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cis-1,2-DICHLOROETHYLENE
CASRN: 156592

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.07 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase II rule (56 FR 3526; 1-30-91). 

Federal Regulatory Limit
The MCL is equal to its MCLG of 0.07 mg/L. 

Basis for Criteria
The MCLG is based on the potential for hepatic toxicity reported for compound-specific studies. The MCLG is derived using the 1,1-dichloroethylene RfD presented below and assuming that a 70 kg adult ingests 2 L/day of water. A relative source contribution factor of 20% is incorporated into this value.

RfD: 0.01 mg/kg/day
UF: 1000 (10 = LOAEL to NOAEL; 10 = interspecies; 10 = intraspecies)

There are limited data on the toxicity of cis-1,2-dichloroethylene. An AADI* was developed based on the toxicity of 1,1-dichloroethylene in response to data suggesting that the non-carcinogenic toxicity induced by the two isomers of dichloroethylene is likely to be no more severe than that of 1,1-dichloroethylene.


*In the November 13, 1985 Federal Register, what we refer to today as the RfD was known as the ADI (Allowable Daily Intake). The term AADI (Adjusted Allowable Daily Intake) was used to describe the concentration value derived from the ADI and assuming the weight of a consumer and the amount of drinking water consumed per day (i.e., in this case, a 70 kg adult who ingests 2 L/day of water). The AADI is equivalent to what is today known as the DWEL.



Critical Effects
Exposure to cis-1,2-dichloroethylene at high dose levels may result in liver and kidney effects. Because no satisfactory dose-response data are available from which to derive an AADI, the AADI for cis-1,2-dichloroethylene was derived based on data for 1,1-dichloroethylene and assuming 20% of the exposure is via drinking water:

Acute exposure to 1,1-dichloroethylene for relatively short periods of time at levels above the MCL may cause liver toxicity. Chronic exposure to 1,1-dichloroethylene may cause liver and kidney damage, fetal toxicity and cancer. A 2-year chronic study in which rats were exposed to 0, 50, 100 and 200 ppm of 1,1-dichloroethylene produced mid-zonal fatty accumulation in liver although no liver degeneration. A LOAEL of 100 ppm (i.e., 10 mg/kg/day) was identified from this study (Fed. Reg., 1985). 

Cancer Assessment
No long-term studies have been carried out on the carcinogenic potential of cis-1,2-dichloroethylene and there are generally non-positive results in mutagenic assays. This chemical has been classified under U.S. EPA’s Group D, not classifiable as to human carcinogenicity. 

Class
VOC

Analytical Information
PQL
: 0.005 mg/L

Analytical Methods
U.S. EPA Methods 502.2 (purge and trap GC)
524 (purge and trap GC/MS)

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at http://www.epa.gov/safewater/methods/methods.html

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at http://www.epa.gov/iris/. Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

References
Federal Register. November 13, 1985. Part IV. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations: Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms; Proposed Rule. (50 FR 46936).

Federal Register. July 8, 1987. National Primary Drinking Water Regulations - Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Final Rule. (52 FR 25690).

Federal Register. January 30, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Final Rule. (56 FR 3526).