An upstream view of the Mississippi River is seen from a bridge in La Crosse, Wis., on July 21, 2022. Regulated industries released about 94.5 million pounds of nitrates into the Mississippi River basin in 2020, an analysis shows. (Coburn Dukehart / Wisconsin Watch)
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This story is a product of the Mississippi River Basin Ag & Water Desk, an editorially independent reporting network based at the University of Missouri School of Journalism in partnership with Report For America and funded by the Walton Family Foundation. Wisconsin Watch is a member of the network. Sign up for our newsletter and donate to support our fact-checked journalism.

Editor’s note: A previous version of this story included incorrect 2020 chemical discharge figures from NextEra Energy’s Point Beach Nuclear Plant after the company erred in its reporting to the U.S. Environmental Protection Agency. NextEra submitted a correction to the EPA, reporting that it discharged 326 pounds of hydrazine in 2020 rather than 15,007 pounds, a company spokesperson said. Wisconsin Watch has removed an information box that previously reported a calculation based upon the incorrect figure. 

Nitrate compounds were the top toxic substances released into U.S. waterways in 2020, including the Mississippi River, according to a recent study conducted by an environmental policy and advocacy group.

Industries — primarily petroleum refineries and meat and poultry processing facilities — discharged more than 175 million pounds of nitrates that year, comprising 91% of all toxic chemicals released by weight in the U.S., according to the report’s analysis of federal data.

The findings pose particular relevance to the Mississippi River basin, which drains a 31-state watershed and conveys nitrates and other chemicals to the Gulf of Mexico. Nitrates encourage algae blooms, which contribute to the gulf’s hypoxic “dead zone,” where oxygen-poor waters suffocate marine wildlife.

“We have huge flows of toxic pollution into our waterways across the country,” said John Rumpler, senior director of the Environment America Research and Policy Center’s clean water program, who co-authored the report along with researchers from the Frontier Group and U.S. Public Interest Research Group Education Fund.

Released in late September, the report analyzed data collected in the U.S. Environmental Protection Agency’s Toxics Release Inventory. The agency requires certain industries to report toxic releases. That does not include runoff from farm fields and animal feeding operations, which is most typically associated with nitrate pollution, meaning that the report includes only a portion of toxic releases.

What is nitrate?

Nitrate is a naturally occurring nutrient found in food and human and animal waste.  But exposure can pose health hazards to babies and pregnant women, and nitrate is one of the most common groundwater contaminants in some states. Some studies suggest that it contaminates at least 10% of wells in Wisconsin, for instance. People who consume water high in nitrate face increased risk of colon, kidney and stomach cancers and thyroid disease. It also is associated with birth defects.

The Environment America report spotlights the vast flows of toxic compounds into the country’s waterways, even under the 1972 Clean Water Act. The landmark legislation sought to make most waterways fishable and swimmable by 1983, while eliminating toxic discharges into navigable waters by 1985. 

The Clean Water Act requires states, territories and tribal governments to develop standards to protect water bodies within their borders based upon designated uses, like recreating, protecting wildlife or providing public drinking water. Waterways that fail to satisfy those standards become subject to a restoration plan, which limits daily discharges of pollutants.

Polluters must comply with those limits until the water body can support its designated uses.

The law has increased the number of fishable waters across the U.S., but about half of U.S. water bodies remain impaired. Toxic substances continue to enter U.S. waterways in large volumes, hindering restoration efforts, the new report illustrates.

This map quantifies reported toxic releases to watersheds nationwide in 2020. (Courtesy of Environment America)

Regulated industries released about 94.5 million pounds of nitrates into the Mississippi River basin in 2020, accounting for nearly half of all reported toxic releases nationwide. More than 30 million pounds of that total originated in slaughterhouses and meat processing industries.

Nitrates and closely associated nitrites are utilized in meat curing, an important process that increases the shelf life of meat products and reduces the transmission of foodborne pathogens.

“Things like hams and bacons, those actually use a solution of nitrite,” said University of Wisconsin-Madison animal science professor Jeffrey Sindelar. “And they would be injected or marinated…The excess and the stuff that isn’t used is typically run down into a drain, and it’s diluted with all the other water and there are U.S. Department of Agriculture regulations to ensure that the levels of ingredients are not creating imbalance in the waste stream.”

Reporting loopholes

Some discharges of nitrates and other chemicals go unreported because of certain industry exemptions from EPA reporting requirements, the September study notes. Likewise, not all toxic substances must be reported, and the EPA exempts reporting for facilities with fewer than 10 employees.

In addition to closing reporting loopholes, the EPA could update permitting standards to reflect current pollution control technology, Rumpler said, to the benefit of public and environmental health.

“State and local and federal officials have the tools,” he said. “Now it just takes the political will to implement those tools as the Clean Water Act intends.”

In an emailed statement, an EPA spokesperson said that the agency is considering updates to pollution standards that would apply to meat and poultry processing plants, power plants and industrial dischargers of PFAS chemicals.

The EPA is pursuing a rule to remove a reporting exemption for low concentrations of perfluoroalkyl and polyfluoroalkyl substances, or PFAS, which have been linked to a range of health problems. President Donald Trump’s administration allowed PFAS releases to qualify for a “de minimis exemption,” which excuses polluters from documenting discharges of toxic chemicals comprising less than 1% of a mixture — or .1% for carcinogens. The EPA is moving to rescind that loophole eligibility, the spokesperson said. 

Bennet Goldstein covers water quality and other environmental issues for Wisconsin Watch and the Mississippi River Basin Ag & Water Desk, a consortium of 10 news organizations. He is a corps member with Report for America, a national service program that places journalists into local newsrooms. The nonprofit Wisconsin Watch (www.WisconsinWatch.org) collaborates with WPR, PBS Wisconsin, other news media and the University of Wisconsin-Madison School of Journalism and Mass Communication. All works created, published, posted or disseminated by Wisconsin Watch do not necessarily reflect the views or opinions of UW-Madison or any of its affiliates necessarily reflect the views or opinions of UW-Madison or any of its affiliates.

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Bennet Goldstein / Wisconsin WatchInvestigative Reporter

Bennet Goldstein reports on water and agriculture as Wisconsin Watch’s Report for America representative on the Mississippi River Basin Ag & Water Desk — a collaborative reporting network across the Basin. Before this, Goldstein was on the breaking news team at the Omaha World-Herald in Nebraska. He has spent most of his career at daily papers in Iowa, including the Dubuque Telegraph Herald. Goldstein’s work has garnered awards, including the Associated Press Media Editors award for an explanatory feature about a police shooting in rural Wisconsin, and an Iowa Newspaper Association award for a series that detailed the impacts of the loss of social safety net programs on Dubuque’s Marshallese community. He holds a master’s degree from the University of Wisconsin-Madison.