Identifying periods of susceptibility to the impact of phthalates on children's cognitive abilities

Abstract Background Early-life phthalate exposures may adversely affect children's neurodevelopment by disrupting thyroid function, reducing gonadal hormone levels, or altering fatty acid concentrations in the brain. This study aimed to identify periods of heightened susceptibility during gestation, infancy, and childhood to the impact of phthalates on children's cognitive abilities. Methods We used data from 253 mother-child pairs in the Health Outcomes and Measures of the Environment (HOME) Study (Cincinnati, Ohio), a longitudinal pregnancy and birth cohort. We quantified urinary concentrations of 11 phthalate metabolites in samples collected twice during gestation and 6 times during study visits when children were aged 1–8 years using a modified method of on-line solid phase extraction coupled with isotope dilution-high performance liquid chromatography-tandem mass spectrometry. We assessed children's intelligence (IQ) at ages 5 and 8 years using the Wechsler Preschool and Primary Scale of Intelligence-III and Wechsler Intelligence Scale for Children-IV, respectively. We estimated covariate-adjusted associations between a 1-standard deviation increase in log 10 -transformed urinary phthalate metabolite concentrations at each visit and children's IQ, adjusting for demographic, perinatal, and child factors; we tested for differences in these associations across visits using multiple informant models. Results Associations between some phthalate metabolites and IQ varied by visit (phthalate x visit interaction p-values Conclusion Urinary concentrations of several phthalate metabolites at age 3 years, compared to other time periods, were more strongly associated with decreased cognitive abilities in these children.