Occurrence of legacy and alternative per- and polyfluoroalkyl substances in serum from high exposure population and their disrupting effects on serum lipids and thyroid function

High exposure of per- and polyfluoroalkyl substances (PFAS) has been reported in main chemical production areas in China, while epidemiological study on exposure risk of PFAS is still limited. In this study, legacy and alternative PFAS were measured in serum samples from 161 adults living in Laizhou Bay, a famous chemical production area located in Shandong province, Northern China. Based on the concentrations of serum PFAS, the disrupting effects of PFAS on serum lipids and thyroid function were further explored. The results showed that the serum perfluorooctanoic acid (PFOA) (geometric mean (GM): 60 ng/mL) in this region was even higher than serum PFOA of residents living in PFOA contaminated water districts in United States and Sweden. 100 a/o of the serum PFOA was higher than the refer-ence dose for increased total cholesterol (TC). Consistently, higher serum PFOA was marginally correlated with in-creased TC level (p = 0.062) and low-density lipoprotein (p = 0.065). In addition, higher perfluoroisopropyl perfluorooctanesulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonates (6,2 Cl-PFESA) were significantly corre-lated with increased high-density lipoprotein (p = 0.040, 0.022). No significant association was observed between in-dividual PFAS and any thyroid function biomarker. However, using the principal component analysis derived factors to represent the co-exposure patterns, co-exposure of legacy long-chain PFAS showed synergistic effects on the free thyroxine, while the mixture of alternative PFAS showed a synergistic influence on the total and free triiodothyronine.