A new study suggests that exposure to high levels of organophosphate pesticides, which are commonly used on fruits and vegetables, can lead to a higher rate of attention-deficit hyperactivity disorder (ADHD) in children.

The study, published yesterday in Pediatrics journal, analyzed the levels of pesticide residue in the urine of 1,100 children ages eight to 15. Children with the highest levels of pesticides, the study found, had the highest incidence of ADHD, which affects about 4.5 million children in the United States, according to the Centers for Disease Control and Prevention (CDC). But even children who had any detectable, above-average level of pesticide residue in their urine were twice as likely to develop ADHD as those with undetectable levels.

“I was quite surprised to see an effect at lower levels of exposure,” said Maryse Bouchard of the University of Montreal, who led the study in conjunction with researchers from Harvard University.

Although the study did not determine where the pesticide exposure originated, experts from the National Academy of Sciences noted that children are most likely to ingest chemicals through their diet. And organophosphate pesticides are found in a variety of produce, including frozen blueberries, strawberries, and celery.

“Organophosphates are one of the most widely used pesticides in agriculture to protect crops and fruits and vegetables,” Bouchard said. “For children, the major source of exposure would be the diet–fruits and vegetables in particular.”
However, Bouchard was clear that the results of her study were merely associative, and did not indicate a direct causal link between pesticide exposure and ADHD.

The author also emphasized the importance of fruits and vegetables in children’s diets. Instead, she affirmed the study’s focus was on an unhealthy exposure to pesticides, and in fact raises the possibility of setting a national threshold for safe levels of exposure.

“I think it’s safe to say that we should as much as possible reduce our exposure to pesticides,” she concluded. According to Bouchard, the best way to avoid unhealthy exposure is to eat produce grown organically.

A 2008 Emory University study found that in children who switched to organically grown fruits and vegetables, urine levels of pesticide compounds dropped to undetectable or close to undetectable levels.

Some experts, however, cautioned against the possible misinterpretation of yesterday’s study. 

“This study could be counterproductive to children’s health,” Tom Stenzel , President and CEO of United Fresh Produce Association, said in a press release. “U.S. health authorities recommend that Americans actually need to double their consumption of fruits and vegetables to protect their health. We must be extremely careful not to frighten consumers away from following that overriding health advice.”    

But others praised the study as innovative and insightful.

“We are fortunate studies like this one advance a very important discussion,” Robyn O’Brien, author and food safety expert, told Food Safety News. “And that is why we have not exercised precaution and attempted to reduce our children’s exposure to these chemicals as has been done in other developed countries, placing the same value on the lives of the American children that has already been placed on the lives of children around the world.”