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CASRN: 72435

Update: August 1993

Current Massachusetts Regulatory Limit
MMCL = 0.04 mg/L (56 FR 3526: 1-30-91)

Federal Regulatory Limit
The MCL for methoxychlor is equal to the MCLG of 0.04 mg/L.

Basis for Criteria
The MCLG is derived 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.

RfD: 0.005 mg/kg/day
UF: 1000 (10 = inter-species; 10 = intra-species; 10 = steep dose-response curve and incompleteness of the database). MF = 1
Confidence in RfD: low

Critical Effects
Methoxychlor has produced effects in many organ systems when administered to animals at high doses, including the central nervous system, the kidney, the liver and the male reproductive system.

In a teratology study, female rabbits were dosed with 5.01, 35.5 or 251.1 mg/kg/day of methoxychlor during days 7 through 19 of gestation. Maternal toxicity was manifested as excessive loss of litters (abortions) and decreases in weight gain at the two highest doses. A NOAEL of 5.01 mg/kg/day was identified from this study (Kincaid Enterprises, Inc. 1986).

Cancer Assessment: 

The U.S. EPA has classified methoxychlor in U.S. EPA's Group D based upon a lack of human studies and inconclusive results in animal studies.


Analytical Information
: 0.01 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.

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).

Kincaid Enterprises, Inc. 1986. MRID NO. 00139929. Available from U.S. EPA.