UCLA and UC Davis researchers found the strongest associations on very smoky days and in areas with cleaner air overall.
New research suggests that exposure to intense wildfire smoke during pregnancy may be associated with increased likelihood of autism in children. The peer-reviewed study, by researchers at UC Davis Health and the UCLA Fielding School of Public Health, was published in the February edition of the journal Environment International.
The study of more than 8.6 million births in California is the largest to date examining how wildfire-specific air pollution may impact early neurodevelopment. Scientists combined detailed wildfire smoke data with state birth records from 2001 to 2019. They matched these with autism diagnoses from California Department of Developmental Services through 2022.
“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,” said Dr. Karl O’Sharkey, a research scientist with the Environmental Health Sciences Department at the UCLA Fielding School of Public Health.
The researchers considered the timing and intensity of wildfire smoke exposure, as well as the type of background air pollution that families usually experienced. They focused on wildfire-related PM 2.5, or tiny particles of smoke about 30 times smaller than the diameter of human hair.
High‑intensity wildfire smoke events show strongest associations
Overall, average wildfire smoke levels during pregnancy showed only weak associations with autism diagnosis. But during high‑intensity smoke events — days with particulate levels in the top 10 percent — the associations grew stronger. In regions with generally cleaner air, such as rural areas, it was most pronounced.
“The most intense wildfire smoke exposure is where we see the clearest links,” said UC Davis Health’s Dr. Rebecca J. Schmidt, senior author and professor in the Department of Public Health Sciences. “And these intense wildfire events are becoming more common in the West.”
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Read the full press release by Marianne Russ Sharp, UC Davis Health at https://ph.ucla.edu/news-events/news/exposure-intense-wildfire-smoke-during-pregnancy-may-be-linked-increased
Photo by Carly Hagins