Effects of simultaneous prenatal exposures to organophosphate and synthetic pyrethroid insecticides on infant neurodevelopment at three months of age.

Both prenatal organophosphate (OP) and pyrethroid (PYRE) insecticide exposures have been inconsistently linked with poorer neurodevelopmental outcomes. However, given that neither exposure occurs in isolation, and both classes are neurotoxic, it is important to consider both classes when evaluating these outcomes. Employing biomarkers of pesticide exposure, this research describes the effects of prenatal urinary metabolite levels of PYRE and OP insecticides, measured in both the second and third trimesters of pregnancy and postnatal urinary metabolite levels measured at 2 months of age, on child neurodevelopment at three months of age. Neurodevelopmental data were obtained by administration of the Bayley Scales of Infant Development-II (BSID-II). Generalized linear models using maximum likelihood estimation were used to evaluate the relationship between the indicators of motor and mental neurobehavioral development obtained for 118 infants and prenatal insecticide exposure, accounting for the concurrent infant insecticide exposure. Urinary measures of the PYRE metabolites 3-phenoxybenzoic acid (3PBA) and trans-3-(2,2-dichlorovinyl)-2,2 dimethylcyclopropane-1-carboxylic acid (trans-DCCA) in the third trimester of pregnancy had significant, albeit opposite, effects on mental functioning at three months of age. We observed no significant (p < 0.05) effects on motor development. These results were robust to second month infant urine measures of 3,5,6-trichloro-2-pyridinol (metabolite of OP chlorpyrifos), which independently had a significant and negative influence on mental functioning. Prenatal PYRE exposures exert heterogeneous effects by class on mental, but not motor, functioning at three months of age.