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Health & Pregnancy

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Pesticide Exposure in Womb Linked to Lower IQ

Studies Show Kids Exposed in Pregnancy May Also Have Later Problems With Attention and Memory

Checking Markers for Pesticide Exposure

Researchers at Columbia University looked at markers for exposure for particular organophosphate, chlorpyrifos, in blood samples taken from umbilical cords in 265 inner-city mothers and infants in New York City.

“Our measure is a direct measure of fetal exposure via fetal blood,” study researcher Virginia Rauh, ScD, a professor at Columbia University’s Mailman School of Public Health.

The mothers were asked detailed questions about their lifestyle and health habits during the third trimester of pregnancy and then every year after that.

At age 7, the kids were given a battery of intelligence tests that measured IQ, working memory, verbal comprehension, perceptual reasoning, and processing speed.

For every increase in exposure of about 5 picograms per gram (pg/g) in their cord blood, the children’s IQ scores dipped by 1.4% and their working memory declined by about 2.8%.

“Keep in mind that we would consider this low-level exposure,” says Rauh. “This is not some sort of high-level industrial exposure.”

When researchers looked at other chemical exposures, including tobacco smoke or air pollutants called polycyclic aromatic hydrocarbons, they saw no associations between those levels and memory or IQ.

Clearing Pesticides From the Body

In the second study, which was also conducted in New York City, researchers at Mount Sinai Medical School looked for markers of pesticide exposure in urine in more than 400 mothers and infants. They also took samples of the mothers’ blood to analyze it for the gene that codes for an enzyme called paraoxonase 1 (PON1), which is involved in the metabolism of organophosphate pesticides.

Overall, about 30% of the mothers tested positive for a version of the gene that causes pesticides to be cleared more slowly from the body.

Their children were given tests for brain development at ages 1 and 2, and again between the ages of 6 and 9.

Overall, they found that increasing levels of pesticide metabolites in mothers during pregnancy were linked to greater deficits in IQ, perceptual reasoning, and working memory in many grade-school aged children.

Among children of genetically slow metabolizers, the deficits were worse compared to children of intermediate and fast pesticide metabolizers.

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