Iowa has the second-highest rate of cancer incidence in the United States, according to the Iowa Cancer Registry. The state is one of only a few in the country with a rising rate of new cancer cases. Many public health and environmental experts point to water quality as a leading cause of this public health crisis—a 2020 investigation by the Environmental Working Group found that Iowa has among the most widespread nitrate contamination of drinking water in the U.S.
“Something that is very difficult living in Iowa is this constant level of anxiety over the fact that you don’t know what kind of cancer you’re going to get,” says John Gilbert, a fourth-generation family farmer near Iowa Falls. “It’s in the back of your mind all the time that you’re living in dangerous times in a dangerous place.”
Nitrate pollution in Iowa’s water is largely due to overuse and misuse of artificial fertilizer and mismanagement of manure from confined animal feeding operations (CAFOs). Iowa is the leading hog producer in the United States, with more than one-third of the nation’s hogs, according to the Economic Research Service. More than 25 million hogs outnumber people in Iowa by a ratio of 7 to 1. And as the state’s pork production nearly doubled from 2000 to 2023, so did its manure production.
“CAFOs have more manure than the crops can reasonably use as fertilizer,” says Michael Schmidt, General Counsel at the nonprofit Iowa Environmental Council (IEC). While information on fertilizer and manure application is not publicly available, “we can assess at a large scale. We know there’s more manure than the crops need and know that synthetic fertilizers are being oversold.”
Almost half of Iowa’s cropland uses tile draining, which removes excess water from fields through a network of underground perforated pipes and releases it into drainage systems. This means that when fertilizer and manure are overapplied to farm fields, excess nutrients are fed straight into water systems. That contaminates drinking water for Iowa residents and fuels algae blooms and dead zones downstream in the Gulf of Mexico.
“Nobody wants to admit this is what’s happening. It’s a structural problem with the system,” says Gilbert. “We have created a situation where no matter what we wanted to do about nitrates in our drinking water, it’s not going to be an easy fix. It’s only getting worse because nobody is shutting down the confinements.”
Numerous studies link high nitrate levels to kidney, bladder, thyroid, and other cancers. Researchers at the Duke University School of Medicine found in 2018 that communities located near hog CAFOs had higher overall rates of infant mortality and mortality due to anemia, kidney disease, tuberculosis, and septicemia. In 2021, a study supported by the National Institutes of Health linked residential proximity to intensive animal agriculture to an elevated risk of non-Hodgkin lymphoma and leukemia.
Nitrate contamination is also an environmental justice issue. This year, an Iowa State University study reported that high nitrate levels in Iowa disproportionately affect low-income individuals, older adults, children, and people of color because these communities are more likely to be located near CAFOs.
Many organizations are advocating for change. The Iowa Farmers Union is pushing for a moratorium on new CAFOs built in the state, better working conditions for CAFO farmers, and protections for communities surrounding existing CAFOs, such as better waste management practices.
“We know CAFOs aren’t going away, but there are many ways to make it safer,” says Tommy Hexter, Policy Director at Iowa Farmers Union. “Unfortunately, what is in the best interest of the food industry is not always what is in the best interest of farmers’ health…and [farmers] don’t feel they can speak out without fear of retribution.”
IEC also advocates for higher standards for CAFOs, including stronger rules to prevent externalized pollution—both in the air and water—and education for hog farmers and pork consumers. But activists agree that changes to the U.S. Farm Bill, which expired in September 2025, are critical to address these complex challenges and public health impacts.
“Our current Farm Bill incentivizes a particular kind of farming, commodity farming, corn and soybeans,” says Hexter. “We know that farmers need certain tools in order to continue farming in the modern system, but we need to incentivize them to make these systems of farming safe.”
Hexter thinks Iowa can help alleviate the public health impact of industrialized farming by strengthening regional food systems and supporting small-scale farms, local food purchasing programs, and local food markets.
“One of the biggest sayings you’ll hear in Iowa is ‘we are feeding the world.’ I don’t think that Iowa needs to feed the world anymore–it’s done more harm than good,” says Hexter. “We can regionalize again, with robust networks of food hubs and farmers working at multiple scales.”
Gilbert himself represents this vision for a more balanced food system: Since the 1990s, he has raised hogs with Niman Ranch, a network of more than 600 small to mid-sized, independent U.S. family farmers and ranchers. Gilbert and his peers uphold high standards of sustainable and humane farming practices in exchange for a stable, premium market for their hogs. In other words, they have the financial stability to produce fewer hogs in a way that is healthy for animals, the environment, and consumers, strengthening regional food systems and promoting more sustainable nutrient management.
Gilbert says that communities across the U.S.—not only in Iowa—should advocate for agricultural policies that incentivize this way of farming. More sustainable practices can promote soil health and, in turn, environmental and human health.
“Confinements are just one part of the structural problems we have in Iowa and the country altogether,” says Gilbert. “People don’t understand the direct link between our farm policy in Washington, D.C., and the health of the soil.”
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Photo courtesy of Don McCulley, Wikimedia Commons
