Abstract
The literature informing susceptible periods of exposure on children's neurodevelopment is limited. We evaluated the impacts of pre- and postnatal fine particulate matter (PM(2.5)) exposure on children's cognitive and motor function among 1303 mother-child pairs in the Spanish INMA (Environment and Childhood) Study. Random forest models with temporal back extrapolation were used to estimate daily residential PM(2.5) exposures that we averaged across 1-week lags during the prenatal period and 4-week lags during the postnatal period. The McCarthy Scales of Children's Abilities (MSCA) were administered around 5 years to assess general cognitive index (GCI) and several subscales (verbal, perceptual-performance, memory, fine motor, gross motor). We applied distributed lag nonlinear models within the Bayesian hierarchical framework to explore periods of susceptibility to PM(2.5) on each MSCA outcome. Effect estimates were calculated per 5 μg/m(3) increase in PM(2.5) and aggregated across adjacent statistically significant lags using cumulative β (β(cum)) and 95% Credible Intervals (95%CrI). We evaluated interactions between PM(2.5) with fetal growth and child sex. We did not observe associations of PM(2.5) exposure with lower GCI scores. We found a period of susceptibility to PM(2.5) on fine motor scores in gestational weeks 1-9 (β(cum) = -2.55, 95%CrI = -3.53,-1.56) and on gross motor scores in weeks 7-17 (β(cum) = -2.27,95%CrI = -3.43,-1.11) though the individual lags for the latter were only borderline statistically significant. Exposure in gestational week 17 was weakly associated with verbal scores (β(cum) = -0.17, 95%CrI = -0.26,-0.09). In the postnatal period (from age 0.5-1.2 years), we observed a window of susceptibility to PM(2.5) on lower perceptual-performance (β = -2.42, 95%CrI = -3.37,-1.46). Unexpected protective associations were observed for several outcomes with exposures in the later postnatal period. We observed no evidence of differences in susceptible periods by fetal growth or child sex. Preschool-aged children's motor function may be particularly susceptible to PM(2.5) exposures experienced in utero whereas the first year of life was identified as a period of susceptibility to PM(2.5) for children's perceptual-performance.