Human dose-excretion studies with the pyrethroid insecticide cyfluthrin : urinary metabolite profile following inhalation

Abstract

1. Nine male volunteers were exposed to the pyrethroid insecticide cyfluthrin. The study was performed in an exposure room, where an aerosol containing cyfluthrin was sprayed to obtain atmospheres with mean cyfluthrin concentrations of 160 and 40 μg/m3. Four volunteers were exposed for 10, 30 and 60 min at 160 μg/m3 and another five volunteers were exposed for 60 min at 40 μg/m3. For 160 μg/m3 exposure urine samples were collected before and immediately after exposure as well as for the periods 1-2, 2-3, 3-4, 4-5, 5-6, 6-12 and 12-24 h after exposure. For 40 μg/m3 exposure urine samples were collected before and 2 h after exposure. 2. The main urinary cyfluthrin metabolites, cis-trans-3-(2,2-dichlorovinyl)- 2,2- dimethylcyclopr opane carboxylic acid (DCCA) and 4-fluoro-3-phenoxybenzoic acid (FPBA), were determined. The limit of detection (LOD) for all metabolites was 0·0025 μg in an urine sample of 5 ml (0·5 μg/l). After inhalative exposure of 40 μg cyfluthrin/m3 air for 60 min, the amount of metabolites in urine collected in the first 2 h after exposure was less than the LOD, namely 0·14 μg for cis-DCCA, 0·15-0·28 μg for trans-DCCA and 0·12-0·23 μg for FPBA. 3. Of the metabolites, 93% was excreted within the first 24 h (peak excretion rates between 0·5 and 3 h) after inhalative exposure of 160 μg/m3. The mean half-lives were 6·9 h for cis-DCCA, 6·2 h for trans-DCCA and 5·3 h for FPBA. 4. The mean trans-:cis-DCCA ratio was 1·9 for the time course as well as for each subject. 5. The amount of metabolites in urine depends on the applied dose, on the exposure time and shows interindividual differences.