1.1 What is dichlorvos? |
1.2 What happens to dichlorvos when it
enters the environment? |
1.3 How might I be exposed to dichlorvos? |
1.4 How can dichlorvos enter and leave
my body? |
1.5 How can dichlorvos affect my health? |
1.6 Is there a medical test to determine
whether I have been exposed to dichlorvos? |
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 |
Dichlorvos |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for dichlorvos. 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 dichlorvos 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.
Dichlorvos has been found in at least 3 of the 1,430 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 dichlorvos may increase.
This 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 dichlorvos, 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 dichlorvos? |
Dichlorvos is a synthetic organic chemical
used as an insecticide. Dichlorvos does not occur naturally
in the environment, but is manufactured by industry.
Dichlorvos is sold under many trade names including Vapona®,
Atgard®, Nuvan®, and Task®. Dichlorvos may
also be called DDVP, which is an abbreviation for its full
chemical name. Pure dichlorvos is a dense colorless
liquid that evaporates easily into the air and dissolves slightly
in water. Dichlorvos has a sweetish smell and readily
reacts with water. The dichlorvos used in pest control
is diluted with other liquids and used as a spray. It
can also be incorporated into plastic that slowly releases
the chemical. The dichlorvos present at hazardous waste
sites will most likely be in a liquid solution or as solid
plastic pellets or strips.
Dichlorvos is manufactured by a reaction
between two other chemicals called chloral and trimethyl phosphite.
It is also manufactured by heating a chemical called trichlorfon.
In 1984, about 1 million pounds of dichlorvos was manufactured
in the United States. The main uses of dichlorvos are
for insect control in food storage areas, greenhouses, and
barns, and for parasite control in livestock. Dichlorvos
is generally not used on outdoor crops. It is sometimes
used for insect control in workplaces and the home.
Veterinarians also use it to control parasites in pets.
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1.2
What happens to dichlorvos when it enters the environment? |
Dichlorvos enters the air, water, and
soil during its manufacture and use. Wastes containing
dichlorvos that are generated during its manufacture and use
are sometimes disposed of in landfills. It can enter
the environment from these landfills. Dichlorvos also
enters the environment from accidental spills during transport
and leaks from storage containers.
Dichlorvos evaporates easily into the
air, which is why it is usually used in enclosed areas.
Once in the air, it can react with water vapor and be broken
down. The higher the temperature and the humidity, the
more rapidly dichlorvos is broken down. Experiments
in greenhouses and food storage areas show that 90% of the
applied dichlorvos disappeared in 3–6 hours. The products
of this breakdown are two chemicals called dimethyl phosphate
and dichloroacetaldehyde. These chemicals are less harmful
than dichlorvos and are not believed to cause health effects
in people.
If dichlorvos is spilled into a lake
or river, it will dissolve in the water. Some dichlorvos
will then evaporate into the air, but most of it will be broken
down when it reacts with the water. The less acid the
water is, the more rapidly dichlorvos is broken down.
Bacteria and other microorganisms (microscopic plants and
animals) in lakes and rivers can also break down dichlorvos.
In an experiment where dichlorvos was applied to a pond, 50%
of the chemical was broken down in 24–36 hours.
Dichlorvos does not seem to bind to soil.
This means it can move through soil fairly rapidly.
The breakdown in soil is less rapid than in air or water.
Dichlorvos breakdown is most rapid in moist soils with low
acidity. In a laboratory experiment with soil that contained
200 parts of dichlorvos per million parts of soil (200 ppm),
37% of the dichlorvos remained in the soil after 3 days.
Dichlorvos remains for longer periods in dry, acidic soil.
Certain bacteria and other microorganisms in the soil can
also break down dichlorvos.
Dichlorvos is not stored, accumulated,
or concentrated by plants, fish, animals, or people.
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1.3
How might I be exposed to dichlorvos? |
The general population is not likely
to be exposed to dichlorvos. It has not been found in
drinking water in the United States and only very rarely in
outdoor air. Dichlorvos has occasionally been found
on raw foods (fruits, vegetables, grains), but washing and
processing destroys the residue. Maximum limits (ranging
from 0.02 to 2 ppm) have been established by the U.S. EPA.
Dichlorvos has not been found in prepared foods.
People living near hazardous waste sites
containing dichlorvos or near its manufacturing, processing,
or storage facilities, could potentially be exposed.
Because of the chemical properties, the most likely way a
person would be exposed is by breathing in air contaminated
with dichlorvos. Another possible route of exposure
is skin contact with soil contaminated with dichlorvos.
You are most likely to be exposed to
dichlorvos if you are involved in manufacturing or using it.
Chemical plant workers, transport workers, and pesticide applicators
are the major occupational groups that might be exposed.
People in these groups are mainly exposed by breathing air
containing dichlorvos, but significant exposure through the
skin can occur as well. An estimated 24,000 workers
in the United States are exposed to dichlorvos because of
their occupations. Measured air levels in factories
and workplaces have ranged from 0.005 to 0.08 ppm dichlorvos.
You might also be exposed to dichlorvos
in the home after pesticide application. You are most
likely to be exposed by breathing air containing dichlorvos,
but skin contact with contaminated surfaces, or eating food
that has been left out during dichlorvos application can also
result in exposure. Measured levels of dichlorvos in
room air immediately after pesticide applications have ranged
from 0.08 to 2.7 ppm. It has been recommended that people
should not reenter a room or house treated with dichlorvos
until after a 10-hour ventilation period.
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1.4
How can dichlorvos enter and leave my body? |
Dichlorvos can enter your body through
your lungs if it is in the air you breathe. It can also
enter your body through your stomach if it is in your drinking
water or food. It can also enter through your skin.
Dichlorvos is taken into your body very rapidly by any of
these routes (lungs, stomach, or skin). How much dichlorvos
enters your body depends on how long you are exposed and the
amount to which you are exposed.
Once dichlorvos enters your body, it
goes into your bloodstream and is carried to all the organs
in your body. There are enzymes in your liver and blood
that rapidly break it down. These breakdown products
are less harmful than dichlorvos. Most of these breakdown
products quickly leave the body in the urine. Some of
these products are broken down further and leave your body
in your breath. Dichlorvos and its breakdown products
are not stored in your body.
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1.5
How can dichlorvos affect my health? |
Dichlorvos is a member of a group of
chemicals called organophosphorus compounds. Some of
these chemicals are extremely harmful to insects and are widely
used as insecticides. At higher doses than those used
to kill insects, these chemicals can also be harmful to people.
Dichlorvos can chemically react with an important enzyme in
your brain and nerves called acetylcholinesterase and stop
them from working properly. When this happens, signals
sent between your nerve cells and to your muscles are disrupted.
To understand the harmful effects of dichlorvos that might
occur at levels of exposure that people are likely to experience,
scientific studies have been done with people and laboratory
animals. 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 guidelines.
We do not know how much dichlorvos is
necessary to cause harmful effects in people. This is
because few people have been exposed to enough dichlorvos
to cause symptoms of poisoning. From the results of
animal testing, we can estimate that if a person breathed
in air containing more than 1 ppm dichlorvos for more than
one hour, harmful effects might result. Accidentally
drinking as little as 1 ounce or 30 milliliters (mL) of a
pesticide containing 5% dichlorvos could also cause harmful
effects. Spilling an ounce of the same strength dichlorvos
solution on your skin and failing to wash it off promptly
could also be harmful.
If you have been poisoned by dichlorvos,
you will suddenly feel nauseated, anxious, and restless.
You may also have teary eyes and heavy sweating. If
this happens, you should seek medical attention immediately.
Emergency rooms have drugs that stop the harmful effects of
dichlorvos. Further symptoms can include loss of bladder
control, muscle tremors, and labored breathing. Severe
poisoning (5 ounces or more of a 5% dichlorvos solution) can
result in coma, inability to breathe, and death.
Most people who have survived poisoning
by dichlorvos make a complete recovery, although this can
sometimes take several months. Dichlorvos poisoning
does not appear to cause permanent damage to the nerves (a
condition called "delayed neuropathy").
A few studies have been done on people
who have been exposed to dichlorvos in the air in their workplaces.
When dichlorvos is used properly, air levels of 0.01–0.03
ppm are achieved. This level kills most insects within
one hour. In tests done with volunteers, exposure at
about 20 times this level (0.23 ppm) for 2 hours a day for
4 days had no harmful effects. In a study in rats exposed
to air with very high levels of dichlorvos (up to 34 ppm),
all the animals died within 3 days. The rats showed
similar signs of effects on the nervous system as in people
that have been poisoned with dichlorvos. In general,
harmful effects have not been seen in animals exposed to air
levels of dichlorvos below 0.5 ppm. In a 2-year study
in rats, breathing air every day with low-to-moderately high
levels (0.006–0.6 ppm) of dichlorvos had no effect on how
long the rats lived or on their general health.
In at least one case, a person who drank
a pesticide containing dichlorvos died. The doctors
who treated this patient were unable to tell exactly how much
dichlorvos she had taken. Volunteers who ate 0.03 milligrams
dichlorvos per kilogram body weight (0.03 mg/kg) for 21 days
showed no harmful effects. In studies where animals
(rats and mice) have been force-fed dichlorvos, about half
the animals died when given approximately 100 mg/kg.
Before the animals died, they showed signs of harmful effects
to their nervous systems similar to those seen in human poisoning
cases.
Two pesticide workers died after spilling
concentrated dichlorvos on their skin and failing to wash
it off promptly. It is not known exactly how much dichlorvos
they absorbed through their skin. Experiments in animals
show that dichlorvos can be just as harmful when it is applied
to the skin as when it is breathed in or swallowed.
Monkeys that had dichlorvos put on their skin (50 mg each
day) died after 10 doses.
It is not known if exposure to dichlorvos
can affect fertility or development of the fetus in people.
Experiments done in animals that were fed or breathed in dichlorvos
did not show any effect on fertility or health of the offspring.
There is no evidence that exposure to
dichlorvos increases the risk of cancer in people. Rats
that breathed in air containing dichlorvos for 2 years had
the same rate of cancer as rats that did not breathe in dichlorvos.
However, a 2-year study in rats and mice force-fed dichlorvos
showed an increase in certain forms of cancer. Rats
had increased rates of cancer in the pancreas and also had
more cases of leukemia than rats that had not been treated
with dichlorvos. Female mice had a higher rate of a
form of stomach cancer.
The U.S. Department of Health and Human
Services (DHHS) has determined that dichlorvos may reasonably
be anticipated to be a carcinogen (a substance that can cause
cancer). The International Agency for Research on Cancer
(IARC) has determined that dichlorvos is possibly carcinogenic
to humans. The U.S. EPA has determined that dichlorvos
is a probable human carcinogen.
The U.S. EPA has calculated that a lifetime
of drinking water containing 0.1 micrograms of dichlorvos
per liter (µg/L) would cause one extra case of cancer
in every million people exposed to this level. Dichlorvos
has not been found in drinking water in the United States.
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1.6
Is there a medical test to determine whether I have been exposed
to dichlorvos? |
Two blood tests exist that can determine
whether you have been exposed to significant levels of dichlorvos.
These tests can be performed by any hospital or clinical laboratory.
These tests measure the activity of two enzymes (called serum
cholinesterase and erythrocyte [red blood cell] acetylcholinesterase)
that are affected by dichlorvos. Dichlorvos affects
these enzymes at lower levels of exposure than necessary to
produce harmful effects. This means that if these enzymes
have been affected, you will not necessarily have effects
on your health. Many other insecticides also affect
these enzymes. To determine whether you have been specifically
exposed to dichlorvos, a laboratory test must measure the
breakdown products in your urine. Tests of this type
are not routinely done in hospital laboratories and your doctor
will have to send a sample to a specialized laboratory.
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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 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 dichlorvos include the following:
- The U.S. OSHA has set a permissible exposure limit (PEL)
of 1 mg/m³ (0.11 ppm) of dichlorvos for workplace air
over a 10-hour workday.
- The U.S. EPA requires reporting of any discharge of dichlorvos
to the environment that exceeds 10 pounds. The EPA
has also designated dichlorvos as a hazardous substance
and specific regulations regarding its disposal are in effect.
- The U.S. EPA has established maximum permissible levels
of dichlorvos in various food products ranging from 0.02
to 2 parts per million (ppm). Samples from the food
supply are regularly tested for dichlorvos.
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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). 1997. Toxicological
profile for dichlorvos. Atlanta, GA: U.S. Department of
Health and Human Services, Public Health Service.
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