Exposure during pregnancy to chlorpyrifos, a widely used pesticide, causes lasting changes in children’s brains and motor function impairments.
A joint observational study by Children’s Hospital Los Angeles (CHLA) and Columbia University has found that prenatal exposure to a common pesticide also used as an insecticide could impair children’s brain development and motor function for years to come.
In this long-term study of children between 6 and 14 years old, followed since birth, prenatal exposure to the pesticide chlorpyrifos (CPF) was associated with alterations in brain structure and impairments in motor function. This is the first study to show that prenatal exposure to a pesticide produces enduring and widespread molecular, cellular, and metabolic effects in the brain. The results were published in JAMA Neurology.
“More CPF exposure led to more thickening of the cerebral cortex—the area of the brain that directs functions like thinking, memory and movement,” says Bradley Peterson, MD, first author on the study and Chief of the Division of Child & Adolescent Psychiatry at Children’s Hospital, where he also leads the Brain Imaging Lab. “We don’t know the consequences of these brain effects, but we found that CPF exposure most impairs motor functioning.”
Fetal exposure to CPF affects neurological development
Between January 1998 and July 2005, the team conducted behavioral assessments and MRI scans of the brains of 270 youths in upper Manhattan whose mothers had been exposed to CPF during pregnancy when their apartments were fumigated. The researchers from CHLA and the Columbia University Mailman School of Public Health also accessed behavioral exposure information from umbilical cord samples from each child at delivery as well as samples of their mothers’ blood collected the day after birth.
The MRI scans found:
- Thickening of the brain cortex
- Alterations in white matter, which could affect brain function
- Changes in the internal capsule, the structure that governs communication between the cortex and subcortical areas, affect motor and sensory pathways
- Fewer neurons in white matter could signal impaired development
- Abnormalities in brain pathways that support motor control
- Impaired nerve insulation (myelination), which can affect function
- Reduced blood flow, indicating less energy use, throughout the brain
“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. 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,” said Virginia Rauh, ScD, senior author on the study and the Jane and Alan Batkin Professor of Population and Family Health at Columbia Mailman School.
The data strongly suggest that one of the fundamental problems of CPF exposure is altered differentiation of neuronal tissue, says Dr. Peterson. “That happens early in pregnancy, when neurons develop in the cortex and differentiate into cortical gray matter—densely packed nerve cells which process information—and underlying white matter—which is mostly nerve fibers that connect neurons,” he says. “All these abnormalities can contribute to poor motor function in these kids. The contributing mechanisms seem to be the inflammation and oxidative stress that CPF and other pesticides produce.”
The researchers also found a dramatic and global reduction in brain blood flow.
“To me, this is the most profound finding because it’s so powerful and very rare to see something like this,” says Dr. Peterson. “Blood flow is an important indicator of underlying metabolism—the energy used by brain tissue. In my opinion, it’s maybe the most important finding of the paper, because it says that globally there’s a problem with brain metabolism in direct proportion to how much CPF exposure they had.”
While this current paper reports results on children up to age 14, the researchers have now collected MRI scans of adolescents up to age 19 and are analyzing the data in preparation for the next release of results from this ongoing study.
CPF is in the food chain
CPF is an organophosphate pesticide—in the same chemical family as nerve gas–that disrupts nerve signaling. In pregnancy, it can cross the placenta to the fetus, easily traversing the fetal blood-brain barrier. Prior studies by other groups have linked maternal CPF exposure to lower birth weight, smaller head size, abnormal newborn reflexes, and neurodevelopmental issues in toddlers—including autism, inattention, and lower intelligence.
CPF was banned from home use in the U.S. in 2001, but it is still used as an agricultural pesticide. A 2020 ban on food crops was reversed in 2023. The EPA wants to continue to allow CPF residues in certain food crops, including apples, strawberries, asparagus, tart cherries, citrus, and peaches.
“It’s in our food supply,” cautions Dr. Peterson. “And other chemicals used in the home act in similar ways and almost certainly increase inflammation and oxidative stress. This is why it is important to do these studies about the chemicals in our environment to protect children’s health.”
Editor’s note: An embargoed copy of the study can be obtained from JAMA Neurology (mediarelations@jamanetwork.org) or CHLA can provide a copy.
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