The study reports that of 29 mothers who lived near agricultural fields where organochlorine pesticides were applied during the mothers' first trimesters of pregnancy, eight children were diagnosed with autism. The state says the rate is six time higher than that of a control group. The research included 19 counties in the Sacramento and San Joaquin valleys. There were 465 children with autism born during 1996 to 1998 who were identified. They were matched to 6,975 live born, normal birth weight, term infants as controls. Nineteen individual pesticides and 10 pesticide groups were examined.

The study found nearly all of the pesticides had no discernable link to autism with the exception of the pesticide group known as organochlorines.  Organochlorines are compounds defined by sharing at least one covalently-bonded chlorine atom. Dicofol, 2, 4-D, heptachlor, endosulfan, chlordane, mirex and pentachlorophenol are some commonly used organochlorine insecticides. CDPH Director Dr. Mark Horton urged caution when making assumptions about the study's findings. He stated “This study is initial research into possible environmental factors in California that may contribute to autism,"   Horton said. “It's important to understand that these preliminary findings do not establish a causal relationship between exposure to these pesticides and autism”.