Autism is on the rise in California, affecting about one in 110 children.
Researchers at Children's Hospital Los Angeles, USC and UC-Davis followed about 600 families in the L.A., Sacramento and San Francisco areas. They found women who lived within 1,000 feet of a freeway at the time they were pregnant were two times as likely to have a child diagnosed with autism.
"It seems like air pollution could potentially affect the brain and be related to autism," said Dr. Heather Volk, Children's Hospital Los Angeles. "There's some nice data coming out of animal studies that seem to indicate that exposure to air pollution is associated with changes in the brain."
The study simply looked at proximity. Researchers did not look at air samples or identify components of pollution. It was not an association study.
Volk said it could be a combination of factors that lead to autism.
Volk, the study's author, said the research does not prove a cause-and-effect relationship between air pollution and autism. But the theory is that something in vehicle emissions may affect the brain of an unborn child.
"We spend more time in our cars now, so that's something that definitely happens, and there's more particulate matter," said Volk. "But really, it's a great thing to think about with autism being on the rise."
Should a woman who is pregnant or planning a pregnancy move if she lives near a freeway? Researchers say no. Volk says there is no reason to panic at this point.
There many harmful components in air pollution, and from this study, scientists can't identify exactly what it is that may increase a person's risk for developing autism. They say more research needs to be done.