Prenatal exposure to organophosphate pesticides, a kind of pesticide considered toxic to humans, has been linked to impaired cognition and significant changes in the brain.

In a major breakthrough, scientists from the University of California, Berkeley (UCB) and Stanford University found that teenagers exposed in utero to organophosphate pesticides demonstrated altered brain activities during tasks that required executive control.

Sharon Sagiv, an assistant professor of disease and environmental health at UCB and the study’s lead author, said that their findings offer insight into the impact of organophosphate pesticides on the brain.

Sagiv and her colleagues are also the first to use advanced brain imaging techniques to demonstrate that exposure in utero to the said toxic chemicals can change brain activities.

Their findings appeared online in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Prenatal pesticide exposure changes the brain

Despite breakthroughs in brain science, the potential impact of pesticides on neurodevelopment is still unclear. To this end, Sagiv and her colleagues used functional near-infrared imaging (fNIRS) to monitor blood circulation in the brains of 95 teenagers born and raised in California’s Salinas Valley.

The use of organophosphate pesticides in Salinas Valley, one of California’s major valleys and most productive agricultural regions, is common practice. This renders the cohort a relevant group to examine for the potential effects of organophosphate pesticide exposure on the brain.

The participants had also been part of an earlier phase of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. This is a longitudinal birth cohort study assessing the possible effects of pesticide exposure and other environmental factors on children’s health and neurodevelopment.

UCB scientists initiated the CHAMACOS study more than 20 years ago. The findings of their earlier research had linked prenatal organophosphate exposure to attention problems and a low intelligence quotient in children.

For this recent second phase, Sagiv and her colleagues used fNIRS to measure cerebral changes as the participants engaged in various tasks that required executive function, attention, social cognition and language comprehension.

They also utilized data from the California Pesticide Use Reporting program to estimate the proximity of the participants’ homes to pesticide-treated sites.

Upon assessing these data, they found that participants with higher prenatal organophosphate pesticide exposure in utero had less blood flow in their prefrontal cortex than their peers during tasks that required cognitive flexibility. This refers to the ability to switch between thinking about two different concepts or to think about multiple concepts at once.

However, the same participants demonstrated greater blood flow to their parietal and temporal lobes than their peers when engaged in tasks that tested memory retrieval, or the process of remembering information stored in long-term memory.

Brenda Eskenazi, a professor of public health at UCB and a member of the research team, said that fNIRS and neuroimaging afforded them insight into the potential impact of prenatal organophosphate pesticide exposure on the brain.

Similar patterns in other brain conditions

However, their findings offered no clear explanation as to how organophosphate pesticide exposure led to reduced blood flow in some regions, but greater blood flow in others during different cognitive tasks.

That being said, the patterns are not unique to organophosphate pesticide exposure. Similar patterns are apparent in other conditions that affect the brain, including Type 1 diabetes, Parkinson’s disease and Alzheimer’s disease, according to Allan Reiss, the study’s co-author and a professor of behavioral sciences at Stanford University.

Reiss also speculated that the increase in blood flow could mean that the brain is utilizing more neural resources to address deficiencies in certain areas as a result of long-term or prenatal organophosphate pesticide exposure.

Therefore, further studies might help shed light on the mechanisms behind the effects of organophosphate pesticide exposure on neurodevelopment.

Sagiv and her colleagues plan to repeat the brain imaging experiments on a larger cohort to determine if the patterns hold.