Nitrates in drinking water sources have become a chronic problem especially in areas of intensive corporate agriculture–like the U.S. Midwest. The U.S. Environmental Protection Agency has not updated standards for nitrates in water for decades. Research indicates that health problems can be caused by levels far below the current U.S. Federal maximum.
Background:
“Nitrate (NO 3−) is a compound commonly found in fertilizers, animal manures, and wastewater sewage. Nitrate originating from agricultural activities, industrial discharges, and wastewater treatment processes can contaminate drinking water sources such as groundwater and surface water bodies … High levels of nitrate have been found in surface and groundwater drinking water sources across the United States, notably in regions characterized by intensive farming and animal production. As the primary producer of corn and swine in the U.S., Iowa faces challenges in managing nutrient levels in the environment.”
From: Mantey, E. P., Liu, L., & Rehmann, C. R. (2025). Disparities in potential nitrate exposures within Iowa public water systems. Environmental Science. Water Research & Technology, 11(4), 959-971. [PDF] [Cited by]
“… 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: Woods, Stacy. (2025). From Fields to Faucets: Fertilizer Overuse Threatens Drinking Water and Health. Union of Concerned Scientists.
See the sources below for research about the connection between nitrate concentrations in rivers, wells, and other bodies of water and the health impacts that result for children and adults.
Sources:
*Sajid, A., & Semprini, J. (2026). Nitrate and Brain/CNS Cancer Diagnoses in the First Year of Life. Pediatric Blood & Cancer, 73(2), e70054.
“Nitrates in drinking water, common in agricultural states like Iowa, pose health risks to young infants. This brief first reviews the plausible biological mechanisms linking nitrate exposure to brain and central nervous system (BCNS) cancers in the first year of life. We then linked historic water quality and cancer registry data at the county level to construct linear and quantile regression models estimating the association between a BCNS diagnosis and nitrate measures. We found significantly higher nitrate levels preceding pediatric zero-year-old BCNS cancer diagnoses. These findings support investigating early-life nitrate exposure as a potential risk factor for infant BCNS tumors.”
*Brender, J. D., & Weyer, P. J. (2016). Agricultural Compounds in Water and Birth Defects. Current Environmental Health Reports, 3(2), 144-152. [Cited by]
“Agricultural compounds have been detected in drinking water, some of which are teratogens in animal models. The most commonly detected agricultural compounds in drinking water include nitrate, atrazine, and desethylatrazine. Arsenic can also be an agricultural contaminant, although arsenic often originates from geologic sources. Nitrate has been the most studied agricultural compound in relation to prenatal exposure and birth defects. In several case-control studies published since 2000, women giving birth to babies with neural tube defects, oral clefts, and limb deficiencies were more likely than control mothers to be exposed to higher concentrations of drinking water nitrate during pregnancy. Higher concentrations of atrazine in drinking water have been associated with abdominal defects, gastroschisis, and other defects. Elevated arsenic in drinking water has also been associated with birth defects. Since these compounds often occur as mixtures, it is suggested that future research focus on the impact of mixtures, such as nitrate and atrazine, on birth defects.“
*Cisneros, R., Amiri, M., & Gharibi, H. (2025). The association between increases in nitrate in drinking water and colorectal cancer incidence rates in California, USA. Cancer Causes & Control, 36(10), 1041-1057. [PDF] [Cited by]
“Purpose: The water resources in California are polluted with nitrate (NO3) due to the ever-increasing application of nitrogen-based fertilizers. Considering the potential connection between NO3 in drinking water and the incidence rate of colorectal cancer, this study aims to investigate the association between long-term exposure to NO3 via drinking water and the incidence of colorectal cancer from 2010 to 2015 in California.
Methods: A total of 56,631 diagnoses of colorectal cancer were recorded from 2010 to 2015. A generalized linear model was used to obtain the risk ratio (RR) and 95% confidence interval associated with a 1 mg/l-NO3 increase in NO3 concentration across five latency periods. The potential effect modification by sex, race/ethnicity, and age (> 40, 41–64, 65–90, and > 90) was explored through stratification.
Results: The association between increases in the concentration of NO3 at lag 0–1, lag 0–5, lag 0–10, lag 0–15, and lag 0–20 (RRs: 1.056 [1.055, 1.058]; 1.066 [1.063, 1.069]; 1.030 [1.028, 1.031]; 1.017 [1.016, 1.018]; 1.035 [1.034, 1.037], respectively) was positively associated with the RR of colorectal cancer. Sex was not found to be a significant modifier. The RRs for Hispanics, Blacks, and other races were greater than those for Whites; the RRs across different age categories were all significantly positive.
Conclusion: This study confirms an association between long-term NO3 exposure in drinking water and the incidence of colorectal cancer in California, emphasizing the need for stringent water quality control and public health strategies to address this risk, particularly in vulnerable populations.”
*Jayasekera, D. H., Munde, S., Snow, D. D., & Rimšaitė, R. (2025). Trends in nitrate contamination: implications for communities reliant on groundwater for drinking. Environmental Research Communications, 7(8), 085008. [PDF]
“Nebraska’s vulnerability to nitrate contamination in water systems is highlighted by agrochemical inputs with leaching potential and the state’s reliance on groundwater for drinking. Nitrate is a regulated compound in drinking water due to its association with methemoglobinemia and other chronic health conditions. This study examines water quality in Nebraska’s groundwater over several decades, focusing on temporal and spatial variations in nitrate concentrations across different well types. The findings reveal increasing statewide trends in nitrate levels, with considerable spatial variability. Private-domestic wells, particularly in agricultural areas, are more susceptible to contamination. These trends suggest a growing risk for communities without access to regulated public water systems. The study emphasizes the need for targeted interventions in vulnerable regions, and provides insights into the broader implications of agricultural contaminant leaching on groundwater quality and public health.”
Other sources:
Dust storms in the United States: a mixture of corporate agriculture and climate change
Corporate farming and its consequences in the U.S. Midwest
What’s the best way to get eggs from chickens?
Bees survive better in cities compared to open agricultural land
Questions? Please let me know (engelk@grinnell.edu).
