EWG's Tap Water Database — 2021 UPDATE



Mid Valley Md

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
20140.385 ppm220.380 ppm - 0.390 ppm
20150.440 ppm220.420 ppm - 0.460 ppm
20160.775 ppm220.740 ppm - 0.810 ppm
20170.360 ppm220.350 ppm - 0.370 ppm
20180.500 ppm220.390 ppm - 0.610 ppm
20190.642 ppm550.350 ppm - 0.850 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
2014-02-240.390 ppm
2014-03-130.380 ppm
2015-06-090.460 ppm
2015-06-090.420 ppm
2016-08-160.810 ppm
2016-08-160.740 ppm
2017-04-250.370 ppm
2017-05-100.350 ppm
2018-04-180.390 ppm
2018-07-160.610 ppm
2019-04-080.350 ppm
2019-04-080.350 ppm
2019-06-100.850 ppm
2019-07-170.840 ppm
2019-10-230.820 ppm