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Air Pollution May Raise Autism Risk

Air Pollution & Autism Risk continued...

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.

She found a link or association. It does not prove cause and effect.

The link held after she considered other factors that affect risk, such as prenatal smoking, the mother's age, race, and ethnicity.

Pollution & Autism Risk: How to Explain It?

Exactly why pollution is linked to autism risk is not certain.

However, some pollutants have been shown to limit the action of a gene important in early brain development. Expression of this gene has been found to be reduced in autistic brains.

Air pollution can also cause inflammation, and that may play a role, Volk says.

The study was funded by the National Institute of Environmental Health Sciences and the University of California Davis MIND Institute, dedicated to research on autism and other neurodevelopmental disorders.

Volk reports receiving support from Autism Speaks to present research findings at a medical meeting.

It's too soon to make specific recommendations for those in high-pollution areas, Volk says.

However, she says, they may want to follow the same recommendations now in place for those who have respiratory disease, such as avoiding outdoor activity on high-pollution days.

"I think we need more study to see when a woman might be most vulnerable," Volk says.

Air Pollution & Autism Risk: Perspective

The study builds on other research, says Andrew Adesman, MD, chief of developmental and behavioral pediatrics at Steven & Alexandra Cohen Children's Medical Center of New York in New Hyde Park.

He reviewed the findings.

Researchers now suspect that genetics and environmental factors often interact in the cases of autism, he says. Air pollution may be one of those factors, but is likely to be one of many risk factors, if it bears out.

"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."

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