A new study found that traffic air pollution exposure during pregnancy could increase a child’s risk of developing autism.
“Children exposed to higher levels of traffic-related pollutants during pregnancy or during the first year of life were at increased risk of autism compared to children exposed to the lowest level,” says Heather E. Volk, PhD, MPH, assistant professor of research at the University of Southern California Keck School of Medicine.
During pregnancy, the highest exposures to pollution were linked with a two-times-higher risk of autism. High levels during the child’s first year tripled the risk.
The risk differed depending on timing.
To examine whether environment played a role in autism risk, USC researchers compared 279 children with autism to a control group of 245 typically-developing children. They analyzed air quality data from the Environmental Protection Agency (EPA) and compared that to the mothers’ addresses to estimate exposure to air pollution during each trimester and the first year of birth.
The researchers found that kids who were exposed to highest levels of traffic-related air pollution were three times more likely to have autism compared with children living in homes with the lowest exposure. Autism risk was also increased for children who were exposed to higher levels of particulate matter and nitrogen dioxide.
“There is evidence that the immune system might be associated with autism, and pollution affects these same pathways,” Volk told HealthDay.
Researchers have been looking at the potential role of air pollution in autism only for about three years, Volk says.
Air pollution has been linked with a variety of ill health outcomes, she says, including babies being born small for their gestational age. “When you think about the birth outcome literature, looking at air pollution [and autism risk] makes some sense,” she says.
In 2011, Volk’s team reported a higher risk of autism for children whose families lived within about 1,000 feet of a freeway.
In her previous study, Volk says, she just looked at how far people lived from roads. The new study went further.
“Now we consider how busy the road was, traffic density, volume of traffic, and how often the road is traveled,” she says.
The risk of autism was higher for those exposed to more pollution, either before birth or during their first year.
Based on the findings, however, Volk says she can’t say that living in a specific area is worse than another.
For instance, those who live in a rural area might be close to a very busy high-traffic intersection, increasing pollution exposure.
Autism is a diverse disorder marked by problems in communicating and interacting socially. It now affects about 1 in 88 children in the U.S.
This study was published in Archives of General Psychiatry on November 26.