EWG's Tap Water Database — 2019 UPDATE



Northwest Utilities

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
20120.193 ppm330.180 ppm - 0.200 ppm
20130.218 ppm330.189 ppm - 0.263 ppm
20140.347 ppm330.217 ppm - 0.566 ppm
20150.172 ppm330.143 ppm - 0.218 ppm
20160.243 ppm330.137 ppm - 0.447 ppm
20170.194 ppm330.107 ppm - 0.290 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
2012-08-210.200 ppm
2012-09-040.180 ppm
2012-09-040.200 ppm
2013-08-060.203 ppm
2013-08-060.189 ppm
2013-08-130.263 ppm
2014-07-210.566 ppm
2014-07-210.258 ppm
2014-07-210.217 ppm
2015-09-150.143 ppm
2015-09-150.218 ppm
2015-09-150.154 ppm
2016-09-120.447 ppm
2016-09-120.144 ppm
2016-09-120.137 ppm
2017-08-230.107 ppm
2017-08-230.184 ppm
2017-08-230.290 ppm