A California Cluster: Studying Pesticides and Autism in One California Community

Article excerpt

Pesticides may be added to the growing list of possible autism triggers. A group of scientists in California examined the statistics on autism and proximity to agricultural fields. They obtained data from the state on pesticide application and autism records from the California Department of Developmental Services. What they found was a 19-county area, known as the Central California Valley, where the risk of autism disorders increased with the nearness to pesticide-sprayed fields.


They studied women living in this area, who could have been exposed to chemicals drifting on the wind. The authors found an autism rate of 14.3 cases per 1,000 births for mothers who lived within 500 meters of the fields, compared with the baseline risk of 6.5/1,000.

"We looked for patterns in space and time," Eric M. Roberts, lead author of the study, says. "First trimester organochlorines popped out."

Records from women pregnant between 1996 and 1998 were compared with pesticide records on a number of different factors: time of application, type of chemical and proximity to fields. Only one combination showed a statistically significant pattern: higher rates of autism for mothers who were exposed to a group of chemicals called organochlorines during their first trimester of pregnancy.

Organochlorines are a group of chemicals used as an insecticide on fruits, vegetables, beans, nuts and cotton. DDT is the most famous organochlorine, and all others have been banned except endosulfan and dicofol, which is chemically similar to DDT.

"Organochlorine usage is not going up," Roberts was careful to caution. "There are several classes of pesticides that may be connected to autism. We're looking at a million possibilities."

Little is known about what is happening at the molecular and cellular level in patients with autism. Scientists are still unsure whether the key differences in brain development are linked to a specific hormone or neurotransmitter. So tracking down which chemical could be causing the disorder is like trying to find the proverbial needle in a haystack--while blindfolded.

"It's not something someone's offering as an answer," Roberts adds. "It's just something to keep in mind."

Sonya Lunder, a senior analyst with the Environmental Working Group, is interested in pesticides as a potential culprit but is cautious because of autism's tangled web of cause-and-effect. …