New evidence of chlorpyrifos harm to kids’ brains amid regulatory retreat

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Children highly exposed to an insecticide prior to birth showed signs of impaired brain development and motor function, according to a new study of chlorpyrifos — a pesticide still used on US crops despite decades of warnings about its impact on children’s health.  

The study, which focused on a group of children born to mothers in New York City, is the first to tie prenatal exposure to the pesticide to “enduring and widespread molecular, cellular, and metabolic effects in the brain,” the authors wrote. The study, published in the peer-reviewed journal JAMA Neurology, comes months after the US Environmental Protection Agency (EPA) announced its plans to partially ban chlorpyrifos but allow continued use on 11 crops.

The EPA was set to ban chlorpyrifos from use in agriculture in 2017 but the newly installed first Trump administration reversed the move. The EPA then banned chlorpyrifos in 2021 after a federal court ordered the agency to take action amid litigation and a wealth of evidence of the risks it poses to children. But the agency reversed course again after a different federal court sided with farm groups in opposition. 

The highest exposure levels in the new study were comparable to current exposures for farmworkers and their families, said Dr. Bradley Peterson, lead author of the study and chief of the Division of Child & Adolescent Psychiatry at the Children’s Hospital Los Angeles. 

But the exposure levels for many non-farmworkers in the US would “still be within the range of many of the women in our cohort,” he said, adding that there is no safe level of exposure. The compound can cross the placenta to the fetus. 

“With more exposure we saw more brain effects, but there is no level below which you don’t see impacts,” he said. 

Changes throughout the brain 

The findings are based on data gathered between 1998 and 2005 when researchers gave behavior tests and MRIs to a group of 270 children aged 6 to 14 years old whose mothers were exposed to chlorpyrifos during pregnancy. The mothers, who were all Dominican or African American, were exposed when their New York City apartments were fumigated with the insecticides. The researchers took blood samples from the mothers and umbilical cords to determine chlorpyrifos exposure. The EPA banned the insecticide from home use more than 20 years ago over fears for children’s health.

“With more exposure we saw more brain effects, but there is no level below which you don’t see impacts.” -Dr. Bradley Peterson, Children’s Hospital in Los Angeles

The MRI scans showed that kids with the highest levels of exposure were more likely to have reduced blood flow to the brain, thickening of the brain cortex, abnormal brain pathways, impaired nerve insulation and other problems. 

Peterson said the thickening of the cortex is concerning as that is responsible for people’s movement, memory and thinking. He said the results suggest that chlorpyrifos alters the neuronal tissue of those exposed in the womb. Neurons start developing in fetuses early in pregnancy and he said it looks like chlorpyrifos alters this development through inflammation and oxidative stress.  

The researchers also found that highly exposed children struggled in tests that involved tapping a keyboard in succession or moving their fingers in a certain sequence, indicating reduced motor skills. 

The authors previously published a study that found increased cognitive deficits in highly exposed children. Other studies have linked chlorpyrifos lower birth weights and smaller head size in exposed children.

“This is a stellar study and there can be absolutely no doubt that exposure to chlorpyrifos damages children’s brains,” Nathan Donley, environmental health science director with the Center for Biological Diversity, said. “It’s up to the Trump administration to decide whether it will prioritize the health of our children or industry profits.” 

Short-term ban and regulatory whiplash 

Environmental and health advocates have long pushed the EPA to ban chlorpyrifos. The European Food Safety Authority banned sales in 2020.

Patti Goldman, a senior attorney at Earthjustice who has led the organization’s work on chlorpyrifos, called the new study “remarkable” and that these kinds of effects are the “whole reason we have been bringing different lawsuits” to the EPA.

In 2021 the EPA announced a ban, a move that Michael Regan, EPA administrator at the time, called “overdue” and designed to protect “children, farmworkers, and all people … from the potentially dangerous consequences” of the pesticide. 

“The ban was in place for the 2022 growing season … but then, unfortunately, chemical companies and growers challenged that ban,” Goldman said. That appeal called the EPA’s move “unlawful … arbitrary and capricious.” 

The US Court of Appeals for the Eighth Circuit vacated the EPA’s proposed ban in 2023. The agency last year proposed a rule that would restrict the pesticide to use on 11 crops: alfalfa, apple, asparagus, cherry, citrus, cotton, peach, soybean, strawberry, sugar beets and wheat.

“It’s up to the Trump administration to decide whether it will prioritize the health of our children or industry profits.” -Nathan Donley, Center for Biological Diversity

The agency said the 11 crops that it plans to exempt from a ban represent roughly 55% of the total chlorpyrifos usage (average annual pounds applied). 

“We do not believe they should keep any uses because there is no safe level that would protect children from the kind of harm observed in the study,” Goldman said.   

The insecticide also wreaks havoc on wildlife. A federal judge in March ordered the US Fish and Wildlife Service to reduce the harms on endangered species from five pesticides, including chlorpyrifos, which an EPA assessment found was harming 97% of protected species.  

Avoiding exposure 

Chlorpyrifos was the 11th most frequently found pesticide in food samples in the most recent Food and Drug Administration (FDA) pesticide residue monitoring report, and a 2023 US Department of Agriculture pesticide residue report found traces of the chemical in baby food made with pears, as well as in samples of blackberries, celery and tomatoes. Peterson said parents or would-be parents concerned about exposure should buy organic food if they can, or, if that’s not possible, wash their fruits and vegetables. 

But there are “myriad” other compounds out there as well that also hamper child development, he said, adding the best bet for limiting exposures is minimizing the use of pesticides in the US.

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