Biomarkers for monitoring transfluthrin exposure: urinary excretion kinetics of transfluthrin metabolites in rats.

The urinary excretion kinetics of a fluorine-containing pyrethroid transfluthrin [(2,3,5,6-tetrafluorophenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate], which is widely used recently as mosquito repellents, was examined in rats to search for urinary metabolites suitable as biomarkers for monitoring transfluthrin exposure of the general population. After a single dose of 26, 64, 160 or 400 mg/kg body weight of transfluthrin had been administered intraperitoneally to male Sprague-Dawley rats, their urine was collected periodically for one week. Three major urinary transfluthrin metabolites were measured: 2,3,5,6-tetrafluorobenzyl alcohol, 2,3,5,6-tetrafluorobenzoic acid and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid. The kinetics was evaluated by moment analysis of the urinary excretion rate of the metabolites versus time curves. The urinary excretion amounts of these three metabolites were estimated to be proportional to the absorption amounts of transfluthrin over a wide exposure range. Urinary 2,3,5,6-tetrafluorobenzoic acid was considered to be an optimal biomarker for monitoring transfluthrin exposure.