ToxFAQs™ for Pyrethrins and Pyrethroids
Spanish: Piretrinas y Piretroideso
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This fact sheet answers the most frequently asked health questions about pyrethrins and pyrethroids. For more information, you may call the ATSDR Information Center at 1-800-232-4636. This fact sheet is one in a series of summaries about hazardous substances and their health effects. 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.
Pyrethrins and pyrethroids are insecticides that are applied to crops, garden plants, pets, and also directly to humans. High levels of pyrethrins or pyrethroids can cause dizziness, headache, nausea, muscle twitching, reduced energy, changes in awareness, convulsions and loss of consciousness. Pyrethrins have been found in at least 5 of the 1,636 current or former NPL sites identified by the Environmental Protection
Agency (EPA), and permethrin (a pyrethroid compound) has been found in at least 2 of the sites. No other pyrethroids were detected at NPL sites.
What are pyrethrins and pyrethroids?
Pyrethrins are naturally-occurring compounds
with insecticidal properties that are found in pyrethrum extract
from certain chrysanthemum flowers. The pyrethrins are often
used in household insecticides and products to control insects
on pets or livestock.
Pyrethroids are manufactured chemicals
that are very similar in structure to the pyrethrins, but
are often more toxic to insects as well as to mammals, and
last longer in the environment than the pyrethrins. More than
1,000 synthetic pyrethroids have been developed, but less
than a dozen of them are currently used in the United States.
Permethrin is the most frequently used pyrethroid in the United
What happens to pyrethrins and pyrethroids when they enter the environment?
- Pyrethroids enter the environment primarily due to their use as insecticides.
- In air, all six of the pyrethrins and many of the pyrethroids
are broken down rapidly (1-2 days) by sunlight or other
compounds found in the atmosphere.
- Pyrethrins and pyrethroids bind strongly to soil and are
eventually degraded by microorganisms in soil and water;
they generally do not move from the soil to groundwater.
How might I be exposed to pyrethrins and pyrethroids?
- Pyrethrins and pyrethroids usually enter the body when
people eat foods contaminated by these chemicals.
- They may also enter your body when you breathe air that
contains these compounds or when you get them on your skin.
- The use of products that contain pyrethrins and pyrethroids,
such as household insecticides, pet sprays and shampoos,
lice treatments that are applied directly to the head, and
mosquito repellents that can be applied to clothing, may
lead to exposure.
How can pyrethrins and pyrethroids affect my health?
Pyrethrins and pyrethroids interfere
with the normal way that the nerves and brain function. Exposure
to very high levels of these compounds for a short period
in air, food, or water may cause dizziness, headache, nausea,
muscle twitching, reduced energy, changes in awareness, convulsions
and loss of consciousness. Changes in mental state may last
several days after exposure to high levels of pyrethroids
has ended. There is no evidence that pyrethrins or pyrethroids
affect the ability of humans to produce children, but some
animal studies have shown reduced fertility in males and females.
How likely are pyrethrins and pyrethroids to cause cancer?
There is no evidence that pyrethrins
or pyrethroids cause cancer in people or in animals. The International
Agency for Research on Cancer (IARC) has determined that the
carcinogenicity to humans for three pyrethroids (deltamethrin,
fenvalerate, permethrin) is not classifiable.
How can pyrethrins and pyrethroids affect children?
It is likely that health effects seen
in children exposed to high levels of pyrethrins or pyrethroids
will be similar to the effects seen in adults. We do not know
whether children differ from adults in their susceptibility
to these chemicals.
Birth defects have not been observed
in humans exposed to pyrethrins or pyrethroids. Offspring
of animals that ingested pyrethrins or pyrethroids while pregnant
showed signs of possible damage to the immune system. Some
animals that were exposed to pyrethrins or pyrethroids right
after birth showed altered behavior as adults.
How can families reduce the risk of exposure to pyrethrins and pyrethroids?
Exposure to pyrethrins and pyrethroids
can be reduced by exercising care when using pesticides containing
these compounds around the house, on pets, and on children
and by storing them properly. Certain pyrethroids are sprayed
to control mosquitos during the spring and summer; remaining
indoors and closing your windows while your neighborhood is
being sprayed will lessen your exposure. Additional ways to
reduce possible exposure include thoroughly washing fruits
and vegetables before eating them, ensuring that children
wash their hands before eating, and discouraging young children
from eating dirt.
Children should avoid playing in soils near uncontrolled hazardous waste sites where pyrethrins and
pyrethroids may have been discarded.
Is there a medical test to show whether I've been exposed to pyrethrins and pyrethroids?
Pyrethrins, pyrethroids, and their breakdown
products can be detected in your blood and urine, but only
within a few days after your last exposure. These tests are
not usually available at your doctors office, but your doctor
can send the samples to a laboratory that can perform the
tests. None of these tests can predict whether you will experience
any related health effects.
Has the federal government made recommendations to protect human health?
The Occupational Safety and Health Administration (OSHA) has set a limit of 5 milligrams of pyrethrins per cubic meter of workplace air (5 mg/m3) for 8 hour shifts and 40 hour work weeks.
The EPA has recommended daily oral exposure limits for 10 different pyrethroids ranging from 0.005 to
0.05 mg per kilogram of body weight per day (0.005-0.05 mg/kg/day).
The EPA has established tolerances for residues of pyrethrins and various pyrethroids that range
from 0.01 to 75 parts per million parts (0.01-75 ppm) of a variety of foods.
Agency for Toxic Substances and Disease Registry (ATSDR). 2003. Toxicological Profile for Pyrethrins and Pyrethroids. 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
Office of Innovation and Analytics, Toxicology Section
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.