Harvard researchers are reporting strong evidence that prenatal exposure to high air pollution can up to double the chance that a child will develop autism. The results – drawn from the large, nationwide U.S. Nurses Health Study – back those of previous studies suggesting this link. The report appears online today in Environmental Health Perspectives.
The researchers mined data from the Nurses' Health Study II, which has tracked the health of 116,430 nurses since 1989. Within this group, they studied 325 women who had children with autism. For comparison, they tracked another 22,000 women whose children did not have the disorder.
The researchers used Environmental Protection Agency pollution tracking to estimate each mother’s exposure during pregnancy. They adjusted for the influence of factors such as income, education and smoking during pregnancy.
In particular, the researchers looked at pollutants known to affect brain development and function. These included air particulates, lead, manganese, mercury and methylene chloride.
The increased risk varied from 20 to 100 percent depending on the pollutant.
The women who lived in locations with the highest levels of air pollution particulates were twice as likely to have a child with autism as those who lived in areas with the lowest levels. Women exposed to the highest levels of other air pollutants were about 50 percent more likely to have a child with autism than those exposed to the lowest concentrations.
Most pollutants were more strongly associated with autism in boys than girls. However, there were relatively few girls with autism in the study. As such, the authors called for further study of this apparent gender difference.
"Our results suggest that new studies should begin the process of measuring metals and other pollutants in the blood of pregnant women or newborn children,” says senior author Marc Weisskopf, Ph.D., an environmental and occupational epidemiologist at the Harvard School of Public Health. “A better understanding can help to develop interventions that reduce pregnant women's exposure to these pollutants."
This study adds to mounting evidence that environmental factors can increase risk of autism spectrum disorder, adds Alycia Halladay, Ph.D., Autism Speaks senior director of environmental and clinical science. “More research is needed to figure out how this is happening. In particular, we need to better understand how genetic predisposition plays a role in this effect. Meanwhile, efforts to improve air quality should not only be continued, but enhanced.”
Halladay spoke on the CBS News program "Up To The Minute" about the study. You can watch the interview below:
For more information on related research, please see Autism Speaks Environmental Factors in Autism Initiative