Nitrates and Nitrites in Drinking Water

Nitrogen can take different forms in nature and is important for life in both plants and animals. The most common form of nitrogen found in well water is nitrate. Nitrate contamination of water usually comes from fertilized agricultural fields, septic system failures, or compost piles that are too close to wells.

Wells with high levels of nitrates are more likely to be privately owned and/or shallow and affected by human activity. If human or animal waste contaminates a well, nitrites will be detected first but will quickly convert to nitrates. Therefore, most well water tests are done for nitrates.

The Health Department recommends testing your private water source for nitrates and other contaminants. Find out what you should test

The maximum contaminant level for nitrates in water is 10.0 mg/L and for nitrites is 1.0 mg/L. Actions to remove or reduce nitrates should be taken if levels exceed 5.0 mg/L

Health Effects of Nitrates and Nitrites in Drinking Water

There are two health concerns when drinking water with high levels of nitrates or nitrites.

The first is risk of “blue baby syndrome,” also called methemoglobinemia:

  • Poisoning can occur when babies drink formula made with nitrate- or nitrite- contaminated tap water.
  • The baby’s blood is less able to carry oxygen due to the poisoning.
  • Affected babies develop a blue-gray color and need emergency medical help immediately.
  • Babies under six months of age are more at risk.

The second is the potential formation of chemicals called nitrosamines in the digestive tract. Nitrosamines are being studied for long-term links to cancer. No standards have been set for this yet.

Treatment Options

Treatment methods such as anion exchange and reverse osmosis can remove nitrates from drinking water.

Anion exchange uses equipment and technology similar to a water softener. It treats all the water for the home. The nitrates are removed from the water as they are exchanged for (harmless) chlorides. The chlorides are supplied from a salt tank which must be re-filled on a schedule.

Reverse osmosis uses a membrane through which water (but not nitrates) can travel. The system is typically installed beneath the kitchen sink with a small tank holding the nitrate-free water. Water used for drinking and food preparation comes from this tank under the sink. If the well water is hard or contains too much iron, a softener or iron removal system must be installed before using the reverse osmosis system.

Call a water treatment professional for details. Do a follow-up nitrate water test to make sure the treatment worked and nitrates are not present. We strongly recommended properly maintaining the treatment system and periodic testing for nitrates to make sure the system is working.