Clean, affordable water is essential for healthy communities and a resilient environment. But the pervasive overuse of synthetic fertilizers in large-scale industrial agriculture is straining the systems that keep our water safe.
Fertilizer provides nutrients like nitrogen and phosphorus that crops need to grow and thrive. But today’s agricultural system, shaped by a powerful fertilizer industry and other corporate interests, pressures farmers to plant more acres and apply far more fertilizer than crops can use. In fact, only about half of the fertilizer applied to fields is actually used by plants. The rest can build up in soil, pollute the air, leach into groundwater, or wash into streams where it becomes “nutrient pollution.”
From plant food to water pollution
Most synthetic fertilizers contain forms of nitrogen like ammonia or urea, which can be transformed into nitrate by bacteria in soil. Nitrate dissolves easily in water, and agricultural runoff has led to nitrate contamination of local waterways.
But nitrate pollution doesn’t just impact waters near fields where fertilizer is applied. Instead, it can travel hundreds of miles through streams, rivers, groundwater, and other connected water bodies. This water-to-water pathway is how fertilizer overuse in the Midwest ultimately leads to nutrient pollution in the Gulf of Mexico, creating a massive “dead zone” where a suffocating overgrowth of algae sucks up oxygen and kills fish and other aquatic life.
Health risks from nitrates in drinking water
When nitrate pollution reaches drinking water supplies through connected waterways, it creates health risks. Decades of research have identified links between nitrate exposure and disease including colorectal cancer, thyroid disease, and dangerously low oxygen levels in infants. Other potential health risks of nitrate exposure include bladder and gastric cancers, ovarian cancer, and birth complications like low birth rate and preterm birth. A 2019 study estimated that nitrate contamination in drinking water may contribute to as many as 12,500 cancer cases in the United States each year, costing Americans up to $1.5 billion annually in medical expenses.
The clear association between nitrate exposure and health risks is why the US Environmental Protection Agency (EPA) sets federal drinking water standards for nitrate. Public drinking water systems must keep nitrate levels below this standard, which is 10 mg/L. However, the federal nitrate standard was set decades ago and doesn’t consider newer evidence showing health risks from long-term exposure to lower levels of nitrate. So despite federal drinking water standards, nitrate pollution from fertilizer overuse remains a significant public health concern.
Nitrate pollution threatens communities
In the agriculturally dense Midwest, nitrate contamination has left many communities with unsafe water. In Kansas, nitrate pollution has forced small cities like Pratt to abandon wells that provide water to much of the population.
Researchers in Nebraska, a state with some of the highest rates of pediatric cancer in the country, have found higher childhood cancer rates in watersheds with elevated nitrate levels, even when those levels were below EPA standards.
In Wisconsin, excess fertilizer and poorly managed manure account for more than 90% of nitrate pollution in state waters. That pollution may start on farmland, but downstream residents and municipalities are stuck paying more than $116 million to remove it from their drinking water.
In Minnesota, where nearly three-quarters of water utilities with high nitrate levels serve residents with incomes below the state average, environmental groups have sued state agencies over nitrate pollution. In response, a judge ordered the state’s pollution control and agriculture agencies to assess whether current rules adequately protect Minnesotans from nitrate exposure in drinking water.
And in Iowa, where agriculture is responsible for about 80% of nitrate contamination in rivers and lakes, nitrate pollution has made its way into the drinking water supply. Nitrate levels in Iowa’s public water systems have risen since 2012, and private wells, which aren’t subject to EPA oversight, often show even higher concentrations. Nitrate exposure may be a factor in Iowa’s climbing cancer rate, already the second-highest in the nation after adjusting for age.
To help address the health risks from agricultural nitrate pollution, Iowa adopted a nutrient reduction strategy in 2013 aimed at cutting nitrogen and phosphorus pollution by 45%. But more than a decade later, significant nitrate pollution persists in places like Des Moines, which had to temporarily ban lawn watering in the summer of 2025 because of high nitrate levels in source water.
Removing nitrate from the water supply is extremely expensive. Des Moines Water Works estimates it costs $16,000 per day to run its nitrate removal system. Previous research by the Union of Concerned Scientists (UCS) found that nitrate removal could cost between $41 and $333 million over five years in Iowa, with most of the expense hitting small and rural communities.
The combination of expensive cleanup costs and high nitrate levels means that communities in rural areas that more often rely on small, underfunded water systems or private wells are disproportionately affected by nitrate pollution. One study found significantly higher nitrate exposure among low-income residents, older adults, very young children, and people of color in Iowa. This is why nitrate pollution from fertilizer overuse is not just a public health threat; it is also an issue of environmental justice.
Protecting public health through better farming practices
Much of the cost of nitrate pollution currently falls at the faucet, as communities and households pay high prices to remove it from their drinking water. But preventing nitrate pollution at the field before it enters the water supply is the most effective way to reduce the public health risks of nitrate pollution.
Agricultural practices can dramatically decrease the amount of fertilizer that runs off fields and pollutes rivers, streams, and groundwater with nitrate. For example, planting strips of native prairie plants on just 10% of farm fields can reduce nitrogen runoff by 85%. Crop rotation and diversification can decrease fertilizer needs, improve soil, and maintain crop profitability. Other practices such as planting cover crops and protecting or restoring wetlands can also reduce fertilizer runoff and prevent nitrate pollution.
Voluntary US Department of Agriculture (USDA) conservation programs offer farmers valuable tools and incentives to adopt these kinds of sustainable practices that improve soil health, reduce fertilizer use, and protect water from agricultural pollution. These programs deliver strong financial returns, too: a 2018 study by UCS found that every dollar invested in the Conservation Stewardship Program (CSP) generated almost $4 in benefits.
USDA conservation programs are popular with farmers, who see them as a way to protect the environment while reducing their reliance on expensive chemical fertilizers (and the giant corporations that make them). But current program funding is insufficient to meet demand: between 2010 and 2020, only 42% of CSP applicants and 31% of Environmental Quality Incentives Program (EQIP) applicants received contracts, largely due to limited funds.
New federal policies are needed to prevent nitrate pollution
Voluntary programs can make a difference, but persistent nitrate pollution demonstrates that existing programs do not prevent fertilizer and other farm runoff from contaminating our water. Combining voluntary conservation programs with federal subsidy rules that require soil- and water-friendly farming practices could further reduce fertilizer overuse and protect water quality.
Existing conservation compliance programs already tie federal subsidies to environmental safeguards. For example, the federal wetland conservation provision known as “Swampbuster” requires farm operators to refrain from converting wetlands to cropland in order to qualify for crop insurance, disaster payments, and other USDA benefits. Wetlands in agricultural areas can trap fertilizer and other runoff and keep it from polluting waterways and drinking water supplies. (They also play an important role in flood prevention: my previous research estimated that the 30 million acres of nontidal wetlands in the Upper Midwest provide almost $23 billion in residential flood mitigation benefits each year.)
Expanding and fully funding programs like Swampbuster can help farmers adopt sustainable practices while keeping their operations productive. Effective conservation compliance, combined with robust and well-funded voluntary programs, can curb fertilizer runoff, reduce nitrate pollution, protect our water, and provide real public health benefits for our communities.