A Harvard University study has found that pregnant women who live in environments with high levels of air pollution are twice as likely to give birth to children with autism as those born in low-pollution environments. The results of the Harvard study have been published in Environment and Health Perspectives. The study began in 1989 with about 116,000 nurses. The researchers focused on 325 of them who were mothers of children with autism, and 22,000 mothers whose children did not have autism. To measure the women’s exposure to air pollutants during pregnancy, the researchers used air pollution information from the Environmental Protection Agency and took into account factors such as household income, education and smoking during pregnancy. The Harvard researchers analyzed the data and found that pregnant women living in air with high levels of diesel particles or mercury had twice the risk of having a child with autism than children born in clean air.