Air Pollution Combines with Genetics to Increase Risk of Autism in Children

There may be an association between air pollution and autism. It turns out that exposure to smoggy air can increase the risk for this neurodevelopmental disorder among people who carry a genetic disposition toward it. The findings reveal how the environment can play a crucial role as to whether or not a person develops this disorder.

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental disability that's characterized by problems with social interaction, communication and repetitive behaviors. Currently, about one in 88 children suffer from an ASD in the United States. Since ASD is highly heritable, it seems as if genetics are an important contributing factor. Yet scientists have long wondered whether the environment could also play a role.

In order to investigate ASD a bit further, the researchers studied 408 children between 2 and 5 years of age from the Childhood Autism Risks from Genetics and the Environment Study. This population-based, case-control study examined preschool children from California. Of the children in this study, 252 met the criteria for autism or autism spectrum disorder. The scientists then determined air pollution exposure by looking at the past residences of the children and their mothers, local traffic-related sources and regional air quality measures.

"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," said Heather Volk, one of the researchers, in a news release.

The findings show the importance of assessing environmental risks if a child is predisposed to a condition. In addition, it reveals how this specific interaction can cause autism risk to increase.

"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," said Daniel Campbell, one of the researchers, in a news release. "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."

The findings are published in the journal Epidemiology.