EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

City of Nampa

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
20162.80 ppm112.80 ppm
20171.30 ppm11110.01000 ppm - 6.20 ppm
20195.70 ppm225.70 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
2016-11-17I16529912.80 ppm
2017-10-18I17487566.20 ppm
2017-10-18I17487491.000 ppm
2017-10-18I17487480.300 ppm
2017-10-18I17487540.900 ppm
2017-10-18I17487501.40 ppm
2017-10-18I17487631.70 ppm
2017-10-18I17487660.200 ppm
2017-10-18I17487730.01000 ppm
2017-10-18I17487742.00 ppm
2017-10-18I17487730.01000 ppm
2017-10-27I17504850.600 ppm
2019-09-18I19470165.70 ppm
2019-09-18I19470155.70 ppm