Relatively low-level exposure to common pesticides -- probably from residues on foods -- doubles kids' risk of ADHD, Harvard researchers find. The findings come from a nationally representative sample of 1,139 U.S. kids aged 8 to 15  who were tested for ADHD (attention deficit hyperactivity disorder) and had urine samples tested for signs of exposure to various organophosphate pesticides such as malathion.

Kids with higher-than-average levels of pesticide metabolites were about twice as likely to have ADHD as kids with undetectable levels of pesticide metabolites, find Marc C. Weisskopf, PhD, ScD, associate professor of environmental health and epidemiology at Harvard School of Public Health, and colleagues.

"This raises concerns that ubiquitous pesticides may be contributing to the national burden of ADHD, which already is quite high," Weisskopf tells WebMD.

It's not just kids who live on farms or otherwise get extremely frequent or high-dose exposure to pesticides. The metabolites detected in the Weisskopf study indicate that these kids have ongoing, low-level exposure to pesticides at levels that may affect their development.

"What I think is so important is this is not a select group of people with unusually high pesticide exposure," Weisskopf says. "This is a general population sample. If this link with ADHD is proved true, there is a big chunk of people this is going to be relevant for."

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