Hexachlorocyclopentadiene
77-47-4
Hazard Summary
Hexachlorocyclopentadiene is an intermediate in the manufacture of some pesticides.
Hexachlorocyclopentadiene is very toxic following acute (short-term) oral and inhalation exposures. The
chemical is a severe eye, skin, and pulmonary irritant in humans, with effects including tearing of the eyes,
sneezing, salivation, blistering, burns, and cough from acute exposures. Limited information is available
on chronic (long-term), reproductive, developmental, and cancer effects of hexachlorocyclopentadiene in
humans. Animal studies have seen effects on the lung, liver, kidney, and blood. EPA has classified
hexachlorocyclopentadiene as a Croup D, not classifiable as to human carcinogenicity.
Please Note: The main source of information for this fact sheet is EPA's Health Assessment Document for
Hexachlorocyclopentadiene. (1) Other secondary sources include EPA's Integrated Risk Information System (IRIS) (2), which
contains information on oral chronic toxicity and the Reference Dose (RfD), and the Agency for Toxic Substances
and Disease Registry's (ATSDR's) Toxicological Profile for Hexachlorocyclopentadiene. (9)
Uses
•	Hexachlorocyclopentadiene is the key intermediate in the manufacture of some pesticides, including
heptachlor, chlordane, aldrin, dieldrin, and endrin. (5,6)
•	Hexachlorocyclopentadiene is also used in the manufacture of flame retardants and some resins and dyes.
(1,8)
Sources a nd Potential Exposure
•	Workers involved in the manufacture of hexachlorocyclopentadiene and during the manufacture of
products containing the chemical would have the highest exposure to hexachlorocyclopentadiene. (1,9)
•	Hexachlorocyclopentadiene has been detected at low levels in ambient air. The sources of the chemical in
air appear to be releases from manufacturing processes or incineration and landfilling of wastes containing
hexachlorocyclopentadiene. (1)
Assessing Personal Exposure
•	Laboratory tests can detect hexachlorocyclopentadiene in blood or urine. (1,9)
Health Hazard Information
Acute Effects:
•	Hexachlorocyclopentadiene is very toxic to humans. (2)
•	Hexachlorocyclopentadiene is a severe eye, skin, and pulmonary irritant in humans. Inhalation of the
chemical causes tearing, sneezing, and salivation, and skin contact can cause blisters and burns. (1,3)
•	The major target organ for acute hexachlorocyclopentadiene toxicity is the lung, with cough, chest pains,
and difficulty in breathing reported in humans. Nervousness, headaches, and abdominal cramps are other
symptoms reported from hexachlorocyclopentadiene toxicity. (1,3)
•	Tests involving acute exposure of rats have shown hexachlorocyclopentadiene to have extreme toxicity by

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inhalation exposure, moderate toxicity by oral exposure, and high to extreme toxicity by dermal
exposure.(3,4)
Chronic Effects (Noncancer):
•	Epidemiologic studies on workers have not shown any significant differences in mortality between workers
exposed to hexachlorocyclopentadiene and those in the general population. However, these studies are
limited by short follow-up periods, lack of data on cigarette smoking, and other factors. (1,2)
•	Chronic exposure to hexachlorocyclopentadiene, via inhalation, has been studied in animals, with effects
noted in the lung, liver, kidney, and blood. (1,3,9)
3
•	EPA has established a Reference Concentration (RfC) of 0.0002 milligrams per cubic meter (mg/m ) for
hexachlorocyclopentadiene, based on respiratory effects in rats. (2)
•	The Reference Dose (RfD) for hexachlorocyclopentadiene is 0.006 milligrams per kilogram body weight per
day (mg/kg/d) based on stomach lesions in rats.
•	The RfC and RfD are not direct estimators of risk but rather reference points to gauge the potential effects.
At exposures increasingly above these levels, the potential for adverse health effects increases. Lifetime
exposure above the RfC or RfD does not imply that an adverse health effect would necessarily occur. (2)
Reproductive/Developmental Effects:
•	No information is available regarding the reproductive or developmental effects of
hexachlorocyclopentadiene in humans. (1,3,9)
•	Animal studies have not reported birth defects from exposure to hexachlorocyclopentadiene by gavage
(placing the chemical experimentally in the stomach), and no information is available regarding
reproductive or developmental effects from inhalation exposure. (1 -3)
Cancer Risk:
•	As discussed above in the chronic effects section, epidemiologic studies have not demonstrated any
differences in mortality between hexachlorocyclopentadiene-exposed workers and the general population.
The observed mortality included deaths from cancer, as well as from other diseases. (1,2)
•	The National Toxicology Program (NTP) completed a 2-year inhalation study and concluded that there was
no evidence of carcinogenic activity in rats and mice. (5)
•	EPA has classified hexachlorocyclopentadiene as a Group D; not classifiable as to human carcinogenicity.
(2)
Physical Properties
¦ Hexachlorocyclopentadiene is a pale-yellow liquid with a characteristic pungent, musty odor; the odor
threshold is 0.03 parts per million (ppm). (1,7,8)
•	The chemical formula for hexachlorocyclopentadiene is C CI , and it has a molecular weight of 272.29
g/mol. (1,8)
•	The vapor pressure for hexachlorocyclopentadiene is 0.08 mm Hg at 2 5 °C, and the log octanol/water
partition coefficient (log K ) is 5.04. (1,8)
ow
Conversion Factors:
3	3
To convert concentrations in air (at 2 5 °C) from ppm to mg / m : mg / m = ^ppm) x (molecular weight of the
compound)/(24.45). For hexachlorocyclopentadiene: 1 ppm = 11.1 mg/m .
Health Data from Inhalation Exposure

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Hexachlorocyclopentadiene
200
100
Health numbers
¦ LCjj (rabbits, | i;5S mgftr)
NQAELC (rab'i i|1<5 rnghi1)
RfC
(QjOOOGmgfri1)
Rftjulatory, advisory
numbers'5
ACGIH TLV —American Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a
time-weighted average; the concentration of a substance to which most workers can be exposed without adverse
effects.
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 were obtained in December 1999.
a
Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
NIOSH and ACGIH numbers are advisory,
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 and ACGIH numbers are
advisory.
Summary created in April 1992, updated January 2000
References
1.	U.S. Environmental Protection Agency. Health Assessment Document for Hexachlorocyclopentadiene.
EPA/600/8-84/001 F. Environmental Criteria and Assessment Office, Office of Health and Environmental
Assessment, Office of Research and Development, Cincinnati, OH. 1 984
2.	U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on
Hexachlorocyclopentadiene. National Center for Environmental Assessment, Office of Research and
Development, Washington, DC. 1 999.
3.	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.
4.	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.
5.	National Toxicology Program (NTP). Toxicology and Carcinogenesis Studies of Hexachlorocyclopentadiene
(CAS No. 77-47-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). TR-437. 1994.
6.	U.S. Environmental Protection Agency. Health Effects Assessment Summary Tables. FY I 997

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Update. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment,
Office of Research and Development, Cincinnati, OH. 1 997.
7.	J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold
limit values and volatilities for 21 4 industrial chemicals in air and water dilution. Journal of Applied
Toxicology, 3(6):272-290. 1983.
8.	U.S. Environmental Protection Agency. Health and Environmental Effects Document for Chlorinated
Cyclopentadienes. ECAO-CIN-G029. Office of Solid Waste and Emergency Response, Washington, DC.
1988.
9.	Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for
Hexachlorocyclopentadiene.Draft for Public Comment. Public Health Service, U.S. Department of Health
and Human Services. Atlanta, GA. 1997.
1 0. 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. 1997.
1 1. 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.

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