This is a fact sheet about a chemical that may be found in some public or
private drinking water supplies. It may cause health problems if found
in amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What is Methoxychlor and how is it used?
Methoxychlor is a colorless organic solid with a slightly fruity odor. It
is an insecticide 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. It
has been used extensively in Canada for the control of biting flies, and
is also effective against mosquitoes and houseflies.
The list of trade names given below may help you find out whether you
are using this chemical at home or work.
Trade Names and Synonyms:
Why is Methoxychlor being regulated?
In 1974, Congress passed the Safe Drinking Water Act. This law requires
EPA to determine safe levels of chemicals in drinking water which do or
may cause health problems. These non-enforceable levels, based solely on
possible health risks and exposure, are called Maximum Contaminant Level
The MCLG for methoxychlor has been set at 40 parts per billion
(ppb) because EPA believes this level of protection would not cause any
of the potential health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a
Maximum Contaminant Level (MCL). MCLs are set as close to the MCLGs as
possible, considering the ability of public water systems to detect and
remove contaminants using suitable treatment technologies.
The MCL has been set at 40 ppb because EPA believes, given present
technology and resources, this is the lowest level to which water
systems can reasonably be required to remove this contaminant should it
occur in drinking water.
These drinking water standards and the regulations for ensuring
these standards are met, are called National Primary Drinking Water
Regulations. All public water supplies must abide by these regulations.
What are the health effects?
Short-term: EPA has found methoxychlor to potentially cause the following
health effects when people are exposed to it at levels above the MCL for
relatively short periods of time: central nervous system depression,
diarrhea, and damage to liver, kidney and heart tissue.
Long-term: Methoxychlor has the potential to cause the following
effects from a lifetime exposure at levels above the MCL: damage to
liver, kidney and heart tissue; retards growth.
How much Methoxychlor is produced and released to the environment?
Production of methoxychlor has decreased: from 3.7 million lbs. in 1978 to
700,000 lbs in 1982. Release of methoxychlor to the environment occurs
due to its use as an insecticide and from losses 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
What happens to Methoxychlor when it is released to the environment?
Methoxychlor does not tend to persist when released to soil or water. If
released to soil, methoxychlor will adhere to soils, though some may
leach into groundwater as suggested by the detection of methoxychlor in
some groundwater samples. It is broken down by soil and sediment
microbes under some conditions. In water, methoxychlor degrades quite
rapidly - within days compared to months as in soil. It may accumulate
in some shellfish, but not in fish.
How will Methoxychlor be detected in and removed from my drinking
The regulation for methoxychlor became effective in 1992. Between 1993 and
1995, EPA required your water supplier to collect water samples every 3
months for one year and analyze them to find out if methoxychlor is
present above 0.1 ppb. If it is present above this level, the system
must continue to monitor this contaminant.
If contaminant levels are found to be consistently above the MCL,
your water supplier must take steps to reduce the amount of methoxychlor
so that it is consistently below that level. The following treatment
methods have been approved by EPA for removing methoxychlor: Granular
How will I know if Methoxychlor is in my drinking water?
If the levels of methoxychlor exceed the MCL, 40 ppb, the system must
notify the public via newspapers, radio, TV and other means. Additional
actions, such as providing alternative drinking water supplies, may be
required to prevent serious risks to public health.
This is a factsheet about a chemical that may be found in some
public or private drinking water supplies. It may cause health problems
if found in amounts greater than the health standard set by the United
States Environmental Protection Agency (EPA).
Drinking Water Standards:
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water
|Mclg: 40 ppb (parts per billion)
Mcl: 40 ppb