Hexachlorobutadeine
87-68-3
Hazard Summary
Hexachlorobutadiene is used mainly as an intermediate in the manufacture of rubber compounds. No
information is available on the health effects of hexachlorobutadiene in humans. Animal studies have
reported effects on the kidney and respiratory system from acute inhalation exposure, and effects on the
kidney from chronic oral exposure to hexachlorobutadiene. Animal studies have not reported
developmental or reproductive effects, other than a reduction in fetal body weights, from inhalation
exposure to hexachlorobutadiene. One study reported kidney tumors in rats exposed to
hexachlorobutadiene orally. EPA has classified hexachlorobutadiene as a Croup C, possible human
carcinogen.
Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS)
(3), which contains information on the carcinogenic effects of hexachlorobutadiene including the unit cancer risk
for inhalation exposure, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile
for Hexachlorobutadiene. (1)
Uses
s Hexachlorobutadiene is used mainly as an intermediate in the manufacture of rubber compounds. It is also
used in the production of lubricants, as a fluid for gyroscopes, as a heat transfer liquid, and in hydraulic
fluids. (1)
Sources and Potential Exposure
¦ Average concentrations of hexachlorobutadiene in ambient air were reported to be around 0.003 parts per
billion (ppb), while much higher levels (0.022 to 43 ppb) were reported near industries where
hexachlorobutadiene is formed or used. (1)
s Very small amounts of hexachlorobutadiene may be present in drinking water (< 1 ppb). (1)
a Levels of hexachlorobutadiene ranging from 0.1 to 4.7 milligrams per kilogram (mg/kg) have been found in
fish. (1)
a Persons working in industries where hexachlorobutadiene is formed or used may be exposed to the
chemical. (1)
Assessing Personal Exposure
a Hexachlorobutadiene or its breakdown products can be measured in urine or fat for several days after the
exposure has occurred. (1)
Health Hazard Information
Acute Effects:
a No information is available regarding the acute (short-term) effects of hexachlorobutadiene in humans
from inhalation or oral exposure. (1)
a Animal studies have reported effects on the kidney and respiratory system from acute inhalation exposure,

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while oral animal studies have reported kidney effects. (1)
s Tests involving acute oral and inhalation exposures of rats and mice have shown hexachlorobutadiene to
have high acute toxicity. (2)
Chronic Effects (Noncancer):
s No information is available regarding the chronic (long-term) effects of hexachlorobutadiene in humans
from inhalation or oral exposure. (1)
•	Animal studies have reported effects on the kidney and liver from chronic oral exposure to
hexachlorobutadiene. (1)
•	EPA has not established a Reference Concentration (RfC) for hexachlorobutadiene. (3)
¦ The California Environmental Protection Agency (CalEPA) has calculated a chronic inhalation reference
exposure level of 0.09 milligrams per cubic meter (mg/m ) for hexachlorobutadiene. The CalEPA reference
exposure level is a concentration at or below which adverse health effects are not likely to occur. It is not a
direct estimator of risk but rather a reference point to gauge the potential effects. At lifetime exposures
increasingly greater than the reference exposure level, the potential for adverse health effects increases. (6)
s The Reference Dose (RfD) for hexachlorobutadiene is under review by EPA. (3)
s EPA has calculated a provisional RfD of 0.0002 milligrams per kilogram body weight per day (mg/kg/d)
based on kidney effects in mice. The provisional RfD is a value that has had some form of Agency review
but is not on IRIS. The RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily oral exposure to the human population (including sensitive subgroups) that is likely to be without
appreciable risk of deleterious noncancer effects during a lifetime. (4)
Reproductive /Developmental Effects:
a No information is available regarding the developmental or reproductive effects of hexachlorobutadiene in
humans. (1)
a One study reported that the frequency of abnormal sperm morphology did not increase significantly over
controls in mice exposed to hexachlorobutadiene via inhalation. A study in rats exposed via inhalation
reported no embryotoxic effects, except for a reduction in fetal body weights. (1)
a Oral animal studies have reported reduced fertility, reduced fetal body weights, but no birth defects or
other developmental effects from hexachlorobutadiene exposure. (1)
Cancer Risk:
a No information is available regarding the carcinogenic effects of hexachlorobutadiene in humans or animals
from inhalation exposure. (1)
a One study reported kidney tumors in rats exposed to hexachlorobutadiene orally. (1,3)
a EPA has classified hexachlorobutadiene as a Group C, possible human carcinogen. (3)
a EPA uses mathematical models, based on animal studies, to estimate the probability of a person developing
cancer from breathing air containing a^specified concentration of a chemical. EPA calculated an inhalation
unit risk estimate of 2.2 x 1 0 (pg/m ) . EPA estimates that, if an individual were to continuously breathe
3-5	3
air containing hexachlorobutadiene at an average of 0.05 |jg/m (5x10 mg/m ) over his or her entire
lifetime, that person would theoretically have no more than a one-in-a-million increased chance of
developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that
breathing air containing 0.5 |jg/m (5x10 mg/m ) would result in not greater than a one-in-a-hundred
3-3	3
thousand increased chance of developing cancer, and air containing 5.0 |jg/m (5x10 mg/m ) would
result in not greater than a one-in-ten-thousand increased chance of developing cancer. For a detailed
discussion of confidence in the potency estimates, please see IRIS. ( 3)
a EPA has calculated an oral cancer slope factor of 0.078 (mg/kg/d) .(3)
Physical Properties

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s Hexachlorobutadiene is a colorless liquid with a turpentine-like odor. (5)
¦ The odor threshold for hexachlorobutadiene is 1 part per million (ppm). (1)
s The chemical formula for hexachlorobutadiene is C4CI6, and the molecular weight is 260.76 g/mol. (1) The
a vapor pressure for hexachlorobutadiene is 0.1 5 mm Hg at 25 °C, and it has an octanol/water partition
coefficient (log K ) of 4.78. (1)
ow
Conversion Factors (only for the gaseous form):
To convert concentrations in air (at 2 5 °C) from ppm to mg/m : mg/jn = (ppm) x (molecular weight of the
compound)/(24.45). For hexachlorobutadiene: 1 ppm = 1 0.7 mg/m . To convert concentrations in air from
|jg/m to mg/m : mg/m = (jjg/m ) x (1 mg/1,000 |jg).
Health Data from Inhalation Exposure
Hexachlorobutadiene
1000
100
10
OjOOI
OjOOOI
0.00001
Health numbers
Regulatory, advisory
numbers'*
LC (mice) (370 rrg/rft
NQAELd(107 mg/rn3)
AIHA ERPG -2
(107 mg/rr?)
AIHA ERPG-1
(32 mg/n?)
CalEPA chronic
reference
exposure level
(0j09 ring/m3)
I EsL
* HsL
I '
I I
EPA Cancer
Risk Level1
(10"6 excess
lifetinre risk =
5x10"5 ring/it?) I
ACGIH TLV,
WDSHREL
(0.24
mg/m5)
AIHA ERPG—American Industrial Hygiene Association's emergency response planning guidelines. ERPG 1 is the
maximum airborne concentration below which it is believed nearly all individuals could be exposed up to one hour
without experiencing other than mild transient adverse health effects or perceiving a clearly defined objectionable
odor; ERPG 2 is the maximum airborne concentration below which it is believed nearly all individuals could be
exposed up to one hour without experiencing or developing irreversible or other serious health effects that could
impair their abilities to take protective action.
ACGIH TLV—American Conference of Governmental and Industrial Hygienists'threshold limit value expressed as a

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time-weighted average; the concentration of a substance to which most workers can be exposed without adverse
effect.
LC (Lethal Concentration )—A calculated concentration of a chemical in air to which exposure for a specific
50	50
length of time is expected to cause death in 50% of a defined experimental animal population.
NIOSH REL—National Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-
recommended exposure limit for an 8- or 1 0-h time-weighted-average exposure and/or ceiling.
The health and regulatory values cited in this factsheet we re obtained in December 1 999.
a
Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
b
Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers
are nonregulatory values provided by the Government or other groups as advice. NIOSH, ACGIH, and AIHA numbers
are advisory.
c
^ These cancer risk estimates we re derived from oral data and converted to provide the estimated inhalation risk.
The NOAEL is from the critical study used as the basis for the CalEPA chronic reference exposure level.
References	Summary created in April 1 992, updated January 2000
1.	Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Hexachlorobutadiene.
U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1 994.
2.	U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS,
online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD.
1993.
3.	U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Hexachlorobutadiene.
National Center for Environmental Assessment, Office of Research and Development, Washington, DC.
1999.
4.	U.S. Environmental Protection Agency. Health Effects Assessment Summary Tables. FY 1 997 Update.
Solid Waste and Emergency Response, Office of Emergency and Remedial Response, Cincinnati, OH.
EPA/540/R-97-036. 1997.
5.	U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database).
National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1 993.
6.	California Environmental Protection Agency (CalEPA). Technical Support Document for the Determination
of Noncancer Chronic Reference Exposure Levels. Draft for Public Comment. Office of Environmental
Health Hazard Assessment, Berkeley, CA. 1 997.
7.	American Conference of Governmental Industrial Hygienists (ACGIH). 1 999 TLVs and BEIs. Threshold Limit
Values for Chemical Substances and Physical Agents. Biological Exposure Indices. Cincinnati, OH. 1 999.
8.	National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards. U.S.
Department of Health and Human Services, Public Health Service, Centers for Disease Control and
Prevention. Cincinnati, OH. 1 997.
9.	American Industrial Hygiene Association (AIHA). The AIHA 1 998 Emergency Response Planning Guidelines
and Workplace Environmental Exposure Level Guides Handbook. 1 998.

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