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DICHLORODIFLUOROMETHANE
CASRN: 75718

Update: August 1993

Current Massachusetts Regulatory Limit
ORSGL = 1.4 mg/L

Federal Regulatory Limit
The U.S. EPA has not published an MCL for dichlorodifluoromethane. 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 of 1.4 mg/L is based on the RfD presented below and assumes that a 70 kg adult ingests 2 L/day of drinking water. A relative source contribution factor of 20% is incorporated into the final value. The RfD is based on a long-term feeding study in rats and dogs (Sherman, 1974). There are no data for classification of the potential for cancer effects of dichlorodifluoromethane.

RfD: 2 x 10-1 mg/kg/day
UF: 100 (10 = interspecies; 10 = intraspecies)
MF: 1 Confidence in RfD: Medium

(U.S. EPA, 1990)

Critical Effects
The RfD of 0.2 mg/kg/day is based on a long-term feeding study in rats and dogs (Sherman 1974). Clinical biomedical, urological, hematological or histopathological evaluations were performed. The only reported effect was decreased body weight gain in female rats receiving 3000 ppm (150 mg/kg/day) of dichlorodifluoromethane. No other adverse effects were attributed to this compound in rats or dogs. A NOAEL of 300 ppm (15 mg/kg/day) was identified from this study.

Cancer Assessment: 
D

Dichlorodifluoromethane has been identified in U.S. EPA's Group D based on inadequate human evidence of carcinogenicity.

Class
Chlorofluorocarbon (CFC), VOC

Analytical Information
PQL
: 0.0003 mg/L

Analytical Methods
524.2; 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. January 14, 1991. Drinking Water Priority List. (56 FR 1470).

Sherman, H. 1974. Long-term feeding studies in rats and dogs with dichlorodifluoromethane (Freon 12 Freezant). Haskill Laboratory for Toxicology and Industrial Medicine Report No. 24-74.

U.S. EPA (U.S. Environmental Protection Agency). August 1, 1990. Integrated Risk Information System (IRIS). Washington, D.C. http://cfpub.epa.gov/ncea/iris/index.cfm.