California's sevenfold increase in autism is most likely due to environmental exposures, according to scientists. A new study advocates a nationwide shift in autism research to focus on environmental factors such as pesticides, viruses and chemicals in household products.
Throughout the U.S., the numbers of autistic children have increased dramatically over the past 15 years. More than 3,000 new cases of autism were reported in California in 2006, compared with 205 in 1990.
Many medical officials argued that the rise was due to changes in diagnoses or migration patterns rather than a real rise in the disorder. But the new study concludes that those factors cannot explain most of the increase in autism.
Researchers analyzed 17 years of state data that tracks developmental disabilities. Migration to the state had no effect, and changes in how and when doctors diagnose the disorder can explain less than half of the increase.
It is possible that a pregnant woman's exposure to chemical pollutants, particularly metals and pesticides, could be altering a developing baby's brain structure, triggering autism. Many parent groups also believe that childhood vaccines could be responsible.