Rutgers study of 893,212 Medicaid pairs links wildfire smoke in pregnancy to higher autism diagnosis rate

Researchers at Rutgers University (USA) report in JAMA Pediatrics that exposure to fine particulate matter from wildfire smoke during pregnancy is associated with a higher risk of an autism diagnosis in children, according to Nauka w Polsce. naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗ The analysis used health insurance data on 893,212 mother-child pairs enrolled in Medicaid, with the children born in 2007–2014 (DOI: 10.1001/jamapediatrics.2026.5045).

Each increase in the mean concentration of wildfire-derived fine particulates of 0.75 micrograms per cubic metre during pregnancy was associated with a 30% higher risk of a later autism diagnosis. The association was strongest for exposure in the second and third trimesters, after week 15 of pregnancy. Lead author Stefania Papatheodorou of Rutgers School of Public Health noted that brain development continues throughout the whole pregnancy.

Particles and exposure estimates

The team focused on PM2.5, suspended particles with a diameter of 2.5 micrometres or smaller. They can penetrate deep into the lungs and cause systemic inflammation, which is one possible mechanism by which exposure could affect pregnancy and fetal development. The study itself did not analyse these biological mechanisms.

Earlier research suggests that particles from wildfires may be more harmful than dust from other sources. In the Rutgers analysis, fine-particle pollution from sources other than fires was linked to a smaller increase in the risk of an autism diagnosis. naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗ Two earlier studies, both limited to California, reached different conclusions about wildfire smoke and autism. The new work extended the geographic scope to the contiguous United States, using modelled estimates of weekly wildfire smoke concentration for the ZIP code of each mother's residence.

The authors note that smoke can travel far beyond burning areas and that exposure can occur even when smoke is not visible. In 2023, smoke from Canadian wildfires affected air quality in New Jersey, New York and other parts of the United States.

Limitations of the study

The study was observational and cannot show that wildfire smoke causes autism. Restricting the sample to people enrolled in Medicaid may limit how far the results apply to other groups. Results were similar across alternative analytical approaches, but unmeasured factors and uncertainty in the exposure estimates remain potential sources of error.

Papatheodorou said additional studies are needed to confirm the association and to better understand the possible effects of wildfire smoke. naukawpolsce.plNauka w Polscenaukawpolsce.plOpen source ↗