Return to Standards Table

CASRN: 1024573

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.0002 mg/L (56 FR 3526; 1-30-91).

Federal Regulatory Limit
The MCL for heptachlor epoxide is based on its detection limit of 0.0002 mg/L. The MCLG is equal to zero.

Basis for Criteria
The MCL of 0.0002 mg/L is set at the PQL of 0.0002 mg/L for heptachlor epoxide. The MCLG is set to zero based on the evidence for carcinogenic potential.

Critical Effects
Heptachlor epoxide is the major metabolite of heptachlor. Symptoms of acute heptachlor intoxication include central nervous system effects such as tremors, convulsions, paralysis and hypothermia. Lower doses result in microsomal enzyme induction, hyperplasia, hepatic vein thrombosis and cirrhosis in mice (50 FR 46936; 11-13-85).

Cancer Assessment: 

The U.S. EPA has classified heptachlor epoxide as a Group B2 carcinogen based upon a study conducted with heptachlor, the parent compound, which indicated a significant increase in hepatocellular carcinomas in male mice as well as a highly significant dose-related trend in hepatocellular carcinomas between high and low dose female mice.

The MCL of 0.0002 mg/L is associated with a maximum individual risk* of 5 x 10-5 (56 FR 3526; 1-30-91).

* This information on risk is extrapolated from information provided in the January 30, 1991 Federal Register that a 1 x 10-4 Excess Lifetime Cancer Risk (ELCR) is associated with a concentration of 0.0004 mg/L.

Chlorinated pesticide

Analytical Information
: 0.0002 mg/L

Analytical Methods
505; microextraction GC
508; GC/ECD
525; 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 US EPA Drinking Water Analytical Methods

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 US EPA Current Drinking Water Health Advisories .

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 Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Dow Chemical Company. 1958. MRID No. 00061912. Available from U.S. EPA.

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. 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).