Groundwater Measurements of Herbicide May Underestimate Human Exposure

Illustration of groundwater
Author’s Note: This version of Pocket Science originally appeared in the January 14, 2022 edition of Nebraska Today.  

Welcome to Pocket Science: a glimpse at recent research from Husker scientists and engineers. For those who want to quickly learn the “What,” “So what” and “Now what” of Husker research. 

What? Atrazine ranks as a common herbicide in the United States, where it’s frequently used to boost corn and sorghum yields by curbing weed growth.

Conversely, the European Union has banned atrazine, which some research suggests can disrupt hormone production in wildlife and potentially humans. A 2021 study from the University of Nebraska Medical Center indicated that Nebraska counties applying the most atrazine also exhibited higher incidences of estrogen-related cancers, including breast and prostate cancer.

Human exposure to herbicides often comes via drinking water, much of which is drawn from groundwater — with many studies consequently using groundwater concentrations as a proxy for local exposure risks. Given that, the UNMC researchers expected to find elevated concentrations of atrazine in the groundwater of highusage counties. They didn’t.

So  what? Seeking answers to the seeming paradox, the UNMC team recently partnered with the University of Nebraska–Lincoln’s Olufemi Abimbola and Shannon Bartelt-Hunt. Together, the researchers analyzed data from 33 eastern Nebraska counties that used the most atrazine between 1995 and 2014. As expected, the study showed that groundwater concentrations of atrazine were generally higher in shallower wells than deeper ones.

The team also analyzed two clusters of wells featuring similar depths but high vs. low levels of atrazine. Lower-concentration wells not only served roughly three times as many people but were also generally used to draw water rather than just monitor its quality, suggesting that excessive extraction of groundwater may lower its atrazine concentrations. Those wells were likewise located in areas of so-called discharge, where groundwater naturally flows to the surface.

Now  what? The findings indicate that groundwater concentrations of atrazine may underestimate the likelihood that people are exposed to it, said the researchers, who recommended measuring atrazine in already-extracted groundwater when studying its potential health implications.