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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Permethrin

Trade and Other Names: Trade names include Ambush, BW-21-Z, Cellutec, Dragnet, Ectiban, Eksmin, Exmin, FMC 33297, Indothrin, Kafil, Kestrel, NRDC 143, Pounce, PP 557, Pramex, Qamlin, and Torpedo.

Regulatory Status: 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. 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.

Chemical Class: pyrethroid

Introduction: 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 mite buildup by reducing mite predator populations. Permethrin is available in dusts, emulsifiable concentrates, smokes, ULV (ultra-low volume), and wettable powder formulations.

Formulation: Permethrin is available in dusts, emulsifiable concentrates, smokes, ULV (ultra-low volume), and wettable powder formulations.

Toxicological Effects:

• Acute toxicity: 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 [12]. 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 [12,2]. Permethrin caused mild irritation of both the intact and abraded skin of rabbits. It also caused conjunctivitis when it was applied to the eyes [9]. 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 [12].
• Chronic toxicity: No adverse effects were observed in dogs fed permethrin at doses of 5 mg/kg/day for 90 days [15]. Rats fed 150 mg/kg/day for 6 months showed a slight increase in liver weights [9]. Very low levels of permethrin in the diet of chickens (0.1 ppm for 3 to 6 weeks after hatching) have been reported to suppress immune system activity [9].
• 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 [25]. It is not likely that reproductive effects will be seen in humans under normal circumstances.
• Teratogenic effects: Permethrin is reported to show no teratogenic activity [9].
• Mutagenic effects: Permethrin is reported to show no mutagenic activity [9].
• Carcinogenic effects: The evidence regarding the carcinogenicity of permethrin is inconclusive.
• Organ toxicity: Permethrin is suspected of causing liver enlargement of the liver and nerve damage [9]. Effects on the immune system have been noted in animal studies.
• Fate in humans and animals: Permethrin is efficiently metabolized by mammalian livers [40]. Breakdown products, or "metabolites," of permethrin are quickly excreted and do not persist significantly in body tissues [41]. 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 [41]. Permethrin may persist in fatty tissues, with half-lives of 4 to 5 days in brain and body fat [9]. Permethrin does not block, or inhibit, cholinesterase enzymes [40].

Ecological Effects:

• Effects on birds: Permethrin is practically non-toxic to birds [12]. 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 [41].
• 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 [41]. The 48-hour LC50 for rainbow trout is 0.0125 mg/L for 24 hours, and 0.0054 mg/L for 48 hours [12]. The 48-hour LC50 in bluegill sunfish and salmon is 0.0018 mg/L [12]. 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 [42]. 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.
• 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 [2,43]. Permethrin is also toxic to wildlife [9]. It should not be applied, or allowed to drift, to crops or weeds in which active foraging takes place [12].

Environmental Fate:

• 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 [12,25]. 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 [44]. Permethrin is tightly bound by soils, especially by organic matter. Very little leaching of permethrin has been reported [45]. It is not very mobile in a wide range of soil types [41]. Because permethrin binds very strongly to soil particles and is nearly insoluble in water, it is not expected to leach or to contaminate groundwater.
• 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 [44]. Permethrin degrades rapidly in water, although it can persist in sediments [15,45]. There was a gradual loss of toxicity after permethrin aged for 48 hours in sunlight at 0.05 mg/L in water [45].
• 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 [12].

Physical Properties:

• Appearance: Permethrin is an odorless, colorless crystalline solid or a viscous liquid that is pale brown [12].
• Chemical Name: 3-phenoxybenzyl(1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate [12]
• CAS Number: 52645-53-1
• Molecular Weight: 391.30
• Water Solubility: ca. 0.2 mg/L @ 20 C [12], insoluble in water
• Solubility in Other Solvents: s. in most organic solvents except ethylene glycol [12]
• Melting Point: 34-35 C [12]
• Vapor Pressure: 0.045 mPa @ 25 C [12]
• Partition Coefficient: 6.1004[12]
• Adsorption Coefficient: 100,000 [26]

Exposure Guidelines:

• ADI: 0.05 mg/kg/day [29]
• MCL: Not Available
• RfD: 0.05 mg/kg/day [30]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Zeneca Ag Products
1800 Concord Pike
Wilmington, DE 19897

• Phone: 800-759-4500
• Emergency: 800-759-2500
  

References:

References for the information in this PIP can be found in Reference List Number 2

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.