Prenatal exposure to a common pesticide is linked to widespread brain changes and slower fine‑motor skills in school‑age children. Digest
Scientists have long suspected that certain pesticides may affect brain development, but direct evidence in humans has been limited. A new study tracked children whose mothers were exposed during pregnancy to chlorpyrifos, a widely used insecticide, to see whether that early contact left a lasting imprint on brain and behavior.
The researchers followed 270 children and adolescents from a long-running New York City pregnancy study. Exposure was estimated from chlorpyrifos measured in umbilical cord plasma at birth or in maternal plasma within a day after delivery. When the children were between 6 and 14 years old, they completed motor tests and underwent advanced brain imaging.
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Higher exposure was linked to changes in both brain structure and motor skills:
- Children with higher prenatal exposure showed variation in the thickness of the brain's outer layer, with thicker regions involved in planning, attention, and memory, and thinner ones near the top of the brain that support spatial awareness and coordination.
- Beneath the thicker cortical regions, the amount of white matter, which carries signals between brain areas, was reduced.
- One key fiber bundle that connects movement-related brain regions showed signs of altered microstructure, consistent with either tighter packing of nerve fibers or differences in myelin, the fatty insulation that surrounds nerve fibers and helps signals travel quickly.
- Blood flow was lower throughout much of the brain in children with higher exposure, suggesting long-term effects on brain metabolism.
- A brain chemical called N-acetylaspartate, which is an index of healthy neuron density, was also reduced in specific areas.
- Children with higher prenatal exposure also performed worse on motor tasks that measure hand speed and coordination, particularly in the non-dominant hand.
These changes point to possible disruptions in early brain development. The researchers propose that chlorpyrifos may impair how brain cells mature by triggering oxidative stress and inflammation — two processes known to harm mitochondria and interfere with myelin production. Together, these effects could lead to the observed differences in brain structure and motor control.
Because this was an observational study, it cannot establish whether the pesticide or other factors caused these changes. However, the results were consistent even after accounting for other exposures, such as air pollution. In conclusion, the findings suggest that avoiding pesticide exposure during pregnancy could play a role in supporting brain development. In Aliquot #100, I discuss factors that influence child development before conception, during pregnancy and infancy, and into the toddler and early childhood years.