October 28, 2026
Molly McVety/PhillyVoice
New research has found a link between prenatal exposure to wildfire pollution and autism risk. Above, wildfire smoke from Canada blankets Philadelphia in July.
Extreme wildfire activity has more than doubled in recent years, and researchers are examining a wide variety of potential health consequences.
A study published Tuesday in JAMA Pediatrics set out to deepen understanding of how wildfire pollution may impact brain development of babies in the womb. Using Medicaid data from nearly 900,000 mother-child pairs, the researchers found a correlation between prenatal wildfire particulate matter exposure and autism.
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The importance of such research is becoming more relevant even in urban areas, such as Philadelphia and New York, which are not necessarily thought of as prone to wildfire pollution. In July, Philadelphia and surrounding regions were blanketed by wildfire smoke and pollution from Canadian wildfires, putting the cities under Code Purple advisories that urged residents to stay indoors and take precautions if they had to go outside.
"Wildfire smoke can travel far beyond the communities where fires are burning, and exposure may occur even when smoke is not visible," said Dr. Stefania Papatheodorou, an epidemiologist at the Rutgers School of Public Health and lead author of the new study. "Our findings highlight the importance of awareness of wildfire events and their potential effects on air quality during pregnancy."
Specifically, the research team found the risk of a child being diagnosed with autism increased by 30% for each 0.75-microgram-per-cubic-meter rise in the average concentration of wildfire fine particles in the air. The strongest link between subsequent autism diagnoses and wildfire exposure was after the 15th week of pregnancy, the study found.
"Pregnancy is a period of rapid brain development, when environmental exposures may interfere with important developmental processes," Papatheodorou said in a news release. "Our findings suggest that the middle and later stages of pregnancy may be particularly relevant for understanding the potential effects of wildfire smoke on the developing brain and risk of autism."
The study could not establish a direct cause and effect relationship between prenatal exposure to wildfire pollution and autism. The findings were observational only and identified an association between an increased concentration of wildfire fine particles and subsequent autism diagnosis.
The researchers examined fine particulates known as PM2.5 — particles with diameters of 2.5 micrometers or smaller. By comparison, a human hair is 80 to 100 micrometers wide.
The study, which used federal Medicaid data collected from 2007 to 2014, did not find a link between prenatal exposure to fine particles from wildfire smoke and attention deficit disorder.
The researchers only used data from mother-child pairs who had been steadily enrolled in the public health coverage plan during the period of the study.
