More evidence suggests link between air pollution and ASD

More evidence suggesting a link between air pollution and autism spectrum disorders (ASD) comes from studies conducted by researchers in Denmark and the United States.

In the first study, Youn-Hee Lim and colleagues analyzed data collected on more than 850,000 children born in Denmark between 1990 and 2004, identifying those diagnosed with autism by 15 years of age. They calculated the pollution exposures of the children based on their mothers’ home addresses during pregnancy, looking specifically for exposure to black carbon (BC), nitrogen dioxide (NO2 ), and PM2.5 (particulate matter with a diameter less than or equal to 2.5 micrometers, which is considered to be especially harmful).

They report, “In this large nationwide cohort study conducted in a low-exposure setting in Denmark, we found that prenatal exposure to all major air pollutants, PM2.5 , NO2 , and BC, was associated with an increased incidence of ASD. Notably, we provided novel evidence that BC was associated with ASD independently of PM2.5 , highlighting the benefits of regulating BC in addition to PM2.5 . We further show that children with older mothers experienced the strongest associations.”

The researchers conclude, “These results underscore the importance of reducing emerging air pollutants as a potential strategy for autism spectrum disorder prevention.”

In the second study, David Luglio and colleagues estimated the exposure of more than 200,000 pregnant women in California’s Kaiser Permanente medical system to wildfires and to PM2.5 . Based on the women’s home addresses, the researchers calculated the mean wildfire PM2.5 concentration to which they were exposed, the number of days of smoke exposure, and the number of waves of smoke exposure. They also differentiated movers (women who left their homes during fires) from nonmovers.

They report, “There were 3,356 autism diagnoses by age five. Autism risk was associated with increased number of wildfire-exposed days during the third trimester and was strongest for nonmovers.” They note, however, that even for nonmovers, the increased odds of children receiving an ASD diagnosis were small to moderate. There was no association between ASD diagnoses and the mean wildfire PM2.5 concentration alone.

Luglio comments, “Further study is needed to understand how wildfire smoke exposure to pregnant mothers could cause autism in their children, and to determine how exposure may interact with biology, genetics and other environmental exposures. This study is just one piece of a much larger puzzle, and the findings tell us there are more pieces to be put together.”

He and his team conclude that while more research is needed on the effects of wildfire exposure, “Public health authorities may consider prioritizing pregnant women for protection from wildfire smoke, perhaps particularly during late pregnancy.”

Citations

“Prenatal exposure to air pollution and the development of autism spectrum disorder from birth to adolescence: A nationwide Danish cohort study,” Youn-Hee Lim, Caleb Lawlor, Marie Bergmann, Jiawei Zhang, Rina So, George Maria Napolitano, Gonzalo Hevia-Ramos, Tanya Andersson Nystedt, Kajsa Pira, Ebba Malmqvist, Anna Oudin, and Zorana Jovanovic Andersen, Environmental Epidemiology, February 9, 2026 (free online). Address: Zorana Jovanovic Andersen, Section of Environmental Health, Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, Building 15, 1 floor, Copenhagen 1014, Denmark, [email protected].

—and—

“Prenatal exposure to wildfire and autism in children,” David G. Luglio, Xin Yu, Jane C. Lin, Ting Chow, Mayra P. Martinez, Zhanghua Chen, Sandrah P. Eckel, Joel Schwartz, Frederick W. Lurmann, Nathan R. Pavlovic, Rob McConnell, Anny H. Xiang, and Md Mostafijur Rahman, Environmental Science & Technology, January 2026 (free online). Address: Anny H. Xiang, Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, California 91101, [email protected], or Md Mostafijur Rahman, Department of Environmental Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana 70118, [email protected].

—and—

“Exposure to wildfire smoke late in pregnancy may raise autism risk in children,” news release, Tulane Medical University, January 20, 2026.