Panelists at nature summit: Certain ag practices are harming public health

Researchers and public health advocates said Wednesday that water quality and land use continue to be modifiable elements impacting public health, and in particular cancer, in Iowa.

The experts spoke to a crowded conference room in the Olmsted Center at Drake University during the 2025 Iowa Nature Summit that touched on policies, practices and programs impacting a variety of Iowa’s natural elements.

Panelists at a session titled, “Nature and Public Health: Cancer, Water Quality and More” agreed that there is enough research demonstrating the link between agricultural practices, like fertilizer and pesticide application, in Iowa and adverse public health outcomes.

“We know enough,” Audrey Tran Lam said. “I think what’s needed is more of a change in our level of acceptance of the evidence that’s out there.”

Tran Lam, the environmental health program director at the University of Northern Iowa, said the public health field looks for “upstream solutions to downstream problems.”

A pressing “downstream problem” in Iowa is the rate of new cancer incidents, which is the second-highest in the nation, according to the latest Cancer in Iowa report. The state is also one of just two states with rising rates of new cancers.

Dr. Richard Deming, the medical director of MercyOne’s Richard Deming Cancer Center in Des Moines, said these trends mean Iowa will soon have the highest rates of new cancers in the nation.

Deming said there are a variety of factors that can contribute to developing cancer, many of which are not unique to Iowa. Two factors he said are unique to Iowa are radon exposure and environmental exposures.

Radon is a naturally occurring, radioactive gas that seeps into houses through cracks in the foundation, or other openings, as soil and rock break down. The U.S. Environmental Protection Agency shows that all counties in Iowa have a high potential of elevated indoor radon levels.

The same EPA map shows other states also have high radon levels.

Deming said pesticide and chemical application in Iowa, however, is “vastly different” than that of other states.

“We have more pounds, if not tons of chemicals per square mile, and that is different,” Deming said.

He said it’s not “realistic” that research will be able to find “exactly which combination” of the hundreds of agricultural chemicals cause which cancers to the same extent that cigarette smoke can be linked to lung cancer.

“But it’s not that we don’t have evidence,” Deming said.

According to Deming, there are already a “number” of scientific reviews that show links of pesticides and nitrate contamination to certain types of cancers.

“We have enough research to show the association, next we need to have public health policy … to help modify behavior,” Deming said.

In the meantime, Deming’s top recommendations for Iowans are to test and mitigate for radon and to filter drinking water.

The environmental correlation to cancer was also the focus of a series of listening sessions led by Iowa Environmental Council, the Harkin Institute for Public Policy & Citizen Engagement and Iowa Farmers Union. The sessions are part of a broader study of the correlation between cancer and the environment, which is set to release in January.

What’s happening upstream?

Tran Lam said Iowa’s landscape is currently about 85 percent farmland, primarily in corn and soybean rotations. She said less than 1 percent of the state is dedicated to organic production. The state also leads in hog and egg production in the country, which Food & Water Watch estimates generates 109 billion pounds of waste each year.

Tran Lam said it takes a “fire hose” of synthetic inputs to “prop up” this landscape. She cited a 2023 USDA figure that found Iowa farmers applied 53 million pounds of herbicides to cropland that year.

“This 53 million pounds number does not encapsulate the entire chemical burden that goes into conventional farming practices,” Tran Lam said, noting that pesticides, fertilizers and fungicides are also part of the “burden.”

According to Tran Lam, research continues to emerge that shows low doses, or “environmentally relevant” doses of these chemicals are showing up in human bodies.

She said nitrate pollution in public drinking water continues to be a problem in Iowa, which is also the “easiest point of public intervention for public health professionals to wrap their heads around.”

Nitrate contamination was a topic of wide discussion in central Iowa this summer as elevated nitrate concentrations in the Des Moines and Raccoon Rivers led Central Iowa Water Works to issue a lawn watering ban for its more than 600,000 customers.

Later in the summer, a multiyear study commissioned by Polk County found that agriculture was the top contributor to central Iowa’s elevated nitrate levels.

Tran Lam said while the EPA limits nitrates in drinking water to 10 milligrams per liter, “the epidemiology is there” to show that exposure to lower concentrations can also cause adverse health outcomes like colorectal cancer, thyroid disease and neural tube defects.

She said crop diversity — “even if it’s not an organic, regenerative system” — is key to solving some of these problems. Rotating in some small grains to a traditional crop rotation can help reduce the inputs put onto the landscape in Iowa, she said.

Adam Shriver, director of nutrition and wellness policy at the Harkin Institute, suggested more public-health oriented policies as a solution moving forward.

“It’s not whether it’s being covered in the media or not, whether people in this room are talking about it, but whether the people who are making decisions and making policy are doing things to address that issue,” Shriver said.

Shriver suggested the state do things like fund a water monitoring network across the state that previously lost funding, modernize manure management plans, develop a map of drainage tile systems across the state and change policies to incentivize farmers to avoid planting crops on marginalized land.

The other panelists agreed that policy, rather than voluntary action, will be necessary to mitigate some of these environmental factors.

“We already know of policies that would be beneficial, and if we just leave everything as voluntary, we probably won’t get much done,” Deming said. “Let’s get the experts in agriculture together and then figure out how to use incentives and penalties to drive behavior that we know will reduce the chemicals getting into the water.”

Water quality was the topic of several other sessions at the summit Wednesday, including one on the economic impacts of Iowa’s water trails, one that called water quality Iowa’s “newest civil rights issue” and another that advocated for citizen water quality monitoring with programs like the Nitrate Watch at Izaak Walton League of America.

This article was first published by Iowa Capital Dispatch.