Two groundbreaking studies have revealed a concerning connection between exposure to wildfire smoke during pregnancy and an increased likelihood of autism spectrum disorder in children.
The largest study, published in the journal Environment International, analyzed data from over 8.6 million births in California between 2001 and 2019. Researchers from UC Davis Health and UCLA found that while average wildfire smoke exposure showed only weak associations with autism diagnosis, the link became significantly stronger during high-intensity smoke events.
“The most intense wildfire smoke exposure is where we see the clearest links,” said UC Davis Health’s Rebecca J. Schmidt, senior author and professor at the UC Davis MIND Institute. “And these intense wildfire events are becoming more common in the West.”
The research team used advanced models to estimate wildfire smoke exposure three months before, during, and one year after pregnancy. They separated particulate matter from vegetation burning and from wildland-urban interface sources such as homes and vehicles.
A second study published in Environmental Science and Technology examined data from over 200,000 children born in Southern California between 2006 and 2014. It found that mothers exposed to 10 or more days of smoke in their third trimester had a 23 percent greater risk of having children diagnosed with autism by age 5, while those with 6-10 days of exposure saw a 12 percent higher risk.
“The more you get exposed the worse it is,” said David Luglio, a postdoctoral fellow at Tulane University and lead author of this study. “But we can’t necessarily answer why that is the case.”
These findings build on previous research showing wildfire smoke is approximately 10 times worse than inhaling car exhaust and other pollution from burning fossil fuels. The ultra-fine particles released during combustion penetrate deep into the lungs and bloodstream, potentially affecting developing brains.
Experts emphasize that these studies show an association rather than direct causation. Autism spectrum disorder, which affects 1 in 31 8-year-old children in the United States, is believed to result from a complex interaction of genetic and environmental factors.
The research underscores the need for targeted policies including vegetation management, land use planning, indoor filtration upgrades, and clean-air shelters to protect vulnerable populations, especially pregnant women, from wildfire smoke exposure.
For those concerned about air quality, experts recommend checking real-time air quality index levels using resources like AirNow or PurpleAir, and taking precautions to limit exposure during smoke events.
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