Pesticide exposure linked to lower intelligence

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Children who were exposed to certain types of organophosphate pesticides before birth could have lower levels of childhood intelligence, according to a UC Berkeley study reported on by the Salinas Californian.

The study examined the effects of pesticide exposure in the Salinas Valley for more than 10 years. The researchers, representing UC Berkeley and the Center for the Health Assessment of Mothers and Children of Salinas, found that every 10-fold increase in the amount of the pesticides found in the mother during pregnancy corresponded with a 5.5 point drop in IQ scores when the children were 7.

"These associations are substantial, especially when viewing this at a population-wide level,” a UC Berkeley news release quoted principal investigator Brenda Eskenazi, professor of epidemiology and of maternal and child health. “That difference could mean, on average, more kids being shifted into the lower end of the spectrum of learning, and more kids needing special services in school.”

The UC Berkeley study is one of three showing an association between pesticide exposure and childhood IQ published online April 21 in the journal Environmental Health Perspectives, the news release said.

Mt. Sinai researchers sampled pesticide metabolites in maternal urine, and researchers at Columbia looked at umbilical cord blood levels of a specific pesticide, chlorpyrifos.

“It is very unusual to see this much consistency across populations in studies, so that speaks to the significance of the findings,” said lead author Maryse Bouchard, who was working as a UC Berkeley post-doctoral researcher with Eskenazi while this study was underway. “The children are now at a stage where they are going to school, so it’s easier to get good, valid assessments of cognitive function.”

The Los Angeles Times reported that some of the data are not as conclusive as they might seem at first glance.

". . . Let’s be cautious—the IQ differences were small, and some only appeared by looking at the data in a certain way," said the article written by LA Times reporter Marissa Cevallos. "Women in the Berkeley study, for example, had their urine measured for traces of pesticides twice—once in the first half of pregnancy and once in the second half. The researchers found no correlation between IQ and pesticide markers in the first urine test or in the second urine test. But then when they averaged the two, voila—a correlation."

The story was picked up widely by the news media, including:

Organophosphate pesticides are approved for use in agriculture. Increasing evidence suggests that prenatal exposure to pesticides may have health impacts in later years.