EWG's Tap Water Database — 2019 UPDATE


Nitrate and nitrite

Centennial Water and Sanitation District

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
20120.0333 ppm31ND - 0.1000 ppm
20130.0800 ppm330.0600 ppm - 0.0900 ppm
20140.0350 ppm220.0200 ppm - 0.0500 ppm
20150.0500 ppm220.0400 ppm - 0.0600 ppm
20160.0600 ppm330.0400 ppm - 0.0900 ppm
20170.0500 ppm32ND - 0.130 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 Result
2012-08-230.1000 ppm
2013-03-190.0900 ppm
2013-03-190.0600 ppm
2013-08-270.0900 ppm
2014-07-230.0500 ppm
2014-07-290.0200 ppm
2015-07-270.0600 ppm
2015-08-120.0400 ppm
2016-07-270.0400 ppm
2016-07-270.0900 ppm
2016-08-170.0500 ppm
2017-01-250.0200 ppm
2017-08-150.130 ppm