Dense Nonaqueous Phase Liquids (DNAPLs)

Halogenated Alkanes

1,2-Dichloroethane

Human Health Toxicity

The synthetic chemical 1,2-DCA has industrial use as a feedstock for the production of other chlorinated compounds, particularly vinyl chloride. The chemical formerly had use as a degreasing agent, a component of varnishes, paints and paint strippers, and as a scavenger for lead in gasoline. Its use as a fumigant for agricultural products has been discontinued in the United States. 1,2-DCA enters the environment from fugitive emissions from plants that manufacture it, and/or use it as a feedstock. It is moderately persistent in the environment, being present in ambient air, drinking water and groundwater at low levels (IARC 1999).

The general population is exposed to 1,2-DCA via the inhalation of ambient air and by ingestion of contaminated drinking water. Drinking water used for showering, bathing, or cooking can expose the user by inhalation, dermal contact, and ingestion (ATSDR 2001). Although foodstuffs have been surveyed to determine if 1,2-DCA is present as a contaminant, it has rarely been found, and it is unlikely that it would bioaccumulate in the food chain (WHO 1998).

1,2-DCA is readily absorbed after ingestion, dermal exposure, and inhalation. Once absorbed, it is rapidly distributed throughout the body and metabolized. Laboratory rodent studies suggest the primary pathway for 1,2-DCA metabolism to be glutathione conjugation, a process generating metabolites that ultimately are excreted in urine. There is evidence that 1,2-DCA toxicity is mediated by reactive metabolites produced by glutathione conjugation, and that these metabolites bind to cellular macromolecules, disrupting normal function (ATSDR 2001).

Short-term (acute) exposures to high concentrations of 1,2-DCA have resulted in human deaths. At high concentrations, 1,2-DCA exerts an anesthetic, narcotic action on the central nervous system, and produces necrosis of the liver and kidney. Long-term oral exposure of laboratory rodents to the chemical resulted in the development of malignant and benign tumors, e.g., cancers of the fore-stomach, mammary gland, liver, endometrium, and lung were observed in test subjects. Epidemiological studies of the potential human carcinogenicity of 1,2-DCA in drinking water were confounded by the presence of other contaminants (ATSDR 2001).

No reliable studies of the effects of 1,2-DCA on human reproduction and development were found. Evidence from animal studies suggests that 1,2-DCA is toxic to the fetus only at doses that cause maternal toxicity. There is little evidence of teratogenicity (ATSDR 2001).

Both in vivo and in vitro genotoxicity tests show 1,2-DCA to be genotoxic. Structural damage to DNA has been reported from in vivo toxicity tests in rodents (ATSDR 2001).

EPA's Integrated Risk Information System (IRIS) classifies 1,2-DCA as "B2 - probable human carcinogen." The basis of this classification is the "induction of several tumor types in rats and mice treated by gavage and lung papillomas in mice after topical application."

EPA's maximum contaminant level (MCL) for 1,2-DCA 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 1,2-DCA for the following common exposure pathways:

Residential soil	4.3 E-01 mg/kg
Industrial soil	2.2 E-00 mg/kg
Residential air	9.4 E-02 ug/m3
Industrial air	4.7 E-01 ug/m3
Tapwater	5 E-01 ug/L

References

1,2-Dichloroethane
International Agency for Research on Cancer (IARC) Monographs, Vol 71, 1999

1,2-Dichloroethane (CASRN 107-06-2)
U.S. EPA, Integrated Risk Information System (IRIS)

1,2-Dichloroethane (Ethylene Dichloride) CAS No. 107-06-2
Report on Carcinogens, Twelfth Edition. U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program (NTP), 2011

Concise International Chemical Assessment Document No.1: 1,2-Dichloroethane
World Health Organization (WHO), 1998

Toxicological Profile for 1,2-Dichloroethane
Agency for Toxic Substances and Disease Registry (ATSDR), 297 pp, 2001

Ecological Toxicity

The Pesticide Action Network (PAN) Pesticides Database provides results of acute aquatic toxicity studies of 1,2-DCA (as ethylene dichloride) that were performed on a wide variety of organisms. The average acute toxicity of 1,2-DCA is summarized for each group of organisms. 1,2-DCA is listed as "not acutely toxic" to annelids, crustaceans, fish, and zooplankton (Kegley et al. 2009). Additional information on the aquatic toxicity of the chemical is provided by the National Park Service in its Environmental Contaminants Encyclopedia

Little information is available regarding the toxicity of 1,2-DCA to terrestrial wildlife receptors; however, an ecological screening level calculated to be protective of burrowing terrestrial animals is provided in Roy et al. (2009).

References

Ethylene Dichloride: 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, 2009

Dichloroethane-1,2 (EDC 1,2-Dichloroethane)
Irwin, R. et al.
Environmental Contaminants Encyclopedia, National Park Service, 1997

Evaluating Vapor Risk Intrusion in Ecological Risk Assessment
Roy M., S. Smith, and B. Elkland.
2009 DoD Environmental Monitoring & Data Quality Workshop, San Antonio, Texas, March 30 - April 3, 2009