Exposure to pesticides is associated with increased risk of Attention-Deficit Hyperactivity Disorder (ADHD) in children, according to a team of scientists from the University of Montreal and Harvard University. Published in the journal Pediatrics, the study focused on 1,139 children from the general U.S. population and measured pesticide levels in their urine. The authors conclude that exposure to organophosphate pesticides, at levels common among U.S. children, may contribute to a diagnosis of ADHD.
In the past, exposure to organophosphates has been associated with negative effects on neurodevelopment, such as behavioral problems and lower cognitive function. However earlier studies have focused on populations with greater pesticide exposure relative to the general population. This study was conducted with 1139 children 8 to 15 years of age, representative of the general U.S. population. The findings showed that children with higher urinary levels of organophosphate metabolites were more likely to meet the diagnostic criteria for ADHD.
According to the study, approximately 40 organophosphate pesticides are registered with the U.S. Environmental Protection Agency (EPA) for use in the United States. The EPA considers food, drinking water, and residential pesticide use major sources of exposure. Residential pesticide use is common, but the important source of exposure to pesticides for infants and children would be from the diet, says the National Academy of Sciences.
The U.S. Pesticide Residue Program Report for 2008 notes that measurable concentrations of the organophosphate malathion were found in 28 percent of frozen blueberry samples, 25 percent of strawberry samples, and 19 percent of celery samples. Children are thought to be at greatest risk from organophosphate toxicity because the developing brain is more susceptible to neurotoxicants and the dose of pesticides per body weight is likely to be larger for children. Children 6 to 11 years of age have the highest urinary concentrations of dialkyl phosphate (DAP) metabolites (markers of organophosphate exposure), compared with other age groups in the U.S. population. As well, children have fewer detoxifying enzymes, which contributes to their vulnerability.
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