A city skyline with pollutionIn the quest to determine the causes of autism, researchers from the University of Southern California Keck School of Medicine have examined how certain genetic and environmental factors collude to create risks for autism spectrum disorders (ASD). Although autism spectrum disorders are considered highly heritable, environmental influences can also risk factors. Among them: air pollution. Heather Volk, PhD and MPH, and Daniel Campbell, PhD, have investigated to relationship between air pollution and ASD previously, but their latest work indicates that children with a particular autism-associated genotype and exposure to higher levels of air pollution have a greater risk or developing an autism spectrum disorder.

The Childhood Autism Risks from Genetics and the Environment Study (CARGES)—a population-based, case-control study of preschool children in California—provided a pool of 408 subjects, children aged two to five, for the research. 252 of the group’s children meet the criteria for an autism spectrum disorder.

The researchers used blood samples from the children to determine whether they carried the MET genotype, which has been associated with autism through multiple studies and is known to control the expression of the MET protein in the brain. The children’s environments were also evaluated for pollution levels. The researchers considered the location of the children’s and mothers’ past residences, local traffic, and air quality measurements.

The results indicate that children with both the high-risk MET genotype and exposure to high air pollutant levels were more likely to have ASD than children without the genotype or with lower pollution exposure.

“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,” stated Campbell, who is an assistant professor of psychiatry and behavioral sciences at USC.

This research will be published in the journal Epidemiology in January.

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