(Beyond Pesticides, May 18, 2010) A team of scientists from the University of Montreal and Harvard University have discovered that exposure to organophosphate pesticides is associated with increased risk of Attention-Deficit Hyperactivity Disorder (ADHD) in children. Using data from the National Health and Nutrition Examination Survey , the study focused on 1,139 children from the general U.S. population and measured pesticide breakdown product levels in their urine. The authors conclude that exposure to organophosphate (OP) pesticides, at levels common among U.S. children, may contribute to a diagnosis of ADHD.

“Previous studies have shown that exposure to some organophosphate compounds cause hyperactivity and cognitive deficits in animals,” says lead author Maryse F. Bouchard, a professor at the University of Montreal Department of Environmental and Occupational Health and scientist at the Sainte-Justine Hospital Research Center. “Our study found that exposure to organophosphates in developing children might have effects on neural systems and could contribute to ADHD behaviors, such as inattention, hyperactivity, and impulsivity.” Marc Weisskopf, PhD, ScD, another study author told Reuters, “What this paper specifically highlights is that this may be true even at low concentrations.”

For children with a 10-fold increase in the concentration of the most common dialkyl phosphate metabolites (an indicator of organophosphate exposure), the odds of ADHD increases by more than half. And for the most common breakdown product, called dimethyl triophosphate, the odds of ADHD almost doubled in kids with above-average levels compared to those without detectable levels.

Because the research links ADHD with pesticide breakdown products in urine, exposure can only be traced to OP pesticide exposure, either on food or in the home, not a specific pesticide. Garry Hamlin of Dow AgroSciences, which manufactures chlorpyrifos , an OP pesticide widely found as a residue in food becuase of its widespread use in chemical-intensive agriculture,...