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Permethrin is a
synthetic pyrethroid. Like most members of this family of insecticides,
it
has four isomers, molecules made up of the same atoms with
different three-dimensional structures.
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Permethrin is a common
synthetic chemical, widely used as an insecticide, acaricide, and insect
repellent. It belongs to the family of synthetic chemicals called
pyrethroids and functions as a neurotoxin, affecting neuron membranes by
prolonging sodium channel activation.
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Technical permethrin
ranges from a colorless crystal to a yellow or brown viscous
liquid.
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It is an ester of the
dichloro analogue of chrysanthemic acid, chemically identified as
(3-phenoxyphenyl)methyl-(±)- cis-trans-3(2,2-dichloroethyenyl)-2,
2dimethylcyclopropanecarboxylate.
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Permethrin was first
registered with the United States Environmental Protection Agency (U.S.
EPA) in 1979, and was re-registered in 2006.
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Permethrin is a
broad-spectrum pyrethroid insecticide. It is available in dusts,
emulsifiable concentrates, smokes, ULV concentrates, and wettable-powder
formulations.
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Permethrin is used to
kill pest in-sects in agriculture, home pest control, forestry, and in
public health programs, including head lice control.
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Permethrin is not
phytotoxic, or poisonous, to most plants when it is used as directed.
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Permethrin is a useful
synthetic insecticide that has proven effective in a number of
environmental and clinical settings. It appears to be more effective
than DEET in protecting individuals from tick bites.
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Permethrin can affect
insects if they eat it or touch it. Permethrin affects the nervous
system in insects, causing muscle spasms, paralysis and death.
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Permethrin can be
effective by contact or ingestion and also acts as a mild
repellent.
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Permethrin is highly
toxic to marine/estuarine, freshwater fish and other aquatic
organisms
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Permethrin is more toxic
to insects than it is to people and dogs.This is because insects can’t
break it down as quickly as people and dogs.
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If permethrin is applied
to plants, it may stay on the leaves for between 1 and 3 weeks.
Scientists applied permethrin to soil and then planted sugar beets,
wheat, lettuce and cotton in the soil. Scientists found trace amounts of
the permethrin residue in the edible parts of the plants at 30 and 120
days after planting.
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The widely-used
synthetic insecticide permethrin dramatically reduces testosterone
levels and sperm counts in adult male mice exposed to it for six
weeks.
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Permethrin is a viscous
liquid at room temperature; it does not dissociate in water and has
extremely low water solubility and volatility. It is stable to
hydrolysis at pH4–7 but is slowly hydrolysed at pH 9.
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Permethrin impurities
were determined by capillary GC with FID detection.
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Permethrin only
decomposes at extremely high temperature and, although photochemical
degradation was observed in
laboratory studies, this was stated by
Sumitomo to be of negligible significance in the field.
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Permethrin was
classified by the International Agency for Research on Cancer (IARC) as
“not
classifiable as to its carcinogenicity
to humans” in
1991.The U.S. EPA
decided that permethrin was “likely to be
carcinogenic to humans” if it was eaten.
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In the U.S., al-most 70
percent of the permethrin used in agriculture is used on corn, wheat,
and alfalfa.