Fine and ultrafine particulate matter components and autism spectrum disorder (ASD)

Particulate matter (PM) composition varies by source components and size. While studies show prenatal and early life exposure to total PM_2.5 mass to be associated with autism spectrum disorder (ASD), little is known about the role of ultrafine (PM_0.1) and fine PM specific components, especially PM_0.1.

We investigated associations between prenatal and early life exposure to size-resolved PM components and ASD in the CHARGE case-control study.

We analyzed 1,281 children (751 ASD, 530 typically developing) from the CHARGE study (enrolled 2003-2020). Daily PM_0.1 and PM_2.5 component concentrations were estimated using a chemical transport model with 4- or 24-km km resolution (for 95% and 5% of addresses, respectively) and bias correction. Daily exposures were averaged over preconception, pregnancy, and the first year of life, and log transformed. Using logistic regression, we estimated PM_0.1 odds ratios (ORs) for ASD per interquartile range (IQR) increase in each component, adjusting for confounders, PM_2.5 remainder, and NO₂.

First-year PM_0.1 iron, manganese, black carbon, and sodium were consistently associated with increased odds of ASD (OR (95% CI): 1.60 (1.21, 2.12), 1.27 (1.04, 1.55), 1.54 (1.00, 2.38), and 1.92 (1.24, 2.99), respectively). Similar results were observed with first-year PM_0.1-2.5 iron and manganese (OR (95% CI): 1.54 (1.13, 2.09) and 1.46 (1.07, 2.01), respectively).

Our findings suggest that exposure to specific PM components during early life, especially in the ultrafine fraction, contribute to ASD risk, with less consistent evidence for prenatal exposures, underscoring the importance of particle composition and exposure timing.