May 17, 2010
Study: Common pesticides linked to ADHD
Another reason to consider organic
Past studies linking pesticide exposure to behavioral problems and poor mental development generally focus on high levels of exposure. But pesticide exposure at levels commonly found in a child’s environment may contribute to the development of attention deficit disorder, according to a study published in the June issue of the journal Pediatrics.
The food supply is the major source of pesticide exposure for infants and children, according to the National Academy of Sciences. Frozen blueberries, strawberries and celery, for example, have been found to contain detectable levels of the pesticide organophosphate malathion, one of about 40 organophosphate pesticides registered in the U.S., according to the study.
In the Pediatrics study, the researchers measured pesticide levels in urine samples in 1,139 children between the ages of 8 and 15. After controlling for other factors, such as socioeconomic status, sex, and age, they found that the higher the concentration of organophosphates, the higher the risk of ADHD in children.
Still, the analysis had limitations. The urine was collected at just one point in time; the data set didn’t include long-term follow up assessments. Taking urine samples over a longer period of time would provide a better assessment of average exposure, the researchers wrote.
But they also said that since organophosphates are eliminated from the body after three to six days, the detection of the metabolites in the urine likely means continuing exposure.
It's also possible that children with ADHD engage in behaviors that expose them to higher levels of organophosphates. But if that were the case, the researchers noted, the children would have had higher levels of all metabolites in their urine, which was not the case.
“Because it’s an observational study, we can only talk about association; we can’t say it’s causal,” said Maryse Bouchard, a researcher in the department of environmental and occupational health at the University of Montreal and at the Hospital Sainte-Justine for Children. “But at least it’s biologically plausible and the effect is strong. I would really like to see the findings duplicated.”
Until then, Bouchard recommends buying more organic fruits and vegetables and purchasing at farmer’s markets, where you can talk to the farmer about pesticide use. Carefully washing fruits and vegetables can also reduce exposure, Bouchard said.
Children are also exposed through through lawn and garden chemicals, lice treatments (Lindane), and home use of pesticides purchased at the corner store, said Rachel Lerner Rosenberg, executive director of the Safer Pest Control Project.
Rosenberg advocates reducing all pesticide exposure whenever possible because "the scientific data on the long term effects of pesticide exposures are unknown," she said. While the Environmental Protection Agency measures levels of risk for each pesticide, "the pesticides are tested on 170-pound men, not children," said Rosenberg.
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