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Advective and diffusive dermal processes for estimating terrestrial amphibian pesticide exposure
Citation:
Van Meter, R. AND Tom Purucker. Advective and diffusive dermal processes for estimating terrestrial amphibian pesticide exposure. Presented at Ecological Society of America Annual Conference, Portland, OR, August 05 - 10, 2012.
Impact/Purpose:
Presentation for 2012 Ecological Society of America Meeting in Portland, OR.
Description:
Background/Question/Methods Dermal exposure presents a potentially significant but understudied route for pesticide uptake in terrestrial amphibians. Historically, evaluation of pesticide risk to both amphibians and reptiles has been achieved by comparing ingestion and inhalation estimates to bird and/or mammal toxicity values. Although some toxicity data exist for amphibians, the focus has largely centered around early aquatic life stages. Beyond providing protection and minimizing desiccation, amphibian skin has unique characteristics for gas and water exchange that may make this group very susceptible to contaminants relative to amniotes. Amphibian skin is very thin, porous, lacks an outer hydrophobic layer and has little keratin relative to reptiles and birds. Hydrophilic pesticides are very likely to be taken up through amphibian skin and this includes uptake from contaminated soil and foliage by terrestrial amphibians at any life stage. To expand on current pesticide screening tools, we surveyed the literature using ISI Web of Knowledge for pesticide toxicity studies in terrestrial amphibians. We used 5 published data sets to parameterize competing dermal exposure models. Parameters used include pesticide specific Kow (octanol-water partitioning coefficient), Kp (permeability coefficient), pesticide soil concentration, species body weight, skin thickness, surface area of exposure, water flux and bioavailability factor. Results/Conclusions We examined two alternative dermal uptake process models with the available datasets on pesticide exposure in terrestrial amphibians. As amphibians became increasingly dehydrated, the advective model incorporating water potential between soil and dermis had more support relative to the diffusion model. Juvenile and adult amphibians living in terrestrial habitats may experience higher pesticide exposures in agricultural environments due to specialized adaptations for maintaining hydration levels. Diffusion-ba
