By contributor
updated 8/19/2010 11:21:56 AM ET 2010-08-19T15:21:56

Children whose mothers were exposed to widely-used pesticides such as malathion during pregnancy may be at increased risk of developing an attention disorder by age 5, a new study shows.

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Researchers found that the risk of attention disorders rose with increasing levels of metabolites — substances created when pesticides break down — measured in a pregnant woman’s urine. For each tenfold increase in pesticide metabolites in a mom’s system, the risk of an attention disorder rose fivefold in her child, according to the report published in the journal Environmental Health Perspectives.

The study results fall in line with a report published earlier this year by Harvard researchers who found that school-aged children exposed to organophosphates, one of the most common types of pesticides, were more likely than others to develop symptoms of attention deficit disorder.

Pregnant women worried about the findings should lower the risk to their fetuses by carefully washing fresh fruits and vegetables before eating them, suggests Brenda Eskenazi, a study co-author and director of the University of California at Berkeley’s Center for Children’s Environmental Health. Other experts suggest that pregnant women should eat organic fruits and vegetables when possible.

Eskenazi doesn't advise pregnant women to avoid eating

fruits and vegetables, however. “I think the risk created by not eating them is far greater than the risk from the pesticides,” said Eskenazi, a professor of epidemiology.

That advice is echoed by experts not affiliated with the study.

While the new results are “concerning and intriguing,” they need to be put in perspective, said Dr. Hyagriv Simhan, chief of the division of maternal-fetal medicine and vice chair of obstetrical services at MaGee-Womens Hospital of the University of Pittsburgh Medical Center.

“I think it’s human nature to see something like this and completely freak out,” said Simhan. “But in absolute terms, the risk attributable to pesticide exposure is not that high. So, at this moment, there are no recommendations I’d make to an individual patient. This is something that needs to be looked at the societal policy level.”

Eskenazi and her colleagues were interested in studying organophosphates because these pesticides are designed to kill insects by attacking the nervous system. The researchers suspected that the compounds might also affect a fetus’s developing nervous system.

To measure the impact of the pesticides on the fetus the researchers followed the pregnancies of 348 Mexican-American women and the first five years of the children born to them. Twice during the women’s pregnancies researchers collected urine samples and measured levels of pesticide metabolites.

Younger kids may wrongly get ADHD diagnosis

The researchers evaluated the children at ages 3 1/2 and 5 for symptoms of attention disorders and ADHD using the reports from the mothers on the children’s behaviors, performance of the children on standardized computer tests, and ratings from examiners who spent time observing the children. While the link between pesticides and attention problems wasn’t strong in the 3 year olds, it was pronounced once the children reached age 5.

Whether the results can be generalized to the average American mother isn’t clear. Because the mothers and children in the study were living in an agricultural community — California’s Salinas Valley — they may have been exposed to a higher level of pesticides than the general population. “I’m not sure how it applies to women living in Chicago or Houston,” Simhan said.

When Eskenazi compared the Salinas moms’ metabolite levels to those from national surveys, they came out a bit on the high side. But, not so high as to skew the results, she said.

Ultimately the message of the study may simply be: better safe than sorry.

That’s how one Morgan Hill, Calif., mom read it.

Julia King was careful all during her pregnancies to avoid anything that might endanger her growing fetus. “"I think it makes sense to avoid any chemical exposure during pregnancy," said the 39-year-old biologist and mother of two. “This just shows that’s the best course.”

Linda Carroll is a health and science writer living in New Jersey. Her work has appeared in The New York Times, Newsday, Health magazine and SmartMoney.

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