Identifying Vulnerable Periods of Neurotoxicity to Triclosan Exposure in Children

BACKGROUND: Exposure to triclosan, an endocrine disrupting chemical, may affect thyroid hormone homeostasis and adversely affect neurodevelopment. OBJECTIVE: Using a longitudinal pregnancy and birth cohort, we investigated associations between triclosan exposures during different time windows, and cognitive test scores at 8 y of age in 198 children from the HOME Study. METHODS: We quantified triclosan in urine samples from mother–child pairs up to nine times between the second trimester of gestation and 8 y of age. The Wechsler Intelligence Scale for Children-IV [i.e., Full-Scale Intelligence Quotient (IQ)] assessment was administered to HOME Study children at 8 y of age. We estimated covariate-adjusted triclosan–IQ associations at each visit. We also tested whether associations between triclosan concentrations and cognitive test scores varied among exposure at different time periods. RESULTS: Full-Scale IQ was not significantly associated with urinary triclosan concentrations during gestation or childhood but was significantly associated with a 10-fold increase in maternal urinary triclosan concentration at delivery [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text])]. Perceptual Reasoning Index (PRI) scores were significantly decreased in association with urinary triclosan concentrations at delivery and at 2 y of age. Associations between repeated triclosan concentrations and cognitive test scores significantly varied among exposure at different time periods for Full-Scale IQ, PRI, Verbal Comprehension Index, and Working Memory (triclosan–visit interaction [Formula: see text]). CONCLUSION: Urinary triclosan concentrations at delivery, but not during mid to late pregnancy and childhood, were associated with significantly lower children’s cognitive test scores at 8 y of age in this cohort of U.S. children. https://doi.org/10.1289/EHP2777