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Nitrate in Drinking Water: Health Concerns and Prevention Tips

TypeContaminantMax. Contaminant Level Goal (ppm)Max. Contaminant Level (ppm)
Required Treatment Technique
Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)Sources of Contaminant in Drinking WaterConsumer Treatment MethodOfficial Sources
Inorganic ChemicalsNitrate (measured as Nitrogen)1010Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.Runoff from fertilizer use; leaking from septic tanks, sewage; erosion of natural depositsReverse Osmosis, Distillation, Ion Exchange, Biological treatmentCDC, NSF, EPA
National Primary Drinking Water Regulations List of Contaminants

Nitrate contamination in drinking water is an issue of growing concern, especially given the potentially adverse effects on human health. Nitrates are naturally occurring in the environment and can seep into groundwater supplies from various sources, such as fertilizers, septic systems, animal feedlots, industrial waste, or food processing waste. Small amounts of nitrate are commonly found in all rainfall and groundwater aquifers, but it is the high concentrations of this contaminant that raise concerns for public safety and wellbeing.

The United States and the World Health Organization (WHO) have each established guidelines for acceptable levels of nitrate in drinking water. In the United States, the maximum contaminant level (MCL) for nitrate in public drinking water supplies is set at 10 mg/L as nitrate-nitrogen (NO3-N), while the WHO guideline is equivalent to 50 mg/L as NO3 or 11.3 mg/L NO3-N. To ensure that drinking water is within these limits, effective removal methods, such as ion exchange, distillation, or reverse osmosis, are implemented for treatment processes. Constant monitoring and adherence to these guidelines can help protect public health and maintain the safety of drinking water supplies.

Nitrate in Drinking Water

Leiem, CC BY-SA 4.0, via Wikimedia Commons

Nitrate is a common environmental contaminant found in drinking water, primarily due to its presence in fertilizers, septic systems, animal feedlots, industrial waste, and food processing waste. When nitrate enters groundwater, it can dissolve and contaminate drinking water sources, posing potential health risks to consumers.

Excessive nitrate levels in drinking water can lead to a condition called methemoglobinemia, also known as “blue-baby syndrome.” This condition mainly affects infants and causes their blood to become less effective in carrying oxygen, resulting in a blue tint to the skin. The Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) for nitrate in public drinking water supplies at 10 mg/L as nitrate-nitrogen (NO3-N), which is approximately equivalent to the World Health Organization (WHO) guideline of 50 mg/L as NO3 or 11.3 mg/L NO3-N.

Some studies have suggested a connection between high nitrate concentrations in drinking water and an increased risk of cancer. Nitrate can be converted to nitrite in the body, and when combined with certain compounds found in food, forms potentially carcinogenic nitrosamines.

Various treatment options are available to remove nitrate from water, such as ion exchange, distillation, and reverse osmosis. Bottled water can also be a safer alternative, as it is subject to strict quality standards set by the EPA, which regulate the nitrate levels in bottled water as well. People living in agricultural areas, particularly those with shallow wells near nitrate sources, may be at a higher risk for nitrate contamination in their drinking water.

It is essential for individuals and communities to test their drinking water for nitrates regularly, especially in areas with potential agricultural or industrial contamination sources. Regular monitoring can help maintain safe nitrate levels in drinking water, protecting public health and the environment.

How to Test for Nitrate in Drinking Water

professional water testing

Nitrates are a common concern for those who rely on private well water for their household needs. High levels of nitrates in drinking water can be harmful, especially for infants and pregnant women. It is essential for homeowners to regularly test their well water for nitrates to ensure its safety.

To test for nitrates in water without a lab, you should get a kit. Many are available online. Once you have your kit, you should follow the instructions, but it may involve something like this:

You will first need to collect a water sample from the tap or well source. For accurate results, follow these steps:

  1. Collect the sample: Fill a clean sample bottle with water from the tap or directly from the well. Ensure that the bottle is free from contaminants and has been thoroughly rinsed before use.
  2. Measure the water sample: Using a clean test tube, measure 2.5 milliliters of the water sample and place it in the test tube.
  3. Add the Mixed Acid Reagent: Carefully top the water sample in the test tube up to 5.0 milliliters with a Mixed Acid Reagent, which helps to analyze nitrate levels in the water sample.
  4. Allow the reaction to occur: After adding the Mixed Acid Reagent, let the test tube rest for approximately 3 minutes. This will allow for the sample and the reagent to react.
  5. Add the nitrate indicator: Using a 0.1-gram spoon, scoop a level amount of nitrate indicator and add it to the test tube. Allow the mixture to sit for about 9 minutes.

Inspect the color change in the test tube to determine nitrate levels. Compare the color against a provided color chart, which will indicate the nitrate concentration in parts per million (ppm). Keep in mind that the maximum contaminant level (MCL) for nitrate in drinking water set by the Environmental Protection Agency (EPA) is 10 ppm.

For homeowners with private wells, it is crucial to conduct nitrate testing at least once a year. If your test results show a nitrate level near or exceeding the MCL, consult a professional to discuss treatment options and further evaluate the source of contamination. Regular well maintenance and proper disposal of chemicals and waste also play a significant role in preventing nitrate contamination in drinking water.

How to Remove Nitrate from Drinking Water

Nitrates can enter drinking water through various sources, such as fertilizers, septic systems, and runoff from agricultural areas. High levels of nitrate in drinking water can pose health risks, especially to infants. The World Health Organization (WHO) has set a guideline for nitrate levels in drinking water at 50 mg/L. There are several methods to remove nitrate from drinking water, including reverse osmosis, distillation, ion exchange, and biological treatment.

Reverse Osmosis

Reverse osmosis (RO) is a popular and effective method for removing nitrates from drinking water. This process uses a semi-permeable membrane to separate water molecules from contaminants, including nitrates. RO systems can remove up to 90% of nitrates, as well as other contaminants like sodium and certain heavy metals. To ensure proper performance, it is crucial to maintain the RO system regularly and replace the membrane as needed. For households with high nitrate levels in their water supply, a water quality report can help determine the feasibility of installing an RO system.


Distillation is another method to remove nitrates from drinking water. In this process, water is heated to produce steam, leaving behind contaminants such as nitrates. The steam is then condensed back into liquid form, resulting in purified water. While distillation is effective in removing nitrates, it requires a significant amount of energy and may not be practical for residential use.

Ion Exchange

Ion exchange is a chemical process used to remove nitrates from water. In this method, water is passed through a resin bed, which contains positively charged ions that attract and hold onto negatively charged nitrates. As a result, nitrates are exchanged for other ions, such as sodium or chloride. Ion exchange systems are effective in reducing nitrate levels in water and require regular maintenance to ensure their effectiveness. It is important to consider the potential impact of increased sodium levels on individuals with sodium-sensitive health conditions.

Biological Treatment

Biological treatment involves the use of microorganisms to break down nitrate contaminants. This process typically occurs within aquifers or shallow wells where water interacts with organic matter that supports the growth of denitrifying bacteria. These bacteria convert nitrate to nitrogen gas, which is released harmlessly into the atmosphere. While biological treatment occurs naturally in some groundwater sources, it can be encouraged by adding organic material to the aquifer or well. This method may not be practical for all households but can be an effective option for some.

How Does Nitrate Get into Drinking Water

Nitrate is a naturally occurring compound of nitrogen and oxygen that can enter drinking water from various sources. One primary contributor to nitrate contamination in water is surface runoff from agricultural lands where fertilizers containing nitrate are used. These fertilizers can make their way into groundwater, rivers, and lakes, eventually reaching public water systems or private wells.

In addition to agricultural activities, nitrate pollution can be traced back to leakage from wastewater, urban drainage, or septic systems. Nitrate may also enter water sources through atmospheric deposition from nitrogen-containing compounds released by automobiles and industrial activities.

When it comes to the human diet, nitrate is found in a variety of foods such as vegetables, meat, and some processed products. Vegetables like spinach contain naturally occurring nitrates, which can contribute to nitrate intake. However, high levels of nitrate in drinking water are a greater cause for concern, particularly for vulnerable populations like infants.

Elevated levels of nitrate in drinking water can have adverse health effects on humans, especially in infants, leading to a condition called methemoglobinemia or “blue baby syndrome.” This occurs when nitrates are consumed in large amounts, and the body is unable to process them effectively. The nitrates combine with hemoglobin, reducing the blood’s ability to carry oxygen, resulting in symptoms like blue or purple skin, difficulty breathing, and even death in severe cases. Pregnant women, older adults, and people with chronic health issues may also be more susceptible to the harmful effects of nitrate exposure.

Ensuring a clean and safe water supply is vital for maintaining public health. As such, effective monitoring and treatment methods must be employed in public water systems to minimize the risk of nitrate contamination. Private well owners should also be vigilant in testing their water supply to avoid exposure to high levels of nitrates.

Effects of Nitrate on the Human Body

Nitrate is a common compound found in drinking water, especially in agricultural areas where inorganic fertilizers and septic tanks can contribute to its increased concentration. Public water systems are regulated by the U.S. Environmental Protection Agency (EPA) to maintain nitrate levels below the safety limit of 10 milligrams per liter. However, even at levels below the regulatory limits, nitrate can have potential health consequences.

One of the primary concerns related to nitrate consumption is the formation of nitrosamines, which are compounds that can be carcinogenic. These compounds can be formed when nitrate reacts with amines in the stomach. It has been observed that high levels of nitrate in drinking water can lead to an increased risk of colon cancer, stomach cancer, and gastric cancer, as well as thyroid disease and adverse pregnancy outcomes.

Blue-baby syndrome, also known as methemoglobinemia, is another health risk associated with nitrate consumption. It affects infants, particularly those under six months of age, when nitrate interferes with the oxygen-carrying capacity of red blood cells, leading to a reduced oxygen supply in the body. Pregnant women, especially those residing near contaminated springs or water sources, are also vulnerable to the harmful effects of nitrate.

Distillation, along with other water purification methods, can help reduce nitrate levels in drinking water. Moreover, guidelines and regulations established by health authorities provide a framework to ensure that water sources have acceptable nitrate levels to minimize potential health risks.


Nitrate contamination in drinking water is a subject of concern due to its potential effects on human health. The strongest evidence for a relationship between drinking water nitrate ingestion and adverse health outcomes exists for colorectal cancer, thyroid disease, and neural tube defects. In some cases, increased risks were observed even with nitrate levels below regulatory limits.

Furthermore, research findings suggest a possible association between increased nitrate in drinking water and preterm birth and some specific congenital anomalies. This highlights the need for regular review of evidence to better understand the potential risks associated with nitrate consumption.

One of the most widely recognized health effects of nitrate in drinking water is methemoglobinemia, also known as “blue-baby syndrome.” This condition primarily affects infants 0-4 months old when their formula is mixed with nitrate-contaminated water.

Despite these concerns, it’s important to note that exposure to nitrate and nitrite concentrations found in U.S. drinking water is unlikely to contribute to human cancer risk. In fact, a significant portion of nitrate intake comes from dietary sources instead of drinking water.

Lastly, to mitigate the effects of nitrate contamination in drinking water, it’s crucial to establish effective monitoring and management practices to safeguard public health.

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