Nitrate in Well Water
Nitrate enters groundwater from fertilizer, animal waste and septic systems, making it one of the most widespread private-well contaminants — especially in agricultural areas. Like arsenic, it's invisible and tasteless.
Why it's dangerous
High nitrate is most dangerous for infants under six months: it interferes with the blood's ability to carry oxygen, causing "blue baby syndrome" (methemoglobinemia). Pregnant women and adults face risks at sustained high levels too. Never mix infant formula with well water that hasn't been tested for nitrate.
The EPA limit
The federal MCL for nitrate (measured as nitrogen) is 10 mg/L. Boiling water does not help — it concentrates nitrate, making it worse.
States with the highest modeled risk
Share of private-well residents above the 10 mg/L limit (USGS model):
- Delaware 12.7%
- California 10.4%
- Maryland 6%
- Oklahoma 6%
- Kansas 5.2%
- Pennsylvania 3.9%
- Idaho 3.7%
- Texas 2.5%
How to remove nitrate
Carbon filters and standard softeners do not remove nitrate. Use reverse osmosis (NSF/ANSI 58) or a nitrate-specific anion-exchange system. Reverse osmosis is the simplest point-of-use fix for drinking and cooking water.
Treating nitrate in your area
Nitrate is not removed by carbon pitchers or faucet filters. Reverse osmosis is the treatment that brings it below the federal limit at your tap.
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