Public Health Statement for Malathion
PDF Versionpdf icon[74.4 KB]
This Public Health Statement is the
summary chapter from the Toxicological
Profile for Malathion. 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 malathion 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.
Malathion has been found in at least 21 of the 1,623 current
or former NPL sites. However, the total number of NPL sites
evaluated for this substance is not known. As more sites are
evaluated, the sites at which malathion is found may increase.
This information is important because exposure to this substance
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 malathion, 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/them. 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 malathion?
Malathion is a pesticide that is used
to kill insects on agricultural crops, on stored products,
on golf courses, in home gardens, and in outdoor sites where
trees and shrubs are grown at home; it is also used to kill
mosquitoes and Mediterranean fruit flies (medflies) in large
outdoor areas. Additionally, malathion is used to kill fleas
on pets and to treat head lice on humans. It is usually sprayed
on crops or sprayed from an airplane over wide land areas,
especially in the states of California and Florida. Malathion
comes in two forms: a pure form of a colorless liquid and
a technical-grade solution (brownish-yellow liquid), which
contains malathion (greater than 90%) and impurities in a
solvent. The technical-grade malathion smells like garlic.
Malathion is a manufactured chemical, so it is only found
in the environment as a result of its manufacture or use.
Malathion has been manufactured in the United States since
1950 and has been used to kill insects on many types of crops
since this time. The Food and Drug Administration (FDA) and
the EPA allow a maximum amount of 8 parts per million (ppm)
of malathion to be present as a residue on specific crops
used as foods. Because malathion can be dangerous to humans,
the EPA requires that a certain amount of time must pass between
the time of application of the insecticide and entry by a
worker into a field where the chemical has been applied. Usually,
at least 12 hours must pass between application and entry,
but in some cases, such as when workers are entering a field
to hand harvest or hand prune the crops, time periods as long
as 6 days must pass between application and entry into the
field. In this way, exposure to malathion can be controlled
and accidental exposures can be prevented.
What happens to malathion when it enters the environment?
Once malathion is introduced into the
environment, usually from spraying on crops or in wide urban/residential
areas, droplets of malathion in the air fall on soil, plants,
water, or man-made surfaces. While most of the malathion will
stay in the areas where it is applied, some can move to areas
away from where it was applied by rain, fog, and wind. Malathion
stays in the environment from a few days to several months,
but is usually broken down within a few weeks. It is broken
down to other chemical compounds by water, sunlight, and bacteria
found in soil and water. Malathion does not tend to stick
to the soil and is rapidly broken down by bacteria; thus,
it is unlikely that malathion will reach groundwater in significant
amounts. In water, malathion breaks down quickly by the action
of the water and the bacteria in the water. In air, malathion
is broken down by reacting with other chemicals formed naturally
in the air by sunlight, to form a more toxic product called
malaoxon. If malathion is present on dry soil or on man-made
surfaces such as sidewalks, pavements, or playground equipment,
it usually does not break down as fast as it would in moist
soil. For more information, see Chapters 4, 5, and 6.
How might I be exposed to malathion?
Most people are not exposed to malathion
in the air that they breathe or on things that they touch,
unless they live near areas being sprayed. The people who
are at the greatest risk of being exposed to malathion are
those who work with this chemical. These include farm workers,
chemical sprayers, and people who work in factories that make
malathion or other products that contain the chemical. They
are exposed to malathion on things they touch where it can
pass through their skin, or by breathing it after it has been
sprayed. Other people who are at risk of being exposed to
malathion are those who use it near their homes and in their
gardens, and people living in areas where malathion is sprayed
to control medflies or mosquitos. Overexposure to malathion
may cause severe poisoning or death. Persons may be exposed
to dangerous amounts if they go into fields too soon after
spraying. The people most likely to be exposed to malathion
can be protected by wearing special clothing and breathing
equipment and by staying out of sprayed fields for the appropriate
amount of time for the job that they are going to do in the
field; this amount of time can be up to 6 days.
Individuals can also be exposed to malathion
if they live near landfills where malathion has been dumped
or near water containing malathion that washes off nearby
land or that is accidentally spilled. The greatest amounts
of malathion are expected to be present near or on the farms
where malathion is used. After spraying, some malathion can
be transported by the wind or fog to areas away from where
it is used, but the amounts present at these locations are
not expected to be at dangerous levels. In a collection of
data gathered by the EPA for the years 1971-1991, it was reported
that malathion was only found in a total of 12 groundwater
monitoring wells in three states. The most that was found
in any of the wells was 6.17 parts of malathion per billion
parts of water (ppb); this was found in a county in Virginia
that is made up mainly of agricultural and forested land.
More recent studies of water samples taken near where malathion
was sprayed indicate that malathion is not usually found in
groundwater. The risk of exposure to malathion from drinking
groundwater appears to be low. For more information, see Chapter
Malathion is approved for use on crops,
in homes and gardens, in urban/residential areas where mosquitos
or medflies pose a problem, and at agricultural sites. The
maximum amount of malathion residue allowed by the FDA and
EPA on crops used as food is 8 ppm of malathion. The FDA has
monitored the food supply for pesticides for a number of years.
FDA purchases many kinds of foods through Total Diet Studies
(also called Market Basket Surveys) and analyzes them for
residue levels of pesticides. These FDA studies allow scientists
to estimate the daily intake of pesticides. Generally, the
FDA monitoring studies conclude that the U.S. food supply
contains only very small amounts of pesticides that are not
a concern. For more information, see Section 1.7 and Chapter
How can malathion enter and leave my body?
For the general population, the most
likely way that malathion can enter the body is by eating
or drinking contaminated food or water or through dermal contact
with contaminated plants, soils, or surfaces such as playground
equipment or pavements. It can also enter your body if you
breathe air containing malathion during or after it has been
sprayed for public health uses. By any means of exposure,
malathion enters your body quickly and passes into the bloodstream.
Once in your bloodstream, malathion can
go to many organs and tissues. Most of the malathion is broken
down in your liver into other substances, called metabolites.
One of these metabolites is more harmful than malathion. Malathion
and its metabolites do not tend to accumulate in the body,
and leave mostly in your urine within a few days.
See Chapter 3 for more information on
how malathion enters and leaves the body.
How can malathion affect my health?
Malathion interferes with the normal
function of the nervous system. Because the nervous system
controls many other organs, malathion indirectly can affect
many additional organs and functions. Exposure to high amounts
of malathion in the air, water, or food may cause difficulty
breathing, chest tightness, vomiting, cramps, diarrhea, watery
eyes, blurred vision, salivation, sweating, headaches, dizziness,
loss of consciousness, and death. If persons who are exposed
accidentally or intentionally to high amounts of malathion
are rapidly given appropriate treatment, there may be no long-term
harmful effects. If people are exposed to levels of malathion
below those that affect the function of the nervous system,
few or no health problems seem to occur. This has been shown
in studies with volunteers who inhaled or swallowed small
known amounts of malathion. There is no evidence that malathion
affects the ability of humans to reproduce. There is also
no conclusive proof that malathion causes cancer in humans,
although some studies have found increased incidence of some
cancers in people who are regularly exposed to pesticides,
such as farmers and pesticide applicators. The International
Agency for Research on Cancer (IARC) has determined that malathion
is unclassifiable as to carcinogenicity to humans.
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
Studies in animals have observed the
same effects that occur in humans after exposure to malathion.
This is because malathion also affects the nervous system
of animals. Some studies in animals suggest that malathion
may produce subtle changes in the immune system, but there
was no evidence indicating that those animals were more susceptible
to infections than animals that were not given malathion.
Some studies in male rats observed temporary alterations in
the testes following short-term exposure to malathion, but
there is no evidence that exposure to malathion affected the
reproductive ability of these animals. A longer-term study
that evaluated the ability of rats to reproduce did not detect
any harmful effects. Most studies of cancer in animals have
not shown evidence of carcinogenicity for malathion, or have
shown evidence of cancer at doses considered excessive. Still,
there is some disagreement among scientists on how to interpret
the results. The EPA has determined that there is suggestive
evidence of carcinogenicity for malathion in animals but it
is not sufficient to assess potential carcinogenicity in humans.
See Chapter 3 for more information on how malathion can affect
How can malathion 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 can be exposed to malathion
from food and drinking water, but these risks are low and
not of concern. Because malathion is a widely used pesticide,
greater concern exists from exposure following application
to recreational areas, parks, and playgrounds and from home
and garden uses of malathion. Children can also be exposed
when malathion is sprayed, for example, to control mosquitos.
Because children spend more time outdoors than adults, they
may be at a greater risk of exposure to malathion than adults.
Because of their smaller weight, children's intake of malathion
per kilogram of body weight may be greater than that of adults.
The EPA permits residues of pesticides to be present in crops
used as food, and these amounts are considered to be safe.
Children may be exposed also by dermal contact with contaminated
surfaces or by placing contaminated objects in their mouths.
The main target of malathion toxicity
in children is the nervous system, the same as in adults.
Children who have accidentally swallowed high amounts of malathion
or who had skin contact with high amounts of malathion experienced
difficulty breathing, chest tightness, vomiting, cramps, diarrhea,
watery eyes, salivation, sweating, headaches, dizziness, and
loss of consciousness, and some died. We do not know whether
or not children are more susceptible than adults to malathion
toxicity. However, studies in animals have shown that very
young animals are more susceptible than older ones when exposed
to high amounts of malathion.
There is no evidence that exposure to
malathion at levels found in the environment causes birth
defects or other developmental effects in people. Malathion
has caused adverse developmental effects in animals, but only
when administered to the pregnant mothers in amounts high
enough to affect the health of the mothers. A study of people
in California found that the use of pesticides, malathion
among them, at home during pregnancy did not increase the
risk of brain tumors in children.
Animal studies have shown that malathion
and/or its breakdown products can be transferred from a pregnant
mother to the developing fetus and that it can also be passed
to newborn animals in the maternal milk. There is no information
in humans regarding transfer of malathion to the fetus or
to nursing infants.
More information regarding children's
health and malathion can be found in Section 3.7.
How can families reduce the risk of exposure to malathion?
If your doctor finds that you have been
exposed to significant amounts of malathion, ask whether your
children might also be exposed. Your doctor might need to
ask your state health department to investigate.
The general population is not likely
to be exposed to large amounts of malathion. The populations
living in the areas where malathion is used on crops or those
who use the insecticide extensively in their gardens or near
their homes, however, may be exposed to greater amounts of
malathion. Malathion is often detected in foods and air samples
collected where malathion is used. People who live close to
areas of malathion use, such as where it is sprayed over urban/residential
areas to control medflies or mosquitos, may also be exposed
to larger amounts of malathion, because small amounts of the
pesticide will move from the place where it is used to nearby
areas. These exposures may take place during activities such
as touching contaminated plants, soils, or man-made surfaces
such as playground equipment, sidewalks, or pavements; breathing
the mist formed from the sprayed chemical; drinking contaminated
water; or eating recently sprayed fruits and vegetables. People
who are most likely to receive the highest exposures are those
who work in the factories that make malathion or make products
that contain the insecticide, workers who spray it on crops,
and farmers. Entry of malathion into the body after contact
with the skin is expected to be the major exposure pathway
for those working in these operations. Breathing the mist
containing malathion may also occur.
Families can reduce the risk of exposure
to malathion in the soil, on plants, or in the air by staying
away from fields that have been recently sprayed. If families
wait at least a week before entering sprayed fields, then
the amount of malathion present in the air or on plants is
expected to be small. In areas where malathion is sprayed
to control medflies or mosquitos, families may reduce the
risk of exposure to the chemical by remaining inside during
the spraying periods, and by washing their hands and clothes
if they come into contact with sprayed surfaces within a few
days of the spraying. For children who play in dry sand boxes,
on sidewalks, or on playground equipment that is located in
or near the treated areas, the amount of time that caution
should be used (that is, the time during which they should
make sure to wash thoroughly after contact with sprayed surfaces)
may need to be longer. Families may also reduce the risk of
exposure to malathion by wearing protective equipment, such
as gloves, when applying the insecticide in their homes and
gardens, and washing their hands and clothes after they have
been in a backyard garden or yard that has been treated with
the insecticide. Foods grown in a garden treated with malathion
may contain some of the residues on their surface. To reduce
the risk of exposure to malathion that may occur when contaminated
vegetables or other produce grown in a backyard garden is
eaten, it is important to wash the foods prior to eating them.
Families should also be aware that sometimes
malathion could be illegally sprayed inside the home to kill
insects. Your children may be exposed to malathion if either
you or another person applies pesticides containing it in
your home. In some cases, the improper use of pesticides not
intended for indoor use in homes has turned homes into hazardous
waste sites. Make sure that any person you hire is licensed
and, if appropriate, certified to apply pesticides. Your state
licenses each person who is qualified to apply pesticides
according to EPA standards and further certifies each person
who is qualified to apply "restricted use" pesticides.
Ask to see the license and certification. 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 whether EPA has designated the
pesticide "for restricted use" and what the approved
uses are. This information is important if you or your family
react to the product. If you buy over-the-counter pesticides
products to apply yourself, be sure the products are in unopened
pesticide containers that are labeled and contain an EPA registration
number. Carefully follow the instructions on the label. If
you plan to spray inside, make sure the products are intended
for indoor use and are in unopened pesticide containers that
are labeled and contain an EPA registration number. Carefully
follow the instructions on the label. If you feel sick after
a pesticide has been used in your home, consult your doctor
or local poison control center.
Is there a medical test to determine whether I have been exposed to malathion?
There are tests available to determine
whether you have been exposed to malathion. Breakdown products
of malathion can be measured in the urine, but the tests need
to be conducted within days of the exposure since these products
are eliminated fairly rapidly. These tests, however, do not
predict whether or not the exposure to malathion will produce
harmful health effects. Another type of test measures the
levels of a substance called cholinesterase in your blood.
This test is not specific for malathion, but can be used to
determine exposure to many other substances that act in a
way similar to malathion. If the levels of cholinesterase
in you blood are less than half of what they should be, then
you may get symptoms of poisoning. Smaller decreases in cholinesterase
may only indicate that you have been exposed to malathion
or similar substances, but you will not necessarily experience
harmful effects. Cholinesterase levels in the blood can stay
low for months after you have been exposed to malathion or
similar chemicals. For more information, see Chapters 3 and
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 malathion include the following:
OSHA has established an exposure limit
for malathion in the workplace of 15 milligrams per cubic
meter (mg/m3), for an 8-hour workday, 40 hours per week.
NIOSH recommends that workers not be exposed to more than
10 mg/m3 of malathion for a 10-hour workday, 40 hours
per workweek. NIOSH also recommends that a level of 250 mg/m3
of malathion in the air be considered as immediately dangerous
to life and health.
According to EPA, the following levels
of malathion in drinking water are not expected to cause effects
that are harmful to health: 0.2 milligrams per liter (mg/L)
for 1 day, 10 days, or longer-term exposure for children,
and 0.1 mg/L for lifetime exposure of adults.
EPA also has set maximum levels of malathion
residues in meat and dairy products, vegetables, fruits, tree
nuts, cereal grains, and grass forage, fodder, and hay. Individual
values are listed in Table 8-1.
EPA requires notification to the Agency
of spills or accidental releases of 100 pounds or more of
malathion to the environment. For more information on regulations
and guidelines applicable to malathion, see Chapter 8.
Agency for Toxic Substances and Disease
Registry (ATSDR). 2003. Toxicological
profile for Malathion. 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
1600 Clifton Road NE, Mailstop S102-1
Atlanta, GA 30333
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.