EWG's Tap Water Database — 2019 UPDATE


Nitrate and nitrite

Oklahoma University

Nitrate and nitrite enter water from fertilizer runoff, septic tanks and urban runoff. These contaminants can cause oxygen deprivation for infants and increase the risk of cancer. Nitrite is significantly more toxic than nitrate. Click here to read more about nitrate.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20120.397 ppm30300.150 ppm - 0.760 ppm
20130.386 ppm3029ND - 0.700 ppm
20140.262 ppm3122ND - 0.658 ppm
20150.116 ppm319ND - 0.775 ppm
20160.439 ppm3121ND - 1.47 ppm
20170.556 ppm3834ND - 2.28 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

The health guideline of 0.14 parts per million, or ppm, for nitrate and nitrite is based on the equivalent health guideline for nitrate, as defined in a peer-reviewed scientific study by EWG. This guideline represents a one-in-one-million annual cancer risk level.

EPA Maximum Contaminant
Level (MCL) 10 ppm

ppm = parts per million

All test results

Date Lab ID Result