Effects strongest in intense wildfire episodes and in areas with cleaner air overall
THURSDAY, Feb. 19, 2026 (HealthDay News) — Wildfire smoke exposure during pregnancy may increase the risk for autism spectrum disorder (ASD), according to a study published in the February issue of Environment International.
Karl O’Sharkey, Ph.D., M.P.H., from the University of California, Los Angeles, and colleagues examined associations between wildfire-specific fine particulate matter <2.5 μm (PM2.5) exposures and ASD risk in California births. The analysis included data from 8.6 million births in California from 2001 to 2019, which were linked to California Department of Developmental Services records through 2022.
The researchers found that continuous wildfire-specific exposures during the pregnancy period were weakly associated with ASD. Stronger effects were seen at high exposure percentiles and during intense wildfire episodes (≥35 µg/m3). Among children in the lowest quartile of prenatal background PM2.5, associations were most pronounced, with odds of ASD increasing by 50 percent for those above the 90th percentile of wildfire PM2.5 during pregnancy. In metro areas, wildland-urban-interface (WUI)-related PM2.5 was associated with ASD, suggesting unique toxicity. In nonmetro regions, the effects were generally stronger, with the exception of WUI-related PM2.5. Additionally, the effects were stronger in White children and for births occurring after the implementation of the Diagnostic and Statistical Manual of Mental Disorders, 5th edition. There were minimal sex differences, but stronger effect estimates for WUI-related PM2.5 and high exposure episodes were seen for males.
“Together, these results suggest that air pollution during pregnancy is not a single, uniform exposure, and that the source and composition of pollution, as well as timing and intensity of exposure, matter when it comes to neurodevelopment,” O’Sharkey said in a statement.
Two authors disclosed financial ties to the biopharmaceutical industry.
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