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., et al. (2025)–see below]
“… 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, S. (2025)–see above]
See the sources below for research about the connection between agricultural practices and nitrate concentrations in rivers, wells, and other bodies of water and the impacts and disparities that result.
Sources:
*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]
“Nitrates (measured as nitrate-nitrogen) in drinking water exceeding the maximum contaminant level (MCL) of 10 mg L−1 can cause significant health risks, such as methemoglobinemia. Even long-term exposure to concentrations below the MCL can also increase the risks of cancer. Iowa, a major agricultural producer, has grappled with decades-long nitrate pollution in its water systems due to intensive farming practices and animal feeding operations. To help in developing interventions and policies to protect public health, this study delves into long-term nitrate levels in 871 Iowa public water systems (PWSs) between 2012 and 2022 and examines sociodemographic disparities in potential nitrate exposure in drinking water. Average nitrate concentration in Iowa’s PWSs increased between 2012 and 2016, reaching an average peak of 3 mg L−1 in 2016. 2.5% of 871 PWSs are classified as ‘high-risk’, with nitrate concentrations consistently exceeding 5 mg L−1 over the study period, primarily in eastern and western Iowa, where animal feeding operations are concentrated. The absence of nitrate removal processes at these PWSs contributes to the sustained elevated levels. On average, 7.4% of the state’s population served by PWSs has been exposed to nitrate levels consistently exceeding 5 mg L−1 in the past decade. Disparities exist among various sociodemographic groups, with statistically significant higher exposure rates (10.1%, 9.6%, 9.2%, and 8.7%) observed for people whose incomes are below the federal poverty threshold ($26,496/year), older adults (65 years and above), people of colour, and children (5 years and younger). These disparities are particularly concerning as these populations often lack the resources to address the consequences of water contamination. Our study highlights inequities in Iowa’s PWSs concerning potential nitrate exposures and underscores a need for nitrate remediation in specific areas. Addressing these disparities is crucial to safeguarding the health of vulnerable populations and promoting environmental justice in water management.”
*Spaur, M., Medgyesi, D. N., Bangia, K., Madrigal, J. M., Hurwitz, L. M., Beane Freeman, L. E., … & Ward, M. H. (2025). Drinking water source and exposure to regulated water contaminants in the California Teachers Study cohort. Journal of Exposure Science & Environmental Epidemiology, 35(3), 454-465. [PDF] [Cited by]
“Background: Pollutants including metals/metalloids, nitrate, disinfection byproducts, and volatile organic compounds contaminate federally regulated community water systems (CWS) and unregulated domestic wells across the United States. Exposures and associated health effects, particularly at levels below regulatory limits, are understudied.
Objective: We described drinking water sources and exposures for the California Teachers Study (CTS), a prospective cohort of female California teachers and administrators.
Methods: Participants’ geocoded addresses at enrollment (1995–1996) were linked to CWS service area boundaries and monitoring data (N = 115,206, 92%); we computed average (1990–2015) concentrations of arsenic, uranium, nitrate, gross alpha (GA), five haloacetic acids (HAA5), total trihalomethanes (TTHM), trichloroethylene (TCE), and tetrachloroethylene (PCE). We used generalized linear regression to estimate geometric mean ratios of CWS exposures across demographic subgroups and neighborhood characteristics. Self-reported drinking water source and consumption at follow-up (2017–2019) were also described.
Results: Medians (interquartile ranges) of average concentrations of all contaminants were below regulatory limits: arsenic: 1.03 (0.54,1.71) µg/L, uranium: 3.48 (1.01,6.18) µg/L, GA: 2.21 (1.32,3.67) pCi/L, nitrate: 0.54 (0.20,1.97) mg/L, HAA5: 8.67 (2.98,14.70) µg/L, and TTHM: 12.86 (4.58,21.95) µg/L. Among those who lived within a CWS boundary and self-reported drinking water information (2017–2019), approximately 74% self-reported their water source as municipal, 15% bottled, 2% private well, 4% other, and 5% did not know/missing. Spatially linked water source was largely consistent with self-reported source at follow-up (2017–2019). Relative to non-Hispanic white participants, average arsenic, uranium, GA, and nitrate concentrations were higher for Black, Hispanic and Native American participants. Relative to participants living in census block groups in the lowest socioeconomic status (SES) quartile, participants in higher SES quartiles had lower arsenic/uranium/GA/nitrate, and higher HAA5/TTHM. Non-metropolitan participants had higher arsenic/uranium/nitrate, and metropolitan participants had higher HAA5/TTHM.
Impact: Though average water contaminant levels were mostly below regulatory limits in this large cohort of California women, we observed heterogeneity in exposures across sociodemographic subgroups and neighborhood characteristics. These data will be used to support future assessments of drinking water exposures and disease risk.”
*Hatfield, J. L., McMullen, L. D., & Jones, C. S. (2009). Nitrate-nitrogen patterns in the Raccoon River Basin related to agricultural practices. Journal of Soil and Water Conservation, 64, 190-199. [PDF] [Cited by]
“Nitrate-N concentrations in the Raccoon River have increased beginning in the early 1970s. Since this river is the predominant water supply for the City of Des Moines in Iowa, there is concern about the potential long-term impacts of these trends. Improvements in water quality from agricultural watersheds are critical to protect the water supply, and understanding the factors affecting water quality will lead to potential changes in agricultural management to improve water quality. The historical database of nitrate-nitrogen (NO3-N) concentrations sampled at the Des Moines Water Works were combined with observations on N fertilizer use, animal production, crop yields, land-use changes, and precipitation patterns to evaluate these interrelationships. Mean annual NO3-N concentrations in the Raccoon River watershed have been increasing since 1970 in spite of no significant change in N fertilizer use for the past 15 years. There have been three years with maximum NO3-N concentrations above 18 mg L-1. However, these spikes occurred throughout the past 30 years and are not isolated to the last 10 years of record. Nitrate-N loads from the Raccoon River watershed have shown a slight decrease in the past ten years because of the increased crop yields and increased removal of N in the corn (Zea mays L.) and soybean (Gylcine max [L.] Merr.) grains. Production numbers for cattle have decreased by 63% since the early 1980s, while hogs have shown a 20% decrease over the same time period. Therefore, N available for application into the basin has decreased by 25%. Annual variations in NO3-N loads are significantly related to precipitation in the first five months of the year. A significant correlation was found between the land area within the watershed cropped to small grains and hay crops and the increase of NO3-N since 1970 (r = -0.76). This relationship was caused by alteration in the seasonal water-use patterns and loss of N during the fall or early spring in the water movement in contrast to corn or soybean, which have a limited N uptake pattern concentrated between June and early September. Changes in the water-use patterns caused by shifts in cropping patterns provide an explanation for the positive correlation between precipitation and flow during the early part of the year. Development of agricultural management practices that can potentially affect water quality will have to be more inclusive of all components in agricultural systems, rather than only changing fertilizer rate or timing.”
*Hall, A. L. (2024). ‘Cropaganda’: Mythology of Corn Belt agriculture. Journal of Rural Studies, 108, 103260. [PDF] [Cited by]
“Even as scholars have increasingly recognized the role of industrial agricultural practices in contributing to non-point source pollution, drinking water in the Corn Belt remains perilously contaminated with excess nitrates, which pose a significant risk to human health and the environment. A recent lawsuit filed by the city of Des Moines, Iowa against three upstream counties over chronic nitrate pollution sparked heated debate around the roles and responsibilities of agricultural production. Drawing on Barthes’ theory of mythology, this paper explores how three core myths influence agricultural management paradigms and practices that contribute to the water quality crisis in Iowa and shape how key stakeholders have responded (Barthes, R. 1972 [1957]. Mythologies. New York: Hill and Wang). This article relies on ethnographic data to explain agricultural nitrate pollution and the stalled progress on water quality improvement. Together these myths draw on post-enlightenment ideas of nature, security, and modernity to perpetuate productivist behavior, claim resources for conventional commodity agriculture, and impede widespread adoption of alternative agricultural practices. By identifying and interrogating each myth, I aim to reveal and complicate the inherent contradictions in its representation of reality to strip it of ideological function and, in doing so, cultivate opportunities to imagine and create an alternative system that benefits both people and the planet.”
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).
