EWG's Tap Water Database — 2021 UPDATE




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
20140.125 ppm21ND - 0.250 ppm
20150.245 ppm220.120 ppm - 0.370 ppm
20160.115 ppm21ND - 0.230 ppm
20170.295 ppm220.210 ppm - 0.380 ppm
20180.270 ppm220.170 ppm - 0.370 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
2014-12-08IN*AE 11363 AND
2014-12-08IN*AE 11363 B0.250 ppm
2015-05-18IN*AE 124540.120 ppm
2015-05-18IN*AE 124550.370 ppm
2016-06-13IN*AE 15200A0.230 ppm
2016-06-13IN*AE 15200BND
2017-03-20IN*AE 16994 A0.380 ppm
2017-03-20IN*AE 16994 B0.210 ppm
2018-05-14IN*AE 19916B0.170 ppm
2018-05-14IN*AE 199160.370 ppm
2019-06-03AE 22565 A0.380 ppm
2019-06-03AE 22564 B0.170 ppm