Nitrite in Tap Water
Nitrite is a nitrogen compound closely related to nitrate, formed as nitrate is converted in the environment or in treatment. It shares nitrate’s sources but is regulated at a lower level.
Runoff and leaching from fertilizer, manure, and septic systems, and conversion of nitrate under low-oxygen conditions.
- 1Agricultural fertilizer
- 2Animal waste
- 3Septic systems
Most affected: Infants under six months (risk of methemoglobinemia, "blue-baby syndrome") and pregnant people.
A result is read with its context
This contaminant is tracked through federal and state compliance monitoring. Private wells near farmland should be tested, especially before use by infants. PurityMap does not yet publish a per-system measured value for Nitrite; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
- Above reference
- Evidence exceeds a reference level.
- Detected
- This substance was found in the monitoring record. Being present is not the same as being above a reference level, and this signal does not say which.
- Not detected
- Somebody looked and the laboratory reported nothing above its reporting limit. This is a result, and it is not the same as nobody looking.
- Not monitored
- No sampling for this substance has been reported for this system. Nothing is known either way, and an empty row is not a clean one.
4 cities with a health-based violation
A violation is a past event with a status, from the federal compliance record (EPA SDWIS, since 2016). It does not describe the water today.
PurityMap does not yet publish a per-system measured value for nitrite. Check your utility’s Consumer Confidence Report, or use a certified home test.
What can carry a nitrite reduction claim
- Reverse osmosis
Semi-permeable membrane separation removing dissolved minerals, heavy metals, and persistent fluorinated chemicals down to 0.0001 microns.
- Anion exchange
Synthetic polyvalent resin beads that exchange unwanted dissolved ionic contaminants for harmless benchmark ions.
- Distillation
Boiling does not remove a dissolved chemical compound and can concentrate it. Many pitcher and refrigerator filters carry no verified claim for a compound like this at all.
A finding establishes the need, the need names the capability, the capability requires a verified certification. No product appears before that sequence completes. Filter Finder →
Frequently asked
Answers cite the same records as the page. How PurityMap analyzes water data
Nitrite is a nitrogen compound closely related to nitrate, formed as nitrate is converted in the environment or in treatment. It shares nitrate’s sources but is regulated at a lower level.
The enforceable federal limit is 1 mg/L as nitrogen (MCL). The health-based goal (MCLG) is 1 mg/L. PurityMap reads every measurement against its stated benchmark and never sets its own.
Agricultural fertilizer, Animal waste, Septic systems.
Like nitrate, high nitrite is an acute risk for infants because it interferes with the blood’s ability to carry oxygen. It is regulated at a lower limit than nitrate because it is the more directly active form. Boiling concentrates nitrite rather than removing it.
Treatment technologies commonly certified to reduce Nitrite include Reverse osmosis, Anion exchange, Distillation. Match the exact certified claim to your water before buying. Holding a format is not the same as holding the claim.
In the federal compliance record (EPA SDWIS, since 2016), 4 cities in PurityMap's record across 4 states had a water system measure Nitrite above the legal limit, most recently in 2025, including Guymon, OK; Hastings, NE; Riverhead, NY. Each violation is a past event with a published status, not a description of the water today.