The common pesticide chlorpyrifos has been banned for indoor use since 2000, but its effects can still be found in the brains of young children now approaching puberty. A recent study used magnetic resonance imaging to reveal that children exposed to chlorpyrifos in the womb had changes in the brain that persisted throughout childhood.

Researchers examined the brain scans of 20 children exposed to higher levels of chlorpyrifos in their mother's blood (as measured by serum from the umbilical cord) and found that they looked markedly different compared with those of children exposed to lower levels of the chemical, says epidemiologist Virginia Rauh of the Mailman School of Public Health at Columbia University. Rauh led the research, which was published online in late April in the Proceedings of the National Academy of Sciences USA. “During brain development, some type of disturbance took place,” she notes.

The six young boys and 14 little girls, whose mothers were exposed to chlorpyrifos when it was commonly used indoors in bug spray before the ban, ranged in age from seven to nearly 10. All came from Dominican or African-American families in the New York City region. Compared with 20 children from the same kinds of New York families who had relatively low levels of chlorpyrifos in umbilical cord blood, the 20 higher-dose kids had protuberances in some regions of the cerebral cortex and thinning in other regions.

Although the study did not map specific disorders tied to any of these brain changes, the regions affected are associated with functions such as attention, decision making, language, impulse control and working memory. The findings echo similar results from animal studies of the insecticide, which remains widely used in agriculture to kill crop-spoiling insects. The good news is that washing fruits and vegetables can rinse away lingering chlorpyrifos and mitigate much of the risk.