Prenatal exposure to widely used insecticide linked to brain development defects

A new study has found that prenatal exposure to chlorpyrifos (CPF) insecticide is associated with defects in the development of certain parts of the child’s brain.

“Even low to moderate levels of exposure to the insecticide chlorpyrifos during pregnancy may lead to long-term, potentially irreversible changes in the brain structure of the child,” Columbia University Mailman School of Public Health said in a release.

Chlorpyrifos is an organophosphate insecticide first marketed in 1965 by Dow Chemical Company under the brand names Dursban and Lorsban. It became one of the most widely used insecticides in agricultural and household applications.

In 2000, the U.S. Environmental Protection Agency (EPA) reached an agreement with chlorpyrifos insecticide manufacturers to phase out chlorpyrifos from household insecticide products by 2001 due to data showing a greater affect on the brains of young rats than previously thought. However, it is still one of the most widely used insecticides in agricultural applications with approximately 10 million pounds applied annually on crops such as grains, fruits, nuts and vegetables, with more than half used on corn crops alone. It is also used on golf courses and as a wood preservative.

Researchers from the Columbia Center for Children's Environmental Health at the Mailman School of Public Health, Duke University Medical Center, Emory University and the New York State Psychiatric Institute used brain imagery to study the brain development of forty children ages 5 to 11. 20 of the children had higher concentrations of chlorpyrifos in their umbilical cord blood at birth and 20 children had lower levels in their umbilical cord blood at birth.

Through use of MRIs, researchers compared their brain structure and found that children with higher exposure of chlorpyrifos in the womb had changes in their brain visible across the surface of the brain, with abnormal enlargement of some areas and thinning in others. Brain areas affected involve IQ, attention, behavior and emotion. There was also evidence that higher chlorpyrifos exposure may eliminate or reverse the male-female differences in the brain and that further study was needed to determine consequences before and after puberty.

These brain abnormalities observed in the MRIs occurred at exposure levels below the current EPA threshold for toxicity.

Higher prenatal exposure to chlorpyrifos was previously associated with lower scores on cognitive functioning tests.

“By measuring a biomarker of CPF exposure during pregnancy, and following the children prospectively from birth into middle childhood, the present study provides evidence that the prenatal period is a vulnerable time for the developing child, and that toxic exposure during this critical period can have far-reaching effects on brain development and behavioral functioning,” said lead author Virginia Rauh, ScD, Professor at the Mailman School of Public Health and Deputy Director of the Columbia Center for Children's Environmental Health.

“By combining brain imaging and community-based research, we now have much stronger evidence linking exposure to chlorpyrifos with neurodevelopmental problems,” adds senior author Bradley S. Peterson, MD, Chief of Child & Adolescent Psychiatry, New York State Psychiatric Institute, and Director of MRI Research in the Department of Psychiatry, Columbia University Medical Center.

The study Brain anomalies in children exposed prenatally to a common organophosphate pesticide appears in the April 30, 2012 issue of Proceedings of the National Academy of Sciences (PNAS).