The insecticide chlorpyrifos is a powerful tool for controlling various pests, making it one of the most widely used pesticides during the latter half of the 20th century.
Like many pesticides, however, chlorpyrifos lacks precision. In addition to harming non-target insects like bees, it has also been linked to health risks for much larger animals – including us.
Now, a new US study suggests those risks may begin before birth. Humans exposed to chlorpyrifos prenatally are more likely to exhibit structural brain abnormalities and reduced motor functions in childhood and adolescence.
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Progressively higher prenatal exposure to chlorpyrifos was associated with incrementally greater deviations in brain structure, function, and metabolism in children and teens, the researchers found, along with poorer measures of motor speed and motor programming.
“The disturbances in brain tissue and metabolism that we observed with prenatal exposure to this one pesticide were remarkably widespread throughout the brain,” says first author Bradley Peterson, a developmental neuroscientist at the University of Southern California’s Keck School of Medicine.
This supports previous research linking chlorpyrifos with impaired cognitive function and brain development, but these findings are the first evidence of widespread and long-lasting molecular, cellular, and metabolic effects in the brain.
The scientists analyzed data collected from families in New York City between 1998 and 2015 as part of a long-term pregnancy cohort established by Columbia University’s Center for Children’s Environmental Health. The original cohort included African-American and Dominican mothers aged 18 to 35.
Mothers completed prenatal questionnaires and some provided additional data, including chlorpyrifos levels of their children at birth, either via umbilical cord or maternal plasma samples.
Years later, researchers collected MRI scans and behavioral data from the children at ages 6 to 14. They ended up with 270 subjects with chlorpyrifos levels measured at birth and usable MRI data provided as kids or teens.
Their analysis found a significant link between prenatal chlorpyrifos levels and brain abnormalities in children, suggesting “prenatal exposure may produce enduring disturbances in brain structure, function, and metabolism in direct proportion to exposure level,” they write.
Subjects in this urban cohort were likely exposed to chlorpyrifos at home, since many were born before or shortly after the US Environmental Protection Agency banned residential use of chlorpyrifos in 2001.
Similar restrictions have since been adopted in other countries, but the pesticide is still used in agriculture around the world.
“Current widespread exposures, at levels comparable to those experienced in this sample, continue to place farm workers, pregnant women, and unborn children in harm’s way,” says senior author Virginia Rauh, an environmental health scientist at Columbia’s Mailman School of Public Health.
“It is vitally important that we continue to monitor the levels of exposure in potentially vulnerable populations, especially in pregnant women in agricultural communities, as their infants continue to be at risk,” Rauh says.
The researchers note some limitations: as an observational study, it can only show associations, not prove causation.
It focused exclusively on prenatal chlorpyrifos exposure, neither measuring nor controlling for postnatal exposure, and it did not test for exposure to other insecticides that often co-occur with chlorpyrifos. The lack of demographic diversity in the sample may also limit how broadly the findings apply.
Yet given the ubiquity of chlorpyrifos and similar compounds in the environment, this study indicates a need for more research into these powerful pesticides.
“Other organophosphate pesticides likely produce similar effects,” says Peterson, “warranting caution to minimize exposures in pregnancy, infancy, and early childhood, when brain development is rapid and especially vulnerable to these toxic chemicals.”
The study was published in JAMA Neurology.
