EWG's Tap Water Database — 2019 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
20120.588 ppm660.340 ppm - 0.810 ppm
20130.449 ppm10100.310 ppm - 0.850 ppm
20140.480 ppm770.360 ppm - 0.720 ppm
20150.432 ppm54ND - 0.700 ppm
20160.397 ppm65ND - 0.600 ppm
20170.265 ppm139ND - 0.500 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
2012-06-192F19086-060.810 ppm
2012-06-282F28082-010.610 ppm
2012-09-252I25080-030.340 ppm
2012-09-252I25080-020.540 ppm
2012-10-152J16062-050.530 ppm
2012-11-262K27053-050.700 ppm
2013-03-113C13003-020.520 ppm
2013-11-253K26108-030.310 ppm
2013-11-253K26108-010.400 ppm
2013-12-173L17097-070.430 ppm
2013-12-173L17097-010.550 ppm
2013-12-173L17097-020.340 ppm
2013-12-173L17097-030.360 ppm
2013-12-173L17097-040.370 ppm
2013-12-173L17097-120.360 ppm
2013-12-173L17097-130.850 ppm
2014-08-114H12133-040.720 ppm
2014-08-184H19104-070.410 ppm
2014-08-184H19104-060.460 ppm
2014-08-184H19104-050.470 ppm
2014-10-094J10006-030.550 ppm
2014-12-044L05007-030.360 ppm
2014-12-044L05007-020.390 ppm
2015-03-105C10136-050.350 ppm
2015-03-105C10136-020.700 ppm
2015-12-085L08161-100.540 ppm
2015-12-085L08161-040.570 ppm
2016-02-236B23061-010.450 ppm
2016-03-246C25003-010.330 ppm
2016-08-186H19025-040.580 ppm
2016-12-286L29051-070.420 ppm
2016-12-286L29051-060.600 ppm
2017-05-157E16017-050.270 ppm
2017-09-117I12038-040.390 ppm
2017-09-117I12038-030.360 ppm
2017-10-037J03118-070.500 ppm
2017-10-037J03118-060.370 ppm
2017-10-037J03118-050.350 ppm
2017-10-037J03118-040.370 ppm
2017-10-037J03118-030.500 ppm
2017-10-317K01144-050.340 ppm