In the United States, nine out of ten people get their tap water from a regulated public water system. Yet, nearly one-fifth of those individuals may be exposed to potentially dangerous levels of nitrates through their taps, according to a new study by the Environmental Working Group (EWG).

Ahead, we explain what nitrates are, how they get into tap water, and what the EWG’s study reveals about their presence in U.S. drinking water. We’ll also cover how exposure to nitrates may impact human health, and most importantly, how to filter them from your home’s water supply.

What are Nitrates?

Nitrates are chemical compounds made up of nitrogen and oxygen. They occur naturally in water, soil, plants, and the bodies of humans and animals. Nearly 80 percent of the nitrates in our diets come from vegetables like spinach and celery, which often absorb the compounds from the soil as they grow. Cured or processed meat products, such as bacon and sausages, contain relatively small amounts of nitrates (~5% of our total intake), commonly used as preservatives. Water may also contain small concentrations of nitrates, but depending on how much you consume, it can be a major source (much more than from processed meats).

How Do Nitrates Get into Tap Water?

Nitrates mainly enter drinking water supplies through runoff from fertilized farmlands and urban landscapes, industrial discharge, leakage from septic tanks and wastewater treatment plants, or the erosion of natural deposits. Because nitrates readily move with water through soil, heavy rainfall, over-irrigation, or other events can send the chemical compounds into nearby surface waters, such as rivers, streams, and lakes. Nitrates can also leach underground and eventually reach groundwater pumped up by wells. The likelihood of nitrates contaminating one’s drinking water will differ based on whether the water comes from a municipal water system or a private well.

Nitration Contamination Risk for Public Water Systems

Once nitrates enter surface waterways or groundwater wells, they may show up at water treatment plants. The Safe Drinking Water Act (SDWA) requires public water systems to test for nitrates and take action if they exceed limits set by the Environmental Protection Agency (EPA). However, while treatment often removes some of the compounds, not all systems can handle high nitrate levels, especially smaller, rural plants in regions with heavy nitrate contamination. These utilities typically lack the necessary infrastructure and funding to remove nitrates from water before it reaches customers. As a result, various concentrations of the compounds may linger in the “treated” water supplied to homes and businesses.

Find out how public water systems treat drinking water.

Nitration Contamination Risk for Private Water Wells

Nitrate contamination is typically higher in drinking water from private wells. One reason for this is that private wells aren’t federally regulated. That means owners are responsible for ensuring the quality and safety of their drinking water, not the government. The lack of federal oversight can lead to gaps in testing and treatment, which may result in dangerously high levels of nitrates in the water supply. Well users may then consume the water, unaware of its contents and the associated health risks. Contamination may be even higher in wells near crop fields, barns, feedlots, pastures, rangelands, and septic systems.

Get insights on what to know when buying a house with a private well system.

What EWG’s Analysis Found About Nitrate Pollution in U.S. Drinking Water

The EWG conducted a first-of-its-kind analysis of nitrate contamination in public water systems across the United States. The research was based on nitrate occurrence data from municipal water systems in all 50 states, except New Hampshire, which did not provide the required data.

How Many Americans May Be Exposed to Nitrates in Their Tap Water?

The study found that, from 2021 to 2023, approximately 62 million people served by about 6,114 community water systems in the U.S. received drinking water with nitrate levels above 3 milligrams per liter (mg/L) at least once. During the same period, tap water of over 3 million people had nitrate levels above the federal safety limit of 10 mg/L. Notably, 70 systems tested at 20 mg/L (twice the EPA’s limit) and 21 systems at or above 30 mg/L (at least three times the EPA’s limit).

Which States Reported the Highest Levels of Nitrate Pollution?

States with major agricultural industries and higher numbers of public water systems reported the highest levels of nitrate-polluted water: California, Pennsylvania, Washington, Kansas, North Carolina, New York, Nebraska, Texas, Arizona, and Wisconsin. Roughly 64 percent of water systems with nitrate levels at or above the legal limit were concentrated in just five states: California, Texas, Kansas, Nebraska, and Oklahoma. Some states, including Iowa, which has significant nitrate pollution linked to agriculture, did not make the top 10 solely because they had fewer municipal water systems.

What are the Health Risks from Nitrate Exposure?

Exposure to nitrates is associated with several adverse health effects, especially in infants and pregnant and nursing women. When ingested, a portion of nitrates is converted to nitrites. These nitrites can then convert hemoglobin, the oxygen-carrying protein in red blood cells, into methemoglobin, an altered form that cannot effectively deliver oxygen to the body’s tissues, the National Institutes of Health (NIH) explains.

Health Risks to Infants

Research shows that impaired oxygen delivery in infants can lead to a condition called methemoglobinemia, also known as “Blue Baby Syndrome,” the most common health concern associated with nitrates. Infants under the age of six months generally face the highest risk of developing this disorder.

According to the American Journal of Medicine (AMJMED), signs and symptoms of methemoglobinemia can include:

• Cyanosis (blue-gray skin, particularly around the eyes and mouth)
• Flu-like symptoms, such as headaches, fatigue, nausea, and vomiting
• Mental status changes
• Loss of consciousness
• Seizure, coma, and death if left untreated or in severe cases

Discover the best water for baby formula and how to protect children from toxic contaminants in water.

Health Risks to Adults

Exposure to high levels of nitrates during pregnancy raises the risk of neural tube defects, such as spina bifida and anencephaly, and preterm births. Nitrates converted to nitrites can also react with other chemicals in the body to form N-nitroso compounds (NOCs). NOCs have been shown to contribute to the development of cancer in animals and potentially humans, including kidney, stomach, colorectal, bladder, and thyroid cancer. Research is still underway to determine other potential health effects from long-term nitrate exposure.

What are the Current Federal Regulations Around Nitrates in U.S. Drinking Water?

The EPA’s current federal limit for nitrate in drinking water is 10 mg/L. This standard, called a “Maximum Contaminant Level” (MCL), was set in the early 1960s to prevent cases of “Blue Baby Syndrome.” Since then, numerous studies have reported potential harms at concentrations of 5 mg/L or lower. Due to these findings, the EWG recommends a much stricter guideline of 0.14 mg/L, based on an estimated one‑in‑a‑million lifetime cancer risk. However, despite calls from health and environmental groups to lower the federal limit, the EPA has yet to update it.

How Can I Find Out If My Tap Water Has High Nitrate Levels?

Since nitrates in water are odorless, tasteless, and invisible to the naked eye, you can’t detect them through your senses. Testing your water is the only way to know if these compounds are present and at what concentrations. Certified laboratory testing is generally recommended because it often provides the most accurate picture of your water quality. The process typically involves purchasing a mail-in water-testing kit, taking a water sample from your tap, sending it to the laboratory for testing, and awaiting the test results. It’s a good idea to have your water tested at least once a year, between April and July, when nitrate and nitrite levels are typically the highest.

Discover 10 common problems a water test can detect in tap water.

Other Ways to Evaluate Your Drinking Water Quality

While less accurate than professional water testing, customers on city water can look up their water provider’s latest Consumer Confidence Report (CCR) or water quality report. This document provides a comprehensive overview of the water quality in specific regions over the past year. Another option is to search your area on the EWG’s Tap Water Database. Simply submit your zip code or select your state to view reported nitrate levels in public water utilities and whether it’s a concern for your area.

Learn how to read your local water quality report.

What Can Homeowners Do To Reduce Nitrates in Their Drinking Water?

So, what do you do if a water test indicates elevated nitrate levels in your home’s water supply? The CDC’s Agency for Toxic Substances and Disease Registry (ATSDR) advises against using the water to prepare formula, feeding it to infants, or consuming it if you are pregnant or planning to become pregnant. The agency instead recommends using bottled water for drinking and cooking, restricting well water usage to bathing and showering, and considering investing in a water filtration system that’s third-party certified to reduce nitrates in the water you and your family consume. There are three common treatment methods for reducing nitrates in drinking water: distillation, reverse osmosis, and ion exchange. For most people, reverse osmosis is the most practical option.

How Reverse Osmosis Filters Out Nitrates

Reverse osmosis (RO) reduces nitrates by forcing water through a semi-permeable membrane under pressure. Like a sieve, this membrane is covered in microscopic pores that trap contaminants, such as nitrates, PFAS, lead, dissolved salts, and heavy metals, while only letting water molecules through. Many RO systems combine multiple filtration stages to achieve the highest possible level of purity. The treated water is collected in a storage tank for future use, and the rejected contaminants are flushed down the drain.

Learn more about how reverse osmosis works and how to install a reverse osmosis system.

Does Boiling Water Remove Nitrates?

No, boiling water will not remove nitrates. Doing so can actually increase the concentration of the chemicals in your water. As the water boils, some of it evaporates, leaving the same amount of nitrates behind in a smaller amount of liquid. The longer you boil the water, the higher the nitrate concentration becomes. Standard carbon filters, like those in most pitcher-style systems, also generally do not reduce or eliminate nitrates.

The Best Reverse Osmosis System for Nitrate Removal

The Moen Reverse Osmosis Water Filtration System uses an advanced four-stage purification process to reduce nitrates and dozens of other contaminants in your cold water. It also enhances the taste, color, and clarity of the water. The system installs under the sink and features a 3.2-gallon storage tank to provide a consistent supply of clean, high‑purity water. This water can be delivered conveniently and stylishly with the optional Sip™ Drinking Water Faucet. The system is also third-party certified to ANSI/NSF 42, 53, 58, 372, and 401 standards, and to NSF Protocol 231, so you can be certain you’re getting a proven product.

Final Thoughts

With nearly one-fifth of Americans potentially consuming water with elevated nitrate levels, it’s important to take steps to reduce your nitrate exposure at home as much as possible. Start by having your drinking water professionally tested, then install a reverse osmosis water system to ensure the cleanest, safest, and best-tasting water for your family.

If you want to learn more about the best water filters for nitrate reduction or removal, or have questions about water quality in general, call SpringWell at 800-589-5592 or use the chat feature on our website to speak to one of our expert water specialists.