Bioaccumulation, tissue distribution, and maternal transfer of novel PFOS alternatives (6:2 Cl-PFESA and OBS) in wild freshwater fish from Poyang Lake, China

As emerging alternatives to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA) and sodium p-perfluorous nonenox-benzenesulfonate (OBS) were frequently detected in the four freshwater fish species collected from Poyang Lake. Median concentrations of 6:2 Cl-PFESA and OBS in fish tissues were 0.046–6.0 and 0.46–5.1 ng/g wet weight, respectively. The highest concentrations of 6:2 Cl-PFESA was found in fish livers, whereas OBS was found in the pancreas, brain, gonads, and skin. The tissue distribution pattern of 6:2 Cl-PFESA is similar to that of PFOS. The tissue/liver ratios of OBS were higher than those of PFOS, suggesting that OBS has a greater tendency to transfer from the liver to other tissues. The logarithmic bioaccumulation factors (log BAFs) of 6:2 Cl-PFESA in three carnivorous fish species were greater than 3.7, whereas those of OBS were less than 3.7, indicating that 6:2 Cl-PFESA had a strong bioaccumulation potential. Notably, sex- and tissue-specific bioaccumulation of OBS has also been observed in catfish. Most tissues (except the gonads) exhibited higher OBS concentrations in males than in females. However, no differences were found for 6:2 Cl-PFESA and PFOS. Maternal transfer efficiency of OBS was higher than that of 6:2 Cl-PFESA and PFOS in catfish (p < 0.05), indicating that OBS presents a higher risk of exposure to males and offspring through maternal offloading.