Oysters for legacy and emerging per- and polyfluoroalkyl substances (PFASs) monitoring in estuarine and coastal waters: Phase distribution and bioconcentration profile

Per- and polyfluoroalkyl substances (PFASs) are a diverse group of widely used anthropogenic chemicals that are environmentally persistent and bioaccumulative, especially in aquatic ecosystem. The heavily industrialized and urbanized Greater Bay Area in China represents a notable contamination source for PFASs, which may potentially influence the health of local oysters as a keystone species in local ecosystems and a popular seafood. In this study, samples of oysters and their surrounding waters were collected from the littoral zones of the Pearl River Estuary (PRE), China during winter 2020, where 44 PFASs, including 19 perfluoroalkyl acids (PFAAs), 8 emerging PFASs, and 17 PFAA precursors (or intermediates), were analyzed. Total PFAS concentrations ranged 13.8-58.8 ng/L in the dissolved phase, 3.60-11.2 ng/g dry weight (dw) in the suspended particulate matter (SPM), and 0.969-1.98 ng/g dw in the oysters. Most short-chain PFASs were present in the dissolved phase (>95%), while long-chain PFASs generally showed higher concentrations in the SPM. Log field-based bioconcentration factors (BCFs) of long-chain PFASs increased linearly (r = 0.95, p < 0.01) with increasing estimated log membrane-water (D-mw) and protein-water (D-pw) distribution coefficients. Perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA) exhibited higher measured BCFs than those estimated by their D-mw and D-pw. Considering the widespread occurrence of their precursors, the contribution of precursor transformation was likely to be a significant source of PFHxA and PFHpA. Oysters from the PRE littoral zones posed low risks to human health associated with PFAS consumption, which might be underestimated due to limited toxicity data available for PFAA precursors and emerging PFASs. This study sheds light on the practicality of applying oysters as biomonitors for timely PFAS monitoring in coastal environments.