EPA legal limit
10 ppm
Maximum Contaminant Level
EWG health guideline
0.14 ppm
Science-based, stricter target
Health effects
At levels above 10 ppm, nitrate can cause methemoglobinemia ("blue baby syndrome") in infants under 6 months by reducing the oxygen-carrying capacity of blood. EWG's health guideline of 0.14 ppm reflects emerging research linking even low nitrate levels to increased cancer risk and adverse fetal outcomes in pregnant women. Standard carbon filters do not remove nitrate.
Where it comes from
The primary source is agricultural fertiliser runoff — nitrogen from fertilisers washes into streams, rivers, and groundwater. Septic systems, animal feedlot waste, and industrial discharge are secondary sources. Nitrate is most prevalent in agricultural regions of the Midwest, California's Central Valley, and parts of the South.
How it's regulated
EPA MCL is 10 ppm, set to protect infants from blue baby syndrome. The EWG health guideline is 0.14 ppm based on cancer risk and reproductive harm research. Many utilities report levels between 0.14 and 10 ppm — legally compliant but above the science-based threshold.
The EPA vs EWG gap
The legal limit (10 ppm) is 71× higher than the EWG health guideline (0.14 ppm). Water can be legally compliant while still exceeding the science-based threshold.
How to filter nitrate
Not all filters address nitrate. Look for independently certified filters — NSF International certification means the removal claim has been independently verified.
Nitrate is not removed by water ionization. Reverse osmosis (NSF 58) or ion exchange is required. Standard carbon block filters, pitcher filters, and Brita-type filters do not remove nitrate — this is important to understand for infant formula preparation.
Frequently asked questions
What is nitrate?
An inorganic compound containing nitrogen and oxygen, found naturally at low levels in soil and water. Agricultural runoff is the primary source of elevated nitrate in U.S. drinking water.
What are the health effects of nitrate?
At levels above 10 ppm, nitrate can cause methemoglobinemia ("blue baby syndrome") in infants under 6 months by reducing the oxygen-carrying capacity of blood. EWG's health guideline of 0.14 ppm reflects emerging research linking even low nitrate levels to increased cancer risk and adverse fetal outcomes in pregnant women. Standard carbon filters do not remove nitrate.
Is nitrate regulated in drinking water?
EPA MCL is 10 ppm, set to protect infants from blue baby syndrome. The EWG health guideline is 0.14 ppm based on cancer risk and reproductive harm research. Many utilities report levels between 0.14 and 10 ppm — legally compliant but above the science-based threshold.
Where does nitrate come from?
The primary source is agricultural fertiliser runoff — nitrogen from fertilisers washes into streams, rivers, and groundwater. Septic systems, animal feedlot waste, and industrial discharge are secondary sources. Nitrate is most prevalent in agricultural regions of the Midwest, California's Central Valley, and parts of the South.
How do I remove nitrate from tap water?
The most effective methods for removing nitrate are: Reverse osmosis (RO), NSF 58 certified RO system, Ion exchange resin, Distillation. Look for NSF-certified systems — independent certification confirms removal claims have been verified.
Is nitrate in your water?
Enter your ZIP code to see the measured level in your specific utility.