Association of exposure to personal care product chemicals with maternal thyroid health: a prospective cohort study integrated with targeted risk assessment for environmental chemicals strategy

Widely used personal care product (PCP) chemicals can disrupt the function of thyroid hormones. Pregnancy-induced vulnerability heightens the risk of PCPs on maternal thyroid health, but their individual, joint, and longitudinal impacts have been underexplored. Moreover, the risk assessment regarding maternal thyroid-impairing effects of PCPs has been lacking from epidemiological and mechanistic insights. In this study, we conducted an integrated risk assessment of PCPs on maternal thyroid functions, synthesizing evidence from 47 epidemiological, 18 in vivo, and 19 in vitro evidences from four major databases. Besides, a separate cohort analysis was prospectively performed among 803 pregnant women to explore associations between real-world PCP exposure and thyroid function. Serum samples in the second trimester (T2) were analyzed for PCP profiles by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Anti-thyroid peroxidase antibodies (ATPO), thyroid stimulating hormone (TSH), and free thyroxine (FT4) during T2 and the third trimester (T3) were measured using immunoassays. The targeted risk assessment of environmental chemicals (TRAEC) strategy yielded a middle-level risk score of 5.01 for PCPs, with category-specific scores of 5.47 for phthalates, 4.85 for per- and polyfluoroalkyl substances (PFASs), and 4.12 for bisphenols. The cohort results revealed significant associations between bisphenol S (BPS), monobutyl phthalate (MEHP), dimethyl phthalate (DMP), di-n-pentyl phthalate (DnPP), dicyclohexyl phthalate (DCHP) , Sodium perfluoro-1-octanesulfonate (L-PFOS), and perfluoro-n-undecanoic acid (PFUdA) with thyroid function markers during T2 and T3. Mixed-exposure models showed negative associations of PCPs with TSH during T2, with PFUdA, DMP, DCHP, and BPS identified as key contributors. These findings highlighted the potential risk of PCP exposure as determined by the TRAEC strategy. In conclusion, PCP exposure may contribute to maternal thyroid dysfunction with trimester-specific effects. Our findings highlighted the need to mitigate PCP-related exposures during pregnancy and improve maternal thyroid health.