Comparative Toxicity of Aquatic Per- and Polyfluoroalkyl Substance Exposure in Three Species of Amphibians

Abstract

Per- and polyfluoroalkyl substances (PFAS) are contaminants of concern due to their widespread occurrence in the environment, persistence, and potential to elicit a range of negative health effects. Per- and polyfluoroalkyl substances are regularly detected in surface waters, but their effects on many aquatic organisms are still poorly understood. Species with thyroid-dependent development, like amphibians, can be especially susceptible to PFAS effects on thyroid hormone regulation. We examined sublethal effects of aquatic exposure to four commonly detected PFAS on larval northern leopard frogs (Rana [Lithobates] pipiens), American toads (Anaxyrus americanus), and eastern tiger salamanders (Ambystoma tigrinum). Animals were exposed for 30 days (frogs and salamanders) or until metamorphosis (toads) to 10, 100, or 1000 μg/L of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), or 6:2 fluorotelomer sulfonate (6:2 FTS). We determined that chronic exposure to common PFAS can negatively affect amphibian body condition and development at concentrations as low as 10 µg/L. These effects were highly species dependent, with species having prolonged larval development (frogs and salamanders) being more sensitive to PFAS than more rapidly developing species (toads). Our results demonstrate that some species could experience sublethal effects at sites with surface waters highly affected by PFAS. Our results also indicate that evaluating PFAS toxicity using a single species may not be sufficient for accurate amphibian risk assessment. Future studies are needed to determine whether these differences in susceptibility can be predicted from species' life histories and whether more commonly occurring environmental levels of PFAS could affect amphibians. Environ Toxicol Chem 2022;41:1407-1415. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Keywords: Amphibians; Aquatic toxicology; Perfluoroalkyl substances.

Figure 1

Model‐derived means (95% confidence interval) associated with (A) snout–vent length, (B) body mass, and (C) body condition (scaled mass index [SMI]) at the conclusion of per‐ and polyfluoroalkyl substances (PFAS) exposure studies for Rana [Lithobates] pipiens (northern leopard frogs; 30 days), Anaxyrus americanus (American toads; metamorphosis, 26–45 days), and Ambystoma tigrinum (eastern tiger salamanders; 30 days). Asterisks denote significant differences of a treatment from the control (p < 0.05). C = control; PFOA = perfluorooctanoic acid; PFOS = perfluorooctane sulfonate; PFHxS = perfluorohexane sulfonate; 6:2 FTS = 6:2 fluorotelomer sulfonate.

Figure 2

Model‐derived means (95% confidence interval) associated with (A) developmental stage of northern leopard frogs after 30 days of exposure to per‐ and polyfluoroalkyl substances (PFAS) and (B) days required for American toads to reach metamorphosis. Asterisks denote significant differences of a treatment from the control (p < 0.05). C = control; PFOA = perfluorooctanoic acid; PFOS = perfluorooctane sulfonate; PFHxS = perfluorohexane sulfonate; 6:2 FTS = 6:2 fluorotelomer sulfonate.

Figure 3

Mean concentrations (95% confidence interval) of triiodothyronine (T3), thyroxine (T4), and reverse T3 (rT3) in whole‐body homogenates of American toads at the climax of metamorphosis. Overall, evidence was scant that per‐ and polyfluoroalkyl substance (PFAS) exposure affected thyroid hormone levels in toads, with the exception of the 1000‐µg/L perfluorohexane sulfonate (PFHxS) treatment, which reduced mean rT3 levels by 27% relative to the control. C = control; PFOA = perfluorooctanoic acid; PFOS = perfluorooctane sulfonate; 6:2 FTS = 6:2 fluorotelomer sulfonate.