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Background Fluoride may be a developmental neurotoxicant at elevated exposures. We merged new data from a prospective Odense Child Cohort (OCC) with results from two previous birth cohort studies from Mexico and Canada to characterize the dose–effect relationship in greater detail. Methods The OCC contributed 837 mother–child pairs to the total of >1500. We measured creatinine-adjusted urine-fluoride concentrations in maternal urine samples obtained during late pregnancy. Child IQ was determined at age 7 years using an abbreviated version of the Wechsler Intelligence Scales for Children. Findings from the three cohorts were used to calculate the joint benchmark concentration (BMC) and the lower confidence limit (BMCL) after adjustment for covariables. Results In the OCC, urine-fluoride concentrations varied between 0.08 and 3.04 mg/l (median 0.52 mg/l) but were not significantly associated with full-scale IQ at age 7 years (β = 0.08; 95% confidence interval −1.14 to 1.30 for a doubling in exposure). No difference was apparent between boys and girls. In the OCC, the BMC was 0.92 mg/l, with a BMCL of 0.30 mg/l. The joint analysis of all three cohorts showed a statistically significant association between urine-fluoride and IQ, with a BMC of 0.45 mg/l (BMCL, 0.28 mg/l), slightly higher than the BMC previously reported for the two North American cohorts alone. Conclusions As the BMCL reflects an approximate threshold for developmental neurotoxicity, the results suggest that pregnant women and children may need protection against fluoride toxicity. [ABSTRACT FROM AUTHOR]

BACKGROUND: Prenatal bisphenol A (BPA) exposure has been associated with adverse neurodevelopment in epidemiological studies. However, prior studies had limited statistical power to examine sex-specific effects, and few examined child cognition. OBJECTIVES: We estimated the association between prenatal BPA exposure and child neurobehavior at 3 y of age in a prospective cohort of 812 mothers and their children. METHODS: We measured BPA concentration in urine samples collected at ∼12 wk gestation among women enrolled in a 10-city Canadian cohort study. At approximately 3 y of age, we assessed children's cognitive abilities with the Wechsler Primary and Preschool Scale of Intelligence™-III (WPPSI-III) and two scales of the Behavior Rating Inventory of Executive Function-Preschool (BRIEF-P). Parents reported children's behavior using the Behavior Assessment System for Children-2 (BASC-2) and the Social Responsiveness Scale™-2 (SRS-2). We estimated covariate-adjusted differences in neurobehavioral outcomes with a doubling in BPA concentration and sex-specific associations. RESULTS: BPA was not associated with WPPSI-III scores; child sex did not modify these associations. The association between BPA and BRIEF-P scores was modified by child sex (BPA×sex p-values≤0.03). For example, a doubling of BPA concentration was associated with 1-point (95% CI: 0.3, 1.7) poorer working memory in boys and 0.5-point (95% CI: -1.1, 0.1) better scores in girls. BPA was not associated with most BASC-2 scales; however, it was associated with more internalizing and somatizing behaviors in boys, but not in girls (BPA×sexp-values≤0.08). A doubling of BPA concentration was associated with poorer SRS-2 scores [β=0.3 ( 95% CI: 0, 0.7)]; this association was not modified by sex. CONCLUSION: Prenatal urinary BPA concentration was associated with some aspects of child behavior in this cohort, and some associations were stronger among boys. [ABSTRACT FROM AUTHOR]