Nitrate in well water

The most common contaminant in private well testing, and one of the few tied to a specific, well-documented health risk: infant methemoglobinemia, better known as blue baby syndrome.

Where it comes from

Septic drain fields, fertilizer, and livestock operations are the three main sources. Nitrate moves easily through soil into groundwater, which is why wells in farm country and wells near an aging septic system deserve testing most often.

The EPA level

The Maximum Contaminant Level is 10 mg/L as nitrogen (N), set to protect infants. Nitrate interferes with how an infant's blood carries oxygen, and formula mixed with contaminated well water is the classic exposure route. A household with an infant, or expecting one, should treat a reading above roughly half the MCL as worth a second look, not just readings that technically cross the line.

What to do about a high reading

Boiling doesn't remove nitrate; it concentrates it as the water evaporates. Reverse osmosis, distillation, and ion exchange are the standard treatment methods. A state-certified lab or your local health department can confirm the result with a fresh sample and advise on next steps.

Have a lab result already? Upload it and check your nitrate reading.