What Do Nitrates Do to the Body?

You might be careful about harmful additives in processed foods or artificial sweeteners in sodas, but what about nitrates in drinking water?

The Environmental Working Group (EWG) says almost 60 million people in the United States were exposed to dangerous nitrate levels in their drinking water between 2017 and 2019. The worst part? Nitrates are linked to a slew of health issues, some of which can be life-threatening. Sadly, many people, perhaps including yourself, are unaware of these risks. With nitrate levels on the rise in U.S. drinking water, it’s crucial that you fill that knowledge gap.

In this article, we’ll delve into everything you need to know about nitrates: what they are, how they get into water, reasons to avoid them, and how to eliminate them from tap water.

What are Nitrates, and Where Do They Come From?

Nitrates are naturally occurring chemical compounds made up of nitrogen and oxygen. They are primarily produced in nature, where nitrifying bacteria convert ammonia from decomposing organic matter into nitrite and then into nitrate. This process is called nitrification.

The Colorado State University explains that plants need nitrates to thrive, so they absorb them through their roots from the surrounding soil. Realizing this, manufacturers began infusing inorganic nitrates into commercial nitrogen-based fertilizers and manure to help encourage plant growth and maximize crop yield.

Beyond fertilizers, nitrates are also used in food preservatives (think cured meats like hot dogs and bacon), explosives, and some medicines. They also occur naturally in various foods, including dairy products, vegetables, and meat (note: nitrates often get passed from plants to animals when consumed).

How Do Nitrates Get into Tap Water?

Per the U.S. Environmental Protection Agency (EPA), nitrates in water mainly originate from human activities, especially through fertilizers and intensive agriculture.

Nitrates are soluble and do not bind to soil, so they can quickly move from soil into groundwater and surface waterways. For example, synthetic fertilizers packed with nitrates are spread across fields to boost crop growth and productivity. However, when it rains or floods (or even via irrigation), nitrates can seep into groundwater or wash into nearby rivers and lakes from the fertilized soil. In the same way, nitrates can leach into groundwater from manure produced at concentrated livestock and feeding operations.

The same usually happens with nitrates from other sources, including:

fertilizer runoff from golf courses, lawns, and gardens
leaking urban drainage or septic systems
erosion of natural nitrate deposits
wastewater runoff

Nitrates can escape from these sources and pollute groundwater and surface waterways (including those downstream) that supply our drinking water. Depending on the local geology, nitrates can take weeks to years to migrate from crop root zones to groundwater. However, according to a recent study by researchers at the University of California, Davis, heavy rains after a drought caused nitrates to seep 33 feet under farm fields in as little as 10 days. Once nitrates reach groundwater, they can persist for decades.

Ultimately, exposure to these chemicals will depend on whether your drinking water comes from a municipal or private water system.

Public Water Systems

Once nitrates enter ground and surface water sources, the compounds eventually end up at water treatment plants. Some amount is filtered there, but not all systems are equipped to handle high levels of nitrate contamination, especially those smaller, rural water systems in regions where nitrates are prevalent. These utilities typically lack the necessary infrastructure and funding to remove nitrate from the water before it reaches customers. Consequently, various amounts may escape into the “treated” water transported to customers’ homes.

Private Wells

Those relying on private wells are more likely to have higher levels of nitrates in their drinking water. One reason is that private well owners are solely responsible for monitoring, testing, and treating their water. With no federal oversight, many residents are left clueless about how much nitrates they are exposed to in their drinking water. And so, they may unknowingly ingest or shower in water dangerously high in nitrates. The risk of exposure is even higher for wells near crop fields, barns, feedlots, pastures, rangelands, septic systems, and other sources that generate nitrate.

Nitrate Levels Are On The Rise in U.S. Water Supplies

The U.S. has a serious nitrate problem on its hands. Nitrate levels in drinking water across various states and cities are trending upward, especially in farming and agricultural regions.

Here are several states facing worsening nitrate levels in their drinking water:

Oregon

“Oregon’s nitrate ground pollution became notably worse in the past 10 years, report finds.” That’s the headline of a recent news piece published by OBP News. Per the article, the state’s Department of Environmental Quality recently released an analysis of groundwater nitrate trends for the Lower Umatilla Basin Groundwater Management Area. It’s concerning, to say the least.

In 1990, wells in Oregon’s testing network had a median nitrate concentration of around 4.6 mg/L. By 2023, that figure had climbed to roughly 6.6 mg/L, with some wells recording nitrate concentrations as high as 75.5 mg/L (multiple times higher than the EPA’s 10 mg/L limit ). Of the 33 wells recently tested in the region, about 40% of them exceeded safe nitrate levels for drinking water.

Nebraska

Beyond its historic landmarks, sweeping Sandhills, and the annual College World Series, Nebraska, dubbed the “Cornhusker State,” also prides itself on its corn production. Nebraska supplies 32 percent of corn globally with a few other states, albeit with a massive tradeoff: nitrate pollution.

Nebraska’s nitrate pollution problem has gone on for decades. Its median statewide nitrate level has nearly doubled since the 1970s, and it doesn’t seem to be getting any better, at least based on a study released by the Nebraska Department of Environment and Energy (NDEE). The NDEE tested nearly 3,500 private wells, making it the most extensive private domestic well nitrate sampling effort in state history. Of the samples tested, 542 (15.5%) private wells exceeded the EPA’s safety limit of 10 mg/L. This is concerning because around 15 percent of Nebraska’s residents get their water from private wells, which could be at risk of nitrate pollution.

Iowa

Residents in Iowa aren’t faring much better when it comes to nitrates in their drinking water. Iowa has a long history of nitrate contamination, with levels consistently rising between 2003 and 2017, according to an EWG report. Furthermore, in June 2022, Des Moines Water Works, the state’s largest drinking water utility, was forced to reactivate its nitrate removal facility for the first time since 2017 due to elevated nitrate levels in raw water sources, Iowa Public Radio (IPR) reports. Two years later, the Des Moines Register says some residents faced restrictions on watering their lawns due to rising nitrate levels.

More recently, data from the Iowa Water Quality Information System shows that several large rivers, including the Boone (25 mg/L), Cedar (24 mg/L), Iowa, and Turkey rivers (18 mg/L), reached four-year peaks in nitrate concentrations. On that note, it’s reported that the EPA recently added segments of five rivers near large Iowa cities, including Cedar Rapids, to the state’s impaired waters list for nitrate.

Wisconsin

Wisconsin’s water is becoming increasingly laced with nitrate. The state ranks among the top 10 with an uptick in nitrate contamination in its water supply. According to the EWG, tests conducted between 2003 and 2017 showed nitrate levels of at least 3 milligrams per liter in drinking water systems serving around 1.1 million people in 303 communities. Nitrate levels increased for 165 (54%) community water systems serving 425,000 people. The problem is particularly acute in smaller communities, with 83% of the systems serving 3,300 people or less experiencing increased contamination.

Other States

California, Illinois, Kansas, Maryland, Oklahoma, Pennsylvania, and Texas—these and the other states above are dubbed America’s agricultural powerhouses. However, they also have one more thing in common: worsening nitrate levels in their water supplies, as reported by the EWG.

5 Science-Backed Reasons to Avoid Nitrates: Health Risks of Nitrate Exposure

So, what’s the big deal about nitrates? Are health officials trying to scare you for some reason, or are there real dangers to nitrate exposure? It turns out there are—nitrates can be incredibly toxic to your health.

That said, here are a few reasons to avoid them:

They may increase your cancer risk.

One of the biggest reasons to avoid nitrates? One word: cancer. When taken into the body through drinking water, food, or other mediums, nitrates convert to N-nitroso compounds (NOCs), which are known to cause cancer in animals and may be carcinogenic to humans.

What types of cancers, you ask? Well, according to the National Cancer Institute, studies have shown increased risks of kidney and stomach cancer among people with higher ingestion of water nitrate compared with low intakes. A recent study published in the journal Environmental Research also linked nitrate exposure to various other cancers, including colorectal and bladder cancer.

Notably, studies show that drinking water with just 5 mg/L of nitrate—half the EPA’s 10 mg/L limit—increases colorectal cancer risk by 15%. In Iowa alone, researchers estimate 300 annual cancer cases are tied to nitrate contamination, while the EWG puts it at over 12,500 cases nationwide for the same period.

They are incredibly toxic to infants.

Nitrates are especially hazardous to pregnant moms and infants. Exposure to higher levels of nitrates during pregnancy is said to increase the chances of neural tube defects (NTDs), preterm births, low birth weight, and miscarriages. A landmark Danish study found that nitrate levels as low as 2.6 mg/L doubled the chance of congenital disabilities like spina bifida. In the U.S., states like Wisconsin report 26 to 149 annual cases of adverse birth outcomes linked to nitrates.

Even after birth, infants face methemoglobinemia, more commonly known as “blue baby syndrome.” Essentially, nitrates impair oxygen transport in the baby’s blood, hindering their breathing. This often results in symptoms, including bluish skin (especially around the eyes and mouth), rapid heartbeat, and shortness of breath.

Learn more: When Can Babies Start Drinking Water? (Plus, the Best Water for Baby Formula) | How to Protect Children from Toxic Contaminants in Water

They may raise your risk of Type 2 Diabetes

You may try to cut back on sweets and alcohol or quit smoking, but it turns out that consuming high levels of nitrates may still increase your risk of type 2 diabetes. A 2023 cohort study tracking 104,168 French adults found that those consuming higher nitrite levels (particularly from food additives like sodium nitrite) had a 27% increased risk of developing type 2 diabetes.

Research explains that salivary glands actively absorb nitrate. When concentrated in saliva, the nitrate partially reduces to nitrite. The same happens when nitrates enter the gut. The nitrite then forms nitrosamines that impair the body’s ability to create insulin by damaging beta cells in the pancreas and disrupting insulin signaling. The body needs insulin to regulate blood sugar, so when production gets hindered, it leads to high blood sugar levels and sets the stage for developing type 2 diabetes.

They can cause thyroid disease and cancer.

Whenever someone mentions “thyroid,” picture a 2-inch-long butterfly-shaped gland in the front of the neck. Though small, it controls metabolism, energy levels, and many other bodily functions. However, when its function gets disrupted, such as when exposed to high amounts of nitrates, it can lead to various problems.

The body needs iodine to create thyroid hormones, among other things. However, nitrates interfere with the uptake of iodine, reducing levels of thyroid hormones (T3 and T4) in the body and increasing levels of thyroid-stimulating hormones (TSHs). This may result in symptoms associated with hypothyroidism, such as fatigue, weight gain, sensitivity to the cold, and feelings of depression. Perhaps even worse, studies found an increased risk of thyroid cancer with higher average nitrate levels in public water supplies and with consumption of water with nitrate levels exceeding 5 mg/L.

They are linked to Alzheimer’s and Parkinson’s Disease.

Tap water is probably the last thing you’d expect to impair your brain’s health and performance, but research shows it’s all possible if your water contains nitrates.

The brain needs glucose to function. But when you ingest nitrates, they may convert into nitrosamines. One particularly harmful nitrosamine, N-nitrosodimethylamine (NDMA), has been flagged as a key player in neurodegeneration, as it impairs glucose signaling, induces DNA damage, and increases oxidative stress in the brain. These complications may trigger neurodegenerative diseases like Alzheimer’s and Parkinson’s.

In a study published in the Journal of Alzheimer’s Disease, rats treated with NDMA developed insulin resistance in the brain, reduced mitochondrial function, and elevated levels of amyloid-beta and tau proteins—hallmark signs of Alzheimer’s Disease (AD).

Human studies mirror these findings, as a 2023 analysis of elderly residents in Shenzhen, China, found that 55.4% of urine samples contained NDMA, with higher concentrations correlating to worse cognitive performance. Still, those with detectable NDMA faced increased risks of mild cognitive impairment (MCI) and cognitive decline (CD), suggesting even low-level exposure to nitrates could accelerate neurodegeneration.

How Much Nitrate is Safe in Drinking Water?

The U.S. EPA has set a maximum contaminant level of 10 mg/L for nitrate in public water supplies. This limit is to protect against “blue-baby syndrome.” But as you’ve read in this article, nitrate levels below this limit can raise the risk of various health issues, including cancer. Clearly, current standards might not be enough to protect public health.

Does Your Water Contain Nitrates? Here’s How to Find Out

Since nitrates are odorless and colorless in water, the only way to know if they’re present in your water supply and at what concentrations is to test your water. However, you want to be sure that a certified laboratory does the testing. Do-it-yourself test strips have their place but cannot produce the same thoroughness and precision as specialized laboratory water testing equipment.

Water Testing for Private Wells

If your water comes from a private well, you are responsible for testing it to ensure its safety. That doesn’t mean you have to do it yourself, though. You can purchase a water test kit and submit a sample to a laboratory for testing. This method provides a thorough and detailed analysis of your well water by testing for different impurities and contaminants like lead, arsenic, bacteria, and others you’d never thought could end up in your water supply. It also evaluates water parameters, including pH and TDS (Total Dissolved Solids). A good rule of thumb is to test your well water once or twice yearly.

Water Testing for Public Water Systems

For those on public water, water utilities must provide an annual water quality report, also called a Consumer Confidence Report (CCR). This report provides a comprehensive overview of your water over the past year. They typically contain details, including:

the source of your drinking water;
levels of contaminants detected;
the treatment process used;
potential health risks associated with any detected contaminants, and
whether the water meets federal and state regulations regarding contaminant levels

That’s all valuable information, for sure. However, relying solely on your CCR to gauge your water quality is not recommended. Why? Because that “treated” water can get contaminated after it leaves the plant. Let’s say a water main break occurs along the public distribution network; it could introduce dirt and other pollutants into the water. Likewise, heavy metals like lead and copper can leach from corroded service lines or your home’s plumbing and enter the water. In either case, your CCR might show a certain concentration level for specific pollutants when you might be exposed to considerably higher doses. The solution? Have your water tested independently now and then.

Learn more: 10 Common Problems a Water Test Can Detect in Tap Water | How to Read Your Water Quality Report: Helpful Tips and Expert Advice

How to Remove Nitrates from Drinking Water

So, your tap water tested positive for nitrates. What do you do? Your first thought might be to boil the water, but doing so will not lower the nitrate level and make the water safe to drink. Your best course of action is to install a suitable water filter system.

Reverse osmosis systems are highly effective and reliable, removing 83 to 92 percent of nitrates from drinking water. These systems force pressurized water through a semipermeable membrane covered in tiny pores. Like a mesh strainer, these pores separate the water molecules from the contaminants. The filters have such fine micron ratings that they can also reduce levels of ions, including nitrates, in the water. The clean, treated water then passes into a storage tank, ready for drinking, cooking, ice-making, or other purposes. The contaminants left behind are discharged from the membrane and flushed down the drain.

The Best Water Filter to Remove Nitrates from Water

If you only want to remove nitrates and other pollutants from the water you and your loved ones consume, the Moen Reverse Osmosis Water Filtration System is a strong choice. It is an advanced 4-stage under-sink system that effectively reduces contaminants like nitrates, arsenic, fluoride, TDS, bacteria, viruses, lead, mercury, chlorine, and pharmaceuticals from your cold water. The result is clean, crisp, great-tasting water delivered conveniently and stylishly with an optional Moen Sip™ Drinking Water Faucet.

Learn more: Reverse Osmosis Water Filtration Explained

Final Thoughts

Nitrate levels are rising in many parts of the country, and as you now know, that’s not something we should take lightly. While the EPA has set a limit of 10 mg/L for nitrates in public drinking water, the science clearly shows that health problems, from various cancers to infant complications, may still occur at doses below that amount.

But look on the bright side: no matter your water source, you can fight against nitrates potentially lurking in your water supply. The first step is to have your water tested by a certified laboratory to determine the level of nitrates (and other potentially toxic contaminants) you might be exposed to through your drinking water. If nitrates are present, a high-quality reverse osmosis system can help reduce levels of these pollutants so you can have peace of mind knowing the water from your tap is clean and safe.