EWG's Tap Water Database


Nitrate and nitrite


Nitrate and nitrite enter water from fertilizer runoff, septic tanks and urban runoff. These contaminants can cause oxygen deprivation for infants and increase the risk of cancer. Nitrite is significantly more toxic than nitrate. 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
20102.18 ppm660.320 ppm - 4.70 ppm
20112.78 ppm770.390 ppm - 5.30 ppm
20122.25 ppm770.470 ppm - 5.00 ppm
20131.48 ppm550.490 ppm - 2.90 ppm
20141.67 ppm43ND - 3.60 ppm
20151.40 ppm440.390 ppm - 2.50 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

Health Guideline 5 ppm

The health guideline of 5 ppm for nitrate and nitrite was defined by EWG based on studies by scientists at the National Cancer Institute and other independent researchers. This health guideline protects against cancer and harm to fetal growth and development.

ppm = parts per million.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppm = parts per million.

EPA Maximum Contaminant
Level Goal (MCLG)10 ppm

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppm = parts per million.

All test results

Date Lab ID Result
2010-05-18AG895363.60 ppm
2010-07-20AG940963.60 ppm
2010-10-19AH086654.70 ppm
2010-11-30AH119070.410 ppm
2010-11-30AH119060.450 ppm
2010-11-30AH119050.320 ppm
2011-03-08AH251525.30 ppm
2011-04-19AH277785.00 ppm
2011-07-26AH352800.710 ppm
2011-07-26AH352812.60 ppm
2011-08-02AH361020.460 ppm
2011-08-02AH361010.390 ppm
2011-10-24AH448535.00 ppm
2012-01-23AH520345.00 ppm
2012-05-15AH647413.60 ppm
2012-07-09AH693092.20 ppm
2012-09-25AH796531.30 ppm
2012-09-25AH796500.470 ppm
2012-09-25AH796490.480 ppm
2012-11-05AH833562.70 ppm
2013-02-11AH888762.90 ppm
2013-04-29AI000451.70 ppm
2013-09-03AI139581.80 ppm
2013-09-03AI139590.490 ppm
2013-09-03AI139600.500 ppm
2014-09-24AI554113.60 ppm
2014-09-24AI554122.60 ppm
2014-09-24AI554140.490 ppm
2015-11-04AJ005200.490 ppm
2015-11-04AJ005190.390 ppm
2015-11-04AJ005182.50 ppm
2015-11-04AJ005172.20 ppm