CHICAGO — A new analysis of U.S. health data links children’s attention-deficit disorder with exposure to common pesticides used on fruits and vegetables.

While the study couldn’t prove that pesticides used in agriculture contribute to childhood learning problems, experts said the research is persuasive.

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Organic produce is shown at the Portland Farmers Market. A study offers evidence that the government should encourage farmers to switch to organic methods, scientists say. 2005 Press Herald file

“I would take it quite seriously,” said Virginia Rauh of Columbia University, who has studied prenatal exposure to pesticides and was not involved in the new study. More research will be needed to confirm the tie, she said.

The new findings are based on one-time urine samples in 1,139 kids and interviews with their parents to determine which children had ADHD. The children, ages 8 to 15, took part in a federal health survey in 2000-2004.

Children may be especially prone to the health risks of pesticides because they’re still growing and they may consume more pesticide residue than adults relative to their body weight.

In the body, pesticides break down into compounds that can be measured in urine. Almost universally, the study found detectable levels: The compounds turned up in the urine of 94 percent of the children.

The kids with higher levels had increased chances of having attention-deficit hyperactivity disorder, a common problem that causes students to have trouble in school. The findings were published today in Pediatrics.

The study didn’t determine how they were exposed. Experts said it’s likely that children who don’t live near farms are exposed through what they eat.
“We’re all exposed,” said lead author Maryse Bouchard of the University of Montreal.

She said people can limit their exposure by eating organic produce. In one government report, strawberries, celery and frozen blueberries had more pesticide residue than other foods.

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.

Because of known dangers of pesticides in humans, the U.S. Environmental Protection Agency limits how much residue can stay on food. But the new study shows it’s possible that even tiny, allowable amounts of pesticide may affect brain chemistry, Rauh said.
The exact causes behind the children’s reported ADHD, however, are unclear. Any number of factors could have caused the symptoms, and the link with pesticides could be by chance.

As reported by their parents, about 150 children in the study either showed the severe inattention, hyperactivity and impulsivity characteristic of ADHD, or were taking drugs to treat it.

The study dealt with one common type of pesticide called organophosphates. Levels of six pesticide compounds were measured. For the most frequent compound detected, 20 percent of the kids with above-average levels had ADHD. In kids with no detectable amount in their urine, 10 percent had ADHD.

“This is a well-conducted study,” said a former EPA administrator, Dr. Lynn Goldman of the Johns Hopkins Bloomberg School of Public Health.

The government health  survey is a “snapshot” of urine levels at one point in time, so it says little about long-term exposures, said epidemiologist Marc Weisskopf of Harvard University, the senior author of the study.

But if the children’s diets remain relatively constant over a long term, he said, then the findings are probably a reasonable estimate of normal levels.

–  The Los Angeles Times contributed to this report

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