Mississippi River Groups Tell Feds to Act on Nitrate Contamination

UPPER MIDWEST—Conservation groups up and down the Mississippi River are among a broad coalition urging the federal government to take action against nitrate contamination in drinking water, which they say has reached “crisis levels” and is a public health emergency. Minnesotans—who have been making that argument for residents in Southeast Minnesota’s karst region—are among them.

Nitrate, which forms when nitrogen-rich sources combine with oxygen, has long been found in the country’s surface waters and groundwater, where it can end up in people’s drinking water. Consuming water with elevated levels of nitrate is linked to birth defects, thyroid problems and some cancers.

While agricultural fertilizer and manure are identified as the most common sources of nitrogen to groundwater, residential septic systems and lawn fertilizers also contribute. And while the emphasis has been on concerns related to rural living, it’s not just an issue for rural families.

An April analysis from the Environmental Working Group found that about 18% of the U.S. population from 2021 to 2023 used drinking water from community systems with 3 milligrams per liter (mg/L) or more of nitrate, the threshold at which the Environmental Protection Agency says indicates contamination.

Advocates say nitrate contamination has struggled to capture public attention but is costly and hazardous to those it affects. 

There are more than 10,000 sinkholes in Fillmore County’s karst topography making groundwater susceptible to surface runoff. Above, spring runoff in March 2023 near Harmony. (Root River Current archives)

A May 5, 2026 letter to the Department of Health and Human Services and the EPA was signed by 80-plus groups, about a third of which are located in or focused on the Mississippi River basin. It calls on the agencies to “immediately identify and eliminate sources of nitrate pollution in drinking water and provide funds to communities to reduce nitrate to safe levels.” 

Among the petitioners are the League of Women Voters of Minnesota; the Minnesota Center for Environmental Advocacy (a group advocating for efforts to address issues in Southeast Minnesota); and the neighboring Iowa Environmental Council (one of several groups seeking emergency action to protect citizens in the karst areas of Northeast Iowa).

The May 5 letter, Nitrate Contamination in U.S. Drinking Water–Urgent Call for Action, cites a recent report from the Iowa Environmental Council and the Harkin Institute at Drake University in Des Moines that found high nitrate levels in drinking water, as well as the presence of pesticides and forever chemicals, are linked to rising cancer rates in Iowa. While not exclusive to Iowa, intensive farming across the state, including corn, soy and hogs, is the dominant source of nitrate pollution, the report notes.

“We understand these are long-term problems,” said Tyler Lobdell, senior attorney at Food & Water Watch, which spearheaded the letter. “The longer we wait to address root causes, the more difficult, and more expensive [it is], and the more harm is caused in the long run.”

The Department of Health and Human Services did not respond to a request for comment on the letter prior to publication. A spokesperson for the EPA said it is beginning the next round of review of national drinking water regulations, which was last published in 2024.

Peering into a forming sinkhole—a direct route for lawn and farmland nitrates to enter the groundwater. A larger, established sinkhole is surrounded by trees in the background. (Photo by Nancy North)

Too much nitrogen taints drinking water, hurts river ecosystem

Nitrate contamination is a widespread problem across the country, especially in the Corn Belt, but actions to address it have been slow-going.

Groups in multiple states, including Minnesota, Iowa and Wisconsin, have previously petitioned the EPA to take emergency action on nitrate problems in specific regions. Lobdell said the agency has either ignored or given an insufficient response to those petitions, dating back several years and multiple presidential administrations.

Under former President Joe Biden, the EPA restarted an assessment—which had been suspended during the first Trump administration—of the impacts of nitrate on human health. Environmental advocates had hoped that it could lead to an adjustment of the national standard for nitrate in drinking water, which currently sits at 10 mg/L, because some research shows impacts to human health below that level. Little progress has been made on the assessment.

Beyond human health impacts, too much nitrogen in surface water can drive excessive algae growth, causing harm to fish and other aquatic life. It’s one culprit, in addition to phosphorus, in the creation of the Gulf of Mexico’s “dead zone,” an area of low oxygen that spans thousands of square miles from the mouth of the Mississippi River.

It’s not just drinking water that’s in jeopardy—surface water filled with too much nitrogen and phosphorus from fertilizers can kill fish and contribute to toxic blooms, like the algae covering a large portion of this spring-fed lake along the Mississippi River near Trempealeau, Wisconsin.  (Photo by: Mike De Sisti, Milwaukee Journal Sentinel)

Kelly McGinnis, executive director of the environmental advocacy organization One Mississippi, a signatory on the letter, said humans aren’t separate from the environment and that addressing nitrate contamination would have positive impacts on both.

She said she hopes the letter catches the attention of Health and Human Services Secretary Robert F. Kennedy Jr., who has pledged to “Make America Healthy Again” and has shown interest in reducing toxins in people’s diets.

“We felt the urgency right now to take advantage of the new [Iowa] research to say, ‘Hey, this is something you guys need to be addressing,'” McGinnis said.

The spokesperson for the EPA said the agency is “committed to Making America Healthy Again by taking real, tangible steps to evaluate risks of nitrates in drinking water while following the law and gold standard science.”

This story was edited for Root River Current by John Gaddo.

This story is a product of the Mississippi River Basin Ag & Water Desk, an independent reporting network based at the University of Missouri in partnership with Report for America, with major funding from the Walton Family Foundation.