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IN VIVO DERMAL ABSORPTION OF PYRETHROID PESTICIDES IN THE RAT
Citation:
HUGHES, M. F. AND B. C. EDWARDS. IN VIVO DERMAL ABSORPTION OF PYRETHROID PESTICIDES IN THE RAT. Presented at Society of Toxicology Annual Meeting, Seattle, WA, March 16 - 20, 2008.
Impact/Purpose:
The objective of this study was to examine the in vivo dermal absorption of bifenthrin, deltamethrin and cis-permethrin in the rat.
Description:
The potential for exposure to pyrethroid pesticides has risen recently because of their increased agricultural and residential use. The objective of this study was to examine the in vivo dermal absorption of bifenthrin, deltamethrin and cis-permethrin in the rat. Hair on the dorsal side of adult male Long-Evans rats was clipped with an electric razor. The next day, the rats were anesthetized and dosed with 1750 nmole (312.5 nmole/cm2) of radiolabeled (5 uCi) bifenthrin (B), deltamethrin (D) or cis-permethrin (P) in acetone. A non-occluding plastic cover was glued to the skin over the dosing site. The animals were placed in individual metabolism cages for the collection of urine and feces. The next day, the animals were anesthetized and the dosing site was washed soap and water. Then the animals were sacrificed by cardiac puncture and several tissues were collected. The washed skin was also tape stripped. The excreta, skin wash, tape strips and tissues were analyzed for radioactivity. The wash removed the greatest percentage of the dose: B, 52.3 ± 4.3% (mean ± SD, N=4); D, 58.0 ± 9.5 %; P, 62.3 ± 3.7%. Of the tissues, the skin had the greatest percentage of the dose: B, 24.1 ± 5.0%; D, 19.0 ± 3.1%; P, 18.7 ± 3.3%. The percentage of the dose removed by tape from the skin was: B, 5.2 ± 1.8%; D, 3.6 ± 0.6%; P, 5.1 ± 3.6%. In urine, the percentage of the dose detected was: B, 0.6 ± 0.1%; D, 0.5 ± 0.6%; P, 3.5 ± 0.9%. In feces, the percentage of the dose detected was: B, 2.0 ± 0.7%; D, 0.4 ± 0.1%; P, 3.7 ± 1.6%. Less than 0.01% of the dose for each of the pyrethroids was detected in the internal tissues analyzed. Complete absorption of the pyrethroids tested through rat skin was low (1-7%). However, a considerable amount of these pyrethroids remained in skin (19-24%) and could potentially be available for systemic absorption. (This abstract does not represent US EPA policy.)