Can Air Quality Cause Autism?
In the quest to find the cause and ultimately the cure for autism, researchers are looking everywhere, from the medicines we take, to the food we eat, and finally, to the air that we breathe. A study published in the Archives of General Psychiatry has drawn a statistically significant link between the air pollution and the number of diagnosed cases of autism in children born in those areas.
The study looked at 500 children born in the state of California, half of whom had been diagnosed with autism. It finds that babies born and living in parts of the state with higher air pollution have a higher likelihood for being diagnosed with autism. This link held true even when the researchers corrected for common confounding variables including poverty, gender, and ethnicity.
It is still not determined exactly what exposures and interactions cause autism, though it is known that some children have a genetic predisposition for the disease. This study found that women who lived within 1,000 feet of a freeway, and thus were near road pollution, were more likely to have children affected with the disease.
However, this correlation is not reason enough to leave your apartment and move out to the country. Despite the significant correlation found, the link is just that, a correlation. The study does not prove that autism is caused by pollution, it simply draws a connection between pollution density and cases of the illness.
Additionally, exposure to pollution may not explain how cases of autism have boomed in the last 30 years, since many of the same pollutants have been around since then. It also fails to explain, if autism is caused by pollution, why there weren’t more children living in industrial cities in the early 1900’s diagnosed with the condition. In fact, in many major industrial cities, the amount of airborne pollution has actually decreased while the number of cases for autism has skyrocketed.
Finally, if you take a look at the graph created by the study, you’ll see that the risk of autism goes fairly steadily up as pollution increases, but then actually goes back down after the pollution rises over a certain threshold. If pollution is directly related to autism risk, we might expect to see the rates of autism diagnoses rising with the increase in pollution, or at least remaining the same.
Searching for a link between environmental factors and autism is a key tactic in the fight to prevent and treat this disease, but it’s important to take all study findings with a grain of salt. Most studies are observational, which means they look at events after they’ve occurred and attempt to draw conclusions from it. The only fully conclusive studies are experiments, which are designed, set up, and executed by researchers to test only one variable. Even correcting for poverty, gender, and ethnicity doesn’t necessarily wipe away all confounding variables.
After years of study, autism has turned out to be a complex and multi-faceted illness, clearly caused by a variety of factors. There is evidence that it is partially genetic as well as evidence that it can occur with and in relation to gastrointestinal issues. Another major theory is that somehow contaminants from the environment enter the body and get through the blood-brain barrier, affecting neurological function and causing the disease. If all these things are true, then it certainly is possible that pollution could have some small effect in pushing the balance one way or another when it comes to a diagnosis. However, it’s important not to fastlane it to the burbs on account of a single study. Over time, if this correlation is indeed causal, more evidence will come out in support of it. Until then, try to stay healthy and make good choices during your pregnancy and while your baby is a little one!
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