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
20140.140 ppm110.140 ppm
20150.170 ppm110.170 ppm
20160.140 ppm110.140 ppm
20170.320 ppm110.320 ppm
20180.130 ppm110.130 ppm
20190.265 ppm220.250 ppm - 0.280 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
2014-02-13039185.0010.140 ppm
2015-01-28053031.0010.170 ppm
2016-03-29SDWA-1024408-000.140 ppm
2017-01-31SDWA-1116336-000.320 ppm
2018-01-30SDWA-1227964-000.130 ppm
2019-02-06SDWA-1338820-000.280 ppm
2019-12-09BL09015-010.250 ppm