A new study suggests that exposure to air pollution could increase the risk for autism among people who carry a genetic disposition for the neurodevelopmental disorder.

"Our research shows that children with both the risk genotype and exposure to high air pollutant levels were at increased risk of autism spectrum disorder compared to those without the risk genotype and lower air pollution exposure," study's first author, Heather E. Volk, Ph.D., M.P.H., assistant professor of research in preventive medicine and pediatrics at the Keck School of Medicine of University of Southern California (USC) and principal investigator at The Saban Research Institute of Children's Hospital Los Angeles, said.

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental disability characterized by problems with social interaction, communication and repetitive behaviors.

The Centers for Disease Control and Prevention estimates that one in 88 children in the United States has an ASD.

ASD is highly heritable, suggesting that genetics are an important contributing factor, but many questions about its causes remain. There currently is no cure for the disorder.

"Although gene-environment interactions are widely believed to contribute to autism risk, this is the first demonstration of a specific interaction between a well-established genetic risk factor and an environmental factor that independently contribute to autism risk," Daniel B. Campbell, Ph.D., assistant professor of psychiatry and the behavioral sciences at the Keck School of Medicine of USC and the study's senior author, said.

"The MET gene variant has been associated with autism in multiple studies, controls expression of MET protein in both the brain and the immune system, and predicts altered brain structure and function. It will be important to replicate this finding and to determine the mechanisms by which these genetic and environmental factors interact to increase the risk for autism," he added.

Independent studies by Volk and Campbell have previously reported associations between autism and air pollution exposure and between autism and a variant in the MET gene.

The current study suggests that air pollution exposure and the genetic variant interact to augment the risk of ASD.

The study, 'Autism spectrum disorder: Interaction of air pollution with the MET receptor tyrosine kinase gene,' is set to be published in the journal Epidemiology.