Dense Nonaqueous Phase Liquids (DNAPLs)

Halogenated Alkenes

trans 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 is more widely used industrially 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 to the chemical and its concentration are unknown. Minimal information exists on the human health effects of trans-1,2-DCE. One low-level inhalation study was performed in 1936 on two human subjects with exposure durations of 5 and 10 minutes. Reported effects included nausea, drowsiness, fatigue, vertigo, and increased intracranial pressure. In another study by the same authors, exposure to trans-1,2,-DCE for 30 minutes caused a slight burning sensation in the eyes of the two human test subjects. However, for both studies, it is unclear whether the subjects were exposed to the chemical as a vapor or an aerosol. Likewise, the purity of the chemical, the isomeric form, and the exposure concentration are all unknown.

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 trans isomer is more slowly metabolized than the cis isomer and that it increases cytochrome P450 activities. The mechanism of excretion of trans-1,2-DCE is unknown for both animals and humans.

In an acute study, a single inhalation exposure to 200 ppm trans-1,2-DCE prolonged the hexobarbital sleeping time and the zoxazolamine paralysis times in rats. This suggests that the compound inhibits the mixed-function oxidase system of the liver. The trans isomer of 1,2-DCE was found to exert less effect than the cis form of the chemical. In contrast, oral administration of trans-1,2-DCE did not produce these effects on the liver enzyme system or hexabarbital-induced sleeping time.

The EPA Integrated Risk Information System has published a reference dose (RfD) of 2 x 10^-2 mg/kg-day for chronic oral exposure to trans-1,2-DCE. This dose is an estimate of a daily exposure to the human population (including sensitive subgroups within the population) that is likely to be without appreciable risk of deleterious effects during a lifetime. The principal study that supports the RfD is a 90-day drinking water study in mice. The principal effect was an increase in serum alkaline phosphatase in male mice. However, EPA states that confidence in the RfD value is low because of the lack of chronic studies and the absence of information on reproductive and developmental toxicity. No reference concentration for chronic inhalation exposure is given in the IRIS summary for trans-1,2-DCE, and the carcinogenic potential of the chemical has not been determined.

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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

trans-1,2-Dichloroethylene (CASRN 156-60-5)
Integrated Risk Information System
U.S. EPA, 1988

Ecological Toxicity

No studies were identified for the toxicity of trans-1,2-DCE to ecological receptors. Sediment screening values have been calculated for trans-1,2-DCE (U.S. EPA Mid Atlantic Risk Assessment Project). The compound is not expected to bioaccumulate. Taken together, the volatility of trans-1,2-DCE and the unlikelihood of its bioaccumulation suggest that it may not present 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.

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.

Toxicity Studies of trans-1,2-Dichloroethylene (CAS No. 156-60-5) Administered in Microcapsules in Feed to F344/N Rats and B6C3F₁ Mice
National Toxicology Program (NTP)
U.S. Department of Health and Human Services, 2002
(Abstract)

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.

trans-1,2-Dichloroethylene (CASRN 156-60-5)
Integrated Risk Information System
U.S. EPA, 1988

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

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.