Cancer in Iowa report shows Iowa farming population had fewer than expected cancers overall

The Cancer in Iowa Report, published annually by the Iowa Cancer Registry, provides an overview of the current burden of cancer in the state. This year, an estimated 21,700 Iowans will be diagnosed with cancer, and about 6,400 Iowans will die from the disease. The number of cancer survivors continues to rise, with approximately 175,290 survivors now living in Iowa.

The 2026 Cancer in Iowa Report features findings from the Agricultural Health Study, one of the world's largest and longest-running active studies of agricultural exposures and health. The study began in the mid-1990s and includes more than 89,000 farmers, commercial pesticide applicators, and their spouses from Iowa and North Carolina. In Iowa, this includes more than 31,000 private pesticide applicators, 4,900 commercial applicators, and nearly 21,000 spouses.

The Agricultural Health Study examines how agricultural, lifestyle, and genetic factors influence the health of farmers and plays a key role in understanding potential risks.

"Iowans are understandably concerned about environmental risk factors, and we hope this report provides helpful context while reinforcing the need for more research," says Mary Charlton, professor of epidemiology in the College of Public Health and co-author of the report.

"Cancer is complex, and it takes multiple research studies to determine whether something causes cancer," Charlton says. "While the Iowa Cancer Registry does not conduct research, we collect the high-quality data that researchers rely on, including those working on the Agricultural Health Study. Because the Agricultural Health Study provides an unparalleled resource for understanding cancer risk in farming communities, plays a critical role in protecting the health of agricultural workers and their families, and draws extensively on Iowa Cancer Registry data, we felt it was important to highlight the study and its significance in this year's report."

Key Findings

• Iowa Farmers in the Agricultural Health Study had 13% fewer cancers overall than expected compared to the general Iowa population after adjusting for age and sex. They had fewer cases than expected of cancers of the colon and rectum, lung, bladder, oral cavity and pharynx, pancreas, esophagus, larynx, liver, and tongue. However, they were diagnosed with more cases of prostate cancer and lip cancer than expected.
• Spouses of Iowa farmers in the study had 10% fewer cancers overall than expected compared to the general Iowa population after adjusting for age and sex, including fewer cases of colon and rectum, lung, bladder, pancreas, and cervical cancers. However, they were diagnosed with more cases of melanoma and thyroid cancer than expected.
• Iowa farmers and spouses reported lower rates of smoking and alcohol use than the general population, which likely contributes to the lower incidence of many cancers. The "healthy worker effect"-the tendency for actively working people to have fewer illnesses-may also play a role.
• Determining whether an exposure causes cancer requires multiple types of studies; For agencies that make these determinations, a single study alone is usually not enough.
• Findings from the Agricultural Health Study have been used by the International Agency for Research on Cancer (IARC) when deciding that eight pesticides should be classified as known or probable causes of cancer.
• While the AHS has identified several pesticides and other environmental exposures that were associated with a higher risk of cancer among highly exposed farmers, lifestyle factors such smoking cessation, healthy eating, and physical activity remain important for cancer prevention. More research is needed to understand how environmental exposures contribute to cancer risk.

The Iowa Cancer Registry remains committed to collecting complete, accurate cancer data and making those data available to researchers and public health professionals to support cancer prevention and control across the state. Its mission is to provide unbiased and evidence-based cancer information to educate the public.

The Iowa Cancer Registry is funded in part with federal funds from the National Cancer Institute, National Institutes of Health, and the Department of Health and Human Services under Contract No. HHSN261201800012I as well as by the University of Iowa and the State of Iowa.

FAQ

What is the purpose of the Cancer in Iowa Report?

The report provides annual estimates of cancer incidence, deaths, and survival in Iowa. Each year, it also highlights a special topic to help educate the public, such as a specific cancer type, a special population, or an important risk factor. New this year is a section on childhood, adolescent, and young adult cancers in Iowa.

Is the Iowa Cancer Registry a research organization?

No. The Iowa Cancer Registry is a statewide cancer surveillance system. It collects information on every cancer diagnosed among Iowa residents, as directed by the Iowa Administrative Code. Oncology Data Specialists abstract and verify cancer information from medical records. While the Registry does not conduct its own research, it provides high-quality data to researchers across the country, including those working on the Agricultural Health Study.

How are Iowa Cancer Registry data used to support cancer research?

The Registry collects detailed information on each cancer case, including tumor characteristics, stage at diagnosis, and the first course of treatment. Certified Oncology Data Specialists across Iowa send these data to the Registry, and researchers can request access for scientific studies following strict privacy and review procedures. The Registry also provides online tools the public can use to explore cancer trends.

Why was the Agricultural Health Study (AHS) the focus of the 2026 report?

Each year's report features a topic selected for its public health relevance and importance to cancer prevention and control in Iowa. Agricultural exposures-and their possible links to cancer-remain an important public health concern in our largely rural state. Because the Registry does not collect information on occupation or other risk factors, this year's report highlights the Agricultural Health Study, a decades-long project that uses Iowa Cancer Registry data to examine how agricultural exposures, including pesticides, may relate to cancer risk.

What is the Iowa Cancer Registry's role in the Agricultural Health Study?

The Registry provides cancer data for AHS participants living in Iowa. Through a data linkage process, researchers determine which study participants have been diagnosed with cancer and obtain standardized information about those diagnoses. This allows the Agricultural Health Study researchers to study potential links between agricultural exposures and cancer.

What is the difference between the Cancer in Iowa Report and the Cancer Drivers in Iowa Project?

The Cancer in Iowa Report is the Registry's annual summary of cancer incidence, mortality, and survival, with an educational section on a selected cancer topic. The Cancer Drivers in Iowa Project is a separate, multi-year research effort led by Iowa Health and Human Services and the University of Iowa College of Public Health. It uses Registry data to examine demographic, behavioral, genetic, and environmental factors that may contribute to Iowa's high cancer rates, focusing on several common cancer types.

Why don't cancer registries collect information about risk factors?

Cancer registries collect standardized information from medical records-such as cancer type, stage, and treatment-to ensure complete and accurate surveillance. Medical records typically do not include full or reliable information on personal risk factors like smoking, diet, or environmental exposures, and collecting this information would add substantial burden for hospitals. Instead, risk-factor data are gathered through national surveys and specialized research studies, which can be combined with cancer registry data to better understand cancer risks.