Children with autism spectrum disorders (ASD) are more likely to have been exposed to high levels of air toxins throughout their mothers’ pregnancies, and during their first two years of life.

Researchers from a University of Pittsburgh Graduate School of Public Health study sought to determine the risk factors associated with an increase in autism spectrum disorders over the past few years.

Principal study investigator Evelyn Talbott, Dr.P.H., professor of epidemiology at Pitt Public Health, and colleagues studied families with and without ASD in six counties in southwestern Pennsylvania. The researchers uncovered associations between higher levels of chromium and styrene and childhood ASD.

According to the Centers for Disease Control and Prevention, about one in 68 children has autism spectrum disorder, which is almost five times more common among boys than among girls.

The researchers discovered that a child’s increased exposure to air toxics like styrene and chromium during their mother’s pregnancy and during the first two years of life were up to twice as likely to develop ASD, compared to children without such exposure.

“Autism spectrum disorders are a major public health problem, and their prevalence has increased dramatically. Despite its serious social impact, the causes of autism are poorly understood. Very few studies of autism have included environmental exposures while taking into account other personal and behavioral risk factors. Our analysis is an addition to the small but growing body of research that considers air toxics as one of the risk factors for ASD,” said Talbott in a statement.