Benzotriazoles and Benzothiazoles, Maternal and Neonatal Thyroid Hormones, and Childhood Growth: A Longitudinal Cohort Study

Prenatal exposure to benzotriazoles and benzothiazoles (BTs) has been associated with pregnancy complications, but their effects on childhood development remain unclear. We investigated these associations and examined the mediating role of maternal and neonatal thyroid hormones in a Chinese birth cohort consisting of 501 mother-child pairs. We found that exposure to 2-hydroxy-benzothiazole (2-OH-BTH) in early pregnancy was inversely associated with childhood body mass index (BMI) (β = -0.041, 95% CI: -0.077, -0.005). Both tolyl-triazole (TTR) (β = -1.35%, 95% CI: -2.45%, -0.24%) and 2-OH-BTH (β = -1.15%, 95% CI: -1.79%, -0.50%) were inversely associated with maternal free thyroxine (FT4) in early pregnancy, which mediated 23.53% of the inverse associations between 2-OH-BTH exposure and childhood BMI. Additionally, third-trimester exposure to 1-hydroxy-benzotriazole, xylyl-triazole, TTR, and 2-OH-BTH was positively linked to neonatal thyroid-stimulating hormone levels. These findings suggest that prenatal exposure to BTs, particularly 2-OH-BTH, may impair early childhood growth by disrupting thyroid hormone homeostasis. Our results add new epidemiological evidence to the growing concern about BTs and underscore the importance of considering thyroid disruption as a mechanistic link between environmental exposures and developmental outcomes. This highlights the need for greater public health attention and regulatory measures targeting these emerging contaminants.