Nitrate
Also known as: Nitrate-nitrogen, NO₃
An agricultural contaminant that's acutely dangerous to infants; common across farm country and rural groundwater.
MCL 10 mg/L (as nitrogen). Nitrite has a separate 1 mg/L limit; both are acute (immediately health-based) contaminants.
High nitrate causes methemoglobinemia — 'blue baby syndrome' — which can be fatal to infants under six months by reducing the blood's ability to carry oxygen. Research also links chronic exposure to certain cancers.
Agriculture above all — nitrogen fertilizer and manure leach into shallow groundwater — plus septic systems and wastewater. It dominates farm-belt and rural well contamination.
Reverse osmosis, ion exchange, or distillation. Do NOT boil — boiling concentrates nitrate. Infants should never drink water above the limit.
Source: EPA Safe Drinking Water Information System (SDWIS) · 2026 Q1
Nitrate is the signature contaminant of agricultural America. Fertilizer and animal manure applied to fields wash nitrogen into shallow aquifers, where it can build to levels dangerous for bottle-fed infants.
Unlike slow-acting carcinogens, nitrate is an acute contaminant: a single exceedance is a health-based violation because the risk to infants is immediate. It's a persistent problem for small groundwater systems and private wells across the Corn Belt, Central Valley, and High Plains.
States with the most nitrate violations
Community water systems with a related health-based violation since 2016.
| # | State | Systems |
|---|---|---|
| 1 | California | 134 |
| 2 | Texas | 76 |
| 3 | Oklahoma | 45 |
| 4 | Kansas | 44 |
| 5 | Nebraska | 42 |
| 6 | Washington | 36 |
| 7 | Arizona | 31 |
| 8 | Iowa | 26 |
| 9 | Pennsylvania | 20 |
| 10 | Montana | 18 |
| 11 | Illinois | 16 |
| 12 | Colorado | 13 |
Common questions
What is the EPA limit for nitrate in drinking water?
MCL 10 mg/L (as nitrogen). Nitrite has a separate 1 mg/L limit; both are acute (immediately health-based) contaminants.
Is nitrate in drinking water dangerous?
High nitrate causes methemoglobinemia — 'blue baby syndrome' — which can be fatal to infants under six months by reducing the blood's ability to carry oxygen. Research also links chronic exposure to certain cancers.
Where does nitrate in water come from?
Agriculture above all — nitrogen fertilizer and manure leach into shallow groundwater — plus septic systems and wastewater. It dominates farm-belt and rural well contamination.
How do I remove nitrate from my water?
Reverse osmosis, ion exchange, or distillation. Do NOT boil — boiling concentrates nitrate. Infants should never drink water above the limit.
Which states have the most nitrate violations?
Across U.S. community water systems, 636 have had a related health-based violation since 2016, led by California with 134.