Prenatal wildfire smoke linked to 30% higher autism risk in new study

For every 0.75 microgram per cubic meter increase in wildfire fine particles in the air, the risk of a child being diagnosed with autism rose by 30%, according to a study published Tuesday in JAMA Pediatrics.

The research team analyzed federal Medicaid data from nearly 900,000 mother-child pairs between 2007 and 2014. They focused on PM2.5, a type of fine particulate matter with a diameter of 2.5 micrometers or less. By comparison, a human hair measures between 80 and 100 micrometers wide. The study identified a correlation between prenatal exposure to these particles and subsequent autism diagnoses, though it did not establish a direct cause-and-effect relationship.

The strongest association emerged after the 15th week of pregnancy. Dr. Stefania Papatheodorou, an epidemiologist at the Rutgers School of Public Health and lead author of the study, noted that pregnancy is a period of rapid brain development. She stated that environmental exposures may interfere with important developmental processes during this time. "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," Papatheodorou said in a news release.

The findings carry implications for urban areas that are not typically associated with local fire activity. In July, Philadelphia and surrounding regions were covered by smoke from Canadian wildfires. Those areas issued Code Purple advisories urging residents to stay indoors and take precautions when going outside. "Wildfire smoke can travel far beyond the communities where fires are burning, and exposure may occur even when smoke is not visible," Papatheodorou said.

Extreme wildfire activity has more than doubled in recent years, prompting researchers to examine various health consequences. The observational study specifically looked at fine particulates from wildfire smoke. It did not find a link between prenatal exposure to these particles and attention deficit disorder.

The data included only mother-child pairs who remained steadily enrolled in public health coverage during the study period. The results were based on an association between increased concentrations of wildfire fine particles and autism diagnoses, providing a basis for further investigation into how air quality affects fetal brain development.