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HEXACHLOROCYCLOPENTADIENE
CASRN: 77474

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.05 mg/L. ORS has adopted the MCL published by the U.S. EPA as part of the Phase V rule (57 FR 31776: 7-17-92).

Federal Regulatory Limit
The MCL of 0.05 mg/kg/day is equal to its MCLG.

Basis for Criteria
The MCLG is derived based on the RfD of 0.007 mg/kg/day 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.

RfD: 7 x 10-3 mg/kg/day (55 FR 30370; 7-25-90)
Exposure adjustment: multiplied by 5/7 to adjust the NOAEL from a 5-day to a 7-day exposure
UF: 1000 (10 = subchronic to chronic; 10 = interspecies; 10 = intraspecies) MF: 1 Confidence in RfD: Low

Critical Effects
Acute exposure to hexachlorocyclopentadiene for relatively short periods of time at levels above the MCL could result in gastrointestinal distress, and damage to liver, kidneys and heart. Chronic lifetime exposure to concentrations above the MCL may produce damage to the stomach and kidneys.

In a subchronic oral toxicity study, hexachlorocyclopentadiene was administered in corn oil by gavage to rats at doses of 0, 10, 19, 38, 75 or 150 mg/kg/day. The only effect noted was a slight depression of body weight at 10 mg/kg. A NOAEL of 10 mg/kg/day was identified from this study.

Cancer Assessment: 
There is no evidence that hexachlorocyclopentadiene has the potential to cause cancer from a lifetime exposure in drinking water.

Class
Chlorinated organic

Analytical Information
PQL
: 0.001 mg/L (57 FR 31776: 7-17-92)

Analytical Methods
U.S. EPA Methods 505; 508; 508.1; 525.2.

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. July 25, 1990. Part II. Environmental Protection Agency. 40 CFR Part 141 et al. National Primary and Secondary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Proposed Rule. (55 FR 30370)

Federal Register. July 17, 1992. Part III. Environmental Protection Agency. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Final Rule. (57 FR 31776).