EWG's Tap Water Database — 2019 UPDATE



Combine Water Supply Corporation

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
20120.720 ppm110.720 ppm
20130.460 ppm110.460 ppm
20140.620 ppm110.620 ppm
20150.522 ppm110.522 ppm
20160.746 ppm110.746 ppm
20171.02 ppm111.02 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 Lab ID Result
2012-05-1612055590010.720 ppm
2013-04-1613045640010.460 ppm
2014-09-02Q14405310010.620 ppm
2015-01-27Q15031490020.522 ppm
2016-01-20Q16023370010.746 ppm
2017-01-11Q17014220011.02 ppm