Per- and polyfluoroalkyl substances (PFAS) in wild amphibians: a call for more research

Amphibians serve a central role in food webs and provide a link between aquatic and terrestrial habitats. Because of their dependence on water, amphibians are susceptible to legacy and emerging contaminants. We investigated mercury (Hg) and per- and polyfluoroalkyl substances (PFAS) concentrations in wild populations of two amphibian species-the green frog (Lithobates clamitans) and the American toad (Anaxyrus americanus)-which exhibit different life histories. We evaluated whether proximity to PFAS point source (State Superfund site) affected PFAS exposures in amphibians and assessed length, mass, sex, diet, and trophic position as predictors of contaminant concentrations. We found higher Hg concentrations in the more aquatic species (i.e., green frog) but higher PFAS concentrations (summed PFAS, perfluorodecanoic acid [PFDA], perfluoroundecanoic acid [PFUnA], perfluorododecanoic acid [PFDoA], perfluorotridecanoic acid [PFTrDA], and perfluorotetradecanoic acid [PFTeDA]) in the more terrestrial species (i.e., American toad). Proximity to the PFAS State Superfund site did not strongly affect PFAS exposures in amphibians. Of the biological predictors tested, diet best explained PFAS concentrations, but other factors (e.g., physiological differences) are likely contributing to the difference in PFAS bioaccumulation between aquatic and terrestrial species. Only three reports on PFAS concentrations in wild amphibians exist, all from contaminated sites in China, reporting much higher concentrations than found here. Additionally, experimental exposure studies have only investigated the effects of exposure to a few PFAS compounds, of which long-chain perfluoroalkyl carboxylic acids detected here (PFDA, PDUnA, PFDoA, PFTrDA, and PFTeDA) are not represented in the literature. To truly understand the effects that detectable PFAS impose on wild amphibians, research is needed on the effects of more PFAS compounds, bioaccumulation in larval and terrestrial amphibians, and the elimination of PFAS via their skin to different media.