Exposure to wildfire smoke during pregnancy is associated with a higher likelihood of an autism diagnosis in children, particularly when exposure occurs during the second and third trimesters, according to a new study involving around 900,000 mother-child pairs in the United States.
The research found that each 0.75-microgram-per-cubic-metre increase in the average concentration of fine particulate matter from wildfires during pregnancy was associated with a 30 per cent higher risk of an autism diagnosis. The strongest associations were observed during the second and third trimesters, when fetal brain development continues at a rapid pace.
The study, published in JAMA Pediatrics, followed participants for an average of 6.3 years. Researchers examined prenatal exposure to wildfire-related air pollution and its association with subsequent autism diagnoses.
“Pregnancy is a period of rapid brain development, when environmental exposures may interfere with important developmental processes,” said Stefania Papatheodorou, an epidemiologist at the Rutgers School of Public Health and the study’s lead author.
Autism is a complex neurodevelopmental condition involving multiple genetic and environmental factors. Processes linked to brain development begin before birth, as nerve cells form connections and develop the networks needed for communication and other functions.
Wildfire smoke contains fine particulate matter, gases and other pollutants. Its chemical composition varies according to the materials burned, with fires involving plastics, electronics and paints potentially releasing additional toxic substances.
Fine particles can travel deep into the lungs and trigger inflammation throughout the body. Researchers said this could be one possible pathway through which wildfire smoke exposure might affect pregnancy and fetal development, although the study did not establish a biological mechanism.
“Wildfire smoke can travel far beyond the communities where fires are burning, and exposure may occur even when smoke is not visible,” Papatheodorou said.
The findings add to existing research into the health effects of wildfire pollution, which has been associated with respiratory problems, including asthma, as well as other physical and mental health conditions.
However, the researchers stressed that the study was observational. This means it identified an association between prenatal wildfire smoke exposure and autism diagnoses but cannot establish that the exposure directly causes autism. Other environmental, genetic and social factors may also contribute to the findings.
“Understanding how prenatal environmental exposures may contribute to autism, alongside genetic and other factors, remains an important research priority,” Papatheodorou said.
The researchers highlighted the importance of monitoring wildfire activity and air quality during pregnancy. They said improved forecasting, public health warnings and measures to prevent smoke from entering indoor spaces could help reduce exposure.
As wildfire events become an increasing concern in many regions, the findings underline the need for further research into how air pollution during pregnancy may influence children’s long-term health and development.
