EWG's Tap Water Database — 2019 UPDATE


Nitrate and nitrite

Tempe Water Supply Corporation 1

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
20120.0400 ppm110.0400 ppm
20130.0375 ppm440.0200 ppm - 0.0500 ppm
20140.0200 ppm32ND - 0.0300 ppm
20150.0300 ppm110.0300 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
2012-02-29AB822590.0400 ppm
2013-02-26AC114770.0500 ppm
2013-02-26AC114750.0200 ppm
2013-02-26AC114760.0300 ppm
2013-02-26AC114710.0500 ppm
2014-01-15AC389120.0300 ppm
2014-01-15AC389180.0300 ppm
2015-02-24AC815430.0300 ppm