Air Pollution from Freeways May Increase Autism Risk
Between 2002 and 2006, the Centers for Disease Control reported a 57% increase in the number of children affected by autism spectrum disorders. Both genetic and environmental factors are being studied for their roles in the incidence and increase in prevalence of children with the disorder. Researchers from the USC Keck School of Medicine and UC Davis MIND Institute have conducted research that finds that children born to mothers living near freeways may be twice as likely to have autism.
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Irva Hertz-Picciotto PhD, principal investigator on the study known as CHARGE (Childhood Autism Risks from Genetics and the Environment), and colleagues followed children between the ages of 14 and 60 months who lived in communities around Los Angeles, San Francisco, and Sacramento.
The researchers examined the locations where the children’s families lived during the pregnancy and at the time of the baby’s birth and noted the proximity of the home to a major road or freeway. Children with autism were matched to healthy controls of the same age, gender and broad geographic area.
“Children born to mothers living within 209 meters (about 1,000 feet) of a freeway appeared to be twice as likely to have autism,” said Dr. Heather Volk PhD MPH, the primary author on the study. The researchers found no consistent pattern of association of autism with proximity to a major road.
Exposure to air pollution is known to have physical and developmental effects on fetuses and infants, including a risk of cognitive developmental delay, likely due to inflammation and oxidative stress. High levels of carbon monoxide, nitrogen dioxide, and particulate matter have been linked to a higher risk of preterm birth and low birth weight.
But the research is still preliminary. “This study isn’t saying exposure to air pollution or exposure to traffic causes autism,” says Dr. Volk.
“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,” adds Dr. Hertz-Picciotto. “It is highly likely that most of them operate in conjunction with other exposures and/or with genes.”
The CHARGE study findings are published online in the journal Environmental Health Perspectives, a monthly journal of peer-reviewed research and news on the impact of the environment on human health.