Page "Pyrethroid" Paragraph 7

By 1974, the Rothamsted team had discovered a 2nd generation of more persistent compounds notably: permethrin, cypermethrin and deltamethrin.

They are substantially more resistant to degradation by light and air, thus making them suitable for use in agriculture, but they have significantly higher mammalian toxicities.

Over the subsequent decades these derivatives were followed with other proprietary compounds such as fenvalerate, lambda-cyhalothrin and beta-cyfluthrin.

Most patents have now expired, making these compounds cheap and therefore popular ( although permethrin and fenvalerate have not been re-registered under the 91 / 414 / EEC process ).

One of the less desirable characteristics, especially of 2nd generation pyrethroids is that they can be an irritant to the skin and eyes, so special formulations such as capsule suspensions ( CS ) have been developed.