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.

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.

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.

Meat processors use nitrates to cure ham, bacon and other foods. That important process increases the shelf life of products and reduces the transmission of foodborne pathogens, said Jeffrey Sindelar, a University of Wisconsin-Madison animal science professor and extension meat specialist.

“The excess and the stuff that isn’t used is typically run down into a drain,” he said.

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

Jоe Fеrrеr, Jаcоb Boomsmа, J. McCоrmіck, and Coburn Dukehart

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