Nitrate Contamination in Drinking Water

The United States has a reliable drinking water system that caters to millions of households. Yet, high-profile cases in Flint, Michigan, and Jackson, Mississippi, remind us that not all households can access safe drinking water. Potential contributors to water quality concerns include aging infrastructure, wastewater and stormwater runoff, and agricultural practices. Climate change and water quantity management alongside increasing demands for agriculture, environment and residential use can exacerbate water quality concerns. These water quality issues can have long-lasting health consequences and add burdens to the health care system and private out-of-pocket expenditures.

Actuaries may use water quality and contamination data to estimate health impacts and costs of exposure to unsafe drinking water. They can also design insurance products related to medical expenses or liabilities. Additionally, actuaries may use their skills to support the implementation and evaluation of regulations, providing analysis and advice on the costs and benefits of water treatment options. With this in mind, this article delves into the issue of nitrate-contaminated drinking water in the United States, considering potential causes and addressing adverse health outcomes linked to nitrate contamination.

Background

As a naturally occurring substance, nitrate is beneficial to our health in small quantities but can be detrimental to our health in larger quantities. In 1974, the U.S. Congress passed the Safe Drinking Water Act in which nitrate was referenced as a contaminant. However, the nitrate rules were not enforced until 1992 when the U.S. Environmental Protection Agency (EPA) mandated public water systems ensure that all drinking water distributed had a maximum contamination level (MLC) of 10mg/L or less. This was primarily based on studies that showed that when babies consumed water with high nitrate levels they developed methemoglobinemia, which affects the oxygen-carrying capacity in the blood. It mostly affects babies and young children, although there have been some isolated reports of adults being affected by methemoglobinemia in recent years.^1,2

Since the first enforceable nitrate rule, we have known that nitrate potentially can lead to other health concerns, even at levels lower than the EPA’s MLC. This is particularly concerning for people who obtain drinking water from private wells because these water sources are the responsibility of the person who owns the well. Private wells do not fall under the Safe Drinking Water Act, so these individuals are not required to test their water or provide treatment if it is above the harmful limit. Private well users often face higher nitrate exposure risks than people who get their water from public systems.³ Most private wells are situated in rural areas and, as a result, are influenced more by agriculture.

Nitrate naturally occurs in our source water and is not usually harmful. However, some nitrate levels we see today indicate anthropogenic contributions because the concentrations are much higher and increasing. Our waters get polluted from nitrate compounds because of septic systems and wastewater runoff.⁴ In areas with high agricultural activity, an additional source of nitrate contamination can be nitrogen fertilizer and effluence from animal agriculture activities.⁵

Filtration is a common method to clean water for drinking. However, most traditional carbon filters cannot separate nitrate. Only more complex systems, like reverse osmosis or ion exchange, can do this. These systems are more expensive to install and need regular maintenance. As a result, small water systems might be paying more for clean water and transferring these costs to their consumers. Private well users must install such systems individually and pay for their upkeep, so these significant costs become the individual’s responsibility.

Human Health Effects of High Nitrate

Nitrate ingestion affects human health in different ways.⁶ For example, it affects human health directly by converting ingested nitrate into compounds that are harmful to the human body. Nitrate levels in drinking water also act as a proxy for other agrochemical contaminants, like atrazine, making any health effects related to nitrate contamination more commonly a response to agrochemical contamination rather than nitrate contamination alone. More evidence may be gleaned from recent research publications looking at the interaction between nitrate and atrazine, and uranium mobilization via nitrate.

The most cited medical concern linked to nitrate contamination in drinking water is methemoglobinemia.⁷ More recent evidence has shown that nitrate levels in drinking water are associated with adverse birth and reproductive outcomes, such as premature labor and congenital abnormalities.⁸ It is important to note that the evidence points to negative health outcomes at lower nitrate concentrations than the EPA regulation of 10mg/L. This evidence is established in human cohort studies as well as animal models, which established a somewhat causal relationship.

For example, a recent California study found that drinking water nitrate levels above the EPA MLC were positively correlated with preterm births in a within-mother analysis. Another study found a positive relationship between nitrate levels in drinking water (in excess of 5mg/L) in a sample of births with congenital abnormalities in Texas and Iowa. Animal models that look at nitroso compounds have found more compelling evidence that nitrate, alongside other contaminants like atrazine, could contribute to adverse birth outcomes.

Most research finds that nitrate could be linked to various cancers. In particular, high nitrate ingestion alongside other compounding agrochemicals could be linked to colorectal, stomach, bladder and various pediatric cancers. The concern over cancer risk stems from externally ingested nitrate being endogenously converted into carcinogenic compounds. Studies show that high nitrate levels are associated with an increased risk of cancer incidence. However, the verdict on cancer risk may be inconclusive because most studies have not been able to establish causality. The scientific consensus is that nitrate is likely to increase the risk of certain types of cancer regardless of whether it directly causes cancer or acts as a catalyst in bringing carcinogenic compounds (e.g., uranium) into the human body.⁹

The Cost of Adverse Health

The financial costs of cancers and congenital disabilities can span many years, and these expenses are usually well understood. In 2020, the projected U.S. national expenditure on cancer care was $209 billion, among which colorectal cancer was one of the most expensive types. According to the Centers for Disease Control and Prevention (CDC), the hospital care costs for birth defect-related hospitalizations (of children and adults) alone reached $23 billion in 2020.¹⁰ Beyond medical expenses, other costs include expenses related to transportation and lost productivity. In addition, significant, often less understood, nonfinancial costs can have lasting impacts on the people who are affected by illness and their families.

Climate Change Implications

Water quality issues are not stand-alone concerns for communities. In many ways, they are connected to a broad range of challenges related to sustainable water management, including water supply variability. Communities frequently lack tested water institutions capable of addressing complex, local context-specific water quantity and quality challenges.

Most water-quality challenges are exacerbated by climate change. For example, droughts may increase the risk related to the depletion of water resources leading to higher concentrations of contaminants left in the remaining body of water (aquifer).¹¹ This could be particularly concerning for users of shallower private wells that are more likely to be affected by competing water needs. For instance, agricultural producers are expected to begin irrigating more and in traditionally rainfed regions to buffer the impacts of more frequently recurring drought events. As a result, we believe water demands for municipal uses and environmental protection are likely to grow, including in areas that are usually more humid.

Only a few options are available for domestic water users concerned about pollution levels in their private wells, which include reverse osmosis and ion exchange systems at point of use (e.g., kitchen sinks). These water purification systems generally need at least two parts of source water to produce one part of water safe for human consumption.¹² Doubling domestic water needs might be especially challenging during droughts due to the higher risk of running out of water, which happened in many cases in the U.S. Midwest during the 2012 drought.

With robust governance and sustainability-focused investments and innovations from public and private sectors, vulnerability across all water stakeholders, including households using private well water, might become easier to avoid. The impacts likely will be more severe among socioeconomically disadvantaged groups and low-income households. Climate change has already been shown to make vulnerable communities susceptible to more risk, and their health burdens are affected in ways that other communities usually do not experience.

Health Care System Implications

Understanding how nitrate contamination in drinking water affects health care utilization and insurance claims is of great importance. However, the best way to incorporate excess risk from exposure to agrochemical-contaminated drinking water is still unknown. It is mainly because causality has not been sufficiently established in how contaminants affect human health and the exact mechanisms of it.

One way to understand better how water quality affects human health and health care utilization is by looking at diseases that go hand-in-hand with impaired water quality. For example, one high-level analysis of health care expenditures in the United States suggests that compliance violations in water quality were related to higher health care costs compared to air quality violations in a statistically significant way. Another study that looked into compliance violations of the Safe Drinking Water Act found that 20 states were trending above the national average. It is possible that these states have higher health care utilization compared to the others.

Although research on nitrate contamination in drinking water has come a long way since the enforceable nitrate rule set 30 years ago, many questions still need to be answered. We need more information on health care utilization patterns in agricultural and nonagricultural states, access to health care data, implications of public health insurance provision and management of drinking water infrastructure. We need interdisciplinary research that delves into mechanisms of contamination, avenues of exposure related to health effects, and prices and risk perceptions that explain human behavior. Parallelly, we need practitioners who are better equipped with science-based information and communication tools. Only then can we understand the true cost of water pollution in the United States and how best to address such costs.

In this article, we explored the issue of drinking water quality and delved into the nuances of understanding the potential causes of the issue and its implications on health. We discussed one specific contaminant—nitrate—that is likely to have human health implications beyond methemoglobinemia. These potential health concerns are long-lasting, costly and have implications on overall wellness, education and labor market outcomes.

Climate change exacerbates water quantity challenges and can aggravate complications from impaired water quality. Such complications are likely to affect many populations, although some communities may be prone to added risks.

Statements of fact and opinions expressed herein are those of the individual authors and are not necessarily those of the Society of Actuaries or the respective authors’ employers.

Copyright © 2023 by the Society of Actuaries, Chicago, Illinois.