Nitrite in Water

A nitrogen compound related to nitrate, but more toxic.

Nitrite is nitrate’s more dangerous relative — the same oxygen-transport risk to infants, at a tenth of the concentration. It also tends to signal something active: sewage intrusion, agricultural contamination, or bacteria converting nitrate in the water system itself. Any detection deserves attention.

What it is

Nitrite is an intermediate form of nitrogen, typically short-lived in nature — which is why finding it in water is more telling than finding nitrate. Like nitrate, it interferes with the blood’s ability to carry oxygen, with infants and sensitive individuals at greatest risk.

How it gets into water

Sewage leaks, agricultural runoff, and industrial wastewater are the main sources. Nitrite can also form inside distribution systems and wells when bacteria convert nitrate — so its presence sometimes points to a microbial problem as well as a chemical one.

What a result can tell you

The EPA limit is 1 mg/L — ten times stricter than nitrate’s. A detection at or near that level means the water shouldn’t be used for drinking or infant formula until a certified lab confirms and the source is found. Pairing the result with a bacteria test is sensible, since the two problems travel together.

What it can’t tell you

A strip can’t tell you whether the nitrite is chemical runoff or microbial conversion — that diagnosis takes lab work and sometimes a well inspection. As with nitrate, boiling concentrates rather than removes it.