ABSTRACT
Permethrin has the chemical name 3-phenoxyphenylmethyl (±)-cis, trans-3-(2,2-dichloroethenyl),2,2-dimethylcyclopropanecarboxylate; the empirical formula is C21H20Cl2O3; the molecular weight, 391.3. Permethrin is a synthetic pyrethroid, and occurs as a mixture of cis and trans isomers (Taplin and Meinking, 1996). Synthetic pyrethroids are structural derivatives of the naturally occurring pyrethrins, extracted from the flowers of Chrysanthemum cinerarifolium. In some countries, including the United States, only formulations having the 25:75 cis:trans ratio are approved for human use because the cis isomer has higher mammalian toxicity than the trans isomer (Taplin and Meinking, 1996). The cis:trans compositions of permethrin products not approved for human use may differ. Permethrin was first formulated by Michael Elliott and colleagues at the Rothampstead Experimental Station (U.K.) in 1973, and, although it was not the first active synthetic pyrethroid produced, its high activity as an insecticide plus its photostability and thermostability made it suitable for commercial development (Elliott et al., 1973). The chemical structure of permethrin is shown in Figure 210.1. Chemical structure of permethrin. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315152110/08d8042d-9481-4a8d-8c27-9bd589f6de6b/content/fig210_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>
