EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite


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
20140.190 ppm220.0390 ppm - 0.340 ppm
20151.21 ppm221.02 ppm - 1.40 ppm
20160.770 ppm220.740 ppm - 0.800 ppm
20170.420 ppm330.120 ppm - 0.920 ppm
20181.03 ppm220.980 ppm - 1.07 ppm
20191.87 ppm221.64 ppm - 2.09 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
2014-08-28AC322230.340 ppm
2014-08-28AC322240.0390 ppm
2015-03-26AC438441.40 ppm
2015-03-26AC438431.02 ppm
2016-03-30AC678580.740 ppm
2016-03-30AC678570.800 ppm
2017-03-27AC923300.120 ppm
2017-03-27AC923310.220 ppm
2017-05-17AC979790.920 ppm
2018-05-22AD167511.07 ppm
2018-05-22AD167520.980 ppm
2019-03-26AD407252.09 ppm
2019-03-26AD407261.64 ppm