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A pyrethroid is a synthetic chemical compound similar to the natural chemical pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids are common in commercial products such as household insecticides and insect repellents. In the concentrations used in such products, they are generally harmless to human beings but can harm sensitive individuals.1 They are usually broken apart by sunlight and the atmosphere in one or two days, and do not significantly affect groundwater quality except for being toxic to fish.2
Pyrethroids are axonic poisons that work by keeping the sodium channels open in the neuronal membranes of insects. The sodium channel is a small hole through which sodium ions are permitted to enter the axon and cause excitation. As the nerves cannot de-excite, the insect is paralyzed.
Pyrethroids are usually combined with piperonyl butoxide, a known inhibitor of key microsomal oxidase enzymes. This prevents these enzymes from clearing the pyrethroid from the body of the insect, and assures the pyrethroid will be lethal and not merely a paralyzing agent. Combined, pyrethroids are toxic to most beneficial insects such as bees and dragonflies.
The pyrethroid chrysanthemic acid is produced industrially in a cyclopropanation reaction of a diene as a mixture of cis- and trans isomers followed by hydrolysis of the ester 3:
The compound is the starting material for many derivatives by re-esterfication.
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Commercial Pyrethroid Insecticides/Repellants
- Allethrin, the first pyrethroid synthesized (active ingredient of Raid)
- Bifenthrin, active ingredient of Talstar, Capture, Ortho Home Defense Max, and Bifenthrine
- Cypermethrin
- Deltamethrin
- Permethrin
- Prallethrin4
- Resmethrin, active ingredient of Scourge
- Sumithrin, active ingredient of Anvil
- Tetramethrin
- Tralomethrin
- Transfluthrin, active ingredient of Baygon
- Imiprothrin, active ingredient of Raid Ant & Roach Killer, synthesized to be an extremely fast-acting toxin by Sumitomo Chemical Co. in Canada. 5
Possible link to Autism
A recent study (2008), led by lead author Irva Hertz-Picciotto, professor in the Department of Public Health Sciences at University of California, Davis, suggested a correlation between pyrethrins and autism. In the study of 500 children (with or without autism), the 138 children with autism and their mothers were twice as likely to "report using pet shampoos and other household products containing pyrenthrins than other mothers". There is no causation link established, however, and the correlation, while considered to be statistically strong, needs to be investigated further.6
References
- ^ Pyrethroids fact sheet from the Illinois Department of Public Health.
- ^ "Permethrin, Resmethrin, Sumithrin: Synthetic Pyrethroids For Mosquito Control". United States Environmental Protection Agency (April 17, 2002). Retrieved on 2008-04-04.
- ^ A synthesis of chrysanthemic ester: An undergraduate experiment. Kelly, Lawrence F. J. Chem. Educ. 1987, 64, 1061.
- ^ prallethrin data sheet
- ^ http://pr-rp.pmra-arla.gc.ca/PR_SOL/pr_web.ve1?p_ukid=6111
- ^ http://abcnews.go.com/Health/OnCall/story?id=4857380&page=1
External links
- Pyrethrins and pyrethroids on the EXTOXNET
- Environmental Health Perspectives Journal Estrogenic Potential of Certain Pyrethroid Compounds...
Wikipedia content modification information:
- This page was last modified on 31 October 2008, at 16:58.
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