SACRAMENTO -- Two older-generation pesticides used on cotton and some other crops may be linked to autism, according to a preliminary state study.

The rate of autism among the children of 29 women who lived near fields sprayed with organochlorine pesticides was so high that researchers concluded it may have been caused by exposure in the womb.

It is the first time a possible link between pesticides and autism has been reported. The neurological disorder affects one in every 150 children.

State scientists warned that their finding should be seen as tentative because the study involved so few cases.

"We want to emphasize that this is exploratory research," said Dr. Mark Horton, director of the California Department of Public Health, who released the study in early August. "We have found very preliminary data that there may be an association. We are in no way concluding that there is a causal relationship between pesticide exposure of pregnant women and autism."

Department researchers examined birth records and pesticide data from 1996 to 1998. They found 29 Central Valley women who lived within 500 meters -- or 547 yards -- of fields that had been sprayed with organochlorine pesticides during their first trimester.

Eight of those women, or 28 percent, had children with autism. That was six times greater than the rate for mothers who did not live near the fields.

Since the years examined in the study, insects built up a resistance to two chemicals, endosulfan and dicofol, and many farmers stopped using them. As a result, pregnant women are much less likely to be exposed to them today.

The chemicals are not found in household or yard pesticides, although traces are found in food. The chemicals are used most widely in Fresno, Kings, Imperial and Tulare counties.

Information from: Los Angeles Times: http://www.latimes.com.