EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

Western Water Company

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
20140.270 ppm110.270 ppm
20150.600 ppm110.600 ppm
20160.380 ppm110.380 ppm
20170.520 ppm110.520 ppm
20190.760 ppm110.760 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
2014-08-14A1402229210.270 ppm
2015-07-28A1502429600.600 ppm
2016-06-29A1604188800.380 ppm
2017-07-11A1705030690.520 ppm
2019-06-209F03093-010.760 ppm