Lead author Andrea Roberts, research associate in the Harvard School of Public Health Department of Social and Behavioral Sciences, said 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 previous studies found associations between exposure to air pollution during pregnancy and autism in children, but those studies looked at data in just three U.S. locations, Roberts said.
"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," Roberts said in a statement.
The researchers examined data from Nurses' Health Study II, a long-term study based at Brigham and Women's Hospital involving 116,430 nurses that began in 1989.
From the group, the authors studied 325 women who had a child with autism and 22,000 women who had a child without the disorder. They examined pollution levels and exposure. They also adjusted for the influence of factors such as income, education and smoking during pregnancy.
The study, published in the Environmental Health Perspectives, showed 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 places with the lowest pollution levels.
Other types of air pollution -- lead, manganese, methylene chloride and combined metal exposure -- were associated with higher autism risk as well, Roberts said.
The study found pregnant women who lived in the 20 percent of locations with the highest levels of pollutants 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.