Pesticide exposure has been linked to many conditions, especially after long-term exposure. These chemicals can cause short-term adverse effects and in some cases, chronic adverse health effects that can emerge months or even years after exposure.
In pregnant women, pesticide exposure is associated with birth defects, learning problems of the child later in life, miscarriage or abortion, premature birth and low-birth weight. However, little information is available on how pesticides affect the infant’s brain in the long run.
Now, a team of researchers at the University of California – Berkeley have found that pesticides, particularly organophosphates, found that changes in brain activity happened when the baby was exposed to these chemicals in the womb. They were able to see the changes in brain activity through brain imaging of adolescents.
Published in the journal Proceedings of the National Academy of Sciences (PNAS), the study shows how the researchers used functional near-infrared imaging (fNIRS) to monitor blood flow to the brain of about 95 adolescents. They were born and rasied in California’s Salinas Valley, a region of agriculture and use of pesticides is rampant.
Tractor spraying pesticides. Image Credit: Fotokostic / Shutterstock
The researchers found that the teens who had pesticide exposure in the womb, compared to their peers, had altered brain activity during performance tasks that needed executive control.
"These results are compelling because they support what we have seen with our neuropsychological testing, which is that organophosphates impact the brain," Sharon Sagiv, associate adjunct professor of epidemiology at UC Berkeley, said.
Potential impact of organophosphate exposure on the brain
To arrive at their findings, the researchers recruited the teens through the Health Assessment of Mothers and Children of Salinas (CHAMACOS), which is a longitudinal study that examines the effects of pesticides and other toxins on the development of children.
The present study used the brain imaging technique to see brain activation and activities while the adolescents, who were between 15 and 17, performed many tasks requiting attention, social cognition, executive function, and language comprehension.
The imaging technique utilizes infrared light to measure and monitor blood flow in the brain cortex.
Aside from these data, the team acquired new data from the California Pesticide Use Reporting program, showing when and where agricultural pesticides are sprayed. This way, they can estimate the residential proximity to pesticide exposure during pregnancy.
The results show that teens who got higher prenatal organophosphate exposure had lesser blood flow to the frontal cortex while performing tasks.
“With fNIRS and other neuroimaging, we are seeing more directly the potential impact of organophosphate exposure on the brain, and it may be more sensitive to neurological deficit than cognitive testing," Prof. Brenda Eskenazi, study lead author, said.
In the future, the team plans to repeat the brain scans on more than 500 participants
Pesticide use in the United States
There are about 800 million pounds of pesticide active ingredient are applied in the country every year. Organophosphates (Ops) are the most commonly applied class of insecticides.
Exposure to these chemicals, which are considered endocrine-disrupting compounds, are rampant in the US population. Pregnant women and children are not spared to exposure to these harmful chemicals.
“The brain has a remarkable ability to utilize compensatory mechanisms to counteract long-term insults," Allan L. Reiss, the Howard C. Robbins Professor of Psychiatry and Behavioral Sciences and a professor of radiology at Stanford University, said.
“Higher activation may represent the recruitment and utilization of extra neural resources to address functional inefficiency related to a long-term insult, and lower activation, then, could be related to the eventual failure to recruit these resources after continued exposure or disease exhausts the brain's ability to bring compensatory responses online,” he added.
Sagiv, S., Bruno, J., Baker, J., Palzes, V., Kogut, K., Rauch, S., Gunier, R., Mora, A., Reiss, A., and Eskenazi, B. (2019). Prenatal exposure to organophosphate pesticides and functional neuroimaging in adolescents living in proximity to pesticide application. Proceedings of the National Academy of Sciences (PNAS). https://www.pnas.org/content/early/2019/08/20/1903940116