Dense nonaqueous phase liquids (dnapls)

Halogenated Alkenes

cis 1,2-Dichloroethene

Human Health Toxicity

The compound 1,2-dichloroethene (1,2-DCE) exists in two forms (known as isomers): trans-1,2-dichloroethene (trans-1,2-DCE) and cis-1,2-dichloroethene (cis-1,2-DCE). Both isomers and mixtures of the isomers are used industrially as solvents and refrigerants, and in the manufacture of pharmaceuticals. The trans isomer of 1,2-DCE has a wider industrial use than either the cis form of the compound or mixtures of the isomers, and most toxicological studies have been performed on trans 1,2-DCE.

Workers in industries manufacturing 1,2-DCE may be exposed to the compound by inhaling contaminated air or by skin contact. The general public may be exposed to 1,2-DCE in drinking water derived from contaminated ground water and by breathing contaminated air in urban and industrial areas.

Although a single death from the inhalation of 1,2-DCE was reported in 1934, the isomeric composition of the vapor was not reported, and the length of exposure and 1,2-DCE concentration are unknown. No human health studies have been identified that are specific to the cis isomer of 1,2-DCE.

Data for 1,2-DCE suggest that the chemical is quickly absorbed via the lungs and metabolized in the liver. Animal studies show that the cis isomer is more rapidly metabolized than the trans isomer, although concomitant inhibitory effects on cytochrome P450 activity have been noted. The mechanism of excretion of cis-1,2-DCE is unknown for both animals and humans.

Very few animal studies address the toxicity of cis-1,2-DCE. In an acute study, a single inhalation exposure to 200 ppm cis-1,2-DCE prolonged the hexobarbital sleeping time and the zoxazolamine paralysis times in rats. The cis isomer of 1,2-DCE exerted a stronger effect than the trans form of the chemical. A three-month animal toxicological study showed changes in the weights of liver and kidney of the test subjects in response to cis-1,2-DCE given orally. However, the changes in organ weight were not accompanied by adverse changes in the histopathology of liver or kidney. This study was intermediate in length, not a chronic (or lifetime) study. No information on the reproductive or developmental effects of cis-1,2-DCE was identified.

The U.S. EPA Integrated Risk Assessment System does not provide chronic health assessments for the non-carcinogenic effects of this chemical by inhalation or oral exposure, but it does give a qualitative weight-of-evidence classification for the chemical. cis-1,2-DCE is classified "D," that is, the chemical is not classifiable as a human carcinogen. The basis of this classification is that there are no data for animals and humans, and mutagenicity assays have provided generally negative results.

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Adapted from:

Toxicological Profile for 1,2-Dichloroethene
Agency for Toxic Substances and Disease Registry (ATSDR)
Department of Health and Human Services, Atlanta, GA, 1996

cis-1,2-Dichloroethylene (CASRN 156-59-2)
Integrated Risk Information System
U.S. EPA, 1990

Ecological Toxicity

No studies were identified for the toxicity of cis-1,2-DCE in ecological receptors. Sediment screening values have been calculated for cis-1,2-DCE (U.S. EPA Mid Atlantic Risk Assessment Project). It is not expected that the compound is bioaccumulative. Taken together, the volatility of cis-1,2-DCE and the unlikelihood of its bioaccumulation suggest that it may not pose a substantial ecological hazard.

Human Health References

1,2-Dichloroethene in Drinking Water: Environmental Criteria Document
World Health Organization (WHO)
Report: WHO/SDE/WSH/03.04/21, 2003

A 10-page background document for the development of WHO drinking-water quality guidelines for 1,2-DCE.

cis-1,2-Dichloroethylene*
U.S. EPA, Substance Registry Services.
*Check for updates using 156-59-2 as the search term.

A database maintained by EPA that provides synonyms and some physical chemical data but is mostly devoted to providing links to regulatory resources and toxicological databases.

cis-1,2-Dichloroethylene (CASRN 156-59-2)
Integrated Risk Information System
U.S. EPA, 1990

An EPA developed and maintained database that contains toxicological data and discussions of effects for a variety of chemicals of regulatory interest.

Public Health Goal for cis- and trans-1,2-Dichloroethylene in Drinking Water
Office of Environmental Health Hazard Assessment
California Environmental Protection Agency (CalEPA)

A 38 page discussion of the health effects of 1,2-DCE for the purpose of providing the scientific basis for setting a maximum contaminant level in drinking water for California.

Toxicological Profile for 1,2-Dichloroethene
Agency for Toxic Substances and Disease Registry (ATSDR)
Department of Health and Human Services, Atlanta, GA, 1996

This profile provides information on human health effects, fate and transport, production, and uses of 1,2-DCE.

Toxicological Review of cis-1,2-Dichloroethylene and trans-1,2-Dichloroethylene in Support of Summary Information on the Integrated Risk Information System (IRIS)
Galizia, A. and D.C. Thompson.
EPA 635-R-09-006F, 174 pp, 2010

The toxicological review of cis-1,2-DCE and trans-1,2-DCE provides scientific support and rationale for the hazard and dose-response assessment in IRIS pertaining to chronic exposure to these compounds. It is not intended to be a comprehensive treatise on the chemical or toxicological nature of cis- and trans-1,2-DCE.

Ecological References

Aquatic Toxicity Reference Values
U.S. DOE
Manual ERD-AG-003 Revision 0, 1999

A 10-page Department of Energy document with toxicity reference value tables for surface water organisms.

Mid Atlantic Risk Assessment Project: Ecological Risk Assessment. Freshwater Sediment Screening Benchmarks
U.S. EPA

This document is a table for screening freshwater sediment contamination.

Preliminary Remediation Goals for Ecological Endpoints
U.S. DOE
Report: ES/ER/TM-162/R2, 1997

This 41-page document provides preliminary remediation goal values for surface water aquatic life, sediments, and soil values for various plants, mammals, earthworms, and birds.

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.