Prenatal Exposure to Popular Pesticide Linked to Abnormal Structural Changes in the Brain

Pregnant women exposed to commonly used pesticides may be putting their children at risk of abnormal irreversible brain changes linked to lower intelligence, according to a new study that examined brain changes in children born before the chemical was banned from household use in the United States.

Researchers compared magnetic resonance imaging of children aged five to eleven with the highest prenatal exposure to chlorpyrifos (CPF), which according to the United States Environmental Protection Agency is “one of the most widely used organophosphate insecticides," to those with the lowest exposure and found "significant abnormalities" in the brain structure of kids with the highest level of exposure to the chemicals. 

Researchers said that some of those structural abnormalities were found in the cortex, the surface portion of the brain that plays a role in governing intelligence, personality, muscle movement and other tasks, with abnormal overgrowth in some areas and thinning in other areas. 

The study, published online in Proceedings of the National Academy of Sciences, was the first to use imaging scans to show that prenatal exposure to the CPF is linked to abnormal structural brain developments, associated with lower IQ scores and working memory deficits, five to ten years after exposure.

Furthermore, the findings also show that children exposed to higher levels of CPFs did not show the expected male and female differences in their brain, which could potentially negatively affect their development, suggesting that “CPF may eliminate or reverse the male-female differences that are ordinarily present in the brain,” according to the authors in a statement.

Investigators warned that even low to moderate levels of exposure to the pesticide can lead to brain abnormalities, because structural changes appeared to occur even when exposure levels were below the current EPA threshold for toxicity.

The latest findings “provide 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,” lead author, Virginia Rauh of Columbia University said in a statement released on Monday.

The latest study consisted of 40 elementary school-aged children living in New York City whose mothers were from a larger cohort study. Researchers had compared 20 children exposed to high levels of CPF with 20 others with lower exposures. All exposures had occurred before EPA banned the household use of the chemical in 2001.

Experts say that since the ban, eleven years ago, there has been a drop in residential exposure levels of CPF, but the insecticide is still widely used for pest control on farms and public spaces. 

Low levels of exposure can also occur by eating agricultural products like fruits and vegetables that have been sprayed by the chemical, and while weather and sunlight rapidly degrades the pesticide, researcher have detected CPF traces in many urban households years after the ban went into effect. 

Researchers say that additional research is needed to determine the consequences of abnormal structural changes caused by CPF before and after puberty, as well as other long-term effects of the changes which are "consistent with the IQ deficits previously reported in the children with high exposure levels of chlorpyrifos," the authors wrote.