EWG's Tap Water Database — 2019 UPDATE


Nitrate and nitrite

East Rio Hondo WSC

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
20120.145 ppm220.0600 ppm - 0.230 ppm
20130.0750 ppm220.0700 ppm - 0.0800 ppm
20140.105 ppm220.0400 ppm - 0.170 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

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

EPA Maximum Contaminant
Level (MCL) 10 ppm

ppm = parts per million

All test results

Date Lab ID Result
2012-07-1712075910010.230 ppm
2012-07-1712075910020.0600 ppm
2013-09-30AC316020.0800 ppm
2013-09-30AC316030.0700 ppm
2014-03-25AC480330.0400 ppm
2014-11-20AC725770.170 ppm