AskDefine | Define pyrethrin

User Contributed Dictionary



  1. either of a number of naturally occurring insecticides extracted from the pyrethrum plant; unusual in having a cyclopropane ring

Extensive Definition

The pyrethrins are a pair of natural organic compounds that have potent insecticidal activity. Pyrethrin I and pyrethrin II are structurally related esters with a cyclopropane core. They differ by the oxidation state of one carbon. They are viscous liquids that oxidize readily to become inactivated.
The pyrethrins are contained in the seed cases of the perennial plant pyrethrum (Chrysanthemum cinerariaefolium), which is grown commercially to supply the insecticide. Although extracts of the plant were already used as insecticide, the structure was first published by Hermann Staudinger and Lavoslav Ružička in 1924. Pyrethrins are neurotoxins that attack the nervous systems of all insects. When present in amounts not fatal to insects, they still appear to have an insect repellent effect. They are harmful to fish, but are far less toxic to mammals and birds than many synthetic insecticides. They are non-persistent, being biodegradable, and also break down easily on exposure to light or oxygen. They are considered to be amongst the safest insecticides for use around food. For humans, pyrethrin is known to irritate eyes, skin, and respiratory systems. Due to its relatively inert properties toward mammals, pyrethrins are gradually replacing organophosphates and organochlorides as the pesticide of first choice.
Recently, a non-peer reviewed claim was made suggesting a link between pyrethrin use and autism in children. It was found that mothers of autistic children were twice as likely to have washed their pet dog with pyrethrin containing anti-flea shampoo in the months preceding the birth of their autistic child. However, correlation does not imply causation. Instead, for example, the increased preference (or recollection) to use cleaning agents amongst mothers of autistic children maybe due to their different psychological profile related to a underlying genetic etiology.
The chemical structure of pyrethrins is the basis for a variety of synthetic insecticides called pyrethroids such as permethrin and cypermethrin.
pyrethrin in Bengali: পাইরেথ্রিন
pyrethrin in Catalan: Piretrina
pyrethrin in German: Pyrethrine
pyrethrin in Spanish: Piretrina
pyrethrin in French: Pyréthrine
pyrethrin in Dutch: Pyrethrine
pyrethrin in Portuguese: Piretrina
pyrethrin in Vietnamese: Pyrethrin
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