Prenatal exposure to particulate matter and risk of autism spectrum disorder in children: a population-based cohort study in South Korea.

BACKGROUND

Prenatal exposure to particulate matter has been investigated as a potential environmental factor for autism spectrum disorder (ASD), but evidence remains heterogeneous, and nationwide data from non-Western populations are limited.

METHODS

We conducted a nationwide retrospective birth cohort study using the Big CHildren's ENvironmental health Study (Big-CHENS) database in South Korea, including 698,907 mother-father-child pairs born between 2015 and 2017 and followed through 2023. Prenatal exposure to PM2.5 and PM10 was estimated using machine learning-based models and averaged over the entire pregnancy and by trimester. ASD was identified using diagnostic codes, with abnormal findings from the Korean Developmental Screening Test. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) per interquartile range increase in pollutant concentrations after adjusting for a broad range of potential confounders.

RESULTS

During follow-up, 5594 children (0.8%) were diagnosed with ASD. Prenatal PM2.5 exposure was not associated with ASD risk during the total pregnancy period (HR, 0.99; 95% CI, 0.95-1.03) or during the first (1.02, 0.99-1.05), second (0.99, 0.97-1.02), or third trimester (0.98, 0.95-1.00). Similarly, prenatal PM10 exposure was not associated with ASD risk during the total pregnancy period (0.99, 0.94-1.04) or during the first (1.02, 0.98-1.05), second (0.99, 0.96-1.02), or third trimester (0.98, 0.96-1.01). Findings were consistent across developmental screening outcomes, subgroup analyses, and sensitivity analyses.

CONCLUSIONS

In this nationwide South Korean cohort, prenatal exposure to PM2.5 or PM10 was not associated with ASD risk after accounting for a broad range of potential confounders. These findings highlight the importance of careful confounder control and outcome definition in studies of prenatal air pollution exposure and neurodevelopmental outcomes.