Sublethal Toxicity of 17 Per- and Polyfluoroalkyl Substances with Diverse Structures to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutes.

Seven-day sublethal toxicity tests were performed with the freshwater invertebrates, Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus, to determine the effects of per- or polyfluorinated alkyl substances (PFASs) of varying chain length within four classes: perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkane sulfonamides (FASAs), and fluorotelomer sulfonic acids (FTSAs). In general, toxicity increased with increasing chain length, but the slopes of these relationships varied markedly by species and chemical class. Toxicity of individual PFCAs was similar among species. Toxicity of PFSAs was similar to PFCAs for C. dubia and H. azteca, whereas PFSAs were much more toxic to C. dilutus, with median effect concentrations (EC50s) as low as 0.022 mg perfluorooctane sulfonate [PFOS]/L and 0.012 mg perfluorononane sulfonate [PFNS]/L. Despite the high sensitivity to PFOS and PFNS, C. dilutus was not very sensitive to structurally similar fluorotelomer sulfonates (6:2 and 8:2). FASAs were the most toxic class tested among all species (e.g., EC50s of 0.011 and 0.017 mg perfluorooctane sulfonamide [FOSA] /L for C. dilutus and H. azteca respectively). The differences in toxicity among species and chemical classes suggest that mechanisms of PFAS toxicity may differ as a function of both.