Environ Health Perspect

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\u2013child 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\u2013IQ 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 [ 124.5\u2009points (95% CI: 127.0, 122.0)]. 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\u2013visit interaction p 640.04).Conclusion:Urinary triclosan concentrations at delivery, but not during mid to late pregnancy and childhood, were associated with significantly lower children\u2019s cognitive test scores at 8 y of age in this cohort of U.S. children. https://doi.org/10.1289/EHP2777P01 ES011261/ES/NIEHS NIH HHS/United StatesR01 ES014575/ES/NIEHS NIH HHS/United StatesR01 ES020349/ES/NIEHS NIH HHS/United StatesR01 ES024381/ES/NIEHS NIH HHS/United States29727133PMC607201