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Constant exposure to pollution, whether it’s in the air, water, or common household products, has been shown to affect human health negatively in a variety of ways. New research suggests that the risks posed by pollution start in the womb, and could drastically increase the chances that a woman will have a child with autism. Conducted by the Harvard School of Public Health and recently published in the journal Environmental Health Perspectives, researchers discovered that expectant mothers who lived in some of the most highly polluted areas of the United States were two times as likely to have a child with autism compared with those who lived in locations with the lowest levels of pollution.

pollution, mercury, toxins, chemicals, air quality, autism, prenatal health, pregnancy, health risks, childhood disordersImage via taja/Flickr

The nationwide study builds on previous research that indicated links between environmental pollution and autism. A study conducted in 2012 found that children with autism are two to three times more likely than other children to have been exposed to car exhaust, smog, and other air pollutants during their earliest days.

Eager to find out if the results of these geographically-limited studies could be extrapolated at the national level, the HSPH researchers analyzed data from a nationwide sample of 116,430 nurses participating in the Nurses’ Health Study II, an ongoing survey that began in 1989.

From that group, the authors studied 325 women who had a child with autism and 22,000 women who had a child without the disorder. Using air pollution data from the U.S. Environmental Protection Agency, they were able to estimate a women’s exposure to pollutants while pregnant. The authors were also careful to adjust for the influence of factors such as income, education, and smoking during pregnancy.

What they found is worrisome. “Our findings raise concerns since, depending on the pollutant, 20% to 60% of the women in our study lived in areas where risk of autism was elevated,” said lead author Andrea Roberts, a research associate in the HSPH Department of Social and Behavioral Sciences, in a press release.

Women who lived in the 20% 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% of areas with the lowest levels. Those who lived in areas known for other types of air pollution—lead, manganese, methylene chloride, and combined metal exposure—fared even worse. Women who were residents of the 20% of locations with the highest levels of these pollutants were about 50% more likely to have a child with autism than those who lived in the 20% of areas with the lowest concentrations.

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