FAQ about Permethrin
NPTN fact sheets are designed to answer questions that are commonly asked by the general public about pesticides that are regulated by the U.S. Environmental Protection Agency (US EPA). This document is intended to be educational in nature and helpful to consumers for making decisions about pesticide use.
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NPTN fact sheets are
designed to answer questions that are commonly asked by the general
public about pesticides that are regulated by the U.S. Environmental
Protection Agency (US EPA). This document is intended to be educational
in nature and helpful to consumers for making decisions about pesticide
use. |
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National
Pesticide
Telecommunications
Network |
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The Pesticide Label: Labels provide directions for
the proper use of a pesticide product. Be sure to read the entire label
before using any product. A signal word on each product label indicates
the product’s toxicity after a single dose.
CAUTION- low toxicity WARNING-
moderate toxicity DANGER- high toxicity |
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What is permethrin?
- Permethrin is an
insecticide (kills or controls insects) registered with the US EPA and
first marketed in 1977.
- Permethrin is a pyrethroid.
It is a synthetic chemical similar to the natural insecticide pyrethrum
which comes from the chrysanthemum plant, but it remains effective for
longer periods of time.
How does permethrin work?
- Pyrethroids work by quickly
paralyzing the nervous system of insects.
- Permethrin kills insects
when it contacts them or when they eat it. It has repellent effects also.
- It is effective against all
stages of insect growth, particularly larvae.
What products contain permethrin?
- household insect foggers
and sprays
- flea dips and sprays for
cats and dogs
- ornamental garden and turf
products
- repellent/insecticide for
clothing
- mosquito abatement products
- termite treatments
- agricultural pesticide
products
- lice shampoos and body
lotions for scabies control (regulated by U.S. Food & Drug
Administration)
What is the toxicity of permethrin?
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Animals:
- Rats fed high doses
of permethrin exhibited tremors, salivation, hyperactivity, hyperexcitability,
urination, defecation and incoordination (1). See box on laboratory
testing.
- In a study
involving newborn and adult rats, the newborn rats were found to be more
sensitive to permethrin than the adults. The enzymes that break down
permethrin in the body are not completely developed in the newborn rats.
The incomplete development of the liver enzymes made the newborn animals
more sensitive to permethrin than mature animals (2)
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Laboratory Testing: Before pesticides are
registered by the US EPA, they must undergo laboratory testing for
short-term and long-term health effects. Laboratory animals are purposely
fed high enough doses to cause toxic effects. These signs of poisoning are
not expected in humans or pets since the amount of a pesticide that people
and pets may be exposed to is low compared to the doses fed to laboratory
animals. |
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Humans:
- Permethrin has low
to moderate toxicity to humans for short-term exposures.
- Results of animal
studies suggest that human newborns may be more sensitive to permethrin
than adults.
- Permethrin acts
similarly to the insecticide pyrethrum (from the chrysanthemum plant).
Pyrethrum can cause skin or respiratory reactions in people with
hayfever or in people who are sensitive to ragweed and pollen. These
reactions may include irritation or inflammation of the skin (contact
dermatitis) or sneezing, nasal stuffiness, or asthmatic breathing.
Although there is no clear evidence that pyrethroids (such as
permethrin) cause allergic-type reactions, it is important to recognize
this possibility (3).
- Exposure to
permethrin may occasionally produce numbing, tingling, and burning
sensations of the skin. These sensations are reversible and usually go
away within 12 hours (4).
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Effects of permethrin on human health and the environment
depend on how much permethrin is present and the length and frequency of
exposure. Effects also depend on the health of a person or the condition of
the environment when exposure occurs. |
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Does permethrin break down and leave the body?
Animals
- In studies involving cows,
goats, and rats, permethrin was broken down and almost completely
eliminated from the body within 12 days (5).
Humans
- When permethrin was fed to
two human volunteers, 18-39% was eliminated from their
bodies in 24 hours (1). Based on animal studies, permethrin is not
expected to accumulate in the body.
Is permethrin likely to cause cancer?
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Animals
- US EPA has
classified permethrin as a possible carcinogen because there is limited
evidence of cancer in animals (6).
- There was no
evidence of cancer in long-term studies in which laboratory rats were
fed large daily doses of permethrin. In mice, long-term feeding studies
of permethrin showed a slight increase in lung tumors in males (5). See
box on cancer.
Humans
- There are no humans
studies of the potential of permethrin to cause cancer.
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Cancer: The U.S. EPA has strict guidelines that
require testing of pesticides for their potential to cause cancer. These
studies involve feeding laboratory animals large daily doses of the
pesticide for up to 2 years. These animals are compared with a group of
animals that did not receive the chemical. Animal studies help show whether
a chemical is a potential human carcinogen. If a pesticide does not cause
cancer in animal tests, then the EPA considers it unlikely the pesticide
will cause cancer in humans. |
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Does permethrin cause developmental or birth defects?
Animals
- Permethrin did not
interfere with pregnancy or cause birth defects in animal studies with
rats, rabbits, or mice (1).
Humans
- There are no human studies
of the potential of permethrin to cause reproductive or developmental
effects.
What happens to permethrin in the environment?
- The typical
half-life of permethrin in soil is 30 days (7). Permethrin breaks down
more rapidly in soil with higher levels of organic matter (humus) (1). See
box on half-life.
- Permethrin has an
extremely low potential to move in soil. It is unlikely to contaminate
groundwater because it binds tightly to soil particles (4). In water and
on soil surfaces, permethrin is degraded by sunlight (1).
- The average
half-life of permethrin on foliage is 10 days (1).
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Half-life is the time required for half of the
compound to degrade.
1 half-life = 50% degraded
2 half-lives = 75% degraded
3 half-lives = 87% degraded
4 half-lives = 94% degraded
5 half-lives = 97% degraded
Remember that the amount of chemical remaining after a half-life will
always depend on the amount of the chemical originally applied. |
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What effect does permethrin have on wildlife?
- Permethrin has been found
to be highly toxic to fish in laboratory experiments. Products for
agricultural and commercial outdoor use are limited to Certified
Applicators and bear specific precautions and directions to avoid
contamination of water. However, when permethrin products are used
properly (i.e. according to the label) around the home or other
residential sites, they pose little risk to aquatic life.
- Permethrin is highly toxic
to bees in laboratory conditions. However, when used properly, permethrin
has a strong repellent effect in the environment and should pose little
risk to bees (1).
- Permethrin is of low
toxicity to birds (1).
Selected References:
(1) World Health Organization. 1990. Environmental Health Criteria 94. Permethrin.
International Programme on Chemical Safety. Geneva, Switzerland.
(2) Cantalamessa, F. 1993. Acute toxicity of two pyrethroids, permethrin and
cypermethrin, in neonatal and adult rats. Arch Toxicol 67:510-513.
(3) Wagner, S.L. 1994. Allergy from Pyrethrin or Pyrethroid Insecticides. Journal
of Agromedicine 1(1):39-45.
(4) FMC Corporation. Princeton, PA. Dragnet FT MSDS, 5-24-95.
(5) World Health Organization. 1990. IARC Monographs on the Evaluation of
Carcinogenic Risks to Humans. Occupational Exposures in Insecticide
Application, and Some Pesticides. Permethrin. Volume 53, October 1990.
(6) U.S. EPA Office of Pesticide Programs Tracking Report. February 19,
1997.
(7) R.D.Wauchope, T.M. Buttler, A.G. Hornsby, P.W.M. Augustijn Beckers, J.P.
Burt. 1992. The SCS/ARS/CES Pesticide Properties Database for Environmental
Decision-Making. Reviews of Environmental Contamination and Toxicology
123:1-156.
For more information, call or write:
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NPTN
Oregon State University
333 Weniger Hall
Corvallis, Oregon 97331-6502
Phone: 1-800-858-7378
Fax: 1-541-737-0761
E-mail: nptn@ace.orst.edu
Reviewed: September 1997 |
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NPTN is sponsored
cooperatively by Oregon State University and the U.S. Environmental
Protection Agency. Data presented through NPTN documents are based on
selected authoritative and peer-reviewed literature. The information in
this profile does not in any way replace or supersede the restrictions,
precautions, directions or other information on the pesticide label/ing or
other regulatory requirements. |
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Actualité épidémiologique
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