Risks associated with consumption of bivalves from PFAS-impacted AFFF sites.

Abstract

To understand the significance of bivalve consumption as an exposure route for PFAS, the presence of PFAS in bivalve tissues at PFAS-impacted sites and bivalve specific bioaccumulation metrics are needed. Case studies from AFFF-impacted sites indicated concentrations of PFOS in bivalves exceeded potentially applicable bivalve tissue screening levels for human consumers of bivalves; however, screening levels for wildlife consumers of bivalves (birds and mammals) were not exceeded. However, PFAS exposure to human and wildlife via bivalve consumption is lower than via fish consumption based on fish case study data. For example, PFOS dietary exposure to humans via bivalve consumption was predicted to be 3 to 10 times lower than exposure via fish consumption. In addition to differences in bivalve and fish consumption rates, a main reason for this observation is that PFAS are less bioaccumulative in bivalves than in fish, as indicated in a review of bivalve PFAS laboratory studies. PFAS bioaccumulation in bivalves is directly related to perfluoroalkyl chain length. For example, for freshwater bivalves, a significant relationship was found between log-transformed bioaccumulation factors (BAFs) and chain length (Log10BAF, L/kg wet weight = 0.65 × (number of perfluorinated carbons) - 4.6; r2 = 0.91). For sites at which bivalves are exposed to PFAS, the consumption of bivalves by humans and wildlife may be an important exposure pathway. However, at most AFFF sites with both bivalve and fish consumption exposure pathways, PFAS exposures associated with fish consumption will likely drive risk management.