Organophosphate Pesticide Metabolite Concentrations in Urine during Pregnancy and Offspring Nonverbal IQ at Age 6 Years

BACKGROUND: Susceptibility to organophosphate (OP) pesticide neurotoxicity may be greatest during the prenatal period; however, previous studies have produced mixed findings concerning in utero OP pesticide exposure and child cognition.
OBJECTIVES: Our objective was to determine whether maternal urinary concentrations of OP pesticide metabolites are inversely associated with child nonverbal IQ at 6 y of age and to examine potential effect measure modification by the PON1 gene.
METHODS: Data came from 708 mother–child pairs participating in the Generation R Study. Maternal urine concentrations of six dialkylphosphates (DAPs), collected at <18, 18–25, and >25 weeks of gestation, were determined. Child nonverbal IQ was measured at 6 y of age using the Mosaics and Categories subtests from the Snijders-Oomen Nonverbal Intelligence Test–Revised. PON1 was determined in cord blood for 474 infants. Multiple linear regression models were fit to estimate the DAP–IQ associations and PON1 interactions.
RESULTS: Overall, associations between child nonverbal IQ and maternal DAP concentrations were small and imprecise, and these associations were inconsistent across urine sampling periods. Howover, for a 10-fold difference in total DAP concentration for the >25 weeks of gestation samples, adjusted child nonverbal IQ was 3.9 points lower (95% CI: −7:5, −0:3). Heterogeneity in the DAP–IQ association by PON1 gene allele status was not observed (n= 474).
CONCLUSIONS: Consistent evidence of an association between higher maternal urinary DAP concentrations and lower child IQ scores at 6 y of age was not observed. There was some evidence for an inverse relation of child nonverbal IQ and late pregnancy urinary DAPs, but the estimated association was imprecise