EWG's Tap Water Database — 2021 UPDATE



Golden State Water Desert View

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
20140.904 ppm220.700 ppm - 1.11 ppm
20150.836 ppm220.745 ppm - 0.926 ppm
20160.840 ppm220.830 ppm - 0.850 ppm
20170.825 ppm220.690 ppm - 0.960 ppm
20180.895 ppm220.690 ppm - 1.10 ppm
20190.860 ppm220.620 ppm - 1.10 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
2014-02-182706-001-12500.700 ppm
2014-02-182706-002-13151.11 ppm
2015-02-102706-002-13100.926 ppm
2015-02-192706-001-10000.745 ppm
2016-02-022706-002-13200.850 ppm
2016-02-162706-001-10000.830 ppm
2017-02-139590-002-08000.960 ppm
2017-02-219590-001-09100.690 ppm
2018-02-129590-001-11250.690 ppm
2018-02-129590-002-11421.10 ppm
2019-02-049590-001-09220.620 ppm
2019-02-049590-002-09101.10 ppm