Public Health Statement for Methoxychlor
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This Public Health Statement is the summary chapter from the Toxicological Profile for Methoxychlor. It is one in a series of Public Health Statements about hazardous substances and their health effects. A shorter version, the ToxFAQsTM, is also available. This information is important because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. For more information, call the ATSDR Information Center at 1-800-232-4636.
This public health statement tells you about methoxychlor and the effects of exposure.
The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the nation. These sites make up the National Priorities List (NPL) and are the sites targeted for long-term federal cleanup activities. Methoxychlor has been found in at least 58 of the 1,613 current or former NPL sites. However, the total number of NPL sites evaluated for methoxychlor is not known. As more sites are evaluated, the sites at which methoxychlor is found may increase. This information is important because exposure to methoxychlor may harm you and because these sites may be sources of exposure.
When a substance is released from a large
area, such as an industrial plant, or from a container, such
as a drum or bottle, it enters the environment. This release
does not always lead to exposure. You are exposed to a substance
only when you come in contact with it. You may be exposed
by breathing, eating, or drinking the substance, or by skin
If you are exposed to methoxychlor, many
factors determine whether you'll be harmed. These factors
include the dose (how much), the duration (how long), and
how you come in contact with it. You must also consider the
other chemicals you're exposed to and your age, sex, diet,
family traits, lifestyle, and state of health.
What is methoxychlor?
Methoxychlor, also known as DMDT, Marlate®, or Metox®, is a manufactured chemical now used in the
United States for controlling insects. Methoxychlor is effective
against flies, mosquitos, cockroaches, and a wide variety
of other insects. This insecticide is used on agricultural
crops and livestock, and in animal feed, barns, and grain
storage bins. Some pesticide products that contain methoxychlor
are used for controlling insects in gardens or on pets.
Pure methoxychlor is a pale-yellow powder
that has a slightly fruity or musty odor. It does not readily
evaporate into air or dissolve in water. Pesticide workers
usually dissolve methoxychlor in a petroleum-based liquid
and apply it as a spray, or they mix it with other chemicals
and apply it as a dust. Application of methoxychlor as an
insect killer accounts for most of the methoxychlor that enters
the environment. Since the use of methoxychlor is highly seasonal,
the amount that is released to the environment tends to be
greater during periods of insect control (spring and summer).
Some methoxychlor is released to the environment from chemical
manufacturing plants that make methoxychlor or from manufacturing
sites that formulate products containing methoxychlor. A small
amount may also be released from hazardous waste sites where
it has been disposed of.
More complete information on the sources, properties, and uses of methoxychlor can be found in Chapters 4 and 5 of this profile.
What happens to methoxychlor when it enters the environment?
Methoxychlor does not occur naturally in the environment. Most methoxychlor enters the environment when it is applied to forests, agricultural crops, and farm animals. Methoxychlor can be applied to forests and crops by aerial spraying. This process can contaminate nearby land and water. Methoxychlor that is released into the air will eventually settle to the ground, although some may travel long distances before settling. Rain and snow cause methoxychlor to settle to the ground more quickly.
Once methoxychlor is deposited on the ground, it becomes bound to the soil. Because of this, methoxychlor does not tend to move rapidly from one place to another. However, soil particles that contain methoxychlor can be blown by the wind or be carried by rainwater or melted snow into rivers or lakes. Most methoxychlor stays in the very top layer of soil, but some of the products that it breaks down into may move deeper into the ground. Smaller amounts of methoxychlor in air may settle directly into rivers, lakes, and other surface waters. Once methoxychlor is in water, it usually binds to sediments or organic matter and settles to the bottom.
Methoxychlor is broken down in the environment
by several processes. However, these processes are slow and
may take months. In soil, some methoxychlor is broken down
by bacteria and other microorganisms, and some is broken down
by a reaction with water or materials in soil. In air and
water, some methoxychlor is broken down by sunlight. Methoxychlor
is also broken down by reactive chemicals normally present
in the air. Some of the breakdown products are capable of
producing harmful effects similar to those caused by exposure
Methoxychlor can accumulate in some living
organisms, including algae, bacteria, snails, clams, and some
fish. However, most fish and animals change methoxychlor into
other substances that are rapidly released from their bodies,
so methoxychlor does not usually build up in the food chain.
More complete information on the environmental
fate of methoxychlor can be found in Chapter 6 of this
How might I be exposed to methoxychlor?
Most people are not exposed to methoxychlor
on a regular basis. Although methoxychlor is not usually detected
in air, people can be exposed to low levels of methoxychlor
by inhaling dusts and aerosols in air surrounding areas where
methoxychlor is used. Since methoxychlor is not usually detected
in surface or well water sources, exposure from drinking water
is not likely to be significant for the general public. However,
surface water that has been treated with methoxychlor for
control of insect larvae should be avoided until methoxychlor
residue has decreased below the level of concern. Methoxychlor
is not usually found in food. However, low levels are sometimes
detected in foods obtained from areas where methoxychlor has
Fish usually do not contain detectable
levels of methoxychlor, but people who eat fish caught in
water contaminated with methoxychlor may occasionally have
above-average intakes of methoxychlor.
People who make or use methoxychlor may
be exposed by breathing in the dust or aerosol, or by getting
it on their skin. For example:
- If you work in a factory that makes methoxychlor or products
containing methoxychlor, you could be exposed to methoxychlor
in air or on your skin during work hours. The government
has estimated that approximately 3,400 people may be exposed
to methoxychlor in this way.
- Methoxychlor is present in some pesticides used for home
gardening or for spraying pets (such as cats and dogs).
If you use these products, you could be exposed to above-average
levels of methoxychlor in air and on your skin.
- If you live or work on or near a farm where methoxychlor
is used on crops or livestock, you could be exposed to above-average
levels of methoxychlor in air, soil, and possibly in water.
If you live near a hazardous waste site
that contains methoxychlor, you could be exposed by breathing
in methoxychlor from the air, by swallowing contaminated soil
or water, or by getting contaminated soil or water on your
skin. The amount of exposure you receive depends on conditions
specific to where you live and can only be evaluated on a
More information on how you may be exposed
to methoxychlor can be found in Chapter 6.
How can methoxychlor enter and leave my body?
Scientists do not know how much or how
quickly methoxychlor is absorbed into your body if you breathe
it in or if it contacts your skin. If you get methoxychlor-contaminated
soil or water on your skin, some of it may pass through your
skin and enter your bloodstream. If you breathe methoxychlor-containing
dust into your lungs, some of the dust will deposit in your
lungs. Dust that deposits in the upper part of your lungs
is likely to be coughed up and swallowed. Dust that deposits
deep in your lungs is likely to remain long enough for the
methoxychlor to pass through the lining of your lungs and
enter your bloodstream. If you swallow food, water, or soil
containing methoxychlor, most of it will rapidly pass through
the lining of your stomach and intestines and enter your bloodstream.
Once methoxychlor enters your bloodstream,
it is distributed to all parts of your body. Animal studies
suggest that methoxychlor is changed into other substances
called metabolites by your liver. Most of these metabolites
leave your body within 24 hours, primarily in your feces,
with lesser amounts in your urine. Some methoxychlor can enter
the fat in your body, but methoxychlor does not accumulate
or build up in fat.
More information on how methoxychlor
enters and leaves your body can be found in Chapter 3.
How can methoxychlor affect my health?
To protect the public from the harmful
effects of toxic chemicals and to find ways to treat people
who have been harmed, scientists use many tests.
One way to see if a chemical will hurt
people is to learn how the chemical is absorbed, used, and
released by the body; for some chemicals, animal testing may
be necessary. Animal testing may also be used to identify
health effects such as cancer or birth defects. Without laboratory
animals, scientists would lose a basic method to get information
needed to make wise decisions to protect public health. Scientists
have the responsibility to treat research animals with care
and compassion. Laws today protect the welfare of research
animals, and scientists must comply with strict animal care
Very few reports exist on the health
effects of methoxychlor in humans. In animals, exposure to
high levels of methoxychlor caused effects on the nervous
system. These effects included tremors, convulsions, and seizures.
These effects are probably caused by methoxychlor itself and
not by its metabolites. Because methoxychlor is quickly transformed
into metabolites by the liver, you are not likely to experience
nervous system effects unless you are exposed to very high
Some of the breakdown products of methoxychlor
cause effects similar to those produced by estrogen. Estrogens
are naturally occurring hormones that are important in women
for the development and maintenance of their ovaries, uterus,
and breasts, and also play a role in the development of the
reproductive system in men. Studies in animals show that exposure
to methoxychlor adversely affects the ovaries, uterus, and
mating cycle in females, and the testes and prostate in males.
Fertility is decreased in both female and male animals. These
effects can occur both in adult animals and in developing
animals exposed prenatally or shortly after birth. Effects
of methoxychlor on reproduction have been studied mainly in
animals given methoxychlor in food or water, but it is expected
that these effects could occur following inhalation and skin
exposures as well. Likewise, it is expected that reproductive
effects seen in animals could occur in humans exposed to methoxychlor,
but this has not been reported.
There is not enough information available
to definitely state whether methoxychlor causes cancer. However,
most of the information that we have indicates that methoxychlor
does not cause cancer. One very small study in humans indicated
a possible link with increased incidence of leukemia. However,
a definitive connection between a cause of leukemia and exposure
to methoxychlor cannot be made with so little information.
Most animal studies with methoxychlor have been negative for
cancer. Therefore, the International Agency for Research on
Cancer (IARC) has determined that methoxychlor is not classifiable
as to its carcinogenicity to humans. Similarly, the EPA has
determined that methoxychlor is not classifiable as to its
More information on how methoxychlor
can affect your health can be found in Chapters 2 and
How can methoxychlor affect children?
This section discusses potential health
effects from exposures during the period from conception to
maturity at 18 years of age in humans.
Children are likely to be exposed to
methoxychlor in the same way as adults, primarily from low-level
contamination of food. Other possible sources of methoxychlor
exposure for children include swallowing soil, crawling on
home carpets, breathing in house dust and residues from methoxychlor-containing
pesticides used for home gardening or pet care, and touching
work clothes or equipment used to apply products that contain
Little information is available regarding
the effects of methoxychlor in children. Exposure to very
high doses of methoxychlor may cause nervous system effects
such as tremors or convulsions. The reproductive system is
likely to be the most sensitive target of methoxychlor in
both adults and children. Methoxychlor is metabolized in the
liver to substances that act like estrogen in the body. This
probably occurs similarly in children and adults. Estrogens
are naturally occurring substances that are necessary for
the proper development and function of the male and female
reproductive system. Elevated levels of estrogen, or substances
like methoxychlor that mimic estrogen, have been shown to
disrupt reproductive development and function in animals.
This has resulted in early puberty in females, delayed puberty
in males, disruption of the reproductive cycle in females,
decreased fertility in males and females, and altered hormone
levels in the blood. These effects can happen when the exposure
occurs before birth or between birth and sexual maturity.
It is thought that similar effects could occur in humans,
but this has not been reported.
There is no evidence in humans that methoxychlor
causes birth defects. Methoxychlor does not cause structural
birth defects in animals, but exposure to high levels of methoxychlor
during pregnancy caused reduced survival of fetuses. It is
unclear whether or at what level of exposure this might occur
Methoxychlor or its metabolites can probably
be transferred from a pregnant mother to a developing fetus
in animals, since abnormal reproductive development has been
seen in the newborn animals born to mothers exposed during
pregnancy. In animals, methoxychlor and metabolites of methoxychlor
that are estrogenic can be transferred from a nursing mother
to her newborn babies through breast milk. Methoxychlor and
its metabolites can probably cross the placenta and have been
detected in human breast milk.
How can families reduce the risk of exposure to methoxychlor?
If your doctor finds that you have been
exposed to significant amounts of methoxychlor, ask whether
your children might also be exposed. Your doctor might need
to ask your state health department to investigate.
You can purchase products containing
methoxychlor as an over-the-counter pesticide product to apply
yourself. If you do purchase such a product, be sure that
the product is in an unopened pesticide container that is
labeled and contains an EPA registration number. If you plan
to apply the pesticide indoors, make sure that the pesticide
is approved for indoor use. Be sure to carefully follow the
instructions on the label and follow any warning statements.
Children can be exposed to pesticides by entering a room or
playing on a lawn too soon after a pesticide has been applied.
Carefully read and follow the directions on the pesticide
label about how long to wait before re-entering the treated
area. If you or any member of your family feels sick after
a pesticide has been applied, consult your doctor or local
poison control center. Pesticides and household chemicals
should be stored out of reach of young children to prevent
unintentional poisonings. Always store pesticides and household
chemicals in their original labeled containers. Never store
pesticides or household chemicals in containers that children
would find attractive to eat or drink from, such as old soda
bottles. Your children may be exposed to methoxychlor if an
unqualified person applies pesticides containing it around
your home. Make sure that any person you hire is licensed.
Your state licenses each person who is qualified to apply
pesticides according to EPA standards. Ask to see the license.
Also ask for the brand name of the pesticide, a Material Safety
Data Sheet (MSDS), the name of the product's active ingredient,
and the EPA registration number. Ask what are the EPA approved
uses. This information is important if you or your family
react to the product.
Children may be exposed to methoxychlor
if they come in contact with family pets or farm animals that
have been treated with the pesticide. Exposure may occur through
skin contact with the animal or application devices, or by
breathing vapor from animal-dipping solutions and baths. Dipping
solution that contains methoxychlor should be disposed of
according to the directions on the product label. Waste methoxychlor
should never be discarded in any area where children might
Although methoxychlor has been found
in some foods, it occurs at very low levels. To reduce your
family's risk of exposure, you should thoroughly wash all
fruits and vegetables before preparing them for consumption.
Methoxychlor may be released to soil
and water, especially near hazardous waste sites. Hazardous
waste sites are often clearly marked, but children have a
tendency to ignore signs that are designed to alert us to
dangers. Your children should be encouraged not to play at
or near hazardous waste sites. Low levels of methoxychlor
have also been found in carpet and house dust.
Is there a medical test to determine whether I have been exposed to methoxychlor?
Specific and sensitive tests have been
developed to detect methoxychlor in blood, fat, semen, and
breast milk of exposed individuals. Because methoxychlor is
removed from the body relatively quickly, these tests are
only useful in detecting recent exposures (within 24 hours)
and are not useful for detecting past exposures to methoxychlor.
These tests currently cannot be used to estimate how much
methoxychlor you have been exposed to or whether adverse health
effects will occur. These tests are not usually performed
in a doctor's office because special equipment is required
and samples must be sent to a laboratory for testing.
More information on tests that detect
methoxychlor and its metabolites can be found in Chapter 7.
What recommendations has the federal government made to protect human health?
The federal government develops regulations
and recommendations to protect public health. Regulations
can be enforced by law. Federal agencies that develop
regulations for toxic substances include the Environmental
Protection Agency (EPA), the Occupational Safety and Health
Administration (OSHA), and the Food and Drug Administration
(FDA). Recommendations provide valuable guidelines to protect
public health but cannot be enforced by law. Federal
organizations that develop recommendations for toxic substances
include the Agency for Toxic Substances and Disease Registry
(ATSDR) and the National Institute for Occupational Safety
and Health (NIOSH).
Regulations and recommendations can be
expressed in not-to-exceed levels in air, water, soil, or
food that are usually based on levels that affect animals;
then they are adjusted to help protect people. Sometimes these
not-to-exceed levels differ among federal organizations because
of different exposure times (an 8-hour workday or a 24-hour
day), the use of different animal studies, or other factors.
Recommendations and regulations are also
periodically updated as more information becomes available.
For the most current information, check with the federal agency
or organization that provides it. Some regulations and recommendations
for methoxychlor include the following:
The federal government has taken several
actions to help protect humans from excess exposure to methoxychlor.
EPA limits the amount of methoxychlor that may be present
in drinking water to 0.04 parts of methoxychlor per million
parts of water (0.04 ppm). EPA has also set limits of
1-100 ppm on the amount of methoxychlor that may be present
in various agricultural products (crops, fruits, vegetables,
grains, meats, milk, and food for livestock). FDA limits the
amount of methoxychlor in bottled water to 0.04 ppm.
EPA restricts the amount of methoxychlor that may be released
to the environment during burning or by disposal in landfills.
OSHA has set a Permissible Exposure Limit (PEL) of 15 milligrams
per cubic meter of air (mg/m3) for the average
amount of methoxychlor that may be present in air during an
8-hour workday. A court decision struck down a proposed PEL
of 10 mg/m3. The American Conference of Governmental
Industrial Hygienists (ACGIH) recommends a Threshold Limit
Value (TLV) of 10 mg/m3.
Agency for Toxic Substances and Disease Registry (ATSDR). 2002. Toxicological profile for Methoxychlor. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
ATSDR can also tell you the location of occupational and environmental health clinics. These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances.