Nitrites/ Nitrates in Water: What You Need to Know in 2022

Nitrates are natural compounds of nitrogen and oxygen. These pose a health risk when found in high levels in tap water. These contaminants are rare in public drinking water supplies, but they’re fairly common in private wells.

This glossary offers information on nitrates in drinking water, including how they get there, their potential health effects, and how to protect your family from nitrates and nitrites.

❔ What are Nitrates?

💡 Nitrates are nitrogen-based compounds that are commonly found in fertilizers and explosives. Nitrates are used as preservatives for metals, and many vegetables naturally contain these compounds. Industrially, nitrates are used to remove air bubbles from glass and oxidize materials in the production of ceramics.

Nitrates are often confused for nitrites, a different type of compound. While nitrates (NO3) are made from one nitrogen atom and three oxygen atoms, nitrites (NO2) are made from one nitrogen atom and only two oxygen atoms. Nitrates aren’t as toxic as nitrites, but both are considered a health concern when found in drinking water.

In Water AsNo3-1 (Nitrate) ; No2-1 (Nitrite)
SourcesLivestock and human sewage
Industrial waste and leaking septic tanks
Contaminant Levels (MCLs)
US EPA: 10.0 mg/L; 10.0 mg/L (MCLG)
WHO Guideline: 11.3 mg/L (for nitrate as N); 50 mg/L (for nitrate as NO3-1)
Health Canada: 10 mg/L

US EPA: 1.0 mg/L; 1.0 mg/L (MCLG)
WHO Guideline: 1 mg/L
Health Canada: 1 mg/L
EWG: 0.14 mg/L
Potential Health RisksBlue baby syndrome
Thyroid disease
Increased risk of colon cancer
TreatmentsReverse Osmosis
Ion Exchange

🩺 What are the Potential Health Effects of Nitrates?

According to a review of studies into the health effects of nitrates in water, about 6% of private wells and 2% of public-supply wells exceeded the MCL for nitrates (more on MCLs later).

Some of the potential health effects of exposure to high nitrate levels in water are:

  • Blue baby syndrome (or methemoglobinemia), a potentially fatal disease that turns hemoglobin into methemoglobin, which affects infants younger than 6 months and reduces the blood’s ability to carry oxygen around the body
  • Birth defects
  • Thyroid disease, caused by nitrates blocking the uptake of iodine
  • Increased risk of colon cancer
  • Recurrent respiratory infections
  • Reproductive complications such as spontaneous abortion

The exact health effects experienced from nitrate contamination depend on the nitrate levels present in the drinking water supply, and the quantity of contaminated water that is consumed.

🚰 How Do Nitrates Get Into Drinking Water?

Nitrogen is found naturally in the earth. Bacteria in the soil convert nitrogen to nitrate, which is picked up by water flowing over or seeping through the earth.

Many agricultural chemicals, including pesticides and herbicides, contain nitrates. These chemicals may leach nitrates into surface water sources through runoff. Industrial waste and leaking septic tanks and septic systems also release nitrates and nitrites into water. Additionally, rainwater may carry manure containing nitrates into lakes and streams.

Most public water systems have a very low nitrite and nitrate concentration. These compounds are most commonly found in private well water supplies in rural or agricultural communities, which aren’t treated to remove contaminants by a public supplier.

nitrates from agriculture fertilizers

📉 Do Water Treatment Facilities Monitor Levels of Nitrates in Drinking Water?

Yes, water treatment facilities are legally obliged to monitor levels of nitrates in drinking water, and there are clear standards for these compounds set by the Environmental Protection Agency (EPA) under the Safe Drinking Water Act.

The following guidelines and regulations are in place for nitrate-nitrogen in drinking water:

  • EPA Maximum Contaminant Level: 10.0 mg/L
  • EPA Maximum Contaminant Level Goal: 10.0 mg/L
  • Health Canada Maximum Acceptable Concentration: 10 mg/L
  • World Health Organization (WHO) Guideline: 11.3 mg/L (for nitrate as N) OR 50 mg/L (for nitrate as NO3-1)

The following guidelines and regulations are in place for nitrite-nitrogen in drinking water:

  • EPA Maximum Contaminant Level: 1.0 mg/L
  • EPA Maximum Contaminant Level Goal: 1.0 mg/L
  • Health Canada Maximum Acceptable Concentration: 1 mg/L
  • World Health Organization (WHO) Guideline: 1 mg/L

According to the EPA’s MCL, private water supplies should minimize nitrate levels to at least 10.0 mg/L and nitrite levels to at least 1.0 mg/L. The Maximum Contaminant Level Goal for these contaminants – the highest nitrite and nitrate levels that are thought to pose no health risk, namely blue baby syndrome – is the same as the Maximum Contaminant Level – the highest amount of nitrate and nitrite allowed in drinking water.

The Environmental Working Group (EWG) has set its own health guideline of 0.14 mg/L for nitrate in drinking water, believing the EPA’s MCL to be too low. According to the EWG’s Tap Water Database, millions of Americans drink water supplied by utilities reporting nitrate and nitrite levels above the EWG’s health guidelines.

Flowing water in sink

🔎 How Can I Tell if Nitrates are in My Drinking Water?

Why are nitrate and nitrite considered such dangerous drinking water contaminants? Partly because of their health risks – but also because they’re undetectable, regardless of how much or how little they’re present in water.

Nitrate-contaminated water looks, smells, and tastes exactly the same as water containing no nitrate. That means you could drink water containing too much nitrate without even knowing it.

The only way to know for certain what’s in your water system is to get your water tested. A private laboratory test provides information on exactly how much nitrate and nitrite your water contains, in PPM or mg/L, as well as the potential health risks of the contaminants, and how to reduce them in your water.

Nitrate occurs naturally in the ground, and private well owners are at the highest risk of drinking water nitrate and nitrite contamination. If you own a private well, your local health department may be able to provide free or discounted water testing.

Water testing with tap score

👩🏽‍⚕️ How Can I Protect My Family from Nitrates in Drinking Water?

The best way to reduce your nitrite and nitrate intake is to install a water treatment system that’s capable of nitrate removal.

Some of the best water treatment methods for removing nitrate and nitrite are:

  • Reverse osmosis – An RO water system forces water through several filtration stages and a semi-permeable membrane, which has tiny pores that can remove almost 100% total dissolved solids, including 50-92% of nitrate & nitrite. Look for a system with a National Sanitation Foundation (NSF) 58 certification for performance, which gives third-party assurance that the system effectively removes contaminants.
  • Ion exchange – An ion exchange system uses a bed of resin beads to remove select contaminants from water. To remove nitrate and nitrite, an ion exchange system exchanges chloride ions with these unwanted compounds. This process can only be effective if water doesn’t contain elevated levels of sulfates.
  • Distillation – A water distiller eliminates virtually all waterborne contaminants – including disease-causing bacteria, chemicals, metals, and up to 100% nitrate & nitrite – by boiling water until it evaporates, then carrying it to a separate container to condense. Water distillation is powerful but slow, taking 4-6 hours to produce a 1-gallon batch of water.

If private testing detects high levels of nitrite or nitrate in drinking water, switch to bottled water while you search for a suitable treatment system to remove these contaminants.

Multi-stage whole house RO water filtration system

⚠️ How Else Can I Be Exposed to Nitrates?

Nitrate ingestion in water is one of the most common sources of nitrate exposure. Some of the other sources of nitrate and nitrite exposure are:

  • Ingesting foods that are contaminated with nitrate or nitrite, such as lettuce, celery, spinach, beetroot, and other vegetables, meat products preserved with sodium nitrate, and infant formula prepared with nitrate-contaminated water.
  • Consuming nitrates in certain medications, such as some antibiotics, diuretics, and local anesthetics.
  • Consuming oral tobacco products that contain nitrates
  • Certain occupations, such as those in fertilizer and explosive industries, which have an increased risk of inhalation of nitrate salts in dusts, and farming industries

📌 The most likely cause of nitrate or nitrite exposure is ingestion. Reduce your exposure to nitrates in foods by avoiding processed meats, and wash and peel your vegetables to remove fertilizer containing nitrates from their surfaces.

📝 Where Can I Get More Information?

You can find more information about nitrates and nitrites in water, including their potential health effects, in the links below.