Over the past century, our industrialized agriculture system has grown reliant on chemical fertilizers to boost crop yields, leading to serious impacts on soil health, biodiversity, water quality, emissions, and human health. This article is the first in a series on the environmental and human health impacts of fertilizer use in agriculture and a review of the potential solutions from innovation to scaling regenerative practices.
A “Big and Small” Problem
I grew up on a Midwestern farm. I loved the quiet, the night skies, and spending hours exploring the creek that split our fields. I did not love our water. We had a shallow well. When it didn’t rain, we had to take “Navy” showers and haul water. That well was all the water we had to drink. In some ways, our water situation was worse when it rained and the water that ran from the tap was reddish to yellow. It smelled metallic.
“Just run it a bit until it clears,” said my dad. “It’ll be fine.” And, decades ago, maybe it was. But the water from wells and rural water systems today is not always fine. In fact, the rate of nitrate contamination in rural water supplies increasingly exceeds the Safe Drinking Water Act’s legal limit of 10 mg/L. Exposure to elevated levels of nitrates in drinking water can have life threatening implications. The smallest among rural populations are the most vulnerable. This is true both for the size of a community’s population and for the tiniest of humans within it.
Health impacts of elevated nitrate levels in rural water supply
Infants exposed to nitrates, often when water with an elevated nitrate level is mixed for formula, can develop methemoglobinemia, or “blue baby syndrome.” Blue baby syndrome occurs when the body metabolizes nitrates to nitrites. Nitrite ions oxidizeiron in the blood to create methemoglobin (Greer & Shannon, 2014). Unlike the hemoglobin in healthy red blood cells, methemoglobin cannot bind to oxygen. The skin in an infant with this condition appears blue, a sign of low oxygen or hypoxia. In serious cases, the baby will experience loss of consciousness, seizures, and sometimes death (Fossen Johnson, 2019). Infants are more susceptible to methemoglobinemia than adults, and infants under three months of age have the highest risk of developing the condition.
Elevated levels of nitrate, especially at or above the legal limit of 10 mg/L, in rural wells and community water systems are also associated with increased risk of pre-term birth (Lin, St. Clair & Gamble, 2023; Sharris et al., 2021).While the birth of a baby is an often-anticipated event, when the contractions come nine weeks early in rural areas far from a hospital with neo-natal intensive care, the outcome can be devastating. Rural areas have the highest infant mortality rates in the U.S., and much of rural Kansas includes counties where only 25.7% of health care facilities include obstetrics (Ehrenthal, Kuo, & Kirby, 2020).
Long-term exposure to elevated nitrate levels in drinking water poses health risks to adults also. Current research indicates that nitrate levels in water less than the legal limit are associated with an increased risk of certain cancers including colorectal and gastric cancers (Temkin et al., 2019).
Financial costs of nitrates in rural drinking water are highest per capita for the smallest populations
Since 2003, nitrate levels in many Kansas rural communities have increased to levels that exceed the Safe Drinking Water Act’s limit for nitrate in drinking water of 10 mg/L (Environmental Working Group, 2020). Agricultural runoff is a primary source of nitrate pollution in groundwater (Shaider et al. 2019). Private water sources like wells, the most common rural water source, do not have requirements for testing. However, surveys of well water by Kansas State University identified an increase in nitrate levels. Half of the tested wells had levels above the 10mg/L limit (Llopis-Jepsen, 2023). For rural community water systems, 98 percent of the water systems with nitrate at or above 5 mg/L served communities of 25,000 or fewer people (Greer et al., 2014) Communities with the smallest population had the highest levels of nitrates in their water (Schaider, 2019). Kansas ranks among the five U.S. states with highest nitrate levels in water due to its large areas of cropland, high nitrogen inputs, and well-drained soils.
The U.S. Clean Water Act (CWA) primarily regulates point source pollution, or “discernible, confined and discrete” sources of pollution. While the CWA delegates authority over nonpoint source pollution, such as agricultural runoff, to the states through requirements for Areawide Waste Treatment Management Plans (Rotman, Hollis, & Traut, 2020) there is limited authority to force states to implement TMDL plans and to mitigate nonpoint source pollution. States often address agricultural runoff through voluntary measures including cost share funding for establishing riparian buffers on farms. Cost share approaches have had limited success in reducing nitrogen runoff (Rotman, Hollis, & Traut, 2020).
Nonpoint source pollution has numerous and diffuse sources, making it hard to identify and regulate. As a result, rural communities bear the costs for nitrate treatment at the point of community water supply or individual household for private wells.
However, rural Kansans face socioeconomic barriers to address water quality and the health impacts from nitrate exposure. These barriers include lower income and a lack of access to adequate health care (Rural Health Information Hub., n.d.; Scanlon et al., 2023).
Rural Kansans face high costs per capita to fund nitrate treatment facilities (Condos, 2024). For example, the 136-person community of Bogue, Kansas, incurred costs of $2.6 million for a nitrate removal facility, costing $19,117 per resident (Kansas Rural Water Association,2023). The average annual income in Bogue is $33,319. On average, one-third of the population in rural Kansas communities that have had to fund nitrate treatment is low-income (EPA, 2024).
Rural populations systematically experience barriers to health care due to socioeconomic status, chronic conditions, limited infrastructure, fewer healthcare and public health services, and geographic distances (Rural Health Information Hub, n.d.). Coombs et al. (2022) identified that only 10 percent of U.S. healthcare resources are in rural areas despite 20 percent of Americans residing in these communities.
Additionally, rural populations are less likely to have health coverage. Cultural studies on attitudes toward health care in rural areas also indicate individuals in these regions may be less likely to seek care until faced with an urgent situation (Coombs, 2022).
Combined, these factors add up to significant financial and health costs to populations that have the least resources to address the issues.
Hotspots of Groundwater Nitrate Pollution in the U.S.
A “big and small” global problem
Kansas is one of the five U.S. states with the highest nitrate pollution levels in the water supply. But the water quality problem is far from limited to this region or to the U.S. alone. Globally, 60 percent of the areas with elevated nitrate levels in ground water are associated with croplands. Bijay-Singh & Craswell(2021) identified four global hot spots for nitrate pollution linked to fertilizer use: the Yangtze River Basin in Central China, the Punjab Province in India, the Baltic Sea, and the Mississippi River Basin. At this “hotspot” level, the problem of nitrate pollution is immense. For example, the Mississippi River Basin drains the Gulf of Mexico where nutrient pollution has caused a 6,000 square mile dead zone in the Gulf of Mexico.
In Punjab, India, the maximum values of nitrates in groundwater from seven districts ranged between 78.20 mg/l to 2553 mg/l (Virk, 2023). The Bureau of Indian Standards sets a limit of 45 mg/l, and World Health Organization has a recommended limit of 50 mg/l, both far exceeding the U.S. EPA limit of 10 mg/l.
Most farms in India, including in the agricultural Punjab region, are smallholder farms. The population relies on the groundwater supply for drinking water. The same “small” problems described for Kansas — fewer healthcare facilities in less populated areas and the youngest of the population at greatest risk — are faced by the rural population in India.
Globally, the overuse of nitrogen fertilizer has occurred for decades. The resulting buildup of nitrate-N in soils and groundwater, called legacy nitrogen, increases the timeline for water quality improvement, often by decades. The persistent nitrogen levels also increase the cost to address excess nitrogen and improve water quality. U.S. EPA estimates that nutrient pollution from fertilizer, both nitrogen and phosphorous, costs about $3.17 billion per year in lost property value, treatment costs, and loss of ecosystem services (US EPA, 2023). Globally, the costs are hard to calculate. However, a World Bank study calculated that the just the health and productivity losses from nitrates in water alone outweigh the value of increased crop yield globally (Damania et al., 2019).
Solving the Nitrate Problem
There are best practices and programs to address excess nitrogen fertilizer use. One of the most widely accepted in the U.S. is the four “Rs” of Right Rate, Right Source, Right Time, Right Place. Changes to farming practices that improve soil health are also linked to reduced reliance on chemical inputs. Not all practices are effective, and implementation and uptake vary.
Commercial fertilizer was first developed over 100 years ago, with the Haber Bosch process. Since then, fertilizer technology advances included controlled release formulations, enhanced efficiency, and seed coatings. However, the core technology remained much the same and nitrogen use efficiency — the amount of nitrogen uptake by the crop — remains about 40-50percent. About half of applied nitrogen is lost to the environment, both atmosphere and water. New approaches offer a promising path toward reducing the negative impacts of nitrogen fertilizer and improving efficiency. These technologies include nitrogen inhibitors, bio-stimulants, algae-based products, and microbials.
Our next articles in the fertilizer series will look at the climate impacts of inorganic nitrogen fertilizer, and the farming practices, water quality programs, and technologies that address the nitrogen problem.
References
Bijay-Singh, Craswell, E. Fertilizers and nitrate pollution of surface and ground water: an increasingly pervasive global problem. SN Appl. Sci. 3, 518 (2021).https://doi.org/10.1007/s42452-021-04521-8
Condos, D. (2024, March 20). As fertilizer pollutes tap water in small towns, rural Kansans pay the price. KCUR -Kansas City News and NPR. https://www.kcur.org/news/2022-03-29/as-fertilizer-pollutes-tap-water-in-small-towns-rural-kansans-pay-the-price
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