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IN VITRO DERMAL ABSORPTION OF PYRETHROID PESTICIDES IN RAT AND HUMAN SKIN
Citation:
HUGHES, M. F. AND B. C. EDWARDS. IN VITRO DERMAL ABSORPTION OF PYRETHROID PESTICIDES IN RAT AND HUMAN SKIN. Presented at 45th Annual Society of Toxicology Meeting 2006, San Diego, CA, March 05 - 09, 2006.
Description:
Pyrethriods are a class of neurotoxic pesticides and their use may lead to dermal exposure. This study examined the in vitro dermal absorption of pyrethroids in rat and human skin. Dorsal skin removed from adult male LD rats (hair clipped 24 h previously) was dermatomed and mounted in flow-through diffusion cells. Dermatomed human cadaver skin was also used. Radiolabeled bifenthrin (B), deltamethrin (D) or cis-permethrin (P) (rat-10, 30 and 100 nmole; human-10 and 100 nmole) was applied in acetone to the skin. Fractions of receptor fluid were collected every 4 h. At 24 h, the skins were washed with a soap:water mixture to remove unabsorbed chemical. The skin was then solubilized. Two additional experiments with rat skin were done after the wash. These were tape-stripping the skin and collection of receptor fluid for an additional 24 h. Receptor fluid, tape strips, solubilized skin and skin washes were analyzed for radioactivity. In rat, the 24 h cumulative % of the applied dose in the receptor fluid ranged from 1.2-1.5$ for B, 1.3-4.0% for D and 2.3-4.5% for P. In the wash, the % dose was 59.4-68.8% for B, 26.0=27.6^ for D and 33.3-41.3% for P. The % dose in skin was 32.9-42.6% for B, 26.0-27.6% for D and 33.3-41.3% for P. Tape stripping washed skin at 24 h removed 5.3% of the dose for B, 4.5% for D and 1.35 for P. The % dose in the receptor fluid collected from 24-48 h was 1.1% for B, 2.0% for D and 3.1% for P. For human skin, the 24 h cumulative % dose in receptor fluid was 1.0-1.2% for B, 1.3-1.5% for D and 2.1-2.2% for P. In the wash, the % dose was 75.4-82.6% for B, 78.1-78.7% for D and 70.6-72.0% for P. The % dose in skin was 13.8-20.7% for B, 13.8-14.8% for D and 21.8-24.4% for P. Rat skin is more permeable than human skin to B, D and P. A low percentage of these compounds completely penetrated rat and human skin. However, a considerable amount remains in the skin after washing and may completely diffuse through the skin. Consideration of the skin type used and fractions analyzed are important when using in vitro dermal absorption data for risk assessment. (This abstract may not represent US EPA policy.)