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Children exposed to common pesticides before birth can have lower IQ levels when they reach school age. That's according to new data from three independent studies published in the journal Environmental Health Perspectives.

NPR's Richard Knox has the story.

RICHARD KNOX: One study from California involved several hundred women and children who lived on or near farms where pesticides are sprayed on crops. Researchers tested the urine of pregnant women for traces of pesticide by-products called metabolites. Then after the children were born, the scientists tracked them as they grew; so far, up to the early grades of school.

Brenda Eskenazi led the study.

Professor BRENDA ESKENAZI (University of California, Berkeley): What we found is that mothers with higher levels of pesticide metabolites in their urine had children with lower IQs at age 7.

KNOX: Eskenazi at the University of California, Berkeley, says children whose mothers had the highest pesticide levels during pregnancy had IQs seven points lower than those with the least exposure.

Prof. ESKENAZI: That's equivalent to a 7-year-old performing like a 6-and-a-half-year-old.

KNOX: In other words, that child has a six-month lag in development. Eskenazi says the pesticide effect is similar to high lead exposure. Lead is known to damage developing brains.

On the other side of the country, New York researchers say the pesticide risk is not just in farm workers and rural families. Two studies there looked at city dwellers.

Scientists at Columbia University studied a specific pesticide named chlorpyrifos. Until 10 years ago, it was found in many household products used to kill roaches and other pests.

Professor VIRGINIA RAUH (Columbia University): These pesticides were widely used in the home for pest control, particularly in New York City.

KNOX: That's Virginia Rauh of Columbia. She says, back then, researchers found chlorpyrifos in nearly a hundred percent of apartment air samples.

The scientists also measured levels of the pesticide in the umbilical cord blood of 265 children in low-income households.

Rauh says those with the highest levels of the pesticide at birth scored measurably lower on tests of working memory and overall IQ when they were 7 years old.

Prof. RAUH: This is the type of thing that could eventually affect learning. So even though it's a small effect that might be seen at 7 years of age, when children are just starting school, it could potentially affect the way in which they read, the way in which they're able to follow instructions, and perhaps the way they're attending to what's happening in the classroom around them.

KNOX: Chlorpyrifos is now banned for household use. But Rauh says it's still sprayed along roadways and on food crops, and many people have some level of it in their blood.

Prof. RAUH: And they may be just as high as some of the indoor residential levels that we saw in New York City.

KNOX: So if she were pregnant, Rauh says she'd take precautions.

Prof. RAUH: I would certainly wash all fruits and vegetables, fresh fruits and vegetables. And if I could afford it, I would prefer to purchase organic fruits and vegetables, where we are quite certain that there have been no pesticides used.

KNOX: And for your children, the same?

Prof. RAUH: Likewise, yeah.

KNOX: Eskenazi, the Berkeley scientist, says she'd be sure to scrub even fruits and vegetables that get peeled, such as oranges.

A third study published today, from Mount Sinai Medical Center in New York City, found that some people are more genetically susceptible to the pesticide risk than others.

Some groups want a total ban on chlorpyrifos. Others think there should be tighter regulation of its use on crops most likely to retain traces of pesticides. That includes fruits such as apples, strawberries and blueberries, and vegetables like celery, sweet peppers and potatoes.

A spokesman for Dow Agrochemicals, which makes chlorpyrifos, says the company won't comment until it's reviewed the new studies. But Dow has criticized earlier claims that children suffered developmental problems, saying its product was not to blame.

Meanwhile, a spokesman for the Environmental Protection Agency told NPR that it's taking another hard look at the risk of chlorpyrifos. The agency says it will take the new studies into account.

Richard Knox, NPR News.

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