Iowa's Nitrate Pollution Warning: What MDA's Decision Means for Minnesota's Drinking Water
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Author: Sarah Horner, MCEA Public Relations Director
Nitrate pollution in Iowa is drawing national attention this year. It's costing millions in water treatment, triggering lawn-watering bans, and leaving residents worried that nitrate in their water could be contributing to the state's high cancer rates.
Minnesota could be headed down a similar path if we don't heed our neighbor's warning. Yet on Aug. 29, the Minnesota Department of Agriculture (MDA) announced it will not update its Groundwater Protection Rule, one of the state's strongest potential tools for keeping nitrate from commercial fertilizer out of drinking water.
The decision leaves Minnesotans more vulnerable to the health harms of elevated nitrate and the state's waters more exposed to nutrient pollution.
"Thousands of Minnesotans in the state's karst and Central Sands regions still have drinking water that is dangerously contaminated with nitrate, and the long-term nitrate trend data doesn’t show meaningful improvements across these vulnerable areas. This rule is intended to prevent exactly that–which means it isn't working," said Joy Anderson, legal director of the Minnesota Center for Environmental Advocacy (MCEA). "MCEA and our allies will continue to fight for public health to come before politics.”
WHAT THE RULE DOES AND WHAT MDA DECIDED
Minnesota's Groundwater Protection Rule, adopted in 2019, designates regions with porous geology as "vulnerable groundwater areas." These areas need special protection because pollutants on the surface can quickly seep into groundwater. But the rule lacks the teeth to be effective. Its only mandatory requirement is that agricultural operators can't apply commercial fertilizer in the fall, when no crops are there to absorb the nitrates. MDA's own research found few farmers do that anyway. The rule's other provisions are mostly voluntary and leave private well owners largely unprotected.
In September 2025, a Ramsey County District Court judge ordered MDA to evaluate whether the rule was doing enough to protect drinking water. His order followed a lawsuit filed months earlier by MCEA, Minnesota Trout Unlimited, and the Minnesota Well Owners Organization (MNWOO). The suit identified the groundwater rule and the state's feedlot rule as central to the problem.
Together, the two rules govern the agricultural sector's use of commercial fertilizer and manure, the state's two biggest sources of nitrate pollution. MDA oversees the groundwater rule, which covers commercial fertilizer. The Minnesota Pollution Control Agency (MPCA) oversees the feedlot rule, which covers manure.
MPCA is already updating the state’s feedlot rule, with a draft rule expected in 2027. By contrast, MDA concluded that the groundwater rule is "adequate to protect Minnesota's groundwater from pollution, impairment, or destruction associated with commercial application of fertilizer to cropland."
MCEA and our partners are appealing that decision.
LESSONS FROM IOWA
Iowa offers a preview of what Minnesota could face if it continues to try to tackle nitrate contamination with a mostly voluntary approach.
Iowa has leaned on voluntary conservation for more than a decade to address its nitrate crisis. Its Nutrient Reduction Strategy, created in 2013, uses educational outreach to encourage farmers to adopt practices that cut nitrogen and phosphorus runoff and prioritizes finding funding for more research. While direct farmer outreach is an important component of agricultural conservation, adoption has lagged behind what researchers say is needed, and a 2023 Iowa Public Radio review of the program's first decade found no significant change in nitrogen levels.
Meanwhile, the costs have landed on water utilities and taxpayers. Central Iowa Water Works ran its nitrate removal plant for 193 days this year, and Iowa's nitrate-related drinking water violations more than doubled between 2024 and 2025. In June, Gov. Kim Reynolds signed a "Farm to Faucet" package expected to direct nearly $320 million over 12 years toward the problem. The package relies on funding incentives to persuade more farmers to adopt conservation practices voluntarily, not new fertilizer or manure application requirements.
HOW NITRATE REACHES DRINKING WATER
When farmers spread more manure and commercial fertilizer on fields than crops can use, the excess washes off and seeps into surface water and groundwater, potentially polluting them with unsafe levels of nitrate. Roughly 75% of Minnesotans get their drinking water from groundwater.
Nitrate above the 10 mg/L federal health limit can cause blue baby syndrome (methemoglobinemia) in infants and other vulnerable people. Recent research has also associated long-term exposure at levels as low as 3 mg/L with colorectal, bladder, and other cancers, as well as thyroid problems and birth defects. The findings led the Environmental Protection Agency (EPA) to consider lowering the federal limit. That effort has stalled under the second Trump administration.
Environmental Working Group's analysis of 2020 EPA data found that nearly half a million Minnesotans are served by public water systems with nitrate at or above 3 mg/L.
A recently updated study by University of Minnesota associate professor Bonnie Keeler estimates that nitrate-attributable health conditions cost Minnesota $745 million a year in direct care costs and quality-of-life impacts. That figure does not include costs to private well users.
PRIVATE WELL OWNERS FACE THE HIGHEST RISK
Minnesota's karst and Central Sands regions are on the front lines. Both are heavily agricultural areas whose geology makes them particularly vulnerable to groundwater pollution, and testing data there consistently show nitrate above federal limits.
Private well owners in these regions are the most exposed. Municipal systems must test for nitrate, which is clear and odorless, and treat water that exceeds the federal standard. Private well owners are on their own, though state funding is now available to help cover testing and treatment.
Nearly 400,000 Minnesotans live in the karst region, and 94,000 of them rely on private wells. EPA found that at least 9,200 of those well users may be drinking water with nitrate above the federal standard.
Concern over the issue led MNWOO, many of whose members live in the karst, to join the lawsuit.
NITRATE'S EFFECTS ON STREAMS, LAKES AND FISH
Agricultural nutrient pollution also contributes to fish kills and to the toxic algal blooms that have made a growing number of Minnesota lakes, rivers, and streams unswimmable and unfishable.
Because groundwater supplies steady, year-round flow to many Minnesota streams, contaminated groundwater degrades them too. Runoff that reaches the Mississippi River also feeds the Gulf of Mexico's “dead zone,” an area of oxygen-depleted water where most marine life can't survive.
Those impacts led Minnesota Trout Unlimited to join the lawsuit. Executive Director John Lenczewski said the organization is disappointed that MDA failed to acknowledge the rule’s failings.
"The state's own water quality data shows that 75% of streams tested in southern Minnesota routinely exceed nitrate levels harmful to aquatic life, including trout and aquatic insects," Lenczewski said.
EPA HAS ALREADY WARNED OF A POSSIBLE ENDANGERMENT TO HUMAN HEALTH
In April 2023, MCEA, Minnesota Trout Unlimited, MNWOO, and eight other environmental organizations petitioned EPA to intervene in the karst region's nitrate crisis. Six months later, EPA directed state agencies to act, finding that nitrate pollution in the region "may present an imminent and substantial endangerment to the health of persons, and that appropriate state and local authorities have not acted to protect the health of such persons."
Agencies were instructed to immediately ensure karst residents have access to safe drinking water. The EPA also directed state agencies to begin developing and implementing "a long-term solution to achieve reductions in nitrate concentrations in drinking water supplies."
The state has stepped up some since. Karst residents now have funding and resources to test and treat their water, and MPCA is undertaking the most extensive overhaul of the feedlot rule since 1990. But there is still a long way to go. Residents in other areas, like the Central Sands, need similar support, and the state needs a more comprehensive plan to curb the sources of the problem long term.
WHAT COMES NEXT
As Iowa shows, relying on agricultural operators to voluntarily change their practices won’t be enough. The good news is, Minnesota still has time to act before our nitrate problem becomes Iowa-sized.
The state’s groundwater protection and feedlot rules give us the tools to get there if we’re willing to acknowledge their shortcomings and improve them.
The groundwater protection rule should extend protections to private well owners, for example, and require large-scale operators in vulnerable areas to implement common-sense and well-documented pollution mitigation strategies. MCEA and our partners will continue to push the state in that direction through our appeal and at the Legislature.
"It's not a mystery how this problem gets solved, and we can do it in a way that protects both agricultural producers and everyone else," Anderson said. "All Minnesota needs to do is look at our neighbor to the south to see what's on the line."
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