Per- and polyfluoroalkyl substances (PFASs) in San Francisco Bay wildlife: Temporal trends, exposure pathways, and notable presence of precursor compounds.

Concentrations of perfluorooctane sulfonate (PFOS) in San Francisco Bay (SF Bay) wildlife have historically been among the highest reported globally. To track continuing exposures to PFASs and assess the impact of the 2002 phase-out of production of PFOS and related chemicals in the US, nine perfluoroalkyl carboxylic acids (PFCAs; C4-C12), three perfluoroalkyl sulfonic acids (PFSAs; C4, C6, C8) and perfluorooctane sulfonamide (PFOSA, a PFOS precursor) were measured in SF Bay cormorant eggs in 2012 and harbor seal serum sampled between 2009 and 2014. PFOS remained the dominant perfluoroalkyl acid (PFAA) in both cormorant eggs (36.1-466 ng/g) and seals (12.6-796 ng/g) from 2012 and 2014, respectively. Concentrations in seal and bird eggs from the South Bay have declined approximately 70% in both matrices. To elucidate potential pathways of exposure, prey fish, sediments and wastewater effluent were analyzed for PFASs, and in the case of sediment and effluent, a suite of PFAA precursors. PFOS was the dominant PFAA in prey fish and sediment. In effluent, different mixtures of PFAAs were measured, with PFOS, PFHxA, and PFOA detected in the highest concentrations. Polyfluoroalkyl phosphate diesters (PFCA-precursors) were observed at concentrations over an order of magnitude higher than PFCAs in sediment, highlighting their importance as a potential, on-going source of PFCAs to SF Bay wildlife. These findings suggest that the PFOS phase-out has resulted in reduced burdens to wildlife in SF Bay, but that exposure to diverse and incompletely characterized PFASs continues.