EWG's Tap Water Database


Nitrate and nitrite

Portland Water Bureau

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
20100.0600 ppm220.0300 ppm - 0.0900 ppm
20110.0500 ppm21ND - 0.1000 ppm
20120.0650 ppm220.0200 ppm - 0.110 ppm
20130.0180 ppm110.0180 ppm
20140.120 ppm21ND - 0.240 ppm
20150.123 ppm220.0250 ppm - 0.220 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
2010-04-13BA91448-I0.0300 ppm
2010-08-11BA95984-I0.0900 ppm
2011-01-18BB1638-I0.1000 ppm
2012-01-22BB13243-I0.110 ppm
2012-04-10BB16085-I0.0200 ppm
2013-04-09BB26971-I0.0180 ppm
2014-07-08BB42035-I0.240 ppm
2015-03-31BB49816-I0.0250 ppm
2015-06-17BB52444-I0.220 ppm