Local Environment Not Cause of Autism 'Clusters'
California Autism Clusters Linked to Parent Education, Not Local Toxins
On the other hand, "it is entirely possible that people with higher education have some kind of exposure that increases autism risk," Hertz-Picciotto says.
But that's unlikely, she suggests. There clearly is a genetic predisposition to autism. But genes don't explain why some people get autism and others don't. Many researchers feel there has to be some kind of environmental trigger -- perhaps something a woman encounters during pregnancy or that a child encounters in infancy -- that triggers the disorder in susceptible children.
"Our study tells us probably the environmental causes of autism are not going to be found in local contamination, at least in California," Hertz-Picciotto says. "Whatever the environmental contributors are, they are probably more widespread and not linked to a hazardous local factor."
The study also suggests that there are a lot more kids with autism -- in California, at least -- who are not getting the services they need. In Denmark, where all kids are screened for autism, parental education doesn't raise autism risk. But it is in the U.S. and the U.K., where access to screening is not universal.
"This calls for some thinking about what we can do to increase autism awareness in the general population and bring services to these families, so that parents with education and means are not the only ones able to address the health of their children in the best possible way," Shih says.
Graduate student Karla C. Van Meter is first author of the Hertz-Picciotto study, which appears in the January issue of Autism Research.