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In vitro dermal absorption of pyrethroid pesticides in human and rat skin
Citation:
HUGHES, M. F. AND B. C. EDWARDS. In vitro dermal absorption of pyrethroid pesticides in human and rat skin. TOXICOLOGY AND APPLIED PHARMACOLOGY. Academic Press Incorporated, Orlando, FL, 246(1-2):29-37, (2010).
Impact/Purpose:
This manuscript examined the in vitro dermal absorption of 3 pyrethroid pesticides in rat and human cadaver skin. Complete absorption was low (5% of the dose or lower) over 24 hr. chemical in skin after washing was available to be absorbed.
Description:
Dermal exposure to pyrethroid pesticides can occur during manufacture and application. This study examined the in vitro dermal absorption of pyrethroids using rat and human skin. Dermatomed skin from adult male Long Evans rats or human cadavers was mounted in flowthrough diffusion cells, and radiolabe1ed bifenthrin, deltamethrin or cis-permethrin was applied in acetone to the skin. Fractions of receptor fluid were collected every 4 h. At 24 h, the skins were washed with soap and water to remove unabsorbed chemical. The skin was then solubilized. Two additional experiments were performed after washing the skin; the first was tape stripping the skin and the second was the collection of receptor fluid for an additional 24 h. Receptor fluid, skin washes, tape strips and skin were analyzed for radioactivity. For rat skin, the wash removed 53-71% ofthe dose and 26-43% remained in the skin. The cumulative percentage ofthe dose at 24 h in the receptor fluid ranged from 1-5%. For human skin, the wash removed 71-83% of the dose and 14-25% remained in the skin. The cumulative percentage of the dose at 24 h in the receptor fluid was 1-2%. Tape stripping removed 50-56% and 79-95% of the dose that remained in rat and human skin, respectively, after the wash. From 24-48 h, 1-3% and about 1% of the dose diffused into the receptor fluid of rat and human skin, respectively. A low percentage ofthe dose ofthe three pyrethroids completely penetrated rat and human skin, although rat skin was more permeable. Most of the dose was removed by skin washing. A higher percentage of the dose of these compounds was in the skin of rat than human and a small percentage was available to diffuse into the receptor fluid after the wash. Therefore, consideration of the skin type used and fractions analyzed are important when using in vitro dermal absorption data for risk assessment. 2
