Applicability of aspecific noninvasive methods for biomonitoring of occupational exposure to deltamethrin: preliminary study using an animal model

Deltamethrin (CAS registry No. 52918-63-5), a synthetic dibromo-pyrethroid insecticide is highly effective against a broad spectrum of insects, and is widely used on crops and in public health programs. Data on the genotoxicity and carcinogenicity of deltamethrin are rather controversial, depending on the genetic system or the assay used. The aim of the present study was to analyze previously demonstrated metabolic changes using aspecific noninvasive methods in rats which are potentially applicable for monitoring occupational exposure. Since human exposure to pesticides occurs not only to active principles but to all chemicals present in a commercial formulation, we tested both the pure compound and a deltamethrin-based commercial formulation. Groups of rats were treated, i.p., consecutively for 7 days. The daily doses tested were 5 and 10 mg/kg body weight for pure deltamethrin, corresponding to volumes of 178.57 and 377.14 microliter/kg body weight for the commercial formulation (containing 2.8% deltamethrin). Urine was analyzed for mutagenic metabolites, thioethers, and D-glucaric acid content. Faeces extracts were tested for mutagenicity. Results show that DGA urinary excretion values did not mirror the phase I enzyme induction capability of the insecticide. Results obtained for urinary thioethers do not agree completely with those obtained on the influence of deltamethrin on glutathione S-transferase activity in rat liver. In fact, after administration of the deltamethrin commercial formulation, highest thioether excretion values were obtained during the treatment time for treated animals, as compared to controls. The mean values (+/-SEM) of thioether excretion were 0. 033 +/- 0.002 micromole -SH/24 h for control animals, 0.122 +/- 0. 004 and 0.185 +/- 0.025 for the two treatment groups. Thence, thioether determination in urine samples seems to be a suitable aspecific noninvasive method for assessing exposure to deltamethrin-based formulations, particularly those containing xylene and mesitylene as solvents, as in the tested formulation. Negative or toxic results obtained in the urinary and faecal mutagenicity test seem to exclude the formation and excretion of mutagenic metabolites following treatment with deltamethrin.