New research shows that there may be a link between air pollution and autism.
A study from Harvard University's School of Public Health found that those who lived in parts of the country with the highest levels of diesel or mercury pollution were twice as likely to have a child with autism than those living in areas with the lowest levels.
Exposure to diesel particulates, lead, manganese, mercury, methylene chloride and other pollutants are known to affect brain function and the developing baby.
The pollution appeared to impact more boys than girls, though there were not as many girls with autism in the study.
The study, the first of its kind in the United States, appeared online on Tuesday in Environmental Health Perspectives.