Agricultural operations across Iowa are a leading cause of significant water pollution problems in the state, posing dire risks to public and environmental health, according to a new scientific report that is sparking heated debate in the key US farm state.

The 227-page “Central Iowa Source Water Research Assessment” (CISWRA) was formally released by Polk County, Iowa, officials on July 1 after months of what multiple sources said were intentional actions by public officials to suppress details of the report.

The report caps a two-year-long research review by a team of 16 scientists that focused on pollution patterns in two “essential” rivers fed from a watershed running from southern Minnesota through the central part of Iowa to the state capital of Des Moines.

Those rivers, the Des Moines and the Raccoon, are the primary source of drinking water for roughly 600,000 people and are considered important recreational state assets, but the rivers are commonly laden with harmful contaminants that include phosphorus and nitrogen, bacteria from animal and human waste, pesticides and other chemicals.

Much, though not all, of the contamination is tied to agriculture, according to the report. Among multiple recommendations, the report calls for the top US corn-growing state to diversify into production of crops that require fewer chemical inputs, and for limits on the density of livestock.

With nearly 87,000 farms, Iowa ranks first not only for corn production but also for pork and egg production, and is within the top five states for growing soybeans and raising cattle. Agriculture is a key engine for the state’s economy.

“A huge public health threat”
Environmentalists and some public officials welcomed the report, which they see as a data-driven catalyst for an overhaul in policies that could improve water quality and environmental and human health. But they say they fear Iowa’s longstanding political allegiance to agricultural interests will continue to thwart such efforts.

“There is a huge public health threat,” said Polk County Administrator John Norris, who helped initiate the study. Polk County, which has its county seat in Des Moines and is the state’s most populous county, provided funding to the study.

“It affects business and the economy too. This report tells us exactly where the problem is coming from,” Norris said. “Now it is up to us to have the courage to tackle it.”

Norris was placed on paid leave of absence earlier this year after battling with the county’s board of supervisors. He would not comment about why he was forced out but said the farm industry holds significant power in Iowa, and nationally.

“There are huge institutional forces in our way. They have been in charge of agricultural policy for a long time,” he said.

Iowa has the second-highest rate of cancer in the nation, and is only one of two US states where cancer is increasing. Leukemia, as well as cancers of the pancreas, breast, stomach, kidney, thyroid and uterus, are among the different cancer types on the rise across the state, according to the National Cancer Institute.

Agricultural pollution is among the factors suspected of causing the high cancer rates. Separate from the water pollution study, an initiative to study the relationship between environmental risk factors and cancer rates is underway, led by the Iowa Environmental Council and the Harkin Institute at Drake University.

In a Polk County Board of Supervisors meeting Tuesday, several people spoke out about what they said was a history of political unwillingness to address mounting problems with agricultural pollution, and called for public officials to take the findings of the new report seriously.

“If we can move the terms of the debate away from politics and onto science, I have no doubt that there are policies and practices that are proven to work in other places that can work in Iowa too,” said Mike Tramontina, a member of the executive committee of the Sierra Club in Iowa. “It doesn’t have to be this way. Our rivers can be cleaned up.”

Chief concerns
Among the chief concerns are nitrogen and phosphorus present in the waterways at levels that are among the highest in the nation, according to the report. Fully 80% of the nitrogen and phosphorus in central Iowa stem from agricultural sources, including from corn growers who consider nitrogen a key tool for boosting yields.

Levels of nitrates, a form of nitrogen, have been so high recently in the key Iowa rivers that public health officials have banned about 600,000 businesses and homeowners from watering lawns to limit demands on utility operations seeking to filter the nitrates from drinking water.

Even as the report was being released, nitrate levels recorded this week in Iowa waterways were well above the federal limit of 10 milligrams per liter for drinking water. Some areas were showing levels at more than double the limit.

When pregnant women are exposed to nitrates in drinking water, it raises the risks of problematic birth outcomes, including low birth weights and pre-term birth. Babies can suffer severe health problems when consuming nitrates in drinking water, and a growing body of literature indicates potential associations that include an increased risk of cancer.

Farmer use of weed killers and other pesticides is also a contributor to the water pollution problems, posing risks to the environment and to public health as pesticides are often found in surface water during spring and early summer.

“Due to their extensive use, pesticides are contaminants of significant concern for Iowa,” the report states.

Pesticide use in the state has increased over the last few decades, with glyphosate herbicide ranking as Iowa’s most widely used pesticide applied through traditional spraying, followed by acetochlor and atrazine, according to the report. Neonicotinoid pesticides are also prevalent in Iowa, used as seed coatings on most corn and soybean seeds planted in the state, the report said. Each of the pesticides is linked in scientific research to human and/or environmental harms.

Another significant threat is seen in the large amounts of manure generated from Iowa’s expansive livestock operations, also known as Concentrated Animal Feeding Operations, or CAFOs. The manure is often spread onto fields as fertilizer but surplus manure leaches into waterways, along with pathogens and pharmaceuticals that can be present in animal waste.

“In parts of the watersheds, manure produced exceeds the capacity of surrounding lands to absorb it as fertilizer. This surplus manure becomes waste, contributing to the contamination of surface and groundwater,” the report states. “The amount of nitrogen excreted on a statewide basis is 800,000 tons annually, which is approximately 50 times the amount excreted by humans in Iowa.”

The agricultural pollution, as well as other pollution sources, have been triggering increasing algal blooms in central Iowa’s waterways, the report notes. Certain algal blooms produce toxins that can harm fish and other aquatic life, humans and animals. One such type of toxin, microcystin, has been found throughout the watershed for the last 20 years.

Microcystin is a “potent liver toxin and possible human carcinogen,” according to the US Environmental Protection Agency.

Also of concern – both antibiotics and antibiotic-resistant bacteria have been found in Iowa’s waterways, the report notes.

A “water quality disaster”
The report makes a number of specific recommendations, including advancing regenerative agricultural practices, reducing pesticide use, better management of manure disposal, improved erosion control, and development of dual water delivery systems to increase the capacity of utilities to treat nitrate contamination in drinking water supplies.

“We need everyone to make improvements on the land they own, whether on the farm or in the city,” said Claire Hruby, an assistant professor of environmental science and sustainability at Drake University and one of the science advisors for the report. “And we need everyone who votes to hold our legislature accountable to make sure that long-term public health and the economic well-being of our communities is a priority.”

Larry Weber, another science advisor on the report and director of the IIHR-Hydroscience and Engineering research center at the University of Iowa, said the findings of the report demonstrate that “we are on the verge of an environmental water quality disaster in this state.”

Still, he said he has little hope that the recommendations in the report will be followed, noting that Iowa lawmakers have cut funding for a monitoring network focused on reducing nutrient loss and water pollution. The monitoring network is now supported by private foundation funding, but that money will run out next year.

“Agriculture is such a dominant force,” he said. “I think industry and politics will prevail.”

www.thenewlede.org/2025/07/iowa-farm-water-pollution-report/