Chlorpyrifos, sold under brand names like Brodan, Detmol UA and Dowco 179, is one of the most widely used pesticides in the world.

Residential use of chlorpyrifos, a chlorinated organophosphate, was banned in the U.S. in 2001. It is still applied, however, for agricultural purposes; and many people are exposed to chlorpyrifos by consuming non-organic fruits, vegetables and grains.

People living in rural areas and agricultural communities are also at risk of airborne exposure when chlorpyrifos is sprayed on crops.

Prenatal exposure to chlorpyrifos was directly proportional to brain abnormalities and children's and adolescents' performance on behavioral tests.

The risks of pesticide exposure are especially serious for unborn children. During pregnancy, chlorpyrifos crosses the placenta and enters the fetal bloodstream, where it can reach concentrations of up to four times that of maternal tissues. It crosses the fetal blood-brain barrier to enter the brain.

Prenatal exposure to chlorpyrifos can lead to conditions such as low birth weight and autism spectrum disorders in babies and toddlers.

A team led by researchers at Columbia University, Children's Hospital Los Angeles and the University of Southern California recently found that prenatal exposure to chlorpyrifos had effects on brain development and behavior in children and adolescents. The effects are likely to last a lifetime.

“If they are there by childhood or early adolescence, they are very unlikely to go away later,” Bradley Peterson, first author on the study, told TheDoctor.

The study analyzed data from 270 children and teens born to Dominican and Black mothers in New York City who were enrolled in the Columbia Center for Children's Environmental Health birth cohort.

They detected chlorpyrifos in their umbilical cord blood or maternal plasma.

When the children were between six and 14 years old, the researchers ran magnetic resonance imaging studies of their brains and behavioral tests. Prenatal exposure to chlorpyrifos was directly proportional to brain abnormalities seen in the imaging studies and the children's and adolescents' performance on behavioral tests.

The more exposure a child had had prenatally, the more pronounced the brain abnormalities that were seen. Increasing levels of chlorpyrifos in umbilical cord blood were also associated with greater changes in brain structure, function and metabolism, as well as with poorer motor skills.

“There is very clearly a dose-response relationship between chlorpyrifos exposure and brain abnormalities,” Peterson, vice chair for research and chief of child and adolescent psychiatry at the Keck School of Medicine at USC, said. The strength of this association and the extent of damage in the brain surprised him.

During pregnancy chlorpyrifos crosses the placenta and enters the fetal bloodstream, where it can reach concentrations of up to four times that of maternal tissues.

Many pesticides that are chemically similar to chlorpyrifos are still used for residential and agricultural purposes in the U.S. These pesticides can produce inflammation in the brain, which the researchers believe caused the damage associated with chlorpyrifos exposure.

The study is published in JAMA Neurology.