EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

Marmarth, City of

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
20140.220 ppm110.220 ppm
20150.210 ppm110.210 ppm
20160.190 ppm110.190 ppm
20170.180 ppm110.180 ppm
20180.200 ppm110.200 ppm
20190.147 ppm110.147 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
2014-02-2514-S3950.220 ppm
2015-02-2315-S2260.210 ppm
2016-02-2216-S2160.190 ppm
2017-01-3117-S1620.180 ppm
2018-01-3018-S1310.200 ppm
2019-05-0119-S5010.147 ppm