Why It Matters
Agricultural runoff from fertilizers and livestock operations has pushed nitrate levels in drinking water to potentially dangerous concentrations across large portions of the United States. While no Idaho-specific data was included in the analysis, the state’s significant agricultural footprint makes it susceptible to similar contamination issues affecting western neighbors.
Nearly one-fifth of Americans relied on water systems with elevated nitrate levels between 2021 and 2023, according to research published Thursday by the Environmental Working Group.
What Happened
The nonprofit examined federal test data from drinking water systems nationwide. Water systems serving more than 3 million people exceeded the federal safety limit of 10 milligrams per liter during the three-year period.
Another 62 million Americans received water from systems that recorded nitrate levels above 3 milligrams per liter at least once. That threshold indicates human-caused contamination rather than naturally occurring nitrate in soil.
Nitrogen fertilizers used in crop farming and runoff from livestock manure drive the contamination. Heavy rains push agricultural residue into streams, rivers, and groundwater supplies.
By the Numbers
• 64% of water systems exceeding the legal limit were in five states: California, Texas, Kansas, Nebraska, and Oklahoma
• 3 million people served by systems that exceeded federal safety limits
• 62 million people exposed to water with contamination indicators
• $16,000 per day: Operating cost for Des Moines’ nitrate removal system, one of the world’s largest
• 2021-2023: Years covered by the analysis
Zoom Out
The contamination extends beyond rural farming communities. Watersheds can carry nitrate far from agricultural sources, affecting urban water supplies.
Researchers increasingly question whether the federal 10 milligrams per liter threshold remains adequate. New studies link even low nitrate consumption to cancer and birth defects. Federal law currently limits nitrate because of its association with blue-baby syndrome.
Climate change compounds the problem. Extreme weather events—heavy rainfall and prolonged droughts—worsen agricultural runoff into water sources. Agriculture itself contributes to greenhouse gas emissions driving those weather patterns.
What’s Next
Water providers face mounting costs to address nitrate contamination. Removal systems strain budgets, particularly for smaller communities forced to dig deeper wells for cleaner groundwater.
The Environmental Working Group created a public map showing community water systems with elevated nitrate levels. New Hampshire was the only state not included due to unavailable data.
About the Author
