Associations between prenatal PM_2.5 exposures and intellectual disability: Are there differential impacts based on...

Prenatal fine particulate matter (PM_2.5) has been associated with intellectual disability (ID) and autism spectrum disorder (ASD), separately. Its role in co-occurring ID with ASD (ID + ASD) is less understood. To address this gap, this study uniquely disaggregates ID-only from ID + ASD to assess the associations between prenatal PM_2.5 exposure and odds of ID-only and ID + ASD across multiple exposure windows and measures. For children born in Utah, U.S.A., children with ID (ID-only and ID + ASD) were matched 1:3 with non-ID affected controls. PM_2.5 exposure was estimated across four prenatal periods (i.e., preconception, 1st, 2nd, and 3rd trimester) using long-term averages and exceedances of WHO and U.S. NAAQS 24-h thresholds and assigned to children. Associations were examined using multilevel multinomial logistic regressions. Results show that increase in long-term PM_2.5 during preconception and first trimester was associated with increased odds of ID-only and ID + ASD. Exceedances of the WHO 24-h threshold (15 μg/m³) during preconception were linked to ID-only, while first trimester WHO 24-h exceedances were linked to both ID-only and ID + ASD. U.S. NAAQS 24-h threshold (35 μg/m³) exceedances during preconception and first trimester were associated with ID + ASD. Results reveal that long-term PM_2.5 exposure during preconception and the first trimester elevates risk for both ID-only and ID + ASD. ID + ASD appears particularly sensitive to preconception and first trimester exceedances of the U.S. NAAQS 24-h threshold, whereas ID-only may be more sensitive to exceedances of the WHO 24-h threshold during preconception. By distinguishing these neurodevelopmental outcomes, these results underscore timing and magnitude of prenatal PM_2.5 exposure differentially influence neurodevelopmental risk. They also highlight the need for targeted public health interventions and stronger air quality regulations to protect early neurodevelopment.