Two years ago, Heather Volk, Ph.D., an assistant professor of research at the University of Southern California, and her colleagues found a provocative association between living near a freeway and autism. This association implied that traffic air pollution might be a culprit in autism. They decided to conduct another study to test the hypothesis. The cohort included 279 preschool children with autism and 145 preschool children with typical development (controls). In addition to vehicle-emission rates, the researchers used local meteorological data, traffic volume, and road geometry to construct mathematical models of traffic-related air pollution in the areas where the subjects lived. The researchers then used the models as well as the addresses of the subjects to see whether they could find any links between traffic air pollution and autism. They could. The children residing in areas with the highest levels of traffic air pollution were three times more likely to have autism than were the children residing in areas with the lowest levels. Moreover, the children with autism were twice as likely as controls to have been exposed to high levels of traffic air pollution during their mothers’ pregnancy and three times as likely as controls to have been exposed to high levels of traffic air pollution during the first year of life. Some specific traffic air pollutants—nitrogen dioxide and particulate matter—were likewise associated with autism during pregnancy and the first year of life. Finally, the findings remained solid even when demographic and socioeconomic factors as well as maternal smoking during pregnancy were considered.
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