Preconception, Prenatal and Postnatal PM2.5 Exposure and Neurodevelopmental Disorder Risk among Medicaid Recipients.

Evidence linking ambient fine particulate matter (PM2.5) exposure to childhood neurodevelopmental disorders (NDDs) remains mixed. We conducted a cohort study (2001-2013) of 1,547,244 Medicaid-enrolled mother-child pairs to assess associations between zip-code-level PM2.5 exposure during preconception (12-week), prenatal (37-week), and postnatal (3-year) periods and children's NDD risk. Cox proportional hazards models estimated risks of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), learning difficulty (LD), speech/language disorder, developmental coordination disorder (DCD), intellectual disability, and behavioral disorder, adjusting for demographics, meteorological characteristics, and area-level socioeconomic indicators. Distributed lag models assessed critical exposure windows and cumulative effects. A 10 μg/m3 increase in cumulative prenatal PM2.5 exposure was associated with higher ASD risk (Hazard ratio (HR):1.17; 95%CI:1.00,1.37). A critical exposure window for ASD existed during gestational weeks 23-31 (HR:1.09 95%CI:[1.02,1.17]). Cumulative prenatal PM2.5 exposure was associated with increased ID risk among Hispanic individuals (HR:1.57 95%CI:[1.02,2.43]) but not among other races/ethnicities. Postnatal PM2.5 exposure was associated with increased ADHD risk (HR:1.17 95%CI:[0.94,1.46]) at age 0 years and DCD risk (HR:1.72 95%CI:[0.97,3.07]) at age 1 year. No associations between PM2.5 exposure and other NDDs were found. Prenatal and postnatal PM2.5 exposure may increase the risk of some NDDs among low-income U.S. children.