Early life exposure to particulate matter air pollution (PM₁, PM_2.5 and PM₁₀) and autism in Shanghai, China: A case-control study

Background: The evidence for adverse effects of ambient particulate matter (PM) pollution on mental health is limited. Studies in Western countries suggested higher risk of autism spectrum disorder (ASD) associated with PM air pollution, but no such study has been done in developing countries. Methods: A case-control study was performed in Shanghai with a multi-stage random sampling design. Children's exposures to PM₁, PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameter < 1 μm, < 2.5 μm and < 10 μm, respectively) during the first three years after birth were estimated with satellite remote sensing data. Conditional logistic regression was used to examine the PM-ASD association. Results: In total, 124 ASD cases and 1240 healthy controls were included in this study. The median levels of PM₁, PM_2.5 and PM₁₀ exposures during the first three years of life were 48.8 μg/m³, 66.2 μg/m³ and 95.4 μg/m³, respectively, and the interquartile range (IQR) for these three pollutants were 4.8 μg/m³, 3.4 μg/m³ and 4.9 μg/m³, respectively. The adjusted odds ratios (and 95% confidence intervals) of ASD associated with an IQR increase for PM₁, PM_2.5 and PM₁₀ were 1.86 (1.09, 3.17), 1.78 (1.14, 2.76) and 1.68 (1.09, 2.59), respectively. Higher ORs of ASD associated with PM pollution were observed in the second and the third year after birth. Conclusions: Exposures to PM₁, PM_2.5 and PM₁₀ during the first three years of life were associated with the increased risk of ASD and there appeared to be stronger effects of ambient PM pollution on ASD in the second and the third years after birth.