Nitrate is the most common chemical contaminant in America’s private wells. Not lead, not PFAS — nitrate. If your water comes from a well anywhere near farmland, a septic system, or livestock, this one is worth understanding.
What it is
Nitrate (NO₃) and nitrite (NO₂) are nitrogen compounds that dissolve easily in water. The EPA’s legal limit is 10 milligrams per liter measured as nitrogen — you’ll see it written “10 mg/L as N.” That number exists for one clear reason, which I’ll get to below.
Where it comes from
Mostly from the surface, working its way down. Synthetic fertilizers and manure spread on fields, septic system drain fields, feedlots, wastewater — rain and irrigation carry the nitrogen down into groundwater. Shallow wells in agricultural areas are the most exposed. This is also why New Jersey’s private-well testing law requires a nitrate test: the state knows it’s the likeliest thing to show up.
The honest health picture
The established, no-argument risk is to infants under six months: “blue baby syndrome” (methemoglobinemia). An infant’s digestive system converts nitrate to nitrite more readily, and nitrite interferes with the blood’s ability to carry oxygen. It is serious, and it is preventable — do not mix infant formula with water over the limit.
For adults, the picture is murkier. You’ll see alarming claims online; here’s the measured version. IARC (the International Agency for Research on Cancer) classifies ingested nitrate and nitrite under conditions that lead to nitrosamine formation in the body as Group 2A — “probably carcinogenic.” A quick framing note, since this series covers classified substances: IARC groups are hazard classifications. They say whether something can cause cancer, not how much risk a given exposure carries. Group 2A does not mean “dangerous at any dose.” The science on adult risk at typical exposures is still debated. What isn’t debated: infants and pregnant women should take the limit seriously.
How to test
A lab test for “nitrate as nitrogen,” usually $20–40 from a certified lab. Test once a year if you’re near farms or septic systems, and retest after heavy flooding — runoff spikes levels. If you’ve never tested your well for nitrate, that test is overdue.
What actually removes it
- Reverse osmosis — yes, effective.
- Anion exchange (nitrate-selective resin) — yes, the whole-house option.
- Distillation — yes.
What doesn’t — and the dangerous myth
- Boiling does NOT remove nitrate. It makes it worse. Water evaporates, nitrate stays, concentration goes up. This is the single most important sentence in this article: if your water is high in nitrate, boiling it for your baby’s formula concentrates the very thing you’re worried about.
- Standard carbon filters — no.
- Standard water softeners — no (they swap calcium for sodium; nitrate sails through).
- UV light — no. UV kills bacteria; it doesn’t touch dissolved chemicals.
Bottom line
Nitrate is common, testable, and fixable — but only by the right equipment. If you’re on a well, test for it. If it’s over 10 mg/L as N, an RO unit at the kitchen sink handles drinking and cooking water, and that’s the honest, proportionate fix.
Wondering what else might be in your water? Start with What’s In Your Water?
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