An estimated 21,700 new cancers will be diagnosed among Iowans, and a projected 6,400 Iowans will die from cancer in 2026, 100 more than in 2025, according to the Iowa Cancer Registry’s 2026 report published March 13.
There are a projected 165 residents who will die from cancer and 6,795 survivors of the disease in Johnson County, according to the 2026 report.
This year, the Iowa Cancer Registry partnered with the Agricultural Health Study an ongoing research study that explores how agricultural lifestyle factors affect the health of farmers in Iowa and North Carolina, to analyze cancer in Iowa’s farming population.
Mary Charlton, professor of epidemiology in the College of Public Health and co-author of the Iowa Cancer Registry report, said partnering with the study stemmed from public concern over pesticide use.
31,433 male farmers signed up for the study when it began in the mid-1990s, along with 22,145 women, either spouses of the farmers or farmers themselves. Farmers were eligible for the study if they obtained or renewed a pesticide license. The study is still ongoing.
The study found that farmers had 13 percent fewer cancer cases than expected based on Iowa’s general population cancer rate. Spouses had 10 percent fewer cancer cases than expected.
The study reports the lower rates could have resulted from a phenomenon known as the “healthy worker effect,” meaning people who work in physically taxing jobs like farming tend to be healthier because they must maintain their health to be able to work.
The study also suggested that the lower cancer rates could be linked to lifestyle choices; farmers and their spouses in the study reported drinking and smoking less than the general population of Iowa.
“Even though these are people who are the most highly exposed population to pesticides, when you sort of put it all together in a healthier cohort that’s more active, probably by virtue of their work, overall, they’re getting cancer less,” Charlton said.
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Charlton said that although farmers in the study reported slightly lower-than-expected cancer rates compared with the state of Iowa as a whole, it still has the second-highest rate in the nation.
Charlton said pesticides can contribute to cancer, but with hundreds of different chemicals and ingredients to study, the relationship is complicated, as not every chemical causes cancer, an already complex disease in and of itself.
“Cancer is not one disease. Cancer is hundreds, if not thousands, of diseases,” she said. “It takes quite a bit of time to sort of painstakingly look at specific chemicals and pesticides and whether they’re associated with specific cancers in humans.”
Charlton said nitrate runoff into water could be a large contributor to cancer rates in Iowa, but the state lacks data to assess what sources of water have the greatest risk of cancer.
“Not very many of us drink from one water source our entire lives,” she said. “There’s not really a good database that tracks all your exposures over your lifetime. And cancer takes decades to develop into a larger problem.”
Charlton also said the state lacks a sophisticated pesticide reporting system. She said states such as California have more specific, granular reporting systems — data analysis that breaks down information in its smallest components — that can indicate which pesticides were applied to an area, and when and where they were applied.
“That allows them to then look at people living around those places and invest in some of their state institutions, like the DNR, then to go out and start to measure exposures in those people who live near where pesticides are being applied,” she said.
Charlton said the report aims to address public concerns about environmental risk factors and highlight the need for further research.
“We know that Iowans are concerned about environmental risk factors, and we hope this report provides some helpful context while reinforcing the need for more research and data collection in that area,” she said.