(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, was quick to say, “The results reported in the paper don’t establish any association specific to our product…”
Environmentalists point to this study, as well as Mr. Hamlin’s reaction, as examples of what is wrong with the approach we take to toxic chemicals, especially pesticide regulation, in the U.S. Risk assessment calculations under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA) — the federal pesticide registration and tolerance laws, respectively — evaluate harm based on false realities about daily toxic exposure and individual sensitivities. Risk management decisions under these laws assume the benefits of toxic pesticide products to society or to various sectors of users, then make a determination that the risks are “reasonable.” Even under FQPA, which has been touted for its health-based standard, there is an inherent assumption that if a pesticide meets a highly questionable “acceptable” risk threshold, it has value or benefit. This is the practice even though there are typically less or non-toxic methods or products available. Pesticides, like the OPs linked to ADHD in the current study, are completely unnecessary given organic alternatives in agriculture and residential integrated pest management techniques, which do not rely on toxic chemicals.
The study, “Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides,” was published May 17, 2010 in the online version of the journal Pediatrics. The research was supported by the Canadian Institutes for Health Research and the National Institute of Environmental Health Sciences.