EWG's Tap Water Database — 2019 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
20120.655 ppm220.380 ppm - 0.930 ppm
20130.510 ppm220.460 ppm - 0.560 ppm
20140.540 ppm220.500 ppm - 0.580 ppm
20150.490 ppm220.400 ppm - 0.580 ppm
20160.655 ppm220.470 ppm - 0.840 ppm
20170.460 ppm220.430 ppm - 0.490 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
2012-08-20AH751610.380 ppm
2012-10-29AH829200.930 ppm
2013-08-06AI093270.460 ppm
2013-08-13AI110000.560 ppm
2014-09-15AI537770.580 ppm
2014-09-15AI537760.500 ppm
2015-08-10AI862730.400 ppm
2015-08-12AI862740.580 ppm
2016-07-26AJ200970.470 ppm
2016-07-27AJ200980.840 ppm
2017-09-14AJ678570.430 ppm
2017-09-14AJ678560.490 ppm