Species- and Tissue-Specific Avian Chronic Toxicity Values for Perfluorooctane Sulfonate (PFOS) and a Binary Mixture of PFOS and Perfluorohexane Sulfonate

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Abstract
To further characterize avian toxicity to environmental levels of select per‐ and poly‐fluoroalkyl substances (PFAS), we established species‐ and tissue‐specific PFAS chronic toxicity values (CTVs) associated with a lowest‐observable‐adverse‐effect‐level (LOAEL) threshold previously established for Northern Bobwhite quail (Colinus virginianus) chronically orally exposed via drinking water to either perfluorooctane sulfonate (PFOS) or a simple PFAS mixture. Aided by advances in analytical techniques, the novel avian oral PFAS CTVs reported in the present study are lower than the previously reported toxicity reference values (TRVs) estimated for birds chronically exposed via feed. Thus, current avian PFOS TRVs may not be fully protective of wild avian populations at PFAS‐impacted sites. Also, likely due to differences in bioavailability, bioaccessibility, and toxicokinetics among individual PFAS between oral exposure types, we found higher bioaccumulation factors (BAFs) in all assessed tissues from birds exposed via water vs feed. Thus, we propose that future characterization of chemical toxicity due to ingestion exposure initially include a full examination of all probable sources of oral exposure for the most accurate derivation of TRVs and a more complete picture of ecological risk. The avian PFAS LOAEL CTVs established in the present study can be modified with the use of uncertainty factors (UFs) to derive site‐specific avian TRVs for ecological risk assessment (ERA) at PFAS‐impacted sites. From differences observed in the behavior of PFOS when administered as either a single chemical or as part of a binary mixture with PFHxS, we verified that PFOS was absorbed and distributed differently when co‐administered with PFHxS and that PFOS likely interacted with PFHxS differently among tissues, helping to explain the differences observed in avian toxicity between exposures.
Funding Information
  • Strategic Environmental Research and Development Program (ER-2627)
  • Strategic Environmental Research and Development Program (ER‐2627)

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