First observations of perfluorooctane sulfonate occurrence and depuration from Sydney Rock Oysters, Saccostrea glomerata, in Port Stephens NSW Australia

Highlights: • This is the first observation of PFA in cultured oysters in Australia. • PFAS levels in both major cultivated species were similar and did not exceed food standard trigger levels. • Current industry pre-sale depuration practices do allow for significant reductions of PFOS from oyster tissue. - Abstract: Following the discovery of potential chronic perfluoroalkyl substances (PFAS) contamination of Tilligerry Creek, Port Stephens (New South Wales Australia), sampling was undertaken to confirm the presence, extent and levels of contamination in commercial oyster crops of Sydney Rock Oyster (Saccostrea glomerata) and Pacific Oyster (Crassostrea gigas) grown within the estuary. Among a range of PFAS tested, only perfluorooctane sulfonate (PFOS) was detected. Concentrations of PFOS in oyster tissues for S. glomerata ranged from 1.6 μg kg^{− 1} ww (wet weight) to below the limit of reporting of 0.3 μg kg^{− 1} ww, with concentrations generally decreasing toward the lower reaches of the estuary. The sample of C. gigas tested had a PFOS concentration of 0.71 μg kg^{− 1} ww that was consistent with concentrations observed in nearby S. glomerata. For harvest size (50–60 g) S. glomerata, both holding contaminated oysters in a depuration system, and relocation to a non-contaminated area, saw significant reductions in the tissue PFOS concentrations. For oysters held in a depuration system, PFOS depurated at a rate of 0.008 h^{− 1} (0.004–0.019 h^{− 1}; 90% CI), which corresponded with a depuration half-life of 87 h (35–155 h; 90%). A more conservative model (fitted to data that assumed concentrations < LOR were equal 0.5·LOR) predicted a depuration half-life of 131 h. PFOS concentrations had fallen to below detectable limits within 162 h. Similar decreases were observed in relocated oysters.