The researchers behind the study, titled "Traffic Related Air Pollution, Particulate Matter, and Autism," say exposure to traffic-related air pollution during pregnancy and early life is linked to a more than two-fold risk of autism.
In addition, exposure to regional pollution consisting of nitrogen dioxide and small pollution particles is also associated with autism, even if the mother did not live near a busy road, according to research published in the Archives of General Psychiatry, a sister publication of the Journal of the American Medical Association.
The USC/CHLA study found that children whose mothers lived in areas with high levels of pollution from traffic or with poor air quality during pregnancy or the first year of life may be more likely to have autism.
"This work has broad potential public health implications," said the study's principal investigator, Dr. Heather Volk, assistant professor of preventive medicine at USC's Keck School of Medicine and an investigator at CHLA.
"We've known for a long time that air pollution is bad for our lungs, and especially for children," she said. "We're now beginning to understand how air pollution may affect the brain."
The research is the first to look at the amount of near-roadway traffic pollution to which individuals were exposed and combine that with measures of regional air quality, Volk said.
The study builds on previous research that examined how close subjects lived to a freeway, Volk said.
"We took into account how far away people lived from roads, meteorology such as which way the wind was blowing, how busy the road was, and other factors to study traffic-related pollution," she said. "We also examined data from air quality monitors, which measure pollution over a larger region that could come from traffic, industry, rail yards or many other sources."