“Cancer is not an abstract problem in Iowa,” oncologist Richard Denning told the people gathered in the Harkin Institute’s auditorium. “It’s not rare, it’s not declining and it’s not evenly distributed. Cancer affects everybody, but it doesn’t affect everybody equally.”
Eighty percent of the 25 counties with highest cancer rates in Iowa are rural, according to a new report from the Iowa Environmental Council (IEC) and the Harkin Institute for Public Policy & Citizen Engagement. The reports found other disparities as well.
Dr. Denning, medical director of Mercy Cancer Center in Des Moines and founder of Above + Beyond Cancer, was speaking as one of the co-authors of the new report, Environmental Risk Factors and Iowa’s Cancer Crisis. He was one of the featured speakers at an event the IEC and the Harkin Institute held on Wednesday for the report’s release.
The report is based on an almost year-long review of the latest scientific studies and academic research on the relationship between environmental factors and cancer risk, and how they illuminate why cancer trends in Iowa differ so greatly from overall national trends. Eighteen experts in a variety of fields worked on and contributed to the report. But before the scientific review began, IEC and the Harkin Institute held a series of listening sessions around the state, in both rural and urban communities, to learn about the personal impact of Iowa’s exceptionally high cancer rates.
“We began each listening session the same way, with one simple question,” IEC Executive Director Sarah Green explained on Wednesday. “Raise your hand if you or someone you love has been diagnosed with cancer. Every time every hand went up.”
“That moment tells you everything you need to know about the scale of this crisis in Iowa. Cancer is touching every corner of the state. It cuts across geography, age and background, rural and urban, young and old.”
According to the annual report on cancer by the Iowa Cancer Registry (ICR) that was published earlier this month, Iowa is the state with the second-highest cancer incident rate in the country for the third year in a row, and is one of the few states where the rate is rising. Dr. Denning highlighted another fact contained in the ICR report.
“Perhaps most concerning is what we’re seeing in young adults,” he said. “Iowa has the second-highest cancer incidence rate in people age 20 to 39, a population where cancer can be uncommon.”
The cancer mortality rate for young adults in Iowa is about the same as the national average, according to the ICR. Overall, the state has seen an increase in survival rate among cancer patients, but cancer is the second-leading cause of death in Iowa, and for some cancers, the mortality rate is above the national average.
“Iowa’s cancer rate started to diverge from national trends in the early 2000s, as our rate declined more slowly than what was being seen nationally,” said Adam Shriver, director of Wellness and Nutrition Policy at the Harkin Institute. “Then, around 2014, even more strikingly, Iowa’s rates reversed course entirely, starting to climb and landing us in the number two spot for new cancers for three years in a row.”
Cancer risk is a complicated topic, and any cancer can have multiple causes. But much of the public discussion of risk is limited to individual behavior.
“We know that personal behavior like smoking or sun exposure play a role in cancer risk,” Green said. “But far less attention has been paid to the environment we live in — the water we drink, the air we breathe and the soil that sustains us. In Iowa, those exposures matter.”
“We face some of the highest nitrate levels in drinking water in the nation. Widespread and intensive pesticide use. Elevated radon levels in homes. And growing concerns about PFAS contamination.”
The report’s executive summary lays out four important conclusions from its review of scientific literature.
- All of the most common cancers in Iowa (breast, prostate, lung, colorectal, and skin melanoma) have associations with environmental risk factors (pesticides, nitrate, PFAS, and radon).
- In Iowa, 13 of the 16 cancer sites identified in the report as connected to pesticides, nitrate, PFAS, and radon exceeded the U.S. incidence rate in the most recent five-year period (2017-2021).
- Of the adult cancers identified as associated with these environmental risk factors, 11 of the 15 cancer types are increasing in the total Iowa population.
- For people under 50 in Iowa, six of 10 cancer types associated with pesticides, nitrate, PFAS, and radon are increasing.
The report contains information about various environmental risk factors like industrial air pollution, but it focuses on four areas associated with environmental cancer risk in Iowa: nitrates, pesticides, radon and PFAS. It’s written in an accessible style, but doesn’t compromise the underlying science.
PFAS may be the least readily familiar of the four risk factors. PFAS are per- and polyfluoroalkyl substances, which includes more than 12,000 different chemical compounds that were extensively used for most of the 20th century, largely to make products water- and stain-resistant, as well as grease- and oil-resistant. PFAS are also used in firefighting foams, and in some cosmetics. Many of the compounds commonly used in the 20th century have now been phased out and banned. But as their nickname “forever chemicals” suggests, PFAS compounds breakdown very slowly and can persist in the environment even after the products they were used on are long gone. Newer versions of PFAS compounds are supposed to lessen any health risk.
“Strong evidence links PFAS to kidney and testicular cancers, with additional associations for prostate, ovarian, and non-Hodgkin lymphoma. Like other environmental risk factors, accumulation of PFAS from multiple sources — including occupational, community, and dietary exposures — can impact one’s likelihood of developing related cancers,” the executive summary says. “The most common PFAS exposure pathway for the general public is through water ingestion, which is considered a repeated and lifelong exposure.”
According to the report, surveys have found PFAS contamination in 94 percent of surface waterways in Iowa and in 30 percent of groundwater sources.
The other three environmental risk factors are more readily familiar to Iowans.
Almost everyone who grew up in the state, and certainly anyone who has bought a house here, has heard of radon. It’s the gas from the decay of radium, a naturally occurring radioactive metal found in relatively large quantities in Iowa’s soil. It is colorless, odorless and tasteless, and is present throughout the state, entering buildings “mainly by seeping in through cracks in floors, ceilings, walls, construction joints, floor drains, sump pump systems, ventilation ducts, and other openings, such as moderately porous concrete,” the report explains. Although radon quickly becomes inert, some of the products created by its decay are carcinogens.
After smoking, radon is the leading cause of lung cancer in Iowa, and lung cancer has the highest mortality rate of any cancer in the state.
Nitrate pollution is also familiar. Nitrate pollution in general, in surface waterways and groundwater, has been widely covered by Iowa media for years. So has the issue of nitrate pollution in drinking water sources, both municipal water systems and private wells. The cause of the state’s exceptionally high nitrate pollution is known. It is the result of the industrial-style approach to agriculture, with heavy use of fertilizer on the two dominant row crops, corn and soybeans, and more massive confined animal feeding operations (CAFOs) than any other state.
But the cause is also the reason politicians and state officials are reluctant, or unwilling, to take action to correct it. Iowa’s political leaders act as if clean water is incompatible with a functioning agriculture-based economy.
Many health problems associated with nitrate pollution have been extensively reported on, but the cancer risk has received less attention. In part that’s because cancers involve multiple factors, but it’s also because research on nitrate exposure and cancer research is lacking.
“A November 2025 literature review of studies conducted between 2016 and 2024 on the health effects of nitrate found patterns of increased risk for cancer, particularly of the urinary tract, bladder, kidney, prostate, and thyroid,” the report states. “Especially noteworthy is that associations with cancer for many of these studies appear at nitrate concentrations below the current EPA safe drinking water limit” of 10 mg per liter.
The EPA standard was set in the early 1960s, and was intended to address the problem of “blue baby syndrome,” a condition in which nitrate exposure causes dangerously low blood-oxygen levels in newborns and infants. The consensus among scientists is that level needs to be lowered to help prevent other known health problems associated with nitrates in drinking water. Many say it should be half the current level, some say it should be even lower.
The cancer risk of pesticide exposure has gotten more attention in recent years, as litigation over the widely used pesticide/herbicide Roundup have proceeded, with the manufacturer paying more than $10 billion to settle cases.
The report examines the literature on potential cancer risks associated with the state’s three most used pesticides, glyphosate — the active ingredient in Roundup — acetochlor and atrazine.
“The leading corn-producing states of the Midwest have the most increased cancer risk associated with pesticide exposure — specifically associations between pesticide use and higher incidence of leukemia, non-Hodgkin lymphoma, bladder, colon, lung, and pancreatic cancer,” the report’s executive states. It also explains that the risk is more than just being exposed when fields are being sprayed.
“Pesticides, including herbicides, fungicides, insecticides, and rodenticides, can remain in the environment for decades and can bioaccumulate in people and animals. Iowans come into contact with pesticides through drinking water, food residues, pesticide drift from fields, house dust, and occupational exposure.”
Even though the report is based on the review of scientific literature, its viewpoint is not limited to the laboratory. It is also informed by the 16 listening sessions conducted at the beginning of the project, in which hundreds of Iowans talked about their experiences. Those listening sessions were set up in partnership with the Iowa Farmers Union (IFU), a 111-year-old organization that works to assist and promote independent farms.
IFU “doesn’t oppose the use of crop protection, like pesticides,” executive director Matt Russelll said at the Harkin Institute event. “We don’t oppose the use of fertilizer and we don’t oppose animal agriculture. We are not against corn and soybeans or biofuels.”
But that doesn’t mean IFU supports the current dominant model of agriculture in Iowa.
“It’s clear that we need to change, and we can,” Russell, a fifth-generation farmer, said. “But it will take the entire state working together to support the changes we need on our farms so we have a healthier state.”
After its review of the risk factors, the report turns its attention to what the government is and is not doing about them, with a review of state and federal regulatory oversight. Anyone aware of the overall environmental problems in Iowa won’t be surprised that the report’s authors find current regulatory efforts inadequate.
The report concludes with a series of policy recommendations, and advice on how individuals can minimize their exposure to environmental cancer risks.
“[S]tudying environmental risk factors is not about assigning blame,” Dr. Richard Denning said in his remarks at the Harkin Institute. “It’s about identifying preventable causes of cancer.”
More than 40 percent of cancers are preventable, he added.
Like the other speakers on Wednesday, IEC Senior Director of Policy and Program Kerri Johannsen emphasized that change is possible, but it will require “honest conversations about what truly matters.”
“We have allowed powerful interests to dictate what happens on our land, in our state, for too long,” she said. “Iowans are asking for change loud and clear, but the response from policymakers has been a deafening silence.”
“This is the moment to come together, to come to the table with a clarity of purpose, to commit to change and to call all of us in to be part of the solution.”
