EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

North Shore Water Commission

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
20140.320 ppm110.320 ppm
20150.340 ppm110.340 ppm
20160.490 ppm110.490 ppm
20170.360 ppm110.360 ppm
20180.380 ppm110.380 ppm
20190.320 ppm110.320 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
2014-04-157805250.320 ppm
2015-03-038459960.340 ppm
2016-03-149098750.490 ppm
2017-04-189838350.360 ppm
2018-03-2010461010.380 ppm
2019-02-1911058890.320 ppm