Chlorinated Polyfluorinated Ether Sulfonates and Thyroid Hormone Levels in Adults: Isomers of C8 Health Project in China

Chlorinated polyfluorinated ether sulfonates (Cl-PFESAs) are one kind of replacement chemistry for perfluor-ooctanesulfonate (PFOS). Recent studies have shown that Cl-PFESAs could interfere with thyroid function in animal models.However, epidemiological evidence on the link between Cl-PFESAs and thyroid function remains scarce. In this study, wefocused on two representative legacy perfluoroalkyl substances(PFAS), including PFOS and perfluorooctanoic acid (PFOA), andtwo PFOS alternatives (6:2 and 8:2 Cl-PFESAs) in the generaladult population from a cross-sectional study, theIsomers of C8Health Project in China. Three serum thyroid hormones (THs),thyroid stimulating hormone (TSH), free triiodothyronine (FT3),and free thyroxine (FT4), were measured. Wefitted generalizedlinear regression, restricted cubic spline regression, and Bayesian kernel machine regression models to assess associations ofindividual Cl-PFESAs, legacy PFAS, and PFAS mixtures with THs, respectively. We found individual PFAS and their mixtures werenonlinearly associated with THs. The estimated changes of the TSH level (mu IU/mL) at the 95th percentile of 6:2 Cl-PFESA andPFOS against the 5th percentile were-0.74 (95% CI:-0.94,-0.54) and-1.18 (95% CI:-1.37,-0.98), respectively. The presentstudy provided epidemiological evidence for the association of 6:2 Cl-PFESA with thyroid hormone levels in the general adultpopulation.

Automated summary

This study provides epidemiological evidence for the association between Cl-PFESAs and thyroid hormone levels in the general adult population.