EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

Okla Christian 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
20140.680 ppm110.680 ppm
20150.580 ppm110.580 ppm
20160.510 ppm110.510 ppm
20180.490 ppm220.460 ppm - 0.520 ppm
20190.560 ppm110.560 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
2014-03-25041042.0010.680 ppm
2015-03-24054541.0010.580 ppm
2016-03-25SDWA-1016121-000.510 ppm
2018-02-20SDWA-1123489-000.520 ppm
2018-03-12SDWA-1244389-000.460 ppm
2019-02-25SDWA-1350164-000.560 ppm