Expectant moms now have something else to worry about -- the traffic driving by their house.
High levels of air pollution from traffic during pregnancy might raise autism risk, researchers claim in a new study.
"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, study author and assistant professor at the University of Southern California Keck School of Medicine.
In 2010, Volk's team reported a higher risk of autism for children who lived within 1,000 feet of a freeway.
This new study goes further, examining traffic density, traffic volume and exposure to particulate matter and nitrogen dioxide.
The new study, published online in the Archives of General Psychiatry, found that autism risk was two times greater for children exposed to high levels of pollutants while in the womb, and it was three times greater for children exposed to high levels of pollution during their first year.
Autism risk was also increased for children exposed to higher levels of particulate matter and nitrogen dioxide — commonly known as smog — CBS News reports.
"There is evidence that the immune system might be associated with autism, and pollution affects these same pathways," Volk tells HealthDay, adding that the toxic chemicals in pollution might trigger a genetic predisposition to autism.
While Volk and her team found an association between air pollution and autism, she clarifies that the study does not yet prove a cause and effect relationship.
"Although additional research to replicate these findings is needed, the public health implications of these findings are large because air pollution exposure is common and may have lasting neurological effects," write the study's authors.
In an editorial accompanying the journal's study, Geraldine Dawson, chief science officer of Autism Speaks and a professor of psychiatry at the University of North Carolina, writes:
"We don't know whether these immune abnormalities are a cause or a response to having autism. Either way, these findings are an important clue that the immune system plays a role in autism," she writes. "There is an urgent need for more research on environmental factors that can influence prenatal brain development and potentially increase risk for autism."
While the findings of the study can certainly sound alarming, Dr. Andrew Adesman from Steven & Alexandra Cohen Children's Medical Center of New York, points out one very important detail.
"Although this study provides further support for the notion that exposure to traffic-related air pollution is a risk factor for autism, most children with autism do not live near highways," he says.
"Undoubtedly, autism has many different causes and risk factors — and only some of these are known at this time," Adesman tells WebMD.
About 1 in 200 Canadians exhibit Autism Spectrum Disorders — "spectrum" refers to a continuum of severity or developmental impairment — Autism Society Canada reports.
One study found that traffic noise ups heart attack risk, with researchers speculating that the stress of the noise, the heart- and blood-vessel-damaging pollution, and the sleep interference all contributed to the increased risk.
A 2010 Health Effects Institute study concluded that air pollution leads to a myriad of health problems, including asthma attacks, impaired lung function and a increased risk of worsening cardiovascular diseases.
And yet another study linked traffic pollution to increased risk of chronic bronchitis.
Maybe it's time to move to the country.
Watch the video below about how long commutes in traffic are linked to a host of health problems.