Association of ambient air pollutants with maternal thyroid hormones during the entire pregnancy.

This study aims to investigate associations between PM10, PM2.5, and NO2 and maternal thyroid hormones. We investigated 443 pregnant women in Zhejiang, China with repeated examinations of serum thyroid hormones at 10, 17, and 32 weeks. Individual exposures to ambient air pollution were retrospectively calculated by inverse distance weighting interpolation. Multivariate linear mixed models were applied to estimate the association between air pollutants and thyroid hormones. PM10 exposure was positively associated with TSH (β: 0.077 [95% CI: 0.003, 0.152]), and negatively associated with FT3 (β: -0.041 [-0.057, -0.025]) and FT4 (β: -0.036 [-0.055, -0.017]) during the 0-90 lag days (per IQR). Similarly, increased exposure to PM2.5 was associated with decreased FT3 (β: -0.016 [-0.032, -0.001]), and increased Tg (β: 0.147 [0.025, 0.269]). Evaluated NO2 levels were associated with decreased FT3 (β: -0.026 [-0.039, -0.014]) and FT4 (β: -0.036 [-0.052, -0.020]), as well as increased Tg (β: 0.129 [0.011, 0.247]). The results indicate that exposure to ambient PM10, PM2.5, and NO2 throughout the entire pregnancy adversely affects thyroid hormones, implying potential health implications of air pollution on maternal thyroid function.