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updated 8/27/2010 3:59:04 PM ET 2010-08-27T19:59:04

Chemicals on our produce may contribute to behavior problems in our kids, suggest three new studies.

The studies, which looked at a class of pesticides called organophosphates (OP), linked exposure to the chemicals with attention disorders in children, with perhaps the most dramatic impacts to kids who are exposed in the womb and those who are genetically most susceptible.

Because pesticide residues linger on fruits and vegetables, the findings suggest that people either buy organic or take the time to wash their produce well.

"We don't want women to not eat fruits and vegetables because it's very important to eat them during pregnancy," said Brenda Eskenazi, an epidemiologist and neuropsychologist at the University of California, Berkeley. "I just let water run really thoroughly over fruits, and I rub them so they're clean."

Organophosphates are a set of common pesticides that work by attacking the nervous systems of insects. When people are exposed to high levels of the chemicals, they can develop anxiety, confusion impaired concentration, and other serious symptoms. More recently, scientists have started to wonder how chronic exposure at low levels might be affecting people, especially kids, whose nervous systems are still developing.

To find out, Eskenazi and colleagues followed up on a long-term study that has tracked more than 300 Mexican-American women in an agriculturally intensive region of California since they first became pregnant in 1999 or 2000. When the women were pregnant, the researchers measured levels of pesticide breakdown products in their urine. More recently, they collected urine samples from the kids and evaluated measures of attention.

By age five, the team reported in the journal Environmental Health Perspectives, kids who had been exposed to higher levels of OP pesticides in the womb were five times more likely to have an attention deficit disorder. The finding was stronger for boys.

In another paper in the same journal, Eskenazi and colleagues zeroed in on a gene that seems to determine how susceptible a person is to OP pesticides. The gene plays a role in how the body breaks down the pesticides. A better understanding of how it works could help scientists figure out what the chemicals do to kids' brains.

In a third study, published by a different research group in the journal Pediatrics in June, kids with higher than average levels of OP pesticide products in their urine were twice as likely to have been diagnosed with Attention Deficit Hyperactivity Disorder, compared to kids with no exposure.

The study, which involved more than 1,100 children between the ages of 8 and 15 from around the country, doesn't prove that the chemicals caused ADHD. But together with the other findings, the work offers reason to be concerned, said lead author Maryse Bouchard, an environmental health researcher at the University of Montreal.

"You would think we know a lot about the effect of pesticides on children's health. But when I started looking through the literature, there were very, very few studies on the subject," Bouchard said. "I think the Eskenazi study is very important in that it's been following children since before they were born."

To avoid exposure to OP pesticides, Bouchard recommends buying organic fruits and vegetables, or produce from farmers markets, which are usually sprayed with fewer chemicals. If you can't afford those options or don't have access to them, turn on the tap before you chop. OP pesticides are soluble in water, Bouchard said, and should wash off with a good scrub.

Whatever you do, Eskenazi added, don't stop eating salad, even if your ingredients come from the conventional aisle.

"I'm not advocating that people eat only organic, because if you advocate that, people who can't afford it are not going to eat fruits and vegetables," she said. "If you had to weigh your risks, it is more risky not to eat fruits and vegetables."

© 2012 Discovery Channel

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