Living Near a Freeway May Increase Autism Risk in Children

Are children who were exposed in utero to greater concentrations of vehicular and other environmental pollutants at greater risk of autism?

Researchers from Children’s Hospital Los Angeles, the Keck School of Medicine of the University of Southern California, and the UC Davis MIND Institute have published study results that demonstrate a possible link between increased risk of autism and living near a freeway.

A news release from Children’s Hospital Los Angeles notes that although exposure to air pollution during gestation has been linked to cognitive developmental delay, the authors of this study claim it is “the first to link exposure to vehicular pollutants with autism risk.” One caveat: the release also notes that for the study “direct measurements of pollutants were not made.”

Nonetheless, using data from the Childhood Autism Risks from Genetics and the Environment (CHARGE) study, a population-based case-control study of children between the ages of 24 and 60 months at the start of the study who lived in communities around Los Angeles, San Francisco, and Sacramento, the authors “examined the locations where the children's families' lived during the first, second and third trimesters of their mothers' pregnancies, and at the time of the baby's birth,” comparing the proximity of these homes to a major road or freeway.

They found that “living within 309 meters of a freeway (or just over 1000 feet) at birth was associated with a two-fold increase in autism risk,” after adjusting for gender, ethnicity, parents’ education level, maternal age, and prenatal smoking. Their study, titled “Residential Proximity to Freeways and Autism in the CHARGE study,” will be published in the journal Environmental Health Perspectives.

With other studies supporting the observation that inflammation and oxidative stress (which can be caused by traffic-related air pollutants, among other factors) are involved in the pathogenesis of autism, this study “supports the theory that environmental factors, in conjunction with a strong genetic risk,” may in part explain (along with changes in diagnostic criteria and increased awareness) the “dramatic increase in the number of children affected. The Centers for Disease Control reported a 57% increase [in autism incidence] between 2002 and 2006.”

Irva Hertz-Picciotto, PhD, chief of the division of environmental and occupational health in the Department of Public Health Sciences at UC Davis, and principal investigator on the CHARGE study, said “We expect to find many, perhaps dozens, of environmental factors over the next few years, with each of them probably contributing to a fraction of autism cases. It is highly likely that most of them operate in conjunction with other exposures and/or with genes.”

HCPLive wants to know:

Have you seen an increase in the number of children with autism or autism spectrum disorders in your practice in the last decade?In your experience, how do the parents of children with autism typically react to news stories such as this one that purport to uncover yet another possible cause/contributing factor to autism?In your opinion, does the media do a good job when reporting stories on the possible causes of autism?