Dense Nonaqueous Phase Liquids (DNAPLs)

Halogenated Alkanes

1,1,2-Trichloroethane

Human Health Toxicity

1,1,2-Trichloroethane, (1,1,2-TCA) enters the atmosphere as fugitive emissions from plants engaged in its manufacture and use, and in addition, is discharged to wastewater from these industries. The general population can be exposed to 1,1,2-TCA by inhaling urban ambient air, but the likelihood of exposure from contaminated drinking water is thought to be low (ATSDR 1989). Occupational exposure to 1,1,2-TCA could be expected to be via inhalation and/or dermal contact.

Animal studies indicate that 1,1,2-TCA is absorbed via inhalation, the gastrointestinal tract, and dermal contact. Once absorbed, fat-soluble 1,1,2-TCA is distributed to fat and those organs with a high fat content. Rodent studies show that the majority of absorbed 1,1,2-TCA is metabolized, and that most metabolism takes place in the liver. Compared to other small organochlorine compounds, little (<10 %) of the chemical is expired unchanged in exhaled air. Most of its products metabolism are excreted in urine and feces (Parker 2006).

Laboratory rodent studies indicate that 1,1,2-TCA exerts acute toxicity by any route of administration. Chronic toxicity studies using male and female rats and mice as test subjects showed no increase in non-cancerous tumors in either species. No cancerous tumors related to the compound were identified in rats, but a significant increase in cancers of the liver were seen in both sexes of mice, as well as a significant increase in adrenal cancers of female mice (Parker 2006). EPA's Integrated Risk Information System (IRIS) classifies 1,1,2-TCA as "C; possible human carcinogen."

No human studies on the developmental or reproductive toxicity of 1,1,2-TCA are available. One rodent study did not identify significant developmental or reproductive effects of 1,1,2-TCA (Parker 2006).

Standard in vivo and in vitro genotoxicity tests yield both positive and negative results for 1,1,2-TCA. There is some positive evidence for cytogenetic damage in fungus and isolated rat liver cells, but not in liver cells isolated from mice.

The maximum contaminant level (MCL) for 1,1,2-TCA in drinking water is 5 ug/L.

The Regional Screening Levels (formerly Preliminary Remediation Goals) posted by EPA Region 9 identify risk-based concentrations for 1,1, 2-TCA for the following common exposure pathways:

Residential soil	1.1 E-00 mg/kg
Industrial soil	5.3 E+01 mg/kg
Residential air	1.5 E-01 ug/m3
Industrial air	7.7 E-01 ug/m3
Tapwater	2.4 E-01 ug/l

References

1,1,2-Trichloroethane (CASRN 79-00-5)
U.S. EPA, Integrated Risk Information System (IRIS)

Public Health Goals for Chemicals in Drinking Water: 1,1,2-Trichloroethane
Parker, T.
California EPA, Office of Environmental Health Hazard Assessment, 29 pp, 2006

Toxicological Profile for 1,1,2-Trichloroethane
Agency for Toxic Substances and Disease Registry (ATSDR), 2021

Ecological Toxicity

Little information is available on the ecological toxicity of 1,1,2-TCA, and the few existing studies report the acute toxicity of the compound to aquatic receptors. These studies are summarized in the Pesticides Action Network Pesticide Database. 1,1,2-TCA is reported to be slightly toxic to crustaceans, fish, zooplankton, and the blue mussel (a mollusk), but not as acutely toxic to annelids, insects, and three species of mollusk (Kegley et al. 2010).

No studies of the toxicity of 1,1,2-TCA to terrestrial ecological receptors are available, but terrestrial toxicity reference values (TRVs) for the mouse and earthworm have been derived by DOE (1999).

References

1,1,2-Trichloroethane: Identification, Toxicity, Use, Water Pollution Potential, Ecological Toxicity, and Regulatory Information
Kegley, S.E., B.R. Hill, S. Orme, and A.H. Choi.
PAN Pesticide Database. Pesticide Action Network, San Francisco, CA, 2010

Terrestrial Toxicity Reference Values
U.S. DOE
Manual ERD-AG-003 Revision 0 (TRVs), 1999

This 13-page Department of Energy manual provides toxicity reference values for earthworms, various mammals, and various bird species.