Prenatal exposure to a mixture of organophosphate esters and intelligence among 8-year-old children of the HOME Study

Many environmental chemicals are being identified as suspected neurotoxicants based on the findings of both experimental and epidemiological studies. Organophosphate esters (OPEs), which are among the chemicals that have replaced neurotoxic polybrominated diphenyl ethers (PBDEs) after 2004, have also become an important public health topic as evidence regarding their potential for early-life neurotoxicity is growing. In 233 mother child pairs from Cincinnati, OH, we measured concentrations of the OPE metabolites bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis-2-chloroethyl phosphate (BCEP), diphenyl phosphate (DPHP), and di-n-butyl phosphate (DNBP) in the urine of pregnant women at 16 and 26 weeks gestation and at delivery. At age 8 years, we assessed children's cognition using the Wechsler Intelligence Scale for Children-IV. In models adjusted for maternal race, income, body mass index, and IQ, maternal urinary BCEP was associated with a modest increase in child full-scale IQ (ß: 0.81 per a ln-unit BCEP increase; 95 % CI: 0.00, 1.61) while other OPEs were not associated with changes in full-scale IQ or any IQ subscales. Maternal serum PBDE concentrations did not confound the relationships between urinary OPE metabolites and child IQ. Using Bayesian kernel machine regression, we did not find that concentrations of a mixture of OPE metabolites during gestation was associated with any child cognition measures. The results of this study are not consistent with other published work, and a larger sample size would be beneficial to explore potential associations more fully. Therefore, additional studies are necessary to continue studying prenatal OPE exposure and child neurodevelopment and behavior.