Riviere, J.E. and R.E. Baynes. Inert Ingredients in Pesticide Mixtures Influence the Dermal Absorption of Carbaryl. The Toxicologist 1998. 42(I-S): 391.

carbaryl - 00063-25-2; dimethyl sulfoxide - 00067-68-5; acetone - 00067-64-1; DEET - 00134-62-3; 1-naphthol - 00090-15-3; sodium lauryl sulfate - 00151-21-3; piperonyl butoxide - 00051-03-6

Insecticides used in animal or crop agriculture are usually formulated to contain inert ingredients, some of which can potentially modulate transdermal flux of active ingredients. The aim of this study was to assess the influence of several formulation additives on the percutaneous absorption and disposition of the carbamate insecticide, carbaryl (CA). In this 8-hour in vitro flow through diffusion study, porcine skin sections were dosed with 40 ug/cm² CA, different levels of solvents (40 or 80% acetone or dimethyl sulfoxide, DMSO), different levels of a surfactant (0, 1, 5% sodium lauryl sulfate, SLS), an insect repellant (0 or 15% Diethyl-m-toluamide, DEET), an insecticide synergist (0 or 2% piperonyl butoxide, PB), and a carbaryl metabolite acetone than with DMSO mixtures, while CA penetration into skin and stratum corneum was greater with DMSO at 8 hours. SLS enhanced CA absorption especially at low solvent concentrations. DEET significantly reduced CA absorption in acetone but not in DMSO mixtures, while 1-NA enhanced CA absorption in acetone, but not in DMSO. PB significantly enhanced carbaryl absorption in acetone, but not in DMSO. PB significantly enhanced carbaryl absorption in acetone and DMSO mixtures. However, addition of PB or PB +SLS did not significantly increase CA flux above that observed with solvent +surfactant mixtures. In conclusion, this study demonstrated that inert ingredients can significantly modulate percutaneous absorption of toxicologically important pesticides.