A new study published in the journal JAMA Neurology raises a troubling and important question: Can exposure to a common pesticide during pregnancy leave a long–term mark on children's brains?
The pesticide examined in the study is called chlorpyrifos, or CPF for short. This is a substance from the organophosphate family, which was used for many years for pest control. In the United States, its residential use was banned as early as 2001, but it was still used and is used in various countries primarily in agriculture, including in Israel. Exposure to it can occur through food, dust, air, skin contact, or inhalation. The researchers note that chlorpyrifos is capable of crossing the placenta, reaching the fetal bloodstream, and from there also the developing brain.
The study was based on a long–term follow–up cohort of pregnant women and their children from Northern Manhattan and the South Bronx in New York. The original cohort included 727 pregnant women of African–American or Dominican descent. At birth, chlorpyrifos levels were measured in maternal blood or umbilical cord blood, and years later, the children underwent advanced brain MRI scans. The final analysis included 270 children aged 6 to 14, for whom there were both prenatal exposure data and imaging scans of appropriate quality.
Not only attention and memory tests
The importance of the study stems from the fact that most previous studies on pesticides and brain development relied primarily on behavioral or cognitive tests. Previous studies have already linked prenatal exposure to organophosphates with lower birth weight, smaller head circumference, abnormal reflexes in newborns, attention problems, lower IQ, and neurodevelopmental symptoms. The current study went a step further and asked whether measurable changes could be seen in the structure, function, and metabolism of the brain itself.
The researchers used several types of MRI. An anatomical MRI scan measured cortical thickness and white matter volume. A DTI scan assessed the microscopic structure of white matter tracts. An ASL scan measured regional cerebral blood flow, which can indirectly indicate metabolic activity. An MRS scan measured various substances in the brain, including N–acetyl–aspartate, which is considered a marker of neuronal density and normal function. That is, the researchers did not look at the brain from just one angle, but rather examined structure, neural connections, blood flow, and metabolism.
The findings were significant. The higher the level of exposure to chlorpyrifos during pregnancy, the greater the changes found in the children's brains. Exposure was linked to increased cortical thickness in frontal, temporal, and inferior–posterior regions, alongside a decrease in white matter volume in similar areas. These are not random areas: The frontal lobes are involved in attention, planning, working memory, executive functions, and behavioral regulation; temporal and posterior regions are associated with memory, visual processing, and self–awareness processes. The researchers interpreted this pattern as a possible alteration in the normal process by which the developing brain differentiates between gray matter and white matter.
Possible damage to the brain's communication tracts
Another finding concerned an area called the internal capsule, an important white matter tract that connects motor and frontal regions with deep brain structures, the brainstem, and the spinal cord. Children exposed to higher levels of chlorpyrifos in utero showed metrics that may correspond to an alteration in myelination or in the organization of white matter fibers. Myelin is a fatty sheath that wraps around nerve fibers and enables fast and efficient communication between nerve cells. When the myelination process is disrupted during sensitive periods of fetal development, the impact can last for years.
One of the most prominent findings was a decrease in cerebral blood flow. The higher the prenatal exposure to chlorpyrifos, the lower the blood flow found in extensive areas of the brain. Since cerebral blood flow is linked to metabolic activity, the researchers suggested that this might indicate a long–term change in brain metabolism. In addition, the spectroscopy scan found lower levels of N–acetyl–aspartate in several deep white matter tracts, a finding that may suggest a decrease in the density or normal function of neurons in these areas.
Functionally, exposure to chlorpyrifos was mainly linked to poorer motor performance. Children with higher exposure levels showed lower performance in tests of fine motor speed and movement sequence planning. In simple words: They had more difficulty with tasks that require rapid finger tapping or performing a precise sequence of movements. Similarly strong associations were not found across all other cognitive and behavioral metrics, but the researchers note that brain imaging may be more sensitive than conventional behavioral tests in detecting subtle changes.
What can explain the link?
How can a pesticide affect a developing brain years after exposure? The researchers point to several possible biological mechanisms, which are also based on previous laboratory studies: Chlorpyrifos may increase oxidative stress and inflammation, impair mitochondrial function, disrupt the development of neurons and glial cells, and interfere with the maturation of oligodendrocytes – the cells responsible for myelin production. When such processes occur during critical periods of fetal development, the impact can last for years.
It is important to emphasize: The study does not prove that every exposure to chlorpyrifos will cause damage, and it does not prove absolute causality. This is an observational study, and therefore it can show associations but cannot prove with certainty that the substance is the sole cause of the changes found. In addition, the participants came from a specific urban population, so it is not certain that the findings apply in the same way to all populations. The researchers also did not measure postnatal exposure or exposure to all other pesticides that could co–occur.
Despite the limitations, the study has significant power. Exposure was measured biologically at birth, the children were examined years later, and the researchers used advanced brain imaging. Furthermore, the relationship was dose–dependent: The higher the exposure, the more prominent the brain changes were. The researchers even note that there did not appear to be a clear threshold below which there was no effect at all.
What is the message and what can be done?
The message to the public is not fear, but awareness. Pregnancy and early childhood are windows of time in which the brain develops rapidly and is particularly sensitive to environmental influences. This study joins a growing body of knowledge showing that it is not only the quantity of fruits, vegetables, and grains we eat that matters, but also the question of what pesticide residues might arrive with them.
The practical recommendation is balanced: Do not stop eating fruits and vegetables. On the contrary, they are essential for health. But it is advisable to make informed choices, especially during pregnancy and early childhood: Diversify food sources, choose organic produce when possible and especially for frequently consumed foods, and support policies that reduce exposure to harmful pesticides.
The bottom line is, this study reminds us that everything that enters the body during pregnancy may affect not only the birth itself, but also the way the child's brain is built, develops, and functions years later. It is not a reason to fear food, but it is definitely a reason to think more deeply about the source of our food, our environmental exposure, and the choices we make, especially during the most sensitive periods of life.
Dr. Dalit Dreman-Medina is a specialist in family medicine and integrative and functional medicine