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Publication #PI-54

Pesticide Toxicity Profile: Synthetic Pyrethroid Pesticides1

Frederick M. Fishel2

This document provides a general overview of human toxicity, provides a listing of laboratory animal and wildlife toxicities and a cross reference of chemical and common names with their trade names of many synthetic pyrethroid pesticides registered for use in Florida.

General

Pyrethrins were originally derived from East African chrysanthemum flowers and were shown to have insecticidal activity. In a natural environment, they were chemically unstable and broke down rapidly upon exposure to air and sunlight. Beginning in the 1970s, synthetic pyrethroids came into the market for agricultural purposes as they were synthesized from petroleum derivatives. They are also widely used as home and garden insecticides along with uses on pets and livestock, mosquito control, treatment of transport vehicles, and for treatment of ectoparasitic disease. Their desirable features provide a quick knockdown of insects at low rates, relatively low mammalian toxicity, and improved stability in outdoor environments, which has increased their marketability in agriculture. They are effective against a wide range of insect and mite pests and may be mixed with other pesticides for a broad spectrum of pest control. Formulations that are commercially available include aerosols, dips, emulsifiable concentrates, wettable powders, granules, and concentrates for ultra low volume applications targeting mosquitoes. Pyrethroids may be mixed with piperonyl butoxide, a synergist, which enhances the effect of the active ingredient. Their mode of action is interference with transmission of nerve impulses.

Toxicity

Pyrethroids are one of the least acutely toxic insecticides to mammals because they are quickly deactivated by metabolic processes. However, rats fed high doses (1,000 mg/kg of body weight) showed liver damage (Hayes 1982). Toxicity by inhalation and dermal absorption is low. Sensitization sometimes occurs in some individuals after a single exposure, which causes either an asthmatic condition or a skin rash or inflammation. After the initial exposure to the sensitizing agent, the sensitized individual responds to a dose smaller than the initial dose. Symptoms are more common with exposure to the pyrethroids whose structures include cyano-groups. Sensations are described as stinging, burning, itching, and tingling, progressing to numbness, with the face most commonly affected. Persons treated with permethrin for lice or flea infestations sometimes experience itching and burning at the site of application, but this is more of a reaction to the effects of the parasites themselves. Due to the inclusion of certain solvents, some formulations of fluvalinate are corrosive to the eyes. Scientists have no data from work-related, accidental poisonings, or epidemiological studies that indicate whether or not pyrethrins are likely to cause cancer in humans. There were no birth defects in pups of rabbits exposed to pyrethrins (Vettorazzi 1979); however, rat pups born to rats fed very high doses of pyrethrins for three weeks prior to mating were of low body weights (Hayes 1982). Pyrethrins are highly toxic to fish and tadpoles. They affect their skin touch receptors and balance organs (Tomlin 1994). Mammalian toxicities for pyrethroid pesticides registered in Florida are shown in Table 1. Table 2 lists the toxicities to wildlife by the common name of the pyrethroid pesticide. Table 3 provides a cross listing of many of the trade names that these products are registered and sold by in Florida.

Additional Information

  • Crop Protection Handbook. 2014. vol. 100. Willoughby, Ohio: Meister Publishing Co. http://www.meistermedia.com/publications/meisterpro-crop-protection-handbook/ [3 April 2013].

  • Hayes, W.J. 1982. Pesticides studied in man. Baltimore: Williams and Wilkins.

  • Nesheim, O.N., F.M. Fishel and M.A. Mossler. 2005. Toxicity of Pesticides UF/IFAS EDIS Document PI-13. (http://edis.ifas.ufl.edu/PI008)

  • Reigart, J.R. and J.R. Roberts. 2013. "Recognition and Management of Pesticide Poisonings." (6th ed.) United States Environmental Protection Agency Publication EPA-735K-13001 .

  • Seyler, L.A., et.al. 1994. Extension Toxicology Network (EXTOXNET). Cornell University and Michigan State University. http://extoxnet.orst.edu/index.html. Visited February 2014.

  • Tomlin, C. (Ed.). 1994. "A World Compendium. The Pesticide Manual. Incorporating the Agrochemicals Handbook." (10th ed.). Bungay, Suffolk, U.K.: Crop Protection Publications.

  • Vettorazzi, G. 1979. "International Regulatory Aspects for Pesticide Chemicals." Toxicity Profiles (vol. 1), Boca Raton, FL: CRC Press, Inc.

Table 1. 

Pyrethroid pesticide mammalian toxicities (mg/kg of body weight).

Common name

Rat oral LD50

Rabbit dermal LD50

Allethrin

860

11,332

Bifenthrin

375

>2,000

Cyfluthrin

869–1271

>5,000 (rat)

Cyhalothrin

79

632 (rat)

Cypermethrin

250

>2,000

Deltamethrin

31–139 (female)

>2,000

Esfenvalerate

451

2,500

Fenpropathrin

70.6–164

>2,000

Fluvalinate

261–282

>20,000

Permethrin

430–4,000

>2,000

Resmethrin

1,244 - >2,500

>2,500

Tefluthrin

969

>2,000 (rat)

Tetramethrin

>5,000

>2,000

Tralomethrin

284

>2,000

Table 2. 

Pyrethroid pesticide wildlife toxicity ranges.

Common name

Bird acute oral LD50 (mg/kg)*

Fish LC50 (ppm)**

Bee LD50

Allethrin

PNT

HT

HT

Bifenthrin

ST–PNT

HT

HT

Cyfluthrin

PNT

VHT

HT

Cyhalothrin

PNT

HT

HT

Cypermethrin

PNT

VHT

HT

Deltamethrin

PNT

HT

HT

Esfenvalerate

PNT

VHT

HT

Fenpropathrin

ST

VHT

HT

Fluvalinate

PNT

VHT

MT

Permethrin

PNT

VHT

HT

Resmethrin

PNT

VHT

HT

Tefluthrin

ST–PNT

VHT

HT

Tetramethrin

PNT

HT

Tralomethrin

VHT

HT

*Bird LD50: Practically nontoxic (PNT) = >2,000; slightly toxic (ST) = 501–2,000; moderately toxic (MT) = 51–500; highly toxic (HT) = 10–50; very highly toxic (VHT) = <10.

**Fish LC50: PNT = >100; ST = 10–100; MT = 1–10; HT = 0.1–1; VHT = <0.1.

Bee: HT = highly toxic (kills upon contact as well as residues); MT = moderately toxic (kills if applied over bees); PNT = relatively nontoxic (relatively few precautions necessary).

Table 3. 

Cross reference list of common, trade and chemical names of pyrethroid insecticides.

Common name*

Trade names**

Chemical name

Allethrin

Many household products

(RS)-3-allyl-2-methyl-4-oxycyclopent-2-enyl (1RS)-cis-trans chrysanthemate

Bifenthrin

Capture®, Talstar®

[1-alpha,3-alpha-(Z)]-(+)-(2 methyl[1,1'-biphenyl]-3yl) methyl 3-(2,chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate

Cyfluthrin

Baythroid®, Tame®

Cyano(4-fluoro-3-phenoxyphenyl)methyl 3-(2,2-dichloro-ethenyl)-2,2-dimethylcyclopropanecarboxylate

Cyhalothrin

Karate®, Warrior®, Demand®, Scimitar®

alpha-cyano-3-phenoxybenzyl 3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropanecarboxylate

Cypermethrin

Ammo®, Fury®, Mustang®

(+)-alpha-cyano-3-phenoxybenzyl (+)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethycyclopropanecarboxylate

Deltamethrin

Decis®, DeltaGard®, Demand®

(S)-cyano(3-phenoxybenzyl) (1R,3R)-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate

Esfenvalerate

Asana®

(S)-cyano(3-phenoxyphenyl)methyl (S)-4-chloro-alpha-(1-methylethyl)-benzeneacetate

Fenpropathrin

Danitol®, Tame®

RS-alpha-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate

Fluvalinate

Mavrik®, Zoecon®

Á-RS,2R)-fluvalinate [(RS)-alpha-cyano-3-phenoxybenzyl (R)-2-[2-chloro-4-(trifluoromethyl)anilino]-3-methyl-butanoate]

Permethrin

Ambush®, Pounce®

(3-phenoxyphenyl)methyl (+)-cis,trans-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate

Resmethrin

Many household products

([5-(phenylmethyl)-3-furanyl]methyl 2,2-dimethyl-3-(2-methyl-1-proenyl)cyclopropanecarboxylate)

Tefluthrin

Force®

2,3,5,6-tetrafluoro-4-methylbenzyl (Z)-(1 RS, 3RS)-3-(2-chloro-3,3,3-trifluoroprop-1-ethyl) -2,2-dimethylcyclopropanecarboxylate

Tetramethrin

Many household products

3,4,5,6-tetrahydrophthalimidomethyl (1RS)-cis,trans-chrysanthemate

Tralomethrin

Scout®

(1R,3S)3[(1',2',2',2',-tetrabromoethyl)]-2,2-dimethylcyclopropanecarboxylic acid (S)-alpha-cyano-3-phenoxybenzyl ester

*Basic molecule; isomers not listed.

**Does not include manufacturers prepackaged mixtures; major agricultural brands for basic manufacturers.

Footnotes

1.

This document is PI54, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date June 2005. Revised February 2014. Reviewed February 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Frederick M. Fishel, professor, Agronomy Department, and director, Pesticide Information Office; UF/IFAS Extension, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.


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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.