Gestational and childhood exposure to phthalates and child behavior

Background: Early-life phthalate exposures may adversely influence neurodevelopment by disrupting thyroid hormone homeostasis, altering brain lipid metabolism, or reducing gonadal hormone concentrations. Previous literature examining gestational phthalate exposure and child behavior were inconclusive and few prospective studies have examined childhood phthalate exposure, particularly phthalate mixtures. We investigated whether gestational and childhood phthalate exposures were associated with child behavior. Methods: We used data from 314 mother-child pairs in the HOME Study, a longitudinal pregnancy and birth cohort that enrolled pregnant women from Cincinnati, Ohio. We quantified urinary concentrations of 11 phthalate metabolites in samples collected twice during gestation from women and six times from their children when they were ages 1, 2, 3, 4, 5, and 8 years. We assessed children's behavior at ages 2, 3, 4, 5, and 8 years using the Behavioral Assessment System for Children-2. Using linear mixed models, we estimated covariate-adjusted associations of measurement-error-corrected gestational and childhood phthalate metabolite concentrations (per interquartile range increase) with repeated child behavior assessments. We used Weighted Quantile Sum (WQS) regression to estimate the association of phthalate mixtures with child behavior. Results: Gestational mono(3-carboxypropyl) phthalate (MCPP) concentrations were associated with more problem behaviors (internalizing: beta = 0.9, 95% confidence interval [CI] = -0.1, 1.9; externalizing: beta = 1.0, 95%CI = -0.1, 2.0; behavioral symptoms index [BSI]: beta = 1.1, 95%CI = 0.1, 2.1). Higher childhood monobenzyl phthalate (MBzP) (beta = 1.4; 95%CI = 0.0, 2.7), monocarboxynonyl phthalate (MCNP) (beta = 3.2; 95%CI = 1.6, 4.8), monocarboxyoctyl phthalate (MCOP) (beta = 0.9; 95%CI = 0.0, 1.7), MCPP (beta = 1.8; 95%CI = 0.2, 3.5), and monoethyl phthalate (MEP) (beta = 1.6; 95%CI = 0.1, 3.1) concentrations were associated with higher BSI composite scores. Consistent with this, the weighted childhood phthalate index was associated with more problem behaviors (internalizing: beta = 1.5, 95%CI = -0.2, 3.1; externalizing: beta = 1.7, 95%CI = 0.1, 3.5; BSI: beta = 1.7, 95%CI = 0.2, 3.2); MBzP, MCNP, and MEP largely contributed to these associations. Conclusion: Our findings suggest that childhood exposure to phthalate mixtures may be associated with children's problem behaviors.