Expert tells Iowa audience the state’s agriculture is ‘too pesticide intensive’

IOWA CITY — An agricultural expert with more than four decades of experience studying pesticide use, food safety and agricultural policy, says Iowa’s agriculture is too pesticide intensive.

“It is harming the soil, harming public health, and it is harming fish populations and birds and the deer,” said Charles Benbrook, a visiting scholar at the Bloomberg School of Public Health at Johns Hopkins University, and president of Benbrook Consulting Services. “It’s harming any critter that lives out there where all this stuff is sprayed.”

Benbrook was in Iowa City Thursday to deliver a lecture titled “Pesticides, Farming and the Future of Public Health in Iowa.” The event, held at the Iowa City Senior Center, was sponsored by the Iowa Farmers Union, Drake Agricultural Law Center, University of Northern Iowa, Food & Water Watch, 100 Grannies, and the UNI Center for Energy & Environmental Education.

Benbrook’s tour brought him to Iowa as state lawmakers consider a bill that would shield pesticide companies from lawsuits over warning labeling on their products.

Senate Study Bill 1051 is supported by Bayer, the company that produces the glyphosate-based herbicide Roundup. The herbicide is used widely by agricultural producers across the state.

Glyphosate controls broadleaf weeds and grasses. It kills plants by preventing them from making proteins needed to grow. It is absorbed through the plant’s leaves and stems, then carried into the plant.

Benbrook, who has served as an expert witness in pesticide and food labeling litigation, said when humans or animals have repeated exposure of large amounts of glyphosate, their health also can be negatively affected.

Although the Environmental Protection Agency has cleared glyphosate of posing cancer risks, Reuters reported in 2022 that a federal district court requested the agency review that decision. The International Agency for Research on Cancer determined it is "probably carcinogenic to humans."

Benbrook said Roundup is a “great product” and there are safe ways to use it.

“Roundup is the safest herbicide option that you can use, and I have felt that way all along. And even with what I know today, I still feel that way because I understand that it takes a lot of exposures over a lot of time to get enough DNA damage in your cells,” he said.

  Buy Photo

A key issue with Roundup, Benbrook said, is people must take proper precautions when applying it.

For example, when mixing and applying the pesticide, people should wear personal protective equipment — including gloves, a respirator and a bodysuit — to protect themselves from the spray. When homeowners use Roundup for weed control on their property, Benbrook said they should be mindful about where they spray it, especially around children’s outdoor play sets, and they should avoid using it in the middle of the day when there may be people nearby outside.

Benbrook said the human body is an incredible machine that has “all these ways to snuff out cancer,” but repeated exposure to chemicals can result in health issues over time.

Expert: There should be more research into Iowa’s cancer rate

One attendee at Benbrook’s Iowa City lecture asked him how pesticide and herbicide use in Iowa is contributing to the state’s high cancer rates.

According to the Iowa Cancer Registry’s 2025 report, released this week, there is an estimated 21,200 new invasive cancers reported statewide, up from 21,000 in 2024. Iowa has the fastest-growing cancer rates in the country, and it ranks second, behind Kentucky, in overall cancer rates.

  Buy Photo

Benbrook said he has worked with Iowa’s Cancer Registry experts in the National Cancer Institute’s Surveillance, Epidemiology and End Results program on what is causing the rising cancer rates in the state and how pesticides — and contaminants like nitrate in drinking water — may be affecting Iowans’ health.

“It's really important to get some subdue epidemiology going in Iowa, to try to figure out (if it’s) nitrates, the nitrates plus the pesticides, what's going on here?” he said. “Because it's only going to get worse. Until Iowans figure out what the risk factors are, it's going to get worse, and as the population ages, and (with) a lousy diet, our bodies are not going to be as able to fight off the diseases.”

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: olivia.cohen@thegazette.com