WASHINGTON, June 18 (Xinhua) -- Women exposed to high levels of air pollution while pregnant were up to twice as likely to have a child with autism as women who lived in areas with low pollution, according to a U.S. study published Tuesday.
Exposure to diesel particulates, lead, manganese, mercury, methylene chloride and other pollutants are known to affect brain function and to affect the developing baby.
Two smaller, regional studies in the U.S. have found possible associations between air pollution and autism risk. The latest research, published in the journal Environmental Health Perspectives, however, is the first large national study to examine the links, according to researchers from the Harvard University.
"Our findings raise concerns since, depending on the pollutant, 20 percent to 60 percent of the women in our study lived in areas where risk of autism was elevated," lead author Andrea Roberts, a research associate at the Harvard School of Public Health, said in a statement.
The researchers examined data from a long-term study involving 116,430 nurses that began in 1989. Among that group, the authors studied 325 women who had a child with autism and 22,000 women who had a child without the disorder.
To estimate women's exposure to pollutants while pregnant, they used air pollution data from the U.S. Environmental Protection Agency and adjusted for the influence of factors such as income, education, and smoking during pregnancy.
The results showed that women who lived in 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 areas with the lowest levels.
Other types of air pollution, lead, manganese, methylene chloride, and combined metal exposure, were associated with higher autism risk as well. Women who lived in locations with the highest levels of these pollutants were about 50 percent more likely to have a child with autism than those who lived in areas with the lowest concentrations.
Most pollutants were associated with autism more strongly in boys than girls. However, since there were few girls with autism in the study, the authors said this finding should be examined further.
"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 to provide stronger evidence that specific pollutants increase risk of autism," said senior author Marc Weisskopf, an associate professor at the Harvard School of Public Health.
"A better understanding of this can help to develop interventions to reduce pregnant women's exposure to these pollutants," Weisskopf said.
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