ADHD linked to pesticide exposure

CNN - Children exposed to higher levels of a type of pesticide found in trace amounts on commercially grown fruit and vegetables are more likely to have attention deficit hyperactivity disorder than children with less exposure, a nationwide study suggests.

Organophosphates are "designed" to have toxic effects on the nervous system, says the lead author of the study, Maryse Bouchard, Ph.D., a researcher in the department of environmental and occupational health at the University of Montreal. "That's how they kill pests."

The pesticides act on a set of brain chemicals closely related to those involved in ADHD, Bouchard explains, "so it seems plausible that exposure to organophosphates could be associated with ADHD-like symptoms."

Detectable levels of pesticides are present in a large number of fruits and vegetables sold in the U.S., according to a 2008 report from the U.S. Department of Agriculture cited in the study. In a representative sample of produce tested by the agency, 28 percent of frozen blueberries, 20 percent of celery, and 25 percent of strawberries contained traces of one type of organophosphate. Other types of organophosphates were found in 27 percent of green beans, 17 percent of peaches, and 8 percent of broccoli.

Although kids should not stop eating fruits and vegetables, buying organic or local produce whenever possible is a good idea, says Bouchard.

The researchers tested the samples for six chemical byproducts (known as metabolites) that result when the body breaks down more than 28 different pesticides. Nearly 95 percent of the children had at least one byproduct detected in their urine.

One group of pesticide byproducts was associated with a substantially increased risk of ADHD. Compared with kids who had the lowest levels, the kids whose levels were 10 times higher were 55 percent more likely to have ADHD. (Another group of byproducts did not appear to be linked to the disorder.)

In addition, children with higher-than-average levels of the most commonly detected byproduct -- found in roughly 6 in 10 kids -- were nearly twice as likely to have ADHD.

"It's not a small effect," says Bouchard. "This is 100 percent more risk."

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