Agricultural pesticides and cancer? Idaho researchers hope to better understand link

·3 min read
Chris Butler/

For years, researchers have questioned whether environmental pollutants can cause cancer in the West. Now, University of Idaho researchers have found an important clue to finding the answer.

Two recently published University of Idaho studies showed a link between agricultural contaminants and cancer.

One study found that Idaho counties with more environmental burden — measured by agricultural pesticide use and metals in groundwater — were closely associated with cancer in children. Another study found that fumigants, a type of agricultural pesticide, were closely associated with cancer in 11 Western states.

In Western states like Idaho, where food crops are prevalent, metam — a type of fumigant — is the most common type of pesticide. The research showed metam had a significant link to cancer.

“Metam continues to be implicated in our studies over and over again,” Kolok said. The fumigant needs to be evaluated further, he added.

The research also highlighted “dramatic” geographical differences in pesticide use, Alan Kolok, co-author of the research and director of the Idaho Water Resources Research Institute, told the Idaho Statesman.

In states like Colorado, Montana, New Mexico, and Wyoming, herbicides are more common, as farmers are growing animal feed, corn, and soybeans, Kolok said.

Cause of cancer not yet known

Researchers emphasized that their studies don’t necessarily mean that pesticides cause cancer. Rather, the studies suggested they need to further investigate the link.

Now, the scientific process needs to follow through and better understand the connection, Kolok said.

This study is the first step toward the long-term goal of establishing that certain chemicals can cause cancer, Naveen Joseph, co-author of the research and postdoctoral fellow at the University of Idaho, told the Statesman.

Researchers used national and state data sets about cancer incidence, pesticide use, and groundwater quality to do their analyses. The data allowed them to search for chemicals that can cause the start of a tumor, Kolok explained, which is “notoriously difficult.”

Future studies can help determine chemicals’ effect. They can feed rodents food laced with pesticides and check whether the animals develop tumors. Or they can do a similar study in vitro, in a test tube. Certain cell lines are known to be responsive to cancers, and if exposed to a cancer-initiating factor, they will grow rapidly, Kolok explained.

Idaho farm workers vulnerable to pesticide exposure

Carly Hyland, a postdoctoral fellow at Boise State University who was not involved in the studies, has done prior research on the health outcomes of pesticide exposure, especially in children.

Hyland said the University of Idaho research is not surprising given the consistent evidence of pesticides’ link to different childhood cancers.

Hyland told the Statesman she sees the need for more studies. In particular, not much research has focused on the occupational hazards of Idaho farm workers, who are more often exposed to potentially harmful pesticides, she said.

“Idaho has a really large agricultural population, and an especially large Latinx agricultural population,” Hyland said.

Currently, her research group is tracking pesticide exposure in Latino farm workers by analyzing health data. The study, which started in April and will run for a few more weeks, coincides with pesticide spray season.

There’s increasing evidence that female farm workers have higher rates of pesticide poisoning, Hyland said. She and her colleagues want to understand whether male and female farm workers have different levels of pesticide exposure, and why that might be. They’re looking at factors like access to properly fitting personal protective equipment and access to pesticide education training.

Unlike the University of Idaho researchers, Hyland’s group is not looking at health outcomes. But they also hope to do future studies that investigate causal relationships, Hyland said.

Science takes time. The public might take solace in that research is done in a pragmatic and stepwise process, Kolok told the Statesman by phone.

“The scientific process grinds slow, but it grinds very fine,” Kolok said.