Autism spectrum disorder and particulate matter air pollution before, during, and after pregnancy: A nested case–control analysis within the nurses’ health study II cohort

Background: Autism spectrum disorder (ASD) is a developmental disorder with increasing prevalence worldwide, yet has unclear etiology. oBjective: We explored the association between maternal exposure to particulate matter (PM) air pollution and odds of ASD in her child. Methods: We conducted a nested case–control study of participants in the Nurses’ Health Study II (NHS II), a prospective cohort of 116,430 U.S. female nurses recruited in 1989, followed by biennial mailed questionnaires. Subjects were NHS II participants’ children born 1990–2002 with ASD (n = 245), and children without ASD (n = 1,522) randomly selected using frequency matching for birth years. Diagnosis of ASD was based on maternal report, which was validated against the Autism Diagnostic Interview-Revised in a subset. Monthly averages of PM with diameters ≤ 2.5 μm (PM_2.5) and 2.5–10 μm (PM_10–2.5) were predicted from a spatiotemporal model for the continental United States and linked to residential addresses. results: PM_2.5 exposure during pregnancy was associated with increased odds of ASD, with an adjusted odds ratio (OR) for ASD per interquartile range (IQR) higher PM_2.5 (4.42 μg/m³) of 1.57 (95% CI: 1.22, 2.03) among women with the same address before and after pregnancy (160 cases, 986 controls). Associations with PM_2.5 exposure 9 months before or after the pregnancy were weaker in independent models and null when all three time periods were included, whereas the association with the 9 months of pregnancy remained (OR = 1.63; 95% CI: 1.08, 2.47). Te association between ASD and PM_2.5 was stronger for exposure during the third trimester (OR = 1.42 per IQR increase in PM_2.5; 95% CI: 1.09, 1.86) than during the first two trimesters (ORs = 1.06 and 1.00) when mutually adjusted. Tere was little association between PM_10–2.5 and ASD.