A study recently reported in the journal Pediatrics draws a link between exposure to a type of pesticide residue found on commercially grown produce and the incidence of attention-deficit/hyperactivity disorder (ADHD) in children. Children exposed to higher levels of pesticides known as organophosphates could have a higher risk of ADHD.

Researchers measured the levels of pesticide byproducts in the urine of 1,139 children between ages 8 -15 from across the US, and found those with high levels of a certain byproduct group were almost twice as likely to develop ADHD as those with undetectable levels.

Because the findings are based on data from the general population, the results indicate that exposure to the pesticides could be harmful even at levels commonly found in children’s environment.

Although the researchers had no way to determine the source of the breakdown products they found, study co-author Marc Weisskopf said the most likely culprits were pesticides and insecticides used on fruits and vegetables and for indoor insect pest control.

According to the U.S. Department of Agriculture in a 2008 report cited in the study, 28 percent of frozen blueberries, 20 percent of celery, and 25 percent of strawberries contained traces of one type of organophosphate. Other types of organophosphates were found in 27 percent of green beans, 17 percent of peaches, and 8 percent of broccoli.

There are about 40 organophosphate pesticides currently registered in the United States. Originally developed for chemical warfare, organophosphates are known to be toxic to the nervous system.

Weisskopf said the compounds have been linked to behavioral symptoms common to ADHD — for instance, impulsivity and attention problems — but exactly how is not fully understood. After accounting for factors such as gender, age and race, researchers found the odds of having ADHD rose with the level of pesticide breakdown products.

For a 10-fold increase in one class of those compounds, the odds of ADHD increased 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.

“That’s a very strong association that, if true, is of very serious concern,” said Weisskopf. “These are widely used pesticides.”

He emphasized that more studies are needed, especially following exposure levels over time, before contemplating a ban on the pesticides. Still, he urged parents to be aware of what insecticides they were using around the house and to wash produce.

Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides: Maryse F. Bouchard, PhD, David C. Bellinger, PhD, Robert O. Wright, MD, MPH, Marc G. Weisskopf, PhD

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