Women who lived within 1.000 feet of a freeway during their third trimester gave birth to autistic children twice as often as those who lived farther away.

Researchers have discovered a link between children who are diagnosed with autism and the proximity to freeway traffic.   Mothers who lived within 1,000 feet of a four-lane highway were twice as likely to have an autistic child.

The research was done by Heather E. Volk, Ph.D., MPH and colleagues at the University of Southern California.  It was printed in the December 16 issue of Environmental Health Perspectives.  The study compared 304 autistic children with 259 children with normal development.

“It has been estimated that 11% of the U.S. population lives within 100 meters [328 feet] of a four-lane highway, so a causal link to autism or other neurodevelopmental disorders would have broad public health implications,” Volk writes.

The number one suspected cause is air pollution.  There are a number of known negative effects on the unborn, especially during the child’s third trimester when the brain development is in high gear.  The study also controlled for maternal smoking, race, child gender, parent’s education, and maternal age.

When a pregnant woman lives about 1,000 feet from the freeway, there is an 86% greater chance her child will be autistic compared with moms who lived farther away.   If the woman lives within 1.000 feet, the number jumps to 2.2 times more likely to have autism.

It is generally accepted that there is a strong connection to genetics with the likelihood of developing autism, however genetics alone cannot explain Volk’s findings. Researchers are looking for something else or a combination of things that can explain the distribution.   Most often, environmental influences are suspected.   The next part of Volk’s study is to determine exactly what kinds of pollutants the pregnant women near freeways are being exposed to.