Children born to mothers living near vehicle-polluted freeways might be twice as likely to have autism, an intriguing new study has found.
Focusing on children living in three California cities, the study examined whether a pregnant mother's increased exposure to vehicle pollutants puts her offspring at greater risk of having autism.
A team of investigators behind the study said Friday this is the first to establish a link between autism risk and exposure to vehicle emissions.
Lead author Dr. Heather Volk and her colleagues "found that living within 309 metres of a freeway at birth was associated with a two-fold increase in autism risk," a press release stated.
They assessed preschool children living in Los Angeles, San Francisco and Sacramento.
The child participants were 24 to 60 months old when the Childhood Autism Risks from Genetics and the Environment (CHARGE) study began.
Researchers looked at the proximity of each child's home to a major road or freeway during the first, second and third trimesters of pregnancy, and at the time of birth.
Researchers didn't measure the amount of pollution exposure.
The study's findings are supported by previously-uncovered evidence that oxidative stress and inflammation contribute to autism development, the authors said.
The potential link between autism and traffic-related pollution was explored by researchers from Children's Hospital Los Angeles, the Keck School of Medicine of the University of Southern California, and the U.C. Davis MIND Institute. Their findings are being published in the online journal Environmental Health Perspectives.
It's the latest effort by researchers to determine the root cause or causes of autism, a developmental disorder which has long been associated to genetic factors.
An analysis by the U.S. Centers for Disease Control and Protection revealed an alarming statistic -- autism cases jumped 57 per cent between 2002 and 2006.
Volk and her colleagues believe the sharp increase cannot be attributed alone to improved diagnosis and the public's increased awareness.
Some believe environmental factors such as pollution, in addition to a strong genetic risk, might be one possible explanation. The authors said their study supports that theory but cautioned that little is known about pollution's effects. More research is necessary, they 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," said Dr. Irva Hertz-Picciotto, CHARGE's principal investigator, in the press release. "It is highly likely that most of them operate in conjunction with other exposures and/or with genes."
Other studies have uncovered links between pollution and physical and developmental effects on the fetus, or cognitive developmental delay in infants.
People with autism can have difficulty relating to others, have speech and language problems, limited and repetitive interests and behaviours.
