Minnesota has spent hundreds of millions of dollars and decades of effort to reduce nitrate that's contaminating drinking water and rivers. The progress so far: negligible.

The main source of the nitrate is nitrogen fertilizer, a pillar of production agriculture that includes animal manure and synthetic chemicals. Farmers apply tens of thousands of tons of fertilizers to their fields every year, and what isn't absorbed by crops can seep into aquifers and any runoff can end up in rivers.

Despite numerous programs designed to encourage farmers to change their ways, purchases of fertilizer keep growing. In many parts of Minnesota farm country, drinking water wells and streams carry that legacy: A decades-old state law limits how much nitrate is allowed in drinking water, although some researchers now say that level needs to be much stricter to protect people.

The three agencies tasked with keeping Minnesota waters clear of harmful levels of nitrate acknowledge that the situation isn't improving, particularly for private wells in the vulnerable topography of the state's hilly southeastern corner. In that region, frustrated residents have called for the federal government to intervene on what environmental groups call a public health emergency — and the EPA recently responded with a directive that Minnesota clean up its act.

A lack of progress

Nitrate levels of 10 milligrams per liter of water or higher have violated federal health standards since the 1960s, since those concentrations are known to cause the potentially life-threatening condition methemoglobinemia, or blue baby syndrome, that starves infants of oxygen.

But there's a push to reduce the state and federal nitrate standard from the 10 mg/l limit, given growing research around links to cancer and other damaging health impacts from drinking water with nitrate at half the legal maximum concentration, or even lower.

Community drinking water supplies, which serve cities, towns and mobile home parks, are regularly tested to assure nitrate levels are below the state and federal health limit.

While those with the highest nitrate concentrations have taken action to reduce it, about 177,000 Minnesotans still lived in communities with average readings above 3 milligrams of nitrate per liter of water as of 2022, levels considered by health authorities to be caused by human activity, not nature.

 

At least 400,000 Minnesotans in more than 100 communities live in areas where water has tested at least once for elevated nitrate levels since 2013. They're mostly spread across central and southern parts of the state.

 

Separately, there are some 980,000 private wells in Minnesota, according to the Minnesota Well Owners Organization. And people who rely on them for drinking water are on their own to have them tested and, if necessary, find remedies.

Far more Minnesotans could be affected by elevated nitrate levels in their water, but a lack of one central testing agency means it is difficult to gather and compare data.

The volunteer private well tests the Department of Agriculture has helped run show the problem is widespread. In southeast Minnesota from 2008 through 2018, about 8% to 15% of the hundreds of private wells tested each year showed nitrate pollution above the 10 mg/L health limit. In 2021, about 30% of those private wells showed results above 3 milligrams.

In the 14-county Central Sands Region from 2011-2018, about 3% to 5% of the hundreds of private wells tested each year were polluted with nitrate above the 10 mg/L limit.

 

Public drinking water systems — not private wells — that violate federal nitrate contamination standards must report them to the EPA. Those violations in Minnesota totaled 34 last year in the EPA's Safe Drinking Water Information System and included gas stations, bars and churches.

Impaired rivers and streams

Nitrate also endangers fish and other aquatic life when it leaches into lakes, streams and rivers.

The nitrate entering the Mississippi River contributes to the huge oxygen-starved dead zone in the Gulf of Mexico. As part of the Hypoxia Task Force of states up and down the river, Minnesota has pledged to cut the nitrate in the Mississippi by 20% by 2025. But nitrate has actually risen in spots, as it has in most of the state's major rivers.

Lawmakers directed the Minnesota Pollution Control Agency in 2010 to set limits on nitrate to protect fish and aquatic life. It hasn't happened. It would be too expensive for small wastewater treatment plants, and wouldn't effectively reduce the nitrate from the farms it has no power to regulate, the agency told the Star Tribune.

About 5% — or 165 miles — of Minnesota's rivers and streams used for drinking water are impaired by nitrogen and/or phosphorus as of 2022, meaning they don't meet federal quality standards. In all, the EPA lists more than 300 bodies of water across the state including parts of the Minnesota, Mississippi and St. Croix rivers, as well as other streams and rivers, as threatened or impaired by nitrogen and phosphorus and in need of a restoration plan.

 

Spending with little impact

Hundreds of millions in federal and state funding has paid for nitrate research, efforts to change farming and other practices and nitrate filtration systems for water supplies in Hastings, Cold Spring, Adrian and four other cities.

That's paid for Nitrogen Smart farmer training in the past, water research, conservation programs, source water protection work and guidance for farmers on adopting best management practices — and that's just a few examples. The state covers this list in its five year progress reports on the state's 2014 Nutrient Reduction Strategy to cut nitrogen and phosphorus in waters.

The state's Clean Water Fund, part of the sales-tax funded Legacy Amendment, has directed at least $148 million to the nitrate problem since 2010, according to a Star Tribune analysis, and is just one of several spending sources.

None of it appears to have made a dent in the overall demand for nitrogen fertilizer. As cropland has expanded, farmers bought a record high 824,000 tons of nitrogen fertilizer in 2020, the most recent year for which data is available, according to sales tracked by the state Department of Agriculture.

Agency response

The responsibility for reducing nitrate lies mostly with three state agencies: Minnesota Department of Health, the Minnesota Department of Agriculture and the Minnesota Pollution Control Agency (MPCA). All said their efforts will pay off eventually.

The MPCA blamed climate change's effect on precipitation for the failure to show progress on nitrate reduction.

"It will take time to see the benefit of this work, especially as more frequent and extreme weather events caused by climate change are both masking our progress and worsening the nitrate problem by forcing nitrate pollution off lands, into groundwater, rivers, and downstream," said MPCA spokeswoman Andrea Cournoyer.

The Health Department said 30 years of data doesn't show increasing nitrate violations in the public water supplies it watches, but that it's a "different story" for private well owners in certain highly vulnerable parts of the state.

The Agriculture Department agrees that in parts of southeast Minnesota, the nitrate in private water wells "has been going up slowly for decades."

"Nowhere in the U.S. is a state tackling nitrate issues like Minnesota," the agriculture department said.

Some in southeast Minnesota, a land of heavy agriculture and a porous karst geography, say they can't wait any longer for help. A group from Dodge, Goodhue, Fillmore, Houston, Mower, Olmstead, Wabasha and Winona counties asked the EPA to declare a public health emergency because state and local authorities haven't controlled nitrate pollution of groundwater.

About 80,000 residents in those counties rely on private wells for their drinking water and about 300,000 use public water systems, according to the request for help, filed in April by the Minnesota Center for Environmental Advocacy, the Minnesota Well Owners Association and others.

The EPA responded with a letter this month, warning Minnesota's three responsible agencies of possible enforcement actions if they don't enact measures to better warn residents of nitrate dangers, provide bottled water and develop plans to reduce nitrate pollution in the region.

Further reading

Sources: Environmental Protection Agency, EPA Safe Drinking Water Information System, Minnesota Pollution Control Agency, Minnesota Department of Health, Minnesota Department of Agriculture, Environmental Working Group, Star Tribune reporting and analysis

Jeff Hargarten is a Minnesota Star Tribune journalist at the intersection of data analysis, reporting, coding and design.

612-673-4642

Jennifer Bjorhus  is a reporter covering the environment for the Star Tribune. 

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