Biomonitoring Summary

Hexachloroethane

CAS No. 67-72-1

General Information

Hexachloroethane is a solid that sublimates at room temperature. It is primarily used in combination with zinc or titanium oxides in military pyrotechnic or smoke generating devices, as an agent to degas or purify molten ores, as an ignition and explosive suppressant, and as a vulcanizing agent. Hexachloroethane is no longer produced in the U.S., and usage has declined since the 1970's (ATSDR, 1997). In the past, hexachloroethane was used as an ingredient in some pesticides, in fire extinguisher fluids, and as a veterinary anti-helminthic (ATSDR, 1997). Hexachloroethane can enter the atmosphere from emissions during its production and use, or as a byproduct from the chlorination of other hydrocarbons. Hexachloroethane is relatively persistent in the environment and has been detected a low levels in ambient air and rarely in drinking water systems (USGS, 2006).

For the general population, hexachloroethane exposure is infrequent and occurs by inhaling contaminated air. A less common pathway is the ingestion of contaminated drinking water. Workers in metal and alloy refining or pyrotechnic and smoke device production may be exposed to larger amounts. Hexachloroethane is absorbed by inhalation, dermal and ingestion routes, and it is preferentially distributed to fat, kidney and liver. Metabolism in the liver results in formation of trichloroacetic acid and trichloroethanol, which are excreted in urine (ATSDR, 1997). A small portion of unmetabolized hexachloroethane is excreted in the feces.

Human health effects from hexachloroethane at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Workers exposed to hexachloroethane reported irritation of the skin and mucous membranes, but no changes were noted in pulmonary function tests or in serum tests of renal, pancreatic, and liver function (Selden et al., 1994, Selden et al., 1997). Animals exposed to high air levels of hexachloroethane developed ataxia, facial twitching, tremors, and pneumonitis (Weeks et al., 1979). In feeding studies, animals developed dose-related abnormalities of the liver (enlargement, transaminase elevation, centrilobular necrosis) and kidney (tubular nephrosis and nephrocalcinosis) (ATSDR, 1997). Animal carcinogenicity studies show inconsistent evidence of hepatocellular carcinomas (NCI, 1978), an increased incidence of renal tumors in males (NTP, 1989), and no clear evidence of mutagenicity or genotoxicity. Hexachloroethane does not appear to be a reproductive or developmental toxicant in animal studies (ATSDR, 1997).

Hexachloroethane is classified as a possible human carcinogen by IARC and is reasonably anticipated to be a human carcinogen by NTP. The U.S. EPA has established drinking water and other environmental regulations for hexachloroethane. Workplace standards and guidelines for hexachloroethane have been established by OSHA and ACGIH, respectively. Information about external exposure (ie., environmental levels) and health effects is available from ATSDR at https://www.atsdr.cdc.gov/toxprofiles/index.asp.

Biomonitoring Information

Levels of hexachloroethane in the blood reflect recent exposure. Blood levels were not detectable in the NHANES 2003-2004 or 2005-2006 subsamples as has been the case in several other general population studies (Ashley et al., 1994; Buckley et al., 1997; Foster, 1995; Selden et al., 1993).

Finding a measureable amount of hexachloroethane in blood does not imply that the level of hexachloroethane causes an adverse health effect. Biomonitoring studies of blood hexachloroethane can provide physicians and public health officials with reference values so that they can determine whether or not people have been exposed to higher levels of hexachloroethane than levels found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.

References

Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for hexachloroethane. 1997 [online]. Available from URL: https://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=870&tid;=169 8/3/012

Ashley DL, Bonin MA, Cardinali FL, McCraw JM, Wooten JV. Blood concentrations of volatile organic compounds in a nonoccupationally exposed US population and in groups with suspected exposure. Clin Chem 1994;40(7 Pt 2):1401-1404.

Buckley TJ, Liddle J, Ashley DL, Paschal DC, Burse VW, Needham LL, Akland G. Environmental and biomarker measurements in nine homes in the lower Rio Grande Valley: multimedia results for pesticides, metals, PAHs, and VOCs. Environ Int 1997;23:705-32.

Foster WG. The reproductive toxicology of Great Lakes contaminants. Environ Health Perspect 1995;103 Suppl 9:63-9.

National Cancer Institute (NCI). Bioassay of hexachloroethane for possible carcinogenicity (CAS No. 67-72-1). NCI-CG-TR-68. Tech Report Ser No. 68. U.S. DHEW. Publ. No. (NIH) 78-1318. Bethesda MD. 1978. Available at URL: https://ntp.niehs.nih.gov/ntp/htdocs/LT_rpts/tr068.pdf. 8/3/12

National Toxicology Program (NTP). Toxicology and carcinogenesis studies of hexachloroethane (CAS No.67-72-1) in F344/N rats (gavage studies). Tech Report Ser No. 361. NIH Publication No. 89-2816. Research Triangle Part, NC: National Toxicology Program. Research Triangle Park NC, 1989 [online]. Available at URL: https://ntp.niehs.nih.gov/ntp/htdocs/lt_rpts/tr361.pdf. 8/3/12

Selden A, Kvamlof A, Bodin L, et al. Health effects of low level occupational exposure to hexachloroethane. J Occup Med Toxicol 1994;3(10):73-79.

Selden A, Nygren M, Kvarnlof A, Sundell K, Spangberg O. Biological monitoring of hexachloroethane. Int Arch Occup Environ Health 1993;65(1 Suppl):S111-S114.

Selden AI, Nygren Y, Westberg HB, Bodin LS. Hexachlorobenzene and octachlorostyrene in plasma of aluminium foundry workers using hexachloroethane for degassing. Occup Environ Med 1997;54(8):613-618.

United States Geological Survey (USGS). Volatile organic compounds in the nation's ground water and drinking-water supply wells. Reston VA. 2006 [online]. Available at URL: https://pubs.usgs.gov/circ/circ1292/. 8/3/012

Weeks MH, Angerhofer RA, Bishop R, Thomasino J, Pope CR. The toxicity of hexachloroethane in laboratory animals. Am Ind Hyg Assoc J 1979;40:187-199.