Women exposed to the highest levels of fine-particulate air pollution late in their pregnancies are two times more likely to give birth to a child with autism. Thats according to the largest study to date looking at the link between autism and pollution. The neurodevelopmental disorder is marked by repetitive behaviors and difficulties with social interaction and communication.
Researchers analyzed data from 116,000 mothers and their children in all 50 states.
Investigators, led by Marc Weisskopf of Harvard University, found women exposed to high levels of fine-particulate matter air pollution, during their third trimester of pregnancy, were at highest risk of having an autistic child.
Their increased risk was double that of women who lived in areas with low levels of particulate pollution.
The Harvard study found that timing of exposure was critical. The researchers detected no increased risk of autism spectrum disorder in children whose mothers were exposed to high levels of pollution before becoming pregnant. And the study found airborne pollution does not appear to increase the risk of children developing autism after they are born.
Weisskopf, an environmental and occupational epidemiologist, says the finding is compelling even though it is not evidence of a direct link between pollution and autism.
Finding an association like this thats very specific in time rules out a lot of other possible explanations for that, said Weisskopf. "So it really ratchets up the strength our confidence that we got something really related to the air pollution here.
To the extent possible, Weisskopf says expectant mothers should avoid exposure to air pollution.
You can avoid being in extremely polluted cities during pregnancy if possible, said Weisskopf. "You can also choose to go running in a park rather than next to a street. But that said, I think also its very important to recognize that autism spectrum disorders is a multi-factorial disorder. And there are lots of reasons why risk could be increased.
Autism, which runs the spectrum from mild to severe impairment, is believed to be caused by a combination of environmental and genetic factors that predispose individuals to the disorder.
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Large US Study Links Air Pollution to Autism