Iowa livestock boom outpaces oversight as manure pollution grows, analysis finds

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The number of large, concentrated animal feeding operations (CAFOs) in Iowa increased 13% over the past six years, according to a new report. It’s a mounting problem in a state that generates more than 100 million tons of manure annually, contributing to persistent water pollution and health problems.

The report, a mapping project from the Environmental Working Group (EWG), finds that Iowa has roughly 15,309 livestock farms that generate 107 million tons of manure each year — but more than one in four of the farms remain unmonitored by the state. A widely cited previous estimate of manure from Iowa’s largest farms using 2022 US Department of Agriculture data put the total at 55 million tons annually. However, EWG’s estimate included manure from smaller farms and as well as the increase in farms since the previous estimate, said Anne Schechinger, senior director for agriculture and climate research at EWG and co-author of the analysis. 

Schechinger believes the report’s findings are significant because Iowa has been grappling with water quality issues and disproportionately high cancer rates, the second highest in the country. 

“We know that nitrogen is in manure, Iowa has really serious nitrate issues in drinking water, and nitrate increases the risk of cancer,” she said.

Using aerial and satellite data to map out the facilities, Schechinger and colleague Ethan Bahe, a senior GIS analyst at EWG, also found that the largest CAFO farms — those holding 1,000 or more animal units — increased from 3,936 to 4,444 farms from 2019 to 2025. Animal units are used by regulators to convert animals into equivalent units. While 1,000 animal units equals 1,000 beef cattle, for hogs, 2,500 animals would equal 1,000 animal units. 

Those CAFOs, the majority of which are hog farms, account for 29% of Iowa’s animal farms but 60% of its manure. 

Chris Jones, a Democrat running for Iowa Secretary of Agriculture, said he was somewhat surprised to see how much the hog CAFO number has grown over the past few years, especially as he’s increasingly seen “more concern and dissatisfaction” with pollution from large farms. 

“There are people in agriculture that would agree with that, there are people in Republican politics that would agree with that,” said Jones, an author and retired University of Iowa researcher who spent much of his career monitoring and studying water quality in the state. 

“People are really feeling like this system that we have here in place when it comes to CAFOs is not delivering beneficial outcomes for everyone,” he said. 

Pollution and cancer rates 

The report comes as several waterways in the state continue to have elevated levels of nitrates, a cancer-causing byproduct of manure or some fertilizers being discharged or washing out into rivers and streams. A separate EWG report in April found 146 community water systems in Iowa had elevated levels of nitrate at least once between 2021 and 2023. Iowa’s Des Moines and Raccoon rivers are in the top 1% of rivers nationwide for nitrate concentration with 80% of the contamination coming from agriculture. 

Just last month, Central Iowa Water Works (CIWW) put water restrictions in place for hundreds of thousands of customers when the utility could not keep up with elevated nitrate levels in the water. 

“Conditions have reached a point where mandatory conservation is necessary to protect reliable water service for more than 600,000 people across central Iowa,” said CIWW Executive Director Tami Madsen in a statement.

In addition, Iowa continues to struggle with elevated cancer rates that are driven, at least in part, by nitrates from CAFOs, according to researchers. Iowa has the second-highest rate of cancer in the nation and is only one of three states where cancer is rising, according to the National Institutes of Health.

For many types of cancer, the state’s numbers dwarf national averages. For example, Iowa’s rate of prostate cancer is 129 people per 100,000, compared to the US average of 116 people. The state’s breast cancer rate is 137 people per 100,000, compared to the US average of 131 people. The state’s overall cancer rate is 498 people per 100,000 — 10% higher than the national rate.  

“It’s not just the fact that phosphorus from manure is creating algae blooms, which is really bad for recreation, but this manure is a problem that’s contributing to Iowa’s status as a high cancer risk state,” Schechinger said. 

Some experts say there is a clear disconnect between public anxiety over Iowa’s rising cancer rates and the actions of state policymakers. “That concern is obviously not being matched by state government and regulatory agencies,” said Silvia Secchi, a researcher and professor at the University of Iowa who studies the environmental impacts of agriculture.

“These are not outsiders or environmentalists wanting answers about CAFOs, these are people who live there who cannot open their windows … people who see their property values decline because they’re next to these operations,” she said. “These are members of the community suffering and not being afforded the kind of protections they should be.” 

County level oversight 

The EWG analysis found 3,276 livestock operations in Iowa have between 950 and 999 animal units, which puts them just under the 1,000 animal-unit threshold that requires National Pollutant Discharge Elimination System (NPDES) federal water permits and manure management plans. 

“Some of these facilities are so close to each other and that proximity is so important on the water quality side,” Bahe said. “If you have two facilities that are just under the large (1,000 animal unit) designation, but they’re considered separate facilities, they don’t need NPDES permits.” 

NPDES permits are issued by state regulatory agencies, and each state varies in its CAFO NPDES permitting. Iowa has issued NPDES permits for about 4% of the large CAFO facilities, according to federal estimates. 

Researchers and advocates have for decades said that Iowa regulators are vastly undercounting and inadequately regulating CAFOs, Secchi explained. In 2013 the state entered into an agreement with the US Environmental Protection Agency (EPA) that, in part, required the state’s Department of Natural Resources, which regulates CAFO pollution, to conduct a statewide survey of CAFOs. In 2017, the state reported back that satellite imagery showed 5,000 additional operations that were previously undetected and unregulated. 

“This new report tells me that they still have not learned any lessons,” Secchi said. “This is why we have so many CAFOs in Iowa, because the DNR is not doing their job.”

“This new report tells me that they still have not learned any lessons. This is why we have so many CAFOs in Iowa, because the DNR is not doing their job.” – Silvia Secchi, University of Iowa

The Iowa DNR did not return requests for comment on CAFO regulation and permitting. 

Jones said the lax enforcement is likely not a “deliberate omission,” by the DNR, but rather “that there just aren’t enough resources within the DNR to track these facilities effectively.” 

Schechinger said one policy to address this is for Iowa to shift decision-making and regulation of CAFOs and other livestock farms to the county level. 

“Right now, any facility that has over 500 animal units in the state has to have a manure management plan, but the number of inspections done by Iowa DNR for those facilities is very small,” she said. “If the regulation went to the counties, you would actually be seeing more inspections, more checking of those manure management plans, and more enforcement.” 

“That’s one idea that I think would have bipartisan support and could make a big difference for the water quality issue,” she added. 

Jones agreed. “We absolutely need the counties to have authority over the zoning for these things for new construction, and to have some authority over expansion of existing facilities,” he said.

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