1.1 What is chlorpyrifos? |
1.2 What happens to chlorpyrifos when
it enters the environment? |
1.3 How might I be exposed to chlorpyrifos? |
1.4 How can chlorpyrifos enter and leave
my body? |
1.5 How can chlorpyrifos affect my health? |
1.6 Is there a medical test to determine
whether I have been exposed to chlorpyrifos? |
1.7 What recommendations has the federal
government made to protect human health? |
1.8 Where can I get more information? |
References |
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September 1997 |
Public Health Statement |
for |
Chlorpyrifos |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for chlorpyrifos. It is one in a series of Public
Health Statements about hazardous substances and their health
effects. A shorter version, the ToxFAQs™,
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 1-888-422-8737.
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This public health statement tells you
about chlorpyrifos 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.
Chlorpyrifos has been found in at least 7 of the 1,428 current
or former NPL sites. However, it's unknown how many
NPL sites have been evaluated for this substance. As
more sites are evaluated, the sites with chlorpyrifos 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 contact.
If you are exposed to chlorpyrifos, 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.
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1.1
What is chlorpyrifos? |
Chlorpyrifos is an organophosphorus insecticide
that has been widely used in the home and on the farm.
In the home, chlorpyrifos has been used to control cockroaches,
fleas, and termites; it has also been an active ingredient
in some pet flea and tick collars. On the farm, it is
used to control ticks on cattle and as a spray to control
crop pests. In 1997, chlorpyrifos was voluntarily
withdrawn from most indoor and pet uses by the manufacturer,
DowElanco.
Chlorpyrifos is a white crystal-like
solid with a strong odor. It does not mix well with
water, so it is usually mixed with oily liquids before it
is applied to crops or animals. It may also be applied
to crops in a microencapsulated form. Chlorpyrifos is
the active ingredient of various commercial insecticides including
Dursban® and Lorsban®.
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1.2
What happens to chlorpyrifos when it enters the environment? |
Chlorpyrifos enters the environment through
direct application to crops, lawns, domesticated animals,
and in the home and workplace. Chlorpyrifos may also
enter the environment through volatilization, spills, and
the disposal of chlorpyrifos waste.
Chlorpyrifos that has been applied to
the soil generally stays in the area where it has been applied
because it sticks tightly to soil particles. Because
of this, there is a low chance that chlorpyrifos will be washed
off the soil and enter local water systems. Also, since
it does not mix well with water, if it does get into the natural
waters, it will be in small amounts and will remain on or
near the surface and will evaporate. Volatilization
is the major way in which chlorpyrifos disperses after it
has been applied. Once in the environment (soil, air,
or water), chlorpyrifos is broken down by sunlight, bacteria,
or other chemical processes.
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1.3
How might I be exposed to chlorpyrifos? |
You can be exposed to chlorpyrifos in
many places because of its wide range of uses. You can
be exposed to it in your home or office if chlorpyrifos has
recently been used to control household pests such as fleas
or cockroaches. Exposure can also occur outside your
home if chlorpyrifos has been applied to the ground around
the foundation to control termites. Chlorpyrifos degrades
rapidly in the environment; however, low levels may persist
for long periods of time after it has been applied either
inside or outside the home. Opening windows before and
after chlorpyrifos spraying rapidly lowers airborne levels
in a house.
You can also be exposed to chlorpyrifos
in a farm setting. The greatest risk occurs soon after
a crop has been sprayed, because that is when its levels will
be the highest. However, chlorpyrifos rapidly degrades
and becomes bound to plants and the ground. The EPA
recommends a 24-hour waiting period before entering fields
where chlorpyrifos has been applied. In addition, there
is the risk of exposure to chlorpyrifos when it is being prepared
for use. Care should be taken to ensure that only a
licensed applicator sprays chlorpyrifos, and that unnecessary
or unprotected individuals remain away from the site of application
during the spraying.
Chlorpyrifos can also be found at some
waste disposal sites, so exposure to higher levels than what
is commonly found after home or commercial use may occur there.
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1.4
How can chlorpyrifos enter and leave my body? |
Chlorpyrifos can enter your body through
your mouth, lungs, and skin. After being eaten or drunk,
chlorpyrifos quickly passes from the intestines to the bloodstream,
where it is distributed to the rest of the body. It
can also enter the body through the lungs by breathing chlorpyrifos
sprays or dust. When chlorpyrifos enters the body this
way, it passes quickly into the blood. It may also enter
your body through the skin, but the chances of being exposed
to harmful levels of chlorpyrifos this way are not as great
as with inhalation and oral exposure, because the amount that
gets through the skin is relatively small (less than 3% of
what was put on the skin). Dermal exposure of infants
represents a greater health risk than with adults because
of the texture of infant skin and because infants laying or
crawling on an area sprayed with chlorpyrifos may have a greater
amount of their skin exposed to chlorpyrifos. Infants
crawling on areas recently sprayed with chlorpyrifos may also
be exposed to greater amounts of chlorpyrifos through inhalation
of its vapors.
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1.5
How can chlorpyrifos 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 can harm
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 guidelines.
In people, short-term oral exposure (one
day) to low (milligrams) levels of chlorpyrifos can cause
dizziness, fatigue, runny nose or eyes, salivation, nausea,
intestinal discomfort, sweating, and changes in heart rate.
Short-term oral exposure to much higher (grams) levels of
chlorpyrifos may cause paralysis, seizures, loss of consciousness,
and death. Reports in people also show that short-term
exposure to chlorpyrifos may cause muscle weakness weeks after
the original symptoms have disappeared. Other effects
of exposure to chlorpyrifos include changes in behavior or
sleeping pattern, mood changes, and effects on the nerves
and/or muscles in the limbs (which may appear as odd sensations
such as numbness or tingling, or as muscle weakness).
The EPA has not classified chlorpyrifos for carcinogenicity
(Class D).
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1.6
Is there a medical test to determine whether I have been exposed
to chlorpyrifos? |
There is a general test that can be performed
to determine if you have been exposed to carbamate or organophosphate
insecticides. Those types of pesticides inhibit the
activity of acetylcholinesterase, the enzyme responsible for
inactivating acetylcholine, the compound ultimately responsible
for most of the toxic symptoms seen with chlorpyrifos.
The test measures the activity of the enzyme acetylcholinesterase
in the blood or a similar enzyme, pseudocholinesterase, in
the plasma, or both. If enzyme activity is inhibited,
then exposure to an organophosphate or carbamate pesticide
is suspected. There is also a biochemical test that
can determine if you have been specifically exposed to chlorpyrifos.
After chlorpyrifos enters the body, it is changed by the liver
into other forms of the compound that may or may not be less
toxic than the original material. The major nontoxic
chlorpyrifos metabolic product formed by the liver is 3,5,6-trichloro-2-pyridinol,
or TCP. TCP is primarily eliminated from the body in
the urine and can be detected in the urine using readily available
laboratory equipment. The extent of the exposure, length
of time after exposure, and the amount of water in the body
will affect the level of TCP in the urine. Typically,
TCP can be found in the urine for several days after exposure
to chlorpyrifos. In addition to chlorpyrifos, TCP is
a metabolite of methyl chlorpyrifos and triclopyr. TCP
may also be found in the environment, but it is unlikely that
urinary levels of TCP result from environmental-TCP exposure.
Direct exposure to chlorpyrifos or chlorpyrifos-like compounds
is the most likely cause.
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1.7
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, on the other hand, 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 the levels 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 chlorpyrifos include the following:
- Chlorpyrifos is one of a list of chemicals regulated under
"The Emergency Planning and Community Right-to-Know Act
of 1986" (EPCRA). This requires owners and operators
of certain facilities that manufacture, import, process,
or otherwise use the chemicals on this list to report their
release of those chemicals to any environmental media annually.
- Chlorpyrifos is designated a hazardous substance and subject
to regulations in the Federal Water Pollution Act and the
Clean Water Act.
- EPA has established tolerances for chlorpyrifos in raw
agricultural commodities, foods, and animal feeds.
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1.8 Where can I get more information? |
If you have any more questions or concerns, please contact
your community or state health or environmental quality department or:
Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Information line and technical assistance:
Phone: 888-422-8737
FAX: (770)-488-4178
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.
To order toxicological profiles, contact:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Phone: 800-553-6847 or 703-605-6000
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References |
Agency for Toxic Substances and Disease
Registry (ATSDR). 1998. Toxicological
profile for chlorpyrifos. Atlanta, GA: U.S. Department
of Health and Human Services, Public Health Service.
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