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Traffic pollution linked to increased risk of autism


Exposure to traffic-related air pollution, particulate matter and nitrogen dioxide during pregnancy and during the first year of a child’s life appears to be associated with an increased risk of autism, according to a study.

Emerging evidence suggests the environment plays a role in autism, but only limited information is available about what exposures are relevant, their mechanisms of action, the stages in development in which they act and the development of effective preventive measures, according to background information in the study, which appeared Nov. 26 on the website of the Archives of General Psychiatry.

Heather E. Volk, PhD, MPH, of the University of Southern California, and colleagues examined the relationship between traffic-related air pollution, air quality and autism in a study that included data obtained from 279 children with autism and a control group of 245 children with typical development who were enrolled in the Childhood Autism Risks from Genetics and the Environment study in California.

The researchers found that “exposures to traffic-related air pollution, particulate matter and nitrogen dioxide were associated with an increased risk of autism. These effects were observed using measures of air pollution with variation on both local and regional levels, suggesting the need for further study to understand both the individual pollutant contributions and the effects of pollutant mixtures on disease.”

The authors used mothers’ addresses to estimate exposure for each pregnancy trimester and for a child’s first year of life. Traffic-related air pollution was estimated based on a model and regional air pollutant measures were based on the Environmental Protection Agency’s Air Quality System data.

Children living in homes with the highest levels of modeled traffic-related air pollution were three times as likely to have autism compared with children living in homes with the lowest exposures. The higher levels of exposure to particulate matter and nitrogen dioxide based on the EPA’’s regional air quality monitoring program also were associated with an increased risk of autism.

“Research on the effects of exposure to pollutants and their interaction with susceptibility factors may lead to the identification of the biologic pathways that are activated in autism and to improved prevention and therapeutic strategies,” the authors wrote. “Although additional research to replicate these findings is needed, the public health implications of these findings are large because air pollution exposure is common and may have lasting neurological effects.”

In an accompanying editorial, Geraldine Dawson, PhD, of the University of North Carolina, Chapel Hill, noted the “urgent need for more research on prenatal and early postnatal brain development in autism, with a focus on how genes and environmental risk factors combine to increase risk for autism spectrum disorder. Despite a substantial increase in autism research publications and funding during the past decade, we have not yet fully described the causes of ASD or developed effective medical treatments for it. More research is needed to develop strategies for preventing or reducing the disabling symptoms associated with this highly prevalent and costly neurodevelopmental disorder.”

The study abstract is available at


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