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
20100.340 ppm110.340 ppm
20110.940 ppm110.940 ppm
20120.655 ppm220.380 ppm - 0.930 ppm
20130.510 ppm220.460 ppm - 0.560 ppm
20140.540 ppm220.500 ppm - 0.580 ppm
20150.490 ppm220.400 ppm - 0.580 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

Health Guideline 0.14 ppm

The health guideline of 0.14 ppm for nitrate and nitrite was defined by based on the equivalent health guideline for nitrate, as defined in a peer-reviewed scientific study by EWG. . This health guideline protects against one-in-one-million annual cancer risk level.

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
2010-09-22AH048950.340 ppm
2011-10-31AH453880.940 ppm
2012-08-20AH751610.380 ppm
2012-10-29AH829200.930 ppm
2013-08-06AI093270.460 ppm
2013-08-13AI110000.560 ppm
2014-09-15AI537770.580 ppm
2014-09-15AI537760.500 ppm
2015-08-10AI862730.400 ppm
2015-08-12AI862740.580 ppm