Update: August 1993
Current Massachusetts Regulatory Limit
ORSGL = 0.07 mg/L.
Federal Regulatory Limit
The U.S. EPA has not published an MCL for 1,1-dichloroethane. This chemical is listed in 1/91 Drinking Water Priority List and may be regulated in the future (56 FR 14703) (Fed Reg, 1991).
Basis for Criteria
The ORSGL was developed based on the RfD presented below and assuming that a 70 kg adult ingests 2 L/day of water. A safety factor of 10 was added to calculation of non-cancer effects to account for possible cancer effects in humans. A relative source contribution factor of 20% is incorporated into this value.
RfD: 0.1 mg/kg/day (U.S. EPA, 1991)
UF: 1000 (10 = interspecies; 10 = intraspecies; 10 = subchronic to chronic)
(U.S. EPA, 1991)
1,1-dichloroethane has produced kidney damage in rats after long-term exposure to high concentrations in air. In addition, delayed growth of offspring occurred when animals inhaled 1,1-dichloromethane during pregnancy. Long-term oral exposure to very high concentrations of 1,1-dichloromethane has produced cancer (hemangiosarcomas) in rats. A NOAEL of 500 ppm (138 mg/kg/day) was identified from the rat inhalation study referenced above (U.S. EPA, 1991).
Cancer Assessment: C
U.S. EPA currently classifies 1,1-dichloroethane as a group C carcinogen. There is currently no potency factor available. The cancer classification is based on no evidence of cancer in human and limited data in animals. An NCI bioassay (1978) shows significant dose-related increases in the incidences of hemangiosarcoma at various rates and mammary carcinoma.
PQL: 0.0005 mg/L
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.
Federal Register. January 14, 1991. Drinking Water Priority List. (56 FR 1470).
NCI ( National Cancer Institute) 1978. Bioassay for 1,1-dichloroethane for possible carcinogenicity.
U.S. EPA (U.S. Environmental Protection Agency). 1991. HEAST (Health Effects Assessment Summary Tables). Office of Research and Development. Office of Emergency and Remedial Response.
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