EWG's Tap Water Database — 2021 UPDATE



Northwest Utility District-SD

Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. 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
20140.760 ppm110.760 ppm
20150.550 ppm110.550 ppm
20160.844 ppm220.618 ppm - 1.07 ppm
20170.730 ppm220.594 ppm - 0.866 ppm
20180.949 ppm220.909 ppm - 0.988 ppm
20190.871 ppm220.601 ppm - 1.14 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

The EWG Health Guideline of 0.14 ppm for nitrate was defined by EWG . This health guideline protects against cancer and harm to fetal growth and development.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The legal limit for nitrate, established in 1962, was developed to protect infants from acute methemoglobinemia, a life-threatening disorder of oxygen transport in the body. This limit does not fully protect against the risk of cancer and harm to the developing fetus.

ppm = parts per million

All test results

Date Result
2014-01-140.760 ppm
2015-02-100.550 ppm
2016-01-120.618 ppm
2016-11-291.07 ppm
2017-01-170.594 ppm
2017-10-170.866 ppm
2018-02-260.988 ppm
2018-08-130.909 ppm
2019-01-140.601 ppm
2019-09-161.14 ppm