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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

Study of Farmworkers

The third study was conducted in a community of California farmworkers.

Researchers at University of California, Berkeley measured metabolites of organophosphates in urine samples collected from 326 pregnant women and from their children at age 6 months and ages 1, 2, 3.5, and 5 years.

About 44% of the women worked on farms during the study, but they were not pesticide applicators.

Kids who were exposed to the highest levels of organophosphates during pregnancy had IQ scores that were an average of 7 points lower than the IQ scores of kids with the lowest pesticide exposures.

In fact, every tenfold increase in a pregnant mother’s pesticide exposure was associated with a more than 5-point drop in her child’s IQ at age 7.

There was no association between the pesticide levels measured in the children’s urine and learning or memory problems.

“This is not a trivial association,” says study researcher Brenda Eskenazi, PhD, professor of epidemiology and maternal and child health at the University of California, Berkeley.

Normal IQs range from 85 to 115. Children who score lower than 85 often need special education classes in school to make up for trouble with reading, comprehension, and attention.

“On a population basis, it means more kids are going to be driven down into the range that we’re concerned about,” Eskenazi says. “You’re going to have more kids below 85 IQ, which means that they may need to have special services.”

The studies were published in the journal Environmental Health Perspectives.

What the Findings Mean

“This range of effects that these three studies are reporting are very similar to the effects that we associate with lower levels of exposure to lead,” says Philip J. Landrigan, MD, a pediatrician and Ethel H. Wise Professor and Chair of the department of community and preventive medicine at the Mount Sinai School of Medicine, in New York City.

“These are kids who are going to be a couple of beats slower in thinking things through,” Landrigan tells WebMD.

“Their working memory, which is the aspect of memory that we use to deal with tasks in the here and now, is going to be somewhat diminished. They’re going to have a shorter attention span, which means that they’re going to have trouble concentrating on tasks, focusing in school,” he says.

Toxicology experts, however, noted that several caveats apply to the findings.

The first is that while the association between organophosphates and brain deficits looks suspicious, and is biologically plausible, the studies can’t prove that the pesticides are responsible for the problems. 

Most of the families in these studies were low-income and less-educated, groups that have been shown to be disproportionately impacted by learning and attention problems. Though researchers tried to tease out those influences, epidemiologists know that it can be tricky to completely eliminate their effects.

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