al., 1987). In sewage sludge, Alberti &
Ploger (1986) measured levels of below 1 µg/kg dry weight (3 samples
of municipal or municipal/industrial sludge), up to 0.6 µg/kg dry
weight (1 sample of municipal/industrial sludge), and 15 µg/kg dry
weight (1 sample of industrial sludge).
5.3 Occupational exposure
Hexachlorobutadiene levels of 1.6-12.2 mg/m3 air have been
measured in the workplace, resulting in reported urine levels of up
to 20 mg/litre in workers at the end of the day (German & Viter,
1985).
Table 3. Levels of hexachlorobutadiene in environmental air
Type of Year Location Detection Levels determineda Reference
air limit (ng/m3) (ng/m3)
Ambient 1985 Atlantic Ocean, lower 0.0001-0.0004 (r) Class & Ballschmiter
troposphere in a south-north 0.0003 (m, north) (1987)
cross section, 8 sites 0.0001 (m, south)
Urban 1978 USA, Niagara Falls, inside nd (n=9) Barkley et al. (1980)
homes near dump site
USA, Niagara Falls, outside nd (n=6)
homes near dump site trace (n=3)
USA, Niagara Falls area nd (n=3)
trace (n=1)
50-390 (r, n=2)
Urban 1980- USA, 7 cities nd-117 (r,m) Singh et al. (1982)
1981 nd-251 (r)
Table 3 (contd).
Type of Year Location Detection Levels determineda Reference
air limit (ng/m3) (ng/m3)
Polluted 1975 USA, 9 sites with chemical nd-460 000 (r) Li et al. (1976)b
industries, on plant property
USA, 9 sites with chemical nd-22 000 (r)
industries, off plant property
Polluted 1978 USA, Niagara Falls, household < 45 (n=1) Barkley et al.
basement near dump site (1980)
Polluted 1978 idem 30-410 (r, n=4) Pellizari (1982)
Polluted 1982 USA, liquid waste lagoon 2 nd (n=2) Guzewich et al.
3-160 (n=4) (1983)
a nd = not detectable; r = range of individual values; r,m = range of mean values; m = mean; n = number of samples
b The highest levels were associated with the production of tetrachloroethene and trichloroethene. At other plants,
levels of hexachlorobutadiene remained below 3 ng/m3. Waste holding areas (especially when involving open storage)
were often the most significant sources of hexachlorobutadiene, contaminated soil being a secondary source. The
total number of samples examined was 405.
Table 4. Levels of hexachlorobutadiene in environmental water
Type of Year Location Detection limit Levels determineda Reference
water (ng/litre) (ng/litre)
Surface Canada, Niagara River 50 1.5 Oliver & Nicol (1982)
Surface 1982 Canada, Niagara River 0.82 (m, n=5) Oliver & Charlton (1984)
Surface 1981-1983 Canada, Niagara River 0.01 0.78 (m, n=104) Oliver & Nicol (1984)
0.67 (median)
0.27-3.2 (r)
Surface 1981 Canada, Niagara River nd-0.6 (n=1) Fox et al. (1983)
Surface 1972-1973 Netherlands, River IJssel, 50-130 (r, n=5) Goldbach et al. (1976)
Ketelmeer, IJsselmeer
Surface 1976-1978 Netherlands, River Rhine 1000-2000 Zoeteman et al. (1980)
Surface 1975 USA, 9 sites with chemical nd-240 000 (r) Li et al. (1976)
industries, on plant property
idem, off plant property nd-23 000 (r)
Table 4 (contd).
Type of Year Location Detection limit Levels determineda Reference
water (ng/litre) (ng/litre)
Surface 1976 Germany, River Rhine, 865 km 10 10 (50-percentile) Alberti (1983)
180 (90-percentile)
1978 Germany, idem 10 20 (50-percentile)
60 (90-percentile)
1981 Germany, idem 10 < 10 (50-percentile)
40 (90-percentile)
1980-1981 Germany, 4 River Rhine 10 nd
tributaries
Germany, River Lippe 10 40-200
Surface 1979-1981 Germany, River Rhine, < 50 Haberer et al. (1988)
1979-1981 Germany, River Main < 1000
Surface 1983 Netherlands, River Rhine, River Lek < 100 (m, n=52) Meijers (1988)
idem, before dune infiltration 70 (m, n=13)
Table 4 (contd).
Type of Year Location Detection limit Levels determineda Reference
water (ng/litre) (ng/litre)
Surface 1984-1985 Germany, River Rhine 10-20 Petersen (1986)
Germany, River Elbe 10-150
Estuarine USA, Calcasieu River estuary, 1298 Pereira et al. (1988)
vicinity of industrial outfall
Sea 1972-1973 United Kingdom, Liverpool Bay 1 4 (m, n=150) Pearson & McConnell
nd-30 (r) (1975)
Sea 1977 USA, Gulf of Mexico, Sauer (1981)
open ocean 1 nd (n=4)
coast 1 nd-15 (n=4)
Ground Switzerland, aquifer contaminated 200-300 (r) Giger & Schaffner (1981)
water by leachate from a chemical waste
disposal site
a nd = not detectable; r = range of individual values; r,m = range of mean values; m = mean; n = number of samples;
x percentile = x percent of samples with values up to that given
Table 5. Levels of hexachlorobutadiene in soil and sediment
Type of soil Year Location Levels determineda Reference
or sediment (µg/kg)
Soil, vineyards infected with Phylloxera < 7300 (8 mo) Vorobyeva (1980)
agricultural and treated at 250 kg/ha < 2990 (32 mo)
Soil 1975 USA, 9 sites with chemical nd-980 000 (r)b Li et al. (1976)
industries, on plant property
idem, off plant property nd-110 (r)b
Sediment 1975 idem, on plant property nd-33 000 (r)b Li et al. (1976)
idem, off plant property nd-40 (r)b
Sediment, United Kingdom, Liverpool Bay < 1 (n=110) Pearson & McConnell
marine > 1 (n=30) (1975)
Sediment, Canada, Niagara Falls 18 Oliver & Nicol (1982)
river/lake
Sediment, 1980 Canada, Lake Ontario nd (n=9) Kaminsky et al. (1983)
lake trace (n=3)
8.7 (n=1)
Table 5 (contd).
Type of soil Year Location Levels determineda Reference
or sediment (µg/kg)
Sediment, 1981 Canada, Niagara River, downstream 9.6-37 (n=5, dwt)c Fox et al. (1983)
river idem, upstream nd (n=1, dwt)
Sediment, 1982 Germany, River Rhine, 707 km 0.002 (dwt) Alberti (1983)
river idem, 815 km 0.005 (dwt)
Sediment, 1981 Canada, Lake Ontario 12-120 (n=5, dwt)
lake
Sediment, 1968-1978 Canada, Niagara Falls sediment nd Durham & Oliver (1983)
lake 1959-1962 core near Niagara River 550
1980-1981 18
1868-1981 nd-550
Sediment, 1980-1982 Canada, lakes 0.04-9.3 (r, n=57) Oliver & Bourbonniere
lake 1980 Canada, Lake Huron 0.08 (m, n=9, dwt) (1985)
1982 Canada, Lake St. Clair 7.3 (m, n=2, dwt)
1982 Canada, Lake Erie 0.2-1.6 (r,m, n=46, dwt)
Sediment, 1982 Canada, Niagara Falls, settling nd (n=1) Oliver & Charlton (1984)
lake particulates at 20 m depth 2.9-11 (r, n=5), 5.9 (m)
idem, settling particulates at
68 m depth 7.4 (m)
bottom sediment 32 (m, n=12)
Table 5 (contd).
Type of soil Year Location Levels determineda Reference
or sediment (µg/kg)
Sediment, lake Canada, Lake Ontario 0.1-75 (r, n=3) Oliver (1984)
Sediment, USA, Eagle Harbour, creosote < 0.79 (m, n=15, dwt) Malins et al. (1985)
sea harbour contaminated sediment, 3 sites
Sediment, USA, President Point, 1 < 2.0 (n=1, dwt)
sea harbour reference site
Sediment USA, Calcasieu River estuary, 85 (bottom) Pereira et al. (1988)
estuarine vicinity of industrial outfall 1.7 (suspended)
a dwt = dry weight; nd = not detectable; r = range of individual values; r,m = range of mean values; m = mean; mo = months after treatment;
n = number of samples
b The highest levels were associated with the production of tetrachloroethene and trichloroethene. Waste holding areas (especially when
involving open storage) were often the most significant sources of hexachlorobutadiene, contaminated soil being a secondary source.
c surficial sediment; the sediment concentration increased with fraction size
d surficial sediment
Table 6. Concentrations of hexachlorobutadiene in aquatic organisms, birds and mammals
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Detritus (bottom) 1972-1976 Netherlands, surface water 200 Goldbach et al. (1976)
Detritus (floating) 220
Invertebrates
Plankton 1972-1973 United Kingdom, sea water nd-2.0 Pearson & McConnell (1975)
Ragworm,
Nereis diversicolor 0.06
Mussel,
Mytilus edulis nd-3.8
Crab,
Cancer pagarus nd-1.1
Others nd
Cerastoderma edule
Ostrea edulis
Buccinum undatum
Crepidula fornicata
Carcinus maenus
Eupagurus bernhardus
Crangon crangon
Asterias rubens
Solaster sp.
Echinus esculentus
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Snail 1972-1976 Netherlands, surface water Goldbach et al. (1976)
Lymnaea peregra 30, 1670
Clam,
Sphaerium sp. 2410
Oligochaetes 0.3 (m, n=3)
Oligochaetes 1981 Canada, Lake Ontario nd-37 (dwt) Fox et al. (1983)
Amphipods 7.5-62 (dwt)
Mysids 6 (dwt)
Benthic organisms in 1983-1984 USA, sea water < 5 (dwt) Malins et al. (1985)
stomachs of fish
Clam, 1982-1983 Canada, Great Lakes area Kauss & Hamdy (1985)
E. complanatus nd-83 (r, n=34)
Marine algae 1972-1973 United Kingdom, sea water Pearson & McConnell (1975)
Enteromorpha compressa nd
Ulva lactuca nd
Fucus vesiculosis 8.9
Fucus serratus 0.6
Fucus spiralis 0.6
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Fish
Ray, 1972-1973 United Kingdom, sea water Pearson & McConnell (1975)
Raja clavata (flesh) 0.1-0.4
Raja clavata (liver) 0.2-1.5
Plaice,
Pleuronectes platessa (flesh) nd-0.4
Pleuronectes platessa (liver) 0.2-1.2
Dab,
Limanda limanda (flesh) < 0.1
Limanda limanda (liver) nd
Mackerel,
Scomber scombrus (flesh) nd-2.6
Cod,
Gadus morrhua (flesh) < 0.1
Gadus morrhua (air bladder) 0.35
Others (liver and/or flesh), nd
Platycthus flesus
Solea solea
Aspitrigla cuculus
Trachurus trachurus
Trisopterus luscus
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Trout, USA, Niagara River, Lake 0.47 Oliver & Nicol (1982)
Salmo gairdneri Ontario
Trout 1981 Canada, Lake Ontario 1.3 (dwt) Fox et al. (1983)
Catfish (flesh) 1973 USA, surface water near trace-4600 Yurawecz et al. (1976)
Gaspergoo (flesh) chemical plants manufacturing 200
Buffalo fish (flesh) tetrachloroethene 100
Mullet (flesh) trace
Sea trout (flesh) trace
Sheepshead minnow (flesh) trace
Catfish 1973 USA, < 40 km from tetrachloro- 10-1200 Yip (1976)
Carp ethene or trichloroethene 62
Gaspergoo manufacturing plants 12-30
Buffalo fish 120
Whiting 20
Drum 10
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Pike perch, Goldbach et al. (1976)
Stizostedion lucioperca 1972-1976 Netherlands, Ketelmeer (lake) 440 (m, n=8)
Netherlands, IJsselmeer (lake) 23 (m, n=4)
Perch,
Perca fluviatilis Netherlands, Ketelmeer 130, 400 (n=2)
Pike,
Esox lucius Netherlands, Ketelmeer 260
Tench,
Tinca tinca Netherlands, Ketelmeer 950
Common bream,
Abramis brama Netherlands, Ketelmeer 1520 (m, n=5)
Netherlands, IJsselmeer 33 (m, n=5)
White bream
Blicca bjoerkna Netherlands, Ketelmeer 360 (m, n=3)
Roach,
Rutilis rutilis Netherlands, Ketelmeer 910 (m, n=10)
Netherlands, IJsselmeer 61 (m, n=4)
Eel,
Anguilla anguilla Netherlands, IJsselmeer 33 (m, n=4)
Smelt
Osmerus eperlanus Netherlands, IJsselmeer 43 (m, n=3)
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
English sole (liver) 1983-1984 USA, sea water < 9 (dwt) Malins et al. (1985)
English sole (muscle) < 0.2 (dwt)
Catfish USA, vicinity of industrial 46 000-120 000 Pereira et al. (1988)
outfall in Calcasieu River (lipid base)
estuary
Atlantic croaker idem, in Calcasieu River 41 000 (lipid base)
Blue crab 12 000 (lipid base)
Spotted sea trout 15 000 (lipid base)
Blue catfish 46 000 (lipid base)
Coho salmon 1980 USA, Great Lakes nd (n=31) Clark et al. (1984)
trace-10 (r, n=5)
Several species 1983 USA, 14 Lake Michigan nd Camanzo et al. (1987)
tributaries and embayments
Birds
Guillemot, 1972-1973 United Kingdom Pearson & McConnell (1975)
Uria aalge (eggs) 1.6-9.9
Table 6 (contd).
Type of biota Year Location Levels determineda Reference
(µg/kg wwt)
Swan, Pearson & McConnell (1975)
Cygnus olor (liver) 5.2
Cygnus olor (kidney) nd
Moorhen, 1972-1973 United Kingdom Pearson & McConnell (1975)
Gallinula chloropus (liver) 0.8
Gallinula chloropus (muscle) 2.6
Gallinula chloropus (eggs) nd
Others nd
Sula bassana (liver, eggs)
Phalacrocerax aristotelis (eggs)
Alca torda (eggs)
Rissa tridactyla (eggs)
Anas platyrhyncos (eggs)
Mammals 1972-1973 United Kingdom Pearson & McConnell (1975)
Grey seal,
Halichoerus grypus (blubber) 0.4-3.6
Halichoerus grypus (liver) nd-0.8
Common shrew,
Sorex araneus nd
a dwt = dry weight; r = range of individual values; m = mean of individueal values; n = number of samples; nd = not detectable; wwt = wet
weight
Table 7. Levels of hexachlorobutadiene in food and drinking-water
Type of food Year Location Levels determineda Reference
or drinking-water (µg/kg wwt or µg/litre)
Tap water 1978 USA, houses bordering Old nd-trace (r, n=3) Barkley et al. (1980)
Love Canal, Niagara Falls 0.06-0.17 (r, n=6)
Well water 1978 USA, Tennessee, contaminated nd-2.53 (r, n=28) Clark et al. (1982)
by leachate from waste dump 0.15 (m, n=22)
Fresh milk United Kingdom 0.08 McConnell et al. (1975)
Butter 2
Cheese, eggs nd
Meat (3 types) nd
Oils/fats (4 out of 5 types) nd
Vegetable cooking oil 0.2
Beverages (5 out of 6 types) nd
Light ale 0.2
Fruits/vegetables (5 out of 7 types) nd
Tomatoes United Kingdom, reclaimed lagoon 0.8
Black grapes United Kingdom, import 3.7
Table 7 (contd).
Type of food Year Location Levels determineda Reference
or drinking-water (µg/kg wwt or µg/litre)
Fresh bread United Kingdom nd
Eggs 1973 USA, < 40 km from tetrachloro- nd (n=15) Yip (1976)
Milk ethylene or trichloroethylene nd (n=19)
manufacturing plants, 6-7 sites 1320 (n=1, fat basis)
Vegetables (7 types) nd (n=20)
Condensed milk 1975 Germany, Bonn 4 Kotzias et al. (1975)
Milk (products) (2 types) nd
Eggs (white) nd
Eggs (yolk) 42
Meats (4 types) nd
Tinned fish (2 types) nd
Onion bread nd
Chicken feed 39
Chicken meal 2
a nd = not detected; m = mean of individual values; n = number of samples; r = range; wwt = wet weight
6. KINETICS AND METABOLISM
6.1 Absorption and distribution
Whole body autoradiography of longitudinal sagittal sections of
male rats after administration of a single oral dose of 200 mg
uniformly labelled hexachlorobutadiene/kg body weight in corn oil
demonstrated that intestinal absorption of the parent compound was
virtually complete by 16 h. The radioactivity in the
gastrointestinal tract at this point in time was mainly due to
water-soluble metabolites, whereas 85% of the radioactivity in the
small intestine was still present as unchanged hexachlorobutadiene
4 h after the administration. At all points in time radioactivity
levels in the stomach were low compared to those in the intestines.
The autoradiogram showed a specific distribution of radioactivity,
especially in the outer medulla of the kidney (Nash et al., 1984).
Reichert et al. (1985) orally administered 1 or 50 mg of
labelled hexachlorobutadiene/kg body weight in tricaprylin to female
rats and recovered, at 72 h, approximately 7% of the label in
carcass and tissues, mainly liver, brain and kidneys. Most of the
label was excreted via urine or faeces within this time period
(section 6.4). In mice given 30 mg of labelled hexachlorobutadiene
per kg body weight in corn oil, over 85% of the label was excreted
within 72 h (section 6.4); 6.7-13.6% was found in the carcass,
especially in adipose tissue (Dekant et al., 1988a). This report
on mice supports the study by Reichert et al. (1985) on rats with
respect to the amount of labelled hexachlorobutadiene absorbed.
6.2 Metabolism
The extent of metabolic transformation and the identity of
excretion products found in studies with rodents are summarized in
Table 8. The available evidence suggests that hexachloro-butadiene
is metabolized in a glutathione-dependent reaction to toxic sulfur
metabolites. The glutathione- S-conjugate 1-(glutathion-S-yl)-
1,2,3,4,4-pentachloro-1,3-butadiene (GPB) is formed in the liver and
excreted with bile. GPB is reabsorbed from the gut both intact and
after degradation to 1-(cystein- S-yl)-1,2,3,4,4-pentachloro-
1,3-butadiene (CPB). Finally, these sulfur conjugates and the
corresponding mercapturic acid 1-( N-acetylcystein- S-yl)-
1,2,3,4,4-pentachloro-1,3-butadiene (ACPB) are delivered to the
kidney. In the kidney, high concentrations of CPB are present due to
renal accumulation, enzymes with acylase activity and
gamma-glutamyltranspeptidase. CPB is finally cleaved by renal
cysteine conjugate ß-lyase to the electrophile
trichlorovinyl-chlorothioketene. The renal accumulation of sulfur
conjugates and the location of ß-lyase along the nephron (MacFarlane
et al., 1989) explain the organ- and site-specific toxicity of
hexachlorobutadiene (Lock, 1987a,b; Anders et al., 1987; Dekant
et al., 1990a,b; Koob & Dekant, 1991).
Table 8. Tracer studies with [14C] hexachlorobutadiene
Species Route Dose (mg/kg Medium Metabolitea Fraction of Time after Reference
body weight) dose (%) dosing (h)
Rat ip 0.1 urine total 29 48 Davis et al. (1980)
water-soluble 25 48
faeces total 40 48
300.1 urine total 7 48
water-soluble 6 48
faeces total 7 48
Rat oral 200 urine total 11 120 Nash et al. (1984)
PBSA 1 120
non-ether soluble 7 120
faeces total 39 120
Rat oral 1 expired air total 8.9 72 Reichert et al. (1985)
HCBD 5.3 72
CO2 3.6 72
urine total 30.6 72
faeces total 42.1 72
50 expired air total 6.6 72
HCBD 5.4 72
Table 8 (contd).
Species Route Dose (mg/kg Medium Metabolitea Fraction of Time after Reference
body weight) dose (%) dosing (h)
CO2 1.2 72
urine total 11.0 72
faeces total 69 72
Rat oral 100 urine total 5.4 24 Reichert et al. (1985);
S-containing ca 4.3 24 Reichert & Schutz (1986)
ACPB }
MTPB } 0.5 24
CMTPB}
faeces total 60 72
oral 1 expired air total 7.45 72
C2 2.2
urine total 17.5
faeces & gitb total 61.8
carcass total 10.5
100 expired air total 7.57 72
CO2 0.7
urine total 9.0
faeces & gitb total 72.1
carcass total 5.8
Table 8 (contd).
Species Route Dose (mg/kg Medium Metabolitea Fraction of Time after Reference
body weight) dose (%) dosing (h)
Rat iv 1 expired air total 8.54 72 Payan et al. (1991)
CO2 2.6
urine total 21.1
faeces & gitb total 59.3
carcass total 12.9
100 expired air total 8.11 72
CO2 0.9
urine total 9.2
faeces & gitb total 71.5
carcass total 11.1
Mouse oral 30 expired air total = HCBD 4.5 72 Dekant et al. (1988a)
urine total 7.2 72
faeces total 72.0 72
HCBD > 57 72
GPB 7.2 72
a For abbreviations see Fig. 1; "total" indicates that no individual chemicals were specified
b git = gastrointestinal tract
6.2.1 In vitro studies
Incubation of hexachlorobutadiene with rat or mouse liver or
kidney subcellular fractions caused a depletion of non-protein
sulfhydryl groups, which was not due to oxidation (Kluwe et al.,
1981).
The formation of GPB and of 1,4-(bis-glutathion- S-yl)-
1,2,3,4-tetrachloro-1,3-butadiene (BGTB) is catalysed by
glutathione- S-transferase in rat and mouse liver microsomes and
cytosol (Wolf et al., 1984; Wallin et al., 1988; Dekant et al.,
1988a,b). GPB formation has also been observed in human liver
microsomes and those from several other species (Oesch & Wolf, 1989;
McLellen et al., 1989). Conjugation in mouse liver microsomes, but
not in those from rat liver, is significantly faster in females than
in males (Wolf et al., 1984; Dekant et al., 1988a).
GPB formation has also been demonstrated in the isolated
perfused rat liver; in this system, GPB formed in the liver was
almost exclusively excreted with bile by a carrier-mediated active
transport mechanism; only after infusing very high concentrations of
hexachlorobutadiene was sinusoidal excretion of GPB into the
perfusate observed (Gietl & Anders, 1991).
A large number of studies have used GPB, CPB and ACPB to
further delineate the fate of hexachlorobutadiene in the organism.
These studies have demonstrated that CPB is the penultimate
intermediate in hexachlorobutadiene metabolism. CPB is a substrate
for renal cysteine conjugate ß-lyase and is metabolized by this
enzyme to 2,3,4,4-tetrachlorobutenoic acid and
2,3,4,4-tetrachlorothionobutenoic acid (Dekant et al., 1988a).
Trichloro-vinyl-chlorothioketene has been identified as the ultimate
reactive intermediate in hexachlorobutadiene metabolism catalysed by
ß-lyase (Dekant et al., 1991). ACPB accumulated by the renal
organic anion transporter is cleaved to CPB by renal acylases
(Vamvakas et al., 1987; Pratt & Lock, 1988).
6.2.2 In vivo studies
In in vivo studies, hexachlorobutadiene caused a marked,
dose-related depletion of renal nonprotein sulfhydryl (NP-SH) in
mice at single intraperitoneal doses of 33-50 mg/kg body weight but
little or no decrease in hepatic NP-SH (Kluwe et al., 1981; Lock
et al., 1984). This pattern was also observed in female rats at
single intraperitoneal doses from 300 mg/kg body weight (Hook
et al., 1983). Conversely, the compound caused a marked,
dose-related depletion of hepatic NP-SH in male rats from 300 mg/kg
body weight intraperitoneally, but no decrease (or even an increase)
in renal NP-SH (Kluwe et al., 1981, 1982; Lock & Ishmael, 1981;
Baggett & Berndt, 1984).
When cannulated male rats were given intravenously either a
tracer dose of 0.071 mg radiolabelled hexachlorobutadiene/kg body
weight or the same dose at 24 h after an intraperitoneal nephrotoxic
dose of 300 mg/kg body weight in corn oil, 13 and 10% of the label
was recovered in the bile, respectively, within the 3 h following
the tracer dose. The labelled material was completely water soluble
(Davis et al., 1980).
In a study by Payan et al. (1991), rats with cannulated bile
ducts received once, either orally or intravenously, 1 or 100 mg of
radiolabelled hexachlorobutadiene/kg body weight. At 72 h after
exposure, fractional urinary excretion (7.5% of the dose) was
independent of the dose and route of administration, in contrast to
the situation in intact rats (see section 6.4). Fractional biliary
excretion decreased with increasing dose following oral
administration (66.8% versus 58%) and intravenous injection (88.7%
versus 72%). Fractional faecal excretion was minimal following
intravenous injection (3.1% following the low oral dose and 16.2%
following the high oral dose). In a group of bile duct-duodenum
cannula-linked rats given one dose of 100 mg/kg body weight, all
tissue concentrations (kidney, liver, plasma, carcass) and the
urinary excretions at 30 h after dosing were higher in bile donor
rats than in recipient rats. The biliary contribution to both
urinary and tissue concentrations was calculated to be 40%. Of the
biliary metabolites entering the recipients, 80% was found to be
reabsorbed.
Nash et al. (1984) administered 200 mg labelled
hexachloro-butadiene in corn oil/kg body weight to male rats with
exteriorized bile flow. They recovered 35% of the label in the bile
during the 48 h following treatment, 40% of which was identified as
GPB (Fig. 1) and 12% as CPB. In another investigation into the
identity of biliary excretion products, male rats were given
intravenously an aqueous suspension of 0.026 mg of labelled
hexachlorobutadiene. During the next two hours over 30% of the label
was recovered in bile; 35% of this radioactivity was identified as
GPB and 6% as BGTB (Fig. 1), but the remaining labelled material was
not identified. Since some of the unidentified peaks disappeared
after treatment of bile with inhibitors of
gamma-glutamyltranspeptidase, they probably represent degradation
products of GPB and BGTP (Jones et al., 1985).
The intestinal absorption of GPB and CPB was studied in rats by
infusing the compounds into the intestine via a biliary cannula.
When GPB was infused, both GPB and CPB were found in the blood in
approximately equal concentrations. Higher blood CPB concentrations
were found after CPB infusion than after GPB infusion (Gietl
et al., 1991).
In studies with radiolabelled hexachlorobutadiene, several
urinary metabolites were identified. The structure of these
metabolites further supported the hypothesis that
hexachloro-butadiene is bioactivated by glutathione conjugation.
ACPB was found to be the main metabolite (representing
approximately 80% of the radioactivity present in urine) excreted
after the administration of [14C] hexachlorobutadiene (200 mg/kg)
in female rats (Reichert & Schütz, 1986).