Study: Prenatal Exposure to Pollutants May Increase Risk for Autism

Concentration of air pollutants in your area may double your baby's autism risk.


The concentration of air pollutants where you live around the time you give birth may double your child's risk of autism, according to a new study from the Harvard School of Public Health.

The study, published last week in the journal Environmental Health Perspectives, looked at 14 pollutants that have been associated with Autism Spectrum Disorder in previous studies, and concluded that perinatal exposure to these pollutants may increase the risk for the neurodevelopmental disorder.

"Women in the cleanest areas had a noticeably lower risk," lead author Andrea Roberts, a research associate in the Harvard School of Public Health Department of Social and Behavioral Sciences, tells, adding that 20 to 60 percent of the women in the study lived in areas where the risk of autism was elevated.

The study, based on children of participants in the Nurses' Health Study II (325 autism cases, 22,101 controls) born in all 50 states between 1987 and 2002, found that women who lived in the 20 percent of locations with the highest levels of diesel particulates or mercury in the air were twice as likely to have a child with autism as those who lived in the 20 percent of areas with the lowest levels.

Women who lived in the 20 percent of locations with the highest levels of air pollution from lead, manganese, methylene chloride and combined metal exposure were about 50 percent more likely to have a child with autism than those who lived in the 20 percent of areas with the lowest concentrations.

Most pollutants were associated with autism more strongly in boys than girls, but Roberts points out that there were few girls with autism in the study (data show that boys are four to five times more likely than girls to have autism, according to the National Institute of Child Health and Human Development).

About one out of every 88 children in the United States currently has autism, according to estimates from the Centers for Disease Control and Prevention. While more people than ever before are being diagnosed with ASD, this could be at least partially due to a broader definition of autism, better efforts in diagnosis or greater awareness about symptoms, according to the NIH.

The study, it's important to note, did not determine air pollution to be a cause of autism, only an association. "We don't know whether what we found is causal — it's still possible the results were because of some other factor associated with air pollution," Roberts says.

Rather than worrying about the air pollution in your area, which you can do very little to control, Roberts suggests pregnant women focus on the positive things they can do: taking prenatal vitamins is associated with a lower risk of autism, she says; eating a lot of foods rich in healthy oils, like nuts and fish, is good for brain development; and keeping your weight within a healthy range may help prevent gestational diabetes, which has been associated with autism, she says.

"People should keep in mind that autism is very heavily genetic — there's not much we can do about that," she says. Plus, the odds are in your favor. "Autism is pretty rare despite all the epidemic scares," she adds.

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