CHEMICALS SUMMARY PAGE

Permethrin (Insecticide):

Summary Information
Classification Chemicals / Complex Chemical Agents/ Chemical:
Alternative Names
  • Chemical Name: 3-phenoxybenzyl(1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate
  • Trade and chemical names include: Ambush; Ectiban; Pounce; 3-(2,2-Dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (3-phenoxyphenyl)methyl ester; (3-phenoxyphenyl)methyl (+/-)-cis,trans-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate; m-phenoxybenzyl (+/-)cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate; FMC 33297; indothrin; BW-21-Z; Eksmin; Kafil; Permasect; Perthrine; Pramex; Outflank; Talcord; Nix; Dragnet; (3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate; Ketokil; Biomist; Pertox; Persect; Anomethrin N; Antiborer 3768; Atroban; Chinetrin; Coopex; Corsair; Cyclopropanecarboxylic acid, 3-(2,2-dichlorovinyl)-2,2-dimethyl-, 3-phenoxybenzyl ester, (+-)-, (cis,trans)-; Diffusil h; Ecsumin; Efmethrin; Exmin; Ipitox; Kavil; Kestrel; Matadan; MP 79; NIA-33297; Outflank-stockade; Perigen; Perigen W; Permanone 10; Permanone 40; Permethrin, mixed cis,trans; 3-Phenoxybenzyl 2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecarboxylate; 3-Phenoxybenzyl 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate; Spartan; Stomoxin; 3-phenoxy benzyl (1RS)-cis,trans-3-(2,2 dichlorovinyl)-2,2 dimethyl-cyclopropane carboxylate. (W324.Oct01.WNV1)
  • Permethrine; 3-phenoxybenzyl (1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate (IUPAC); (3-phenoxyphenyl)methyl (±)-cis,trans-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate (CAS). (W325.May01.WNV1)
Chemical Formulation Permethrin is available in dusts, emulsifiable concentrates, smokes, ULV (ultra-low volume), and wettable powder formulations. (W180.Feb02.WNV6; W325.May01.WNV1)
Chemical Formula C21H20Cl2O3 (W324.Oct01.WNV1)
Chemical Structure

(W325.May01.WNV1)

Molecular Weight 391.30 (W180.Feb02.WNV6; W325.May01.WNV1); 391.2932 (W324.Oct01.WNV1)
Appearance
  • Odourless, colourless crystalline solid or a pale brown viscous liquid. (W180.Feb02.WNV6); colourless crystals to a viscious liquid. Colour, water white to pale yellow. (W325.May01.WNV1)
Physical Properties
  • Melting point: 34 – 35°C (W324.Oct01.WNV1); approximately 35°C (analytical grade). (W325.May01.WNV1)
  • Boiling point: 200°C at 0.05 mm Hg (W324.Oct01.WNV1); 220°C at 0.05 mm Hg. (W325.May01.WNV1)
  • Density: 1.19 (W324.Oct01.WNV1); specific gravity 1.190-1.272 at 20°C. (W325.May01.WNV1)
  • Water solubility: Insoluble. 0.00002 g/100 ml (W324.Oct01.WNV1); less than1 ppm. (W325.May01.WNV1)
  • Other solubility: Soluble, miscible with most organic solvents except ethylene glycol. Soluble in acetone, ethanol, ether, and xylene. (W325.May01.WNV1)
  • Vapour pressure: <10 Torr. at 50°C. (W325.May01.WNV1)
Chemical Actions  Synthetic pyrethroid insecticide.(W325.May01.WNV1)
  • Pyrethroids are contact poisons which rapidly penetrate the nervous system of an insect. They produce a quick "knock down" and are highly toxic to insects at very low rates of application. They are more effective against insects and less toxic to mammals than are the natural pyrethrins. (B250, W180.Feb02.WNV9)
Chemical Uses Permethrin is 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 build up of mites by reducing mite predator populations. (W180.Feb02.WNV6)
  • For mosquito (Culicidae - Mosquitoes (Family)) control: pyrethroids are applied in an Ultra-Low-Volume Spray formulation, typically mixed with a synergist compound, piperonyl butoxide, which enhances the effectiveness of the active ingredient. The product is applied at rates of between 0.003 and 0.007 pounds of active ingredient per acre (equivalent to 2 to 3.5 fluid ounces of the mixed formulation per acre). (W179.Nov01.WNV13)

Toxicity Rating Permethrin is a moderately to practically non-toxic pesticide in 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.
  • Pyrethroids are considered to pose slight risks of acute toxicity to humans (Homo sapiens - Human), but at high doses, pyrethroids can affect the nervous system. (W179.Nov01.WNV13)

  • Tech (Rat) (Laboratory rat (Rattus norvegicus - Brown rat)): Oral LD50 430-4000 mg/kg. Value varies depending upon factors such as carrier, test species, etc. Dermal LD50 >2500 mg/kg. Inhalation LC50 >685 mg/m3 of air. (Rabbit) (Oryctolagus cuniculus - European rabbit (Domestic rabbit)): Dermal LD50 >2000 mg/kg.(W325.May01.WNV1)

  • Acute toxicity:
    • Comparatively non-toxic in many mammals including humans. (P32.1.w8)
    • 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 permethrin 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. 
    • Permethrin 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.

    (W180.Feb02.WNV6, P32.1.w8)

    • Following very high exposure to pyrethroids (e.g. workers involved in mixing or applying pyrethroids), abnormal facial sensation, dizziness, salivation, headache, fatigue, vomiting, diarrhoea and irritability to sound/touch may occur. In severe cases there may be pulmonary oedema, seizures, paraesthesias and fasciculations. (W214.Nov01.WNV6)
  • Chronic toxicity:

    (W180.Feb02.WNV6)

  • Reproductive effects:
    • The fertility of female rats was affected when they received very high oral doses of 250 mg/kg/day of permethrin during the 6th to 15th day of pregnancy. 
    • It is not likely that reproductive effects will be seen in humans under normal circumstances. 

    (W180.Feb02.WNV6)

  • Teratogenic effects:
    • Permethrin is reported to show no teratogenic activity. (W180.Feb02.WNV6)
  • Mutagenic effects:
    • Permethrin is reported to show no mutagenic activity. (W180.Feb02.WNV6)
  • Carcinogenic effects:
    • The evidence regarding the carcinogenicity of permethrin is inconclusive. (W180.Feb02.WNV6)
  • Organ toxicity:
    • Permethrin is suspected of causing liver enlargement and nerve damage. 
    • Effects on the immune system have been noted in animal studies.

    (W180.Feb02.WNV6)

  • Fate in humans and animals:
    • 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 enzymes. 

    (W180.Feb02.WNV6)

"PROTECTIVE CLOTHING: Hat or other suitable head covering, long-sleeved shirt, long-legged trousers or coverall type garment (all of closely woven fabric covering the body, including the arms and legs), shoes, and socks." (W325.May01.WNV1)

"HANDLING AND STORAGE CAUTIONS: Keep out of lakes, streams, or ponds. Do not apply when weather conditions favor drift from treated areas. Do not contaminate water by cleaning of equipment, or disposal of wastes near a body of water. Avoid contact with eyes, skin, or clothing. Avoid breathing vapor or spray mist. Wash thoroughly after handling. Do not store near food, feed, heat, or open flame." (W325.May01.WNV1)

Environmental Persistence
  • 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. 

    (W180.Feb02.WNV6)

  • Breakdown in 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 water.

    (W180.Feb02.WNV6)

  • Breakdown 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.

    (W180.Feb02.WNV6)

Effects on Non-target Species
  • Effects on birds (Aves - Birds (Class)):
    • Permethrin is practically non-toxic to birds.
      • The oral LD50 for the permethrin formulation "Pramex" is greater than 9900 mg/kg in mallard ducks, greater than 13,500 mg/kg in pheasants, and greater than 15,500 mg/kg in Japanese quail.
      • Very low levels in the diet (0.1 ppm) for chickens for three to six weeks after hatching were reported to be immunosuppressive. (P32.1.w8)

    (W180.Feb02.WNV6)

  • 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 bluegill sunfish and 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. 
    • The bioconcentration factor for permethrin in bluefish is 715 times the concentrations in water and is 703 in catfish. This indicates that the compound has a low to moderate potential to accumulate in these organisms. 

    (W180.Feb02.WNV6)

  • 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 should not be applied, or allowed to drift, to crops or weeds in which active foraging by bees takes place.

    (W180.Feb02.WNV6, P32.1.w8)

Management Techniques

ORGANISATIONS
(USA Contacts for Managing WNV Disease)

ELECTRONIC LIBRARY
(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

Authors Debra Bourne (V.w5)
Referee Suzanne I. Boardman (V.w6); Becki Lawson (V.w26)

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