2 nd
~ 6000
70M
100 %
A rising cancer rate demands attention
In 2025, data from the Iowa Cancer Registry confirmed that Iowa has the second highest age-adjusted rate of new cancers diagnosed in the United States, and is one of only two states where that rate is increasing. Cancers of the breast, prostate, lung, and skin are the primary drivers of the state's rising incidence. With a population of 3.2 million, approximately 6,000 Iowans could die from cancer in a given year.
While behavioral factors such as diet, lack of exercise, UV exposure, smoking, and alcohol consumption are well-established risk factors, researchers have identified additional environmental factors in Iowa that may be contributing to these exceptional rates.
Arsenic and radon: threats beneath the surface
Iowa's underlying geology contains naturally occurring cancer-causing agents that pose distinct risks to residents across the state.
Arsenic in groundwater
A colorless, odorless substance found in Iowa's groundwater that is linked to increased risk of skin, bladder, and lung cancer. Public water systems are regulated under the Safe Drinking Water Act, but private well owners should contact their local health department to have their water tested.
Radon gas
A naturally occurring gas from uranium decay present in air, water, and soil. Radon is the second leading cause of lung cancer nationally, and risk increases with exposure level and time spent in the home. The EPA classifies the entire state of Iowa as high-risk, and the Iowa DHHS recommends testing every two years or after any home renovation.
Farming, pesticides and cancer risk
Iowa's extensive agricultural land use brings unique exposure concerns. The Agricultural Health Study has monitored the health of farmers and their families across Iowa and North Carolina since 1993, producing valuable data on how agricultural chemicals, lifestyle, and genetic factors affect health.
Based on available data from the United States Geological Survey, Iowa farmers applied up to 70 million pounds of 150 different pesticides in 2018 alone. Atrazine — a widely used corn herbicide — was previously considered to have insufficient evidence of cancer risk for humans. Long considered unclassifiable as a carcinogen, atrazine was reclassified by the International Agency for Research on Cancer in November 2025 as "probably carcinogenic to humans," based in part on a landmark 2024 study of over 53,000 pesticide applicators that found suggestive associations with lung cancer, non-Hodgkin lymphoma, as well as risks for prostate cancer, soft-tissue sarcoma, and pharyngeal and kidney cancers. More than 60 countries have banned atrazine, which is also a suspected endocrine disrupting compound. In the United States, the EPA reapproved atrazine for continued use in October 2025, and maintains that the herbicide does not pose a cancer risk at current exposure levels. The case of atrazine demonstrates how our understanding of chemical risk can change as new information becomes available and illustrates why there is need for ongoing monitoring and research even for chemicals that are approved for use.
Beyond the farm: Community-level risk
A 2020 study using Agricultural Health Study data found a link between residential proximity to intensive animal agriculture operations and elevated risk of non-Hodgkin lymphoma and leukemia. This finding suggests that Iowa's high concentration of animal feeding operations may be a risk factor that extends beyond farming populations and into nearby communities.
For pesticides, individuals who regularly handle and apply these chemicals are likely at the greatest risk due to frequent contact over time, compared to those not directly involved in their use. However, further research is needed to characterize risks across both direct and indirect exposure groups, with the greatest uncertainty surrounding individuals not directly engaged in pesticide application.
Nitrate in drinking water: a growing concern below the regulatory standard
Many Iowans are concerned about high levels of nitrate in their drinking water, which comes primarily from agricultural runoff and wastewater discharges. While the EPA regulates nitrate at 10 milligrams per liter to protect infants from methemoglobinemia ("blue baby syndrome"), a growing body of scientific evidence — including work by CHEEC at the University of Iowa — has found strong connections between nitrate and multiple cancers at levels well below the current standard.
These include bladder, ovarian, and thyroid cancers as well as thyroid disease and neural tube defects. In 2010, the EPA acknowledged the need for a new health assessment of nitrate that could lead to a more protective standard, but this assessment has not yet been completed.
Is the drinking water standard for nitrate sufficiently protective?
A growing body of research suggests that the risk of certain forms of cancer may be increased through exposure to nitrate in drinking water, even at levels below the current Safe Drinking Water Act standard of 10 mg/L (as nitrogen). This has caused many to question whether the current drinking water standard is sufficiently protective of public health while also raising doubt among consumers about the safety of their drinking water even when it’s fully compliant with standards under the Safe Drinking Water Act.
Stalled regulatory review
In 2010, the US EPA acknowledged the need for a new evaluation of available science to determine whether nitrate in drinking water increases the risk of certain forms of cancer, the outcome of which would help to determine if a stricter drinking water standard was necessary. Unfortunately, this new health assessment has not yet been completed. Meanwhile, the available evidence continues to grow and evolve, and there remains a need for well-designed research studies to better understand these associations, inform new risk assessment and guide future policy decisions.
What you can do
There is no need to wait for more definitive proof. Given the state's naturally occurring risk factors and the suggestive evidence from research on agricultural exposures, there are concrete steps Iowans can take now to reduce environmental risks.
Test your home
Have your drinking water and indoor air tested for radon, nitrate, arsenic, and other contaminants. Your local water provider, county public health office, or the State Hygienic Laboratory of Iowa can help with testing options and available resources.
Install mitigation technologies
Reverse osmosis systems can remove nitrates, arsenic, and PFAS ("forever chemicals") from drinking water, while radon mitigation systems reduce gas exposure. Always work with a trained technician and purchase certified technologies to ensure you get the right solution.
Check alternative water sources
If you switch to bottled water due to nitrate concerns, ensure that the source is actually low in nitrate — not all alternatives are equally safe.
Advocate for Policy Solutions
Neighboring states like Nebraska have provided funding for private well owners to acquire reverse osmosis systems and commissioned studies to address nitrate-affected water. Iowa could pursue similar programs along with expanded statewide environmental monitoring, especially for emerging threats like PFAS.
Educational videos
An overview of Iowa's rising cancer rates, key environmental risk factors, and steps residents can take to reduce exposure, available in English and Spanish.
Cancer Incidence in Iowa
An overview of Iowa's rising cancer rates, environmental risk factors from arsenic and radon to agricultural chemicals and nitrate in drinking water, and what Iowans can do to reduce their exposure.
Incidencia del Cáncer en Iowa
Una presentación sobre las tasas crecientes de cáncer en Iowa, los factores de riesgo ambientales — desde el arsénico y el radón hasta los químicos agrícolas y el nitrato en el agua potable — y lo que los habitantes de Iowa pueden hacer para reducir su exposición.