a broad spectrum synthetic pyrethroid insecticide, used against a variety
of pests, on nut, fruit, vegetable, cotton, ornamental, mushroom, potato,
and cereal crops. It is used in greenhouses, home gardens, and for termite
control. It also controls animal ectoparasites, biting flies, and cockroaches.
It may cause a mite buildup by reducing mite predator populations. Permethrin
is available in dusts, emulsifiable concentrates, smokes, ULV (ultra-low
volume), and wettable powder formulations.
is a moderately to practically non-toxic pesticide in American EPA toxicity
class II or III, depending on the formulation. Formulations are placed in
class II due to their potential to cause eye and skin irritation. Products
containing permethrin must bear the Signal Word WARNING or CAUTION, depending
on the toxicity of the particular formulation. All products for agricultural
uses (except livestock and premises uses) are Restricted Use Pesticides
(RUPs) because of their possible adverse effects on aquatic organisms. Restricted
Use Pesticides may be purchased and used only by certified applicators.
cyclopropanecarboxylic acid, 3-(2,2-dichloroethenyl)2,2-dimethyl-(3-phenoxyphenyl)methyl
Permethrin is moderately to practically non-toxic via the oral route, with
a reported LD50 for technical permethrin in rats of 430 to 4000 mg/kg. Via
the dermal route, it is slightly toxic, with a reported dermal LD50 in rats
of over 4000 mg/kg, and in rabbits of greater 2000 mg/kg. Permethrin caused
mild irritation of both the intact and abraded skin of rabbits. It also
caused conjunctivitis when it was applied to the eyes. The 4-hour inhalation
LC50 for rats was greater than 23.5 mg/L, indicating practically no inhalation
toxicity. The toxicity of permethrin is dependent on the ratio of the isomers
present; the cis-isomer being more toxic.
In human beings permethrin
is efficiently metabolized by mammalian livers. Breakdown products, or "metabolites,"
of permethrin are quickly excreted and do not persist significantly in body
tissues. When permethrin is administered orally to rats, it is rapidly metabolized
and almost completely eliminated from the body in a few days. Only 3 to
6% of the original dose was excreted unchanged in the feces of experimental
animals. Permethrin may persist in fatty tissues, with half-lives of 4 to
5 days in brain and body fat. Permethrin does not block, or inhibit, cholinesterase
Effects on birds:
Permethrin is practically non-toxic to birds. The oral LD50
for the permethrin formulation, Pramex, is greater than 9900 mg/kg in mallard
ducks and greater than 13,500 mg/kg in pheasants.
Effects on aquatic organisms:
Aquatic ecosystems are particularly vulnerable to the impact
of permethrin. A fragile balance exists between the quality and quantity
of insects and other invertebrates that serve as fish food. The 48-hour
LC50 for rainbow trout is 0.0125 mg/L for 24 hours, and 0.0054 mg/L for
48 hours. The 48-hour LC50 in salmon is 0.0018 mg/L. As a group, synthetic
pyrethroids were toxic to all estuarine species tested. They had a 96-hour
LC50 of less than or equal to 0.0078 mg/L for these species.
Effects on other organisms:
Permethrin is extremely toxic to bees. Severe losses may be expected if
bees are present at treatment time, or within a day thereafter. Permethrin
is also toxic to wildlife. It should not be applied, or allowed to drift,
to crops or weeds in which active foraging takes place.
Breakdown in soil and groundwater:
Permethrin is of low to moderate persistence in the soil environment, with
reported half-lives of 30 to 38 days. Permethrin is readily broken down,
or degraded, in most soils except organic types. Soil microorganisms play
a large role in the degradation of permethrin in the soil. The addition
of nutrients to soil may increase the degradation of permethrin. It has
been observed that the availability of sodium and phosphorous decreases
when permethrin is added to the soil. Permethrin is tightly bound by soils,
especially by organic matter. Very little leaching of permethrin has been
reported. It is not very mobile in a wide range of soil types. Because permethrin
binds very strongly to soil particles and is nearly insoluble in water,
it is not expected to leach or to contaminate groundwater.
water: The results of one study near estuarine areas
showed that permethrin had a half-life of less than 2.5 days. When exposed
to sunlight, the half-life was 4.6 days. Permethrin degrades rapidly in
water, although it can persist in sediments. There was a gradual loss of
toxicity after permethrin aged for 48 hours in sunlight at 0.05 mg/L in
vegetation: Permethrin is not phytotoxic, or poisonous,
to most plants when it is used as directed. Some injury has occurred on
certain ornamental plants. No incompatibility has been observed with permethrin
on cultivated plants. Treated apples, grapes, and cereal grains contain
less than one mg/kg of permethrin at harvest time.
Permethrin is an odorless, colorless crystalline solid or a viscous liquid
that is pale brown.
- Chemical Name: 3-phenoxybenzyl(1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate.
- CAS Number:
- Molecular Weight: 391.30
- Water Solubility: ca. 0.2 mg/L
@ 20°C, insoluble in water
- Solubility in Other Solvents:
s. in most organic solvents except ethylene glycol.
- Melting Point:
- Vapor Pressure:
0.045 mPa @ 25°C.
- Partition Coefficient:
- Adsorption Coefficient: 100,000.
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