Prenatal exposure to ambient PM 2.5 and its chemical constituents and child intelligence quotient at 6 years of age.

There are limited studies on the associations between prenatal exposure to constituents of fine particulate matter (PM) and children's intelligence quotient (IQ). Our study aimed to explore the associations between prenatal PM and its six constituents and the IQ levels of 6-year-old children. We included 512 mother-child pairs. We used a satellite-based modelling framework to estimate prenatal PM and its six constituents (ammonium, sulfate, nitrate, organic carbon, soil dust, and black carbon). We assessed the children's IQ using the short form of the Wechsler Intelligence Scale. Perceptual Reasoning Index (PRI), Verbal Comprehension Index (VCI), and Full Scale IQ (FSIQ) scores were computed. The multiple informant model (MIM) was applied to explore the trimester specific effects of PM and its six constituents' exposure on children's PRI, VCI, and FSIQ. To examine whether the duration of breastfeeding and physical activity (PA) could modify the effects of PM on children's IQ, we stratified the analyses according to the duration of breastfeeding (≤6 and >6 months) and time of outdoor activities after school (≤2 and >2 h/week). The first trimester PM and its five constituents' exposures were inversely associated with FSIQ [β = -1.34, 95 % confidence interval [CI] (-2.71, 0.04) for PM] and PRI [β = -2.18, 95 %CI (-3.80, -0.57) for PM] in children. The associations were magnified among boys and those with less outdoor activities or shorter breastfeeding duration. Our results indicate that prenatal PM and several of its main constituents' exposure may disrupt cognitive development in children aged 6 years. More PA and longer breastfeeding duration may alleviate the detrimental effects of prenatal PM exposure on children's cognitive function.