Earth Watch: Iowa’s Nitrate Crisis Challenges EPA Limits and Industrial Agriculture

Author: Charity Isely

Earth Watch: Iowa’s Nitrate Crisis Challenges EPA Limits and Industrial Agriculture

“No river is safe now. No beach is safe."
— Iowa resident Joe Henry¹

Iowa's state motto reads, "Our liberties we prize, and our rights we will maintain."² Yet in 2025, Iowans' liberty to safely swim in the river, or right to access clean drinking water is being eroded by a nitrate pollution crisis. Nitrate levels are near record highs, and public utilities can't keep up, prompting Central Iowa Water Works' first-ever lawn watering ban this past June.^{3 4} As treatment plants work to keep nitrate levels within the Environmental Protection Agency’s (EPA) 10 mg/L safety limit, a June 2025 study published in PLOS Water suggests that standard may not be safe enough, especially for pregnant women and their developing babies.^{5 6}

Image of a lake with a "Danger Contaminated Water" sign

"No level of nitrate in drinking water appears safe during pregnancy."
— Jason Semprini⁷

Jason Semprini, assistant professor of public health at Des Moines University and the study's author, reviewed more than 350,000 Iowa birth records, matching them to nitrate levels in public drinking water within 30 days of conception.^{8 9} His analysis found that nitrate exposure as low as 0.1 mg/L increased the probability of pre-term birth, while 5 mg/L, which is half the EPA standard, was linked to greater risk of low birth weight.^{10 11} Interestingly, exposures above 10 mg/L showed no added risk, highlighting flaws in the standard, which was set in 1992 and never updated.¹² A growing body of evidence, including Semprini's findings, also links long-term low-level nitrate exposure (below EPA standards) to serious health issues, including cancer and thyroid disease.¹³

Although nitrate pollution can't be pinned to a single source, agricultural runoff from synthetic fertilizers and manure from concentrated animal feeding operations are major culprits.^{14 15 16 17} And Iowa, the national leader in conventional corn production, and concentrated feeding operations for pork, and egg production, has some of the highest groundwater nitrate levels in the world.^{18 19} The state's concentrated animal feeding operations have also significantly increased in size over the past decades. According to the environmental advocacy group Food & Water Watch, almost 90 percent of small to medium Iowa hog farms have disappeared since 1982,²⁰ yet it produces 23.5 million hogs each year, one-third of the U.S. total.²¹ These increasingly larger farms generate 109 billion pounds of manure annually—more than 25 times the waste from the state's residents.²² Much of it is spread on cropland as fertilizer, often at rates beyond what the soil can absorb.^{23 24}

Iowa has also been the leader in U.S. conventional corn production for decades.²⁵ Approximately 68 percent of the state's land area is dedicated to crops, and more than 94 percent of that cropland grows just two things: corn and soybeans.²⁶ Chris Jones, author of The Swine Republic: Struggles with the Truth about Agriculture and Water Quality, believes Iowa farmers are over-applying nitrogen, at significant rates, to grow that corn.²⁷ Using Iowa Department of Agriculture data, he calculates that in 2024 they used as much as 302 pounds of nitrogen per acre from synthetic fertilizer and manure, when the expert recommendation was 159 pounds per acre.²⁸

Research shows that on-farm conservation practices, like utilizing cover crops, can significantly reduce nitrate pollution when utilized consistently over time,²⁹ yet, in the six states, including Iowa, contributing the most nitrogen to the Mississippi River Basin, these types of methods are used on less than three percent of cropland.³⁰

Organic farming, by contrast, already incorporates conservation techniques, like cover cropping, into its standard practices and does not allow the use of any synthetic fertilizers.^{31 32 33} A United States Department of Agriculture analysis indicates that these practices pay off in reducing nutrient pollution—it found that conventional farms lost twice as much nitrate to water runoff compared to organic farms, while organic pastureland contributed the least.³⁴

For Jason Semprini, the message is clear. He says that "until we act upstream" to address nitrate pollution, Iowans will keep paying an excessive toll—both human and financial.³⁵"Whether our children continue paying will be up to us."³⁶

References

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