Per- and polyfluoroalkyl substances bioaccumulation, depuration, and associated energetic costs in the Eastern oyster...

Per- and polyfluoroalkyl substances (PFAS) are a class of human-made chemicals that are widespread and persistent in the environment. Impacts of PFAS on the health of oysters are an emerging concern to conservationists and oyster farmers alike. Depuration of contaminants has been shown to be energetically expensive in some bivalves, and there is concern that this metabolic cost may have a negative effect on organismal health. To address bioaccumulation concerns, eastern oysters (Crassostrea virginica) were exposed to a mixture of PFAS (perfluorooctane sulfonate [PFOS], perfluorooctanoic acid [PFOA], perfluorohexanoic acid [PFHxA], perfluoropentanoic acid [PFPeA], perfluorobutanesulfonic acid [PFBS]) at a nominal concentration of 2 µg/L per compound for 28 days and then transferred to clean water for 5 days. Concentration of PFAS in soft tissues was measured on a subset of oysters seven times throughout exposure by ultrahigh-performance liquid chromatography coupled to triple quadruple mass spectrometry to determine PFAS bioaccumulation and subsequent depuration. The bioaccumulation factor was higher for >6-carbon chained compounds as compared with <6-carbon chained compounds, and PFAS tissue concentration was below detection limits within 24 hr of transfer to clean water. To determine the metabolic cost of PFAS exposure and depuration, an additional group of oysters was exposed to either a mixture of PFOS + PFOA (5 µg/L each) or a mixture of PFOS, PFOA, PFHxA, PFPeA, and PFBS (2 µg/L each) for 10 days, and optical respirometry was used to assess changes in mass-specific oxygen uptake. There was no significant difference in mass-specific oxygen uptake between treatment and control oysters during exposure or depuration. There was no evidence that exposure and depuration of PFAS mixtures at concentrations higher than those measured in coastal environments adversely affected oyster metabolism.