Human dose-excretion studies with the pyrethroid insecticide, cypermethrin.

1. An analytical method for monitoring human exposure to cypermethrin has been developed, based on the detection of the free and conjugated forms of the urinary metabolite, the cyclopropanecarboxylic acid. 2. Four male subjects were given a single oral dose, ranging from 0.25 mg to 1.5 mg, of a 1:1 cis/trans mixture of cypermethrin, and urine was monitored for the free and conjugated cyclopropanecarboxylic acid. Urinary excretion of the individual metabolites (cis and trans isomers) was similar for the different dosages. Subjects excreted, on average, 78% of the trans isomer dose, and 49% of the cis isomer dose respectively in 24 h. 3. Thus, as in other mammals, ester cleavage and elimination of the cis and trans cyclopropanecarboxylic acid moieties in the free and conjugated form is a major route of metabolism of cypermethrin in man.