Study: Autism Linked to Air Pollution From Traffic

Children born to women have been exposed to high pollution levels are at higher risk for autism.

People hold signs in Washington, D.C., showing the faces of children with autism before a march calling for healthier vaccines on June 4, 2008.

People hold signs in Washington, D.C., showing the faces of children with autism before a march calling for healthier vaccines on June 4, 2008.

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Exposure to traffic-related pollution during pregnancy or the first year of a child's life has been linked to autism, according to a new study released Monday.

Using data from Califonia's Childhood Autism Risks from Genetics and the Environment, University of Southern California researcher Heather Volk found that pregnant women who were exposed to high levels of traffic-related air pollution were nearly three times as likely to have a child with autism as people who were in the lowest quartile of exposure.

Volk says the study was unable to take into account daily commutes or a specific amount of time that pregnant women and their infants were exposed, but notes that "children with autism were more likely to live at residences that had the highest quartile of exposure to traffic-related air pollution, during gestation and during the first year of life."

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Families who lived within 1,000 feet of a freeway seemed to have the most risk. Scientists are split about what causes autism, but most agree that there is both a genetic and environmental component to the disease. Volk says her study suggests, but does not confirm, that air pollution may play a role in whether a child develops autism. The study was published Monday in Archives of General Psychiatry.

"It's likely there are many environmental and genetic factors to the disease that work together to cause it," she says. "Think of it like Trivial Pursuit pies — you put the pieces of the pie together in order to get a diagnosis."

Scientists disagree on whether autism is becoming more prevalent or whether doctors are simply getting better at diagnosing the disease: Earlier this year, the Centers for Disease Control said autism affects 1 in 88 children, a 78 percent increase over 2002 numbers. At the time, Thomas Frieden, director of the CDC, said the disease is a "complex condition with many unanswered questions."

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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at jkoebler@usnews.com.