Hexachloroethane 

CAS NO. 67-72-1 

First Listed in the Seventh Annual Report on Carcinogens 12 Apr 00

Reasonably anticipated to be a human carcinogen

Hexachloroethane is reasonably anticipated to be a human carcinogen sufficient evidence of carcinogenicity in experimental animals (NTP 361, 1989). When administered in corn oil by gavage, hexachloroethane induced increased incidences of renal neoplasms and marginally increased incidences of adrenal pheochromocytoma in male rats. There was no corresponding evidence of carcinogenic activity in female rats. A significant increase in incidence of hepatocellular carcinomas was observed in similarly treated mice of both sexes (IARC V.20, 1979).

There is no data available to evaluate the carcinogenicity of hexachloroethane in humans (IARC V.20, 1979).

PROPERTIES

Hexachloroethane is a colorless, nonflammable, crystalline solid with a camphor-like odor that is generally chemically inert. It is insoluble in water, but is soluble in ethanol, diethyl ether, benzene, chloroform, and oils. Hexachloroethane may emit tetrachloroethylene, carbon tetrachloride, and chlorine when thermally decomposed. Powdered zinc reacts violently with hexachloroethane in alcoholic solution to yield the metal chloride and tetrachloroethylene.

USE

The applications of hexachloroethane have been quite extensive. It has been used as an anthelmintic to treat fascioliasis (liver flukes) in sheep and cattle, although use is very limited since approval from the FDA was withdrawn in 1971. It has also been added to the feed of ruminants to prevent methanogenesis and increase feed efficiency. Hexachloroethane has been used in metal and alloy production, mainly in refining aluminum alloys. It is also used for removing impurities from molten metals, recovering metals from ores or smelting products, and improving the quality of various metals and alloys. Hexachloroethane has been used as a degassing agent for magnesium, and it inhibits the explosiveness of methane and the combustion of ammonium perchlorate. Hexachloroethane mixed with stochiometric amounts of zinc, zinc oxide, or titanium dioxide is commonly used in military smoke munition. Hexachloroethane is also a constituent of candles, grenades (for the generation of "smoke" or "fog"), and pyrotechnics. Hexachloroethane has been used as an additive in combustible liquids (ignition suppressant) and fire extinguishing fluids (smoke generated by hexachloroethane is used as a flame retardant). Hexachloroethane has had a variety of applications as a polymer additive. It has flame-proofing qualities, increases sensitivity to radiation cross linking, and it is used as a vulcanizing agent. Added to polymer fibers, hexachloroethane acts as a swelling agent and increases affinity for dyes. Hexachloroethane has also served as a fixer for some types of experimental photography and xerography.

Miscellaneous applications of hexachloroethane are also quite extensive. It is an initiator in the formation of polyethylenes and has been used in the preparation of certain catalysts. Hexachloroethane, when added to spectrographic samples, improves analysis. Hexachloroethane reduces corrosion when added to flue gas cleaning systems and oil when used as a coating on metal machinery. It increases specific gravity when added to drilling mud used in oil and gas wells. It is a main ingredient in production of some types of synthetic diamonds. Other uses of hexachloroethane in the U.S. have included: a plasticizer for cellulose esters; an accelerator in rubber; a retardant in fermentation processes; a moth repellent; a component of submarine paints; a constituent of various fungicidal and insecticidal formulations; and a softening agent in hair setting and styling agents. With the possible exception of use for smoke generation, only limited quantities of hexachloroethane are used in these applications.

Prior to 1979, more than 50% of the hexachloroethane distributed was used by the military to produce smoke and pyrotechnic devices. It was estimated that an average of 192,802 lb of hexachloroethane was used annually at the major facility manufacturing these devices between 1966 and 1977.

The USITC does not currently list any producers or production volumes for hexachloroethane. Hexachloroethane is apparently not manufactured as an end-use product in the United States (NTP 361, 1989). TR196 (1996) identified 12 companies that did produce hexacholorethane as a byproduct in the chlorination processes of saturated and unsaturated two-carbon hydrocarbons. Two US Army desert depot or arsenals were also identified as producing hexachloroethane either as an impurity or as a by-product. U.S. imports of hexachloroethane increased from the 1970s to the 1980s. Imports were reported at 1.6 million lb in 1976, more than 2 million lb in 1977, approximately 2.5 million lb in 1985 and approximately 4.5 million lb in 1986 (USHHS, 1997). Imports lagged in 1989 as total U.S. imports for hexachloroethane and tetrachloroethane combined only exceeded 1.5 million lb (USDOC Imports, 1990).

The primary routes of potential human exposure to hexachloroethane are through inhalation or drinking contaminated water. Hexachloroethane exposure to the general public is expected to be relatively low. Hexachloroethane was not found in the blood of 13 individuals even though the method used had a detection limit of 0.028 ppb (Ashley et al. 1992). Occupational exposure of workers in industrial facilities manufacturing or using hexachloroethane may occur through inhalation or dermal absorption.

Hexachloroethane is fairly persistent in the atmosphere. Half-life in some bodies of water is less than one day (USHHS, 1997). Hexachloroethane has been detected in river water, drinking water, industrial effluent water, and effluent from sewage treatment plants that use chlorination (NTP 361, 1989). Hexachloroethane also was detected in waste streams and stack emissions of incinerators burning pesticide-related wastes. However, only one sample of surface water from 204 sites in the vicinity of heavily industrialized areas contained hexachloroethane at detectable levels. In 1981, the findings of a collaborative study undertaken by the National Cancer Institute, U.S. Department of Energy, Mitre Corporation, and SRI International identified hexachloroethane as a contaminant in drinking water. Chemical analysis of the organic phase of Love Canal chemical dump site leachate showed a small amount of hexachloroethane (0.66% of total of organic phase) (NTP 361, 1989). While hexachloroethane has been detected in the atmosphere and in drinking water at low levels, rarely is it found in surface waters or biota, ambient soil, sediments or commercial food products. While bioconcentration in fish has been reported, biomagnification through the food chain is unlikely (USHHS, 1997). TR196 (1996) reported that total industrial release into the environment in 1996 was 4937 lb. Total air release was 2881 lb, total water release was 32 lb, and total underground injection was 2024 lb.

In 1976, an initial list of 671 potential airborne pollutants was developed. From this list, only 77, including hexachloroethane, have actually been measured in ambient air (NTP 361, 1989). Class and Ballschmitter (1987) analyzed several atmospheric halocarbons in air samples from sampling sites distant from inhabited areas in the region of the North and South Atlantic and the Indian Oceans and estimated that the emissions of hexachloroethane into the northern hemisphere were less than 1 kiloton per year and that the tropospheric lifetime was very long.

A NIOSH survey lists the real estate, paper and allied products, lumber and wood products, and amusement and recreation services industries as those that use hexachloroethane. Workers who use this chemical include cleaning people, millwrights, machine operators, plumbers and pipefitters, and electricians. The U.S. Army reportedly uses relatively large amounts in pyrotechnics and smoke devices. In an occupational hazard survey conducted from 1972 to 1974, it was estimated that about 1,500 workers were potentially exposed to hexachloroethane. Occupational health standards for exposure to atmospheric hexachloroethane require that exposure not exceed an 8-hour time weighted average of 10 mg/m3 (1 ppm). The National Occupational Exposure Survey conducted by NIOSH from 1980 to 1983 indicated that 8,515 workers, including 575 women, were potentially exposed to hexachloroethane in 1980. This estimate was derived from observations of the actual use of the compound (62% of total observations) and the use of trade name products known to contain the compound (38%) (NIOSH, 1984).

Additional information on exposure to hexachloroethane may be found in the Toxicological Profile for Hexachloroethane (ATSDR, 1994e)

EPA regulates hexachloroethane under the Clean Air Act (CAA), Clean Water Act (CWA), Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Resource Conservation and Recovery Act (RCRA), and Superfund Amendments and Reauthorization Act (SARA). Hexachloroethane is a toxic pollutant of air and water. EPA has established water quality criteria for hexachloroethane, effluent guidelines, rules for regulating hazardous spills, general threshold amounts, and requirements for handling and disposal of hexachloroethane wastes. A reportable quantity (RQ) of 1 lb has been established for hexachloroethane under CWA and RCRA and an RQ of 100 lb under CERCLA/SARA. Hexachloroethane is regulated as a hazardous constituent of waste water under RCRA. The OSHA final rule regulates both the permissible exposure limit (PEL) and 8-hr time-weighted average (TWA) to 1 ppm with the note of potential skin absorption. OSHA regulates hexachloroethane under the Hazard Communication Standard and as a chemical hazard in laboratories. Regulations are summarized in Volume II, Table B-70.