California wildfire smoke linked to increased autism diagnoses, new study finds
January 21, 2026
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Smoke from California wildfires linked to increase in autism diagnoses, new study finds
Children born to mothers exposed to smoke in Southern California had increased rates of autism, although the reason is unclear.
Svetlana Repnitskaya via Getty Images
A new study of more than 200,000 children in Southern California found a link between mothers’ exposure to wildfire smoke and higher rates of autism in children. The causes of autism are not fully known and are likely multifaceted, but the new research builds on existing evidence that air pollution may be linked to autism.
The study, published Tuesday in Environmental sciences and technologies, analyzed data from children born in the wildfire hotspot from 2006 to 2014. Pregnant women who were in their third trimester and exposed to just one to five days of smoke were about 11 percent more likely to have a child diagnosed with autism by age five than those who had not seen smoke-free days. The more mothers were exposed to smoke, the higher the likelihood that their children would be diagnosed with autism: women exposed to between six and ten days of smoke were 12 percent more likely to have a child with such a diagnosis by age five, while the odds were 23 percent higher among those who had been exposed to more than 10 days of smoke.
“This is one of the first large population studies to specifically examine prenatal wildfire smoke exposure and autism risk,” says Mostafijur Rahman, assistant professor of environmental health sciences at Tulane University and author of the new study. “Our results suggest that exposure to wildfire smoke during sensitive periods of pregnancy, particularly late pregnancy, may be associated with an increased risk of autism diagnosis in children.”
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It’s important to note that the study does not identify a direct causal link between autism and wildfire smoke, Rahman says. Most experts believe that autism is complex and likely results from a combination of environmental and genetic factors.
Rather, the study “highlights wildfire smoke as a potentially modifiable environmental risk factor that may contribute to risk in combination with other factors,” he says.
The study has several limitations. Some mothers included in the study may have had different levels of smoke exposure than those estimated by the researchers. And wildfires can also be extremely stressful — an experience that may have also played a role.
David Mandell, a professor of psychiatry at the University of Pennsylvania who was not involved in the study, says the paper’s association between wildfire smoke and autism is “certainly concerning” and “deserves further attention.”
Mandell notes, however, that some children whose mothers experienced higher concentrations of wildfire smoke during their third trimester and did not move during the study period did not show higher rates of autism, which is not the “dose-response gradient one might expect,” he says.
Autism and its causes have been a focus of the Trump administration and Health and Human Services Secretary Robert F. Kennedy, Jr., who has in the past claimed that autism is most likely caused by various environmental exposures, not all of which have been supported by solid scientific data. According to the U.S. Centers for Disease Control and Prevention, approximately one in 31 children is diagnosed with autism before the age of nine.
The new study is consistent with previous research showing that children whose mothers were exposed to high levels of fine particle pollution, as well as diesel engine exhaust and mercury, were more likely to be diagnosed with autism than the children of those who breathed cleaner air.
Wildfires have become an ever-present risk in the United States, especially for Californians. According to the U.S. Department of Agriculture, between 2003 and 2012, large wildfires in the western United States lasted an average of 52 days, compared to just six days in the 1970s and 1980s.
“As wildfires become more frequent and more intense due to climate change, it is increasingly important to understand their potential long-term health impacts,” says Rahman.
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