In-utero exposure to phenols and phthalates and the intelligence quotient of boys at 5 years

Dorothy Nakiwala, Hugo Peyre, Barbara Heude, Jonathan Y. Bernard, Rémi Béranger, Rémy Slama, Claire Philippat, The EDEN mother-child study group

There are concerns that developmental exposure to endocrine disrupting chemicals such as phenolic compounds and phthalates could affect child cognitive function. Epidemiological studies tackling this question have mainly focused on phthalate metabolites and bisphenol A, but not on the other phenolic compounds. Our study aimed to assess the relationship between in-utero exposure to phthalates, bisphenol A and other phenolic compounds (parabens, triclosan, dichlorophenols and benzophenone-3) and the Intelligence Quotient (IQ) of boys at 5-6 years. In 452 mother-son dyads from the French EDEN cohort, we measured 11 phthalate metabolites and 9 phenolic compounds (4 parabens, benzophenone-3, bisphenol A, 2 dichlorophenols and triclosan) in spot urine samples collected between 22 and 29 gestational weeks. Verbal and performance IQ of children were assessed at 5-6 years by a psychologist using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). We used adjusted Structural Equation Models (SEM) combined with Benjamini and Hochberg false discovery rate correction to assess the associations between maternal urine phenol and phthalate metabolite concentrations considered simultaneously and the boys' IQ. No phenol or phthalate metabolite concentration was negatively associated with the boys' verbal or performance IQ (uncorrected p-values ≥0.09). Mono(3-carboxypropyl) phthalate tended to be associated with increased verbal IQ (β = 0.136, 95% confidence interval, 0.01; 0.27). This association disappeared after correction for multiple comparison (corrected p-value, 0.71). Our results did not provide evidence of an inverse association between in-utero exposure to phenols or phthalates and verbal and performance IQ among boys. Since phenols and phthalates may have sex-specific effects, these null findings cannot be generalized to girls. Limitations included use of a single spot urine sample to assess exposures and lack of consideration of postnatal exposures.