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updated 4/21/2011 10:12:56 AM ET 2011-04-21T14:12:56

Exposure to pesticides in the womb may harm a baby's brain and hinder the child's intelligence, according to three new studies published April 21.

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All the studies found a link between prenatal pesticideexposure and lower IQ scores at age 7. One study found children with the highest levels of exposure in the womb scored 7 points lower on an IQ test than those who had the lowest levels of exposure.

That IQ drop is equivalent to a 7-year-old performing as if they were 6 1/2 years old, said Brenda Eskenazi, a professor of epidemiology and maternal and child health at the University of California, Berkeley, who led one of the studies.

Eating foods that have been treated with pesticides is one way a fetus can be exposed to these chemicals.

Discuss: Moms, what do you do to avoid pesticides during pregnancy -- and beyond?

The findings do not appear to be limited to one region of the country or to rural environments — two studies were conducted in urban areas of New York and one in an agricultural town in Northern California.

It's important to note the studies only show an association, and not a direct cause-effect link, between pesticide exposure and intelligence. But if these chemicals really do have an effect on IQ, they could impact a child's ability to learn and could result in more children requiring special services in school, the researchers say.

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Pesticide use in the United States has gone down since the women in the study were pregnantmore than 10 years ago. This means the children of pregnant women today might be at lower risk for pesticide exposure than those in the study.

Pregnant women can reduce their unborn child's pesticide exposure by thoroughly washing fruits and vegetables, using a soft brush, if practical. Eating organic foods, which are grown without synthetic pesticides, can also limit exposure.

The studies were published in the April 21 issue of the journal Environmental Health Perspectives.

Pesticides and pregnancy
Pesticides known as organophosphates are widely used on food crops and some are approved for use in home gardens. These chemicals are known to be toxic to nerve cells — they may affect the way brain cellscommunicate — and indoor use of some organophosphates has been phased out due to the health risks they pose to children. The developing brainsof children are more susceptible to pesticides' toxic effects, the researchers say.

Eskenazi and her colleagues collected urine samples from women who were pregnant in 1999 and 2000. The samples were tested for a breakdown product of organophosphates. Samples were also collected and tested from the children when they were 6 months old until age 5.

At age 7,329 children took an IQ test designed to assess verbal comprehension, reasoning skills, working memory and the speed at which they processed information.

Every tenfold increase in the concentration of organophosphates detected during a mother's pregnancy corresponded to a 5.5 point drop in overall IQ scores, the researchers found.

The results held even after the researchers took into account other factors that could influence the child's IQ score, including the mother's education, family income and exposure to other environmental contaminants, including DDT, lead and flame retardants.

There was no link between exposure to pesticides after birth and the child's IQ score. This may mean a baby's exposure to chemicals while in the womb has a greater impact on brain development than exposure during childhood.

One of the New York studies, conducted by researchers at Mount Sinai Medical Center, found that organophosphates had a particularly strong effect on children's reasoning skills. The other New York study, by researchers at Columbia University, found a link between pesticide levels in umbilical blood and a decrease in the child's IQ and memory scores.

Other pesticide sources
The levels of pesticides in the urine of the pregnant mothers in Eskenazi's study were somewhat higher than those seen in the average U.S. population, but they are realistic levels, she said. About 25 percent of pregnant women in a national study had pesticide levels higher than those seen in the study.

In addition to exposure from foods, people can be exposed to pesticides around their homes, schools and other buildings. Farm workers, gardeners and florists are among those who might have a greater exposure to pesticides than the general population.

The researchers recommend consumers lower their use of pesticides at home, noting that most home and garden pests can be controlled without using those chemicals.

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Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner.

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