Shortcomings of study linking autism to air pollution highlight need for better research

Every few weeks, a new research study makes headlines elucidating a possible link to autism such as a father’s advanced age at conception or the flu. The cause du jour this week is air pollution, with a study linking an increased autism risk to a baby’s living in a place with a high amount of air pollution.

I could tell you about the study findings, which were published online in the Archives of General Psychiatry: The researchers found that children with autism were three times as likely to have been exposed to high levels of air pollution, either prenatally or during their first year of life, compared with a control group of kids who didn’t have autism.


I could also tell you that the researchers couldn’t prove that air pollution caused autism even though they tried to take into account a host of other things that might also be associated with heightened autism risk: a mother’s lack of education, her poor socioeconomic class, and whether living in a city with plenty of psychologists who diagnose autism made a diagnosis more likely.

The researchers offered plenty of good scientific reasons to explain how it could be plausible for toxins in the air to interfere with the delicate neural wiring that’s laid down in the brain during the first crucial years of life. But they weren’t able to directly measure the levels of pollutants that the mothers were exposed to during their pregnancies or shortly afterward, instead relying on previous weather data and traffic volume to estimate emission rates in particular geographic areas where the women were living at the time.

While all of these caveats don’t necessarily invalidate the findings, they do point to a larger issue: the need for better designed, better funded studies to determine with more finality what’s leading to the precipitous rise in autism in American children.

Where autism was basically unknown two generations ago (or at least wasn’t recognized as a definable condition), it’s now estimated to occur in 1 in 88 children. The 78 percent increase in autism rates that has occured over the past six years can only be partly explained by improved diagnosis, according to Autism Speaks, an autism research and advocacy organization.


Autism research is booming with three new studies published in the Archives of General Psychiatry in this week alone; a decade ago. that was the total number published by the same journal in a year, pointed out Geraldine Dawson, a professor of psychiatry at the University of North Carolina at Chapel Hill in an editorial that accompanied the study.

“I really do think studies like this one on air pollution are raising more questions than they are providing answers,’’ Dawson said in an interview. “It’s so critical that we follow up on these studies.’’

There are several major studies in the works that should provide more definitive answers in the next few years, said Dawson, who is also the chief financial officer at Autism Speaks. One is a $2.5 million study looking at babies at higher risk of autism because they have a sibling with the condition; researchers are examining 1,000 children during their first three years of life looking at their diet, environmental exposures, and images of their developing brains to learn more about autism’s causes.

Another is a project to combine international health registries composed of millions of people from six countries that keep exhaustive medical records — the Scandinavian countries, Israel, and Australia — to understand how a mother’s diet, pesticide exposure, medications, and other lifestyle factors before and during pregnancy interact with genes to determine her child’s autism risk.

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