Technical Factsheet on Methoxychlor

Technical Factsheet on: METHOXYCHLOR
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: 0.04 mg/L
MCL: 0.04 mg/L
HAL(child): 1 day: 0.05 mg/L; Longer-term: 0.05 mg/L
Health Effects Summary
Acute: EPA has found methoxychlorto potentially cause central nervous system depression, diarrhea,
and damage to liver, kidney and heart tissue from short-term exposures at levels above the MCL.
Drinking water levels which are considered "safe" for short-term exposures: For a 10-kg (22 lb.) child
consuming 1 liter of water per day, upto a 7-year exposure to 0.05 mg/L.
Chronic: Methoxychlor has the potential to damage liver, kidney and heart tissue and to retard growth
from long-term exposure at levels above the MCL.
Cancer: There is no evidence that methoxychlor has the potential to cause cancer from lifetime
exposures in drinking water.
Usage Patterns
Methoxychlor is preferred to DDT for use on animals, in animal feed, and on DDT-sensitive crops such as
squash, melons, etc. Since methoxychlor is more unstable than DDT, it has less residual effect.
Compared to DDT, methoxychlor, is more toxic to some insects & less toxic to others. It has been used
extensively in Canada for the control of biting flies, and is also effective against mosquitoes and
houseflies.
Available information indicates production of methoxychlor has decreased: from 3.7 million lbs. in 1978 to
700,000 lbs in 1982.
In 1982 it was estimated that industries consumed methoxychlor as follows: 43 percent as an insecticide
for livestock and poultry, 29 percent on alfalfa crops and 29 percent on citrus.
Release Patterns
Release of methoxychlorto the environment occurs due to its use as an insecticide for home and garden
applications, livestock and poultry, alfalfa, soya beans, forests (Dutch Elm disease) , ornamental shrubs,
deciduous fruits and nuts, and vegetables Other sources of release may include loss during the
manufacture, formulation, packaging, and disposal of methoxychlor.
From 1987 to 1993, according to EPA's Toxic Chemical Release Inventory, methoxychlor releases to land
and water totalled only about 2000 lbs.

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Environmental Fate
Methoxychlor does not tend to persist when released to soil or water, and does not accumulate in fish.
If released to soil, methoxychlor is expected to remain immobilized primarily in the upper layer of soil
although a small percentage may migrate to lower depths, possibly into groundwater as suggested by the
detection of methoxychlor in some groundwater samples.
Measured soil sorption coefficient (Koc) values in various soil are as follows: 9700 to 41,000 in sand,
80,000 to 86,000 in coarse silt, 73,000 to 100,000 in medium silt, 80,000 to 100,000 in fine silt and 73,000
to 92,000 in clay. In another study, a Koc of 620 was found in a water-sediment system.
This range of Koc values suggests that methoxychlor would be moderately mobile to immobile in soil and
adsorb significantly to suspended solids and sediments in water. Methoxychlor was found to migrate as
much as 100 cm under conditions in which 95 to 97% of the residues remained in the top 10 cm of soil.
Under anaerobic soil/sediment conditions, biodegradation appears to be the dominant removal
mechanism. In sediments, methoxychlor was found to have a half-life of >100 days under relatively
aerobic conditions and < 28 days under anaerobic conditions. Half-lives in anaerobic soils are about 3
months. Methoxychlor may undergo indirect "sensitized" photolysis on the soil surfaces and it may
undergo chemical hydrolysis in moist soils (half-life > 1 year).
If released to water, methoxychlor may be removed or transported by several different mechanisms.
Methoxychlor may adsorb to suspended solids and sediments. It may undergo direct photolysis (half-life
4.5 months) or indirect "sensitized" photolysis (half-life <5 hours) depending upon the presence of
photosensitizers. Based on the Henry's law constant, volatilization of methoxychlor may be significant
(half-life 4.5 days from a shallow river).
Methoxychlor may also biodegrade in sediments, as mentioned above, but oxidation and chemical
hydrolysis are not expected to be significant fate processes.
If released to the atmosphere, methoxychlor may exist in either vapor or particulate form. Methoxychlor
may undergo reaction with photochemically generated hydroxyl radicals (estimated vapor phase half-life
3.7 hours) or physical removal by settling out or washing out in precipitation.
Significant bioconcentration has been measured in certain shellfish, insects, algae and fish, although fish
are generally reported to metabolize methoxychlor fairly rapidly and do not accumulate it.
The most probable route of exposure to methoxychlor would be inhalation or dermal contact during home
use of this insecticide, inhalation of airborne particulate matter containing methoxychlor or ingestion of
food or drinking water contaminated with methoxychlor.
Chemical/ Physical Properties
CAS Number: 72-43-5
Color/ Form/Odor: Colorless crystals with slightly fruity odor; available as: wettable powder; emulsifiable,
dust and aerosol concentrates; oil solutions
M.P.: 89 C B.P.: N/A
Vapor Pressure: very low

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Density/Spec. Grav.: 1.41 at 25 C
Octanol/Water Partition (Kow): Log Kow = 4.83, 4.91 and 5.08
Solubility: 0.10 mg/L of water at 25 C; Slightly soluble in water
Henry's Law Coefficient: 1.6x10-5 atm-cu m/mole at 25 C
Odor/Taste Thresholds: odor threshold is 4.7 mg/L in water
Soil sorption coefficient: measured Koc ranges from 9700 to 41,000 in sand to 80,000 to 100,000 in fine
silt; low mobility in soil
Bioconcentration Factor: BCFs of 1500 to 8500 in shellfish and algae, much lower in fish; expected to
bioconcentrate in aquatic organisms.
Trade Names/Synonyms: 2,2-bis(p-methoxyphenyl)-1,1,1-trichloroethane, dianisyl trichloroethane,
Dimethoxy-DDT, Methoxy-DDT, Chemform, Maralate, Methoxo, Methoxcide, Metox, Moxie
Other Regulatory Information
Monitoring For Ground/Surface Water Sources:
Initial Frequency- 4 quarterly samples every 3 years
Repeat Frequency- If no detections during initial round:
2 quarterly per year if serving >3300 persons;
1 sample per 3 years for smaller systems
Triggers - Return to Initial Freq. if detect at > 0.0001 mg/L
Analysis:
Reference Source Method Numbers
EPA 600/4-88-039 505; 508; 508.1; 525.2
Treatment- Best Available Technologies:
Granular Activated Charcoal
For Additional Information:
EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
Agency for Toxic Substances and Disease Registry - 404/639-6000
National Pesticide Hotline - 800/858-7378

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