INFLUENCE OF INERT INGREDIENTS IN PESTICIDE FORMULATIONS ON DERMAL ABSORPTION OF CARBARYL

Objectives-To assess the influence of solvent plus various mixtures on percutaneous absorption and disposition of the carbamate insecticide, carbaryl (CA). Animals-Skin was obtained from the dorsum of 14 female weanling specific-pathogen-free Yorkshire pigs, Procedure-In this 8-h our in vitro flow-through diffusion study, porcine skin sections were dosed with 40 mu g of CA/cm(2) of surface area, different amounts of s olvents (40 or 80% acetone or dimethyl sulfoxide [DMSO]), different am ounts of a surfactant (0, 1, or 5% sodium lauryl sulfate [SLS]), an in sect repellent (0 or 15% diethyl-m-toluamide [DEET]), an insecticide s ynergist (0 or 2% piperonyl butoxide [PB]), and a CA metabolite (40 mu g/cm(2) 1-naphthol [1-NA]). Results-In general, CA absorption was gre ater from acetone than from DMSO mixtures, and CA penetration into ski n and stratum corneum was greater from DMSO at 8 hours. This is consis tent with the flux-time profiles, which depicted initial peak flux wit hin 2 to 3 hours for most acetone mixtures, but a slow increase in flu x for DMSO mixtures. Irrespective of the solvent, increasing water con tent in pesticide dosing mixtures significantly increased CA absorptio n from SLS mixtures only, The SLS also enhanced CA absorption, especia lly at low solvent concentrations. The DEET significantly reduced CA a bsorption from acetone, but not from DMSO mixtures, and 1-NA enhanced CA absorption from acetone, but not from DMSO mixtures. Piperonyl buto xide significantly enhanced CA absorption from acetone and DMSO mixtur es, However, addition of PB or PB plus SLS did not significantly incre ase CA flux above that observed from solvent plus surfactant mixtures. Conclusions-Inert ingredients can modulate percutaneous absorption of toxicologically important pesticides and their effect or activity on CA disposition is dependent on solvent specificity and solvent concent ration, Whereas SLS, PB, and 1-NA can enhance pesticide absorption, DE ET can reduce absorption.