EWG's Tap Water Database — 2021 UPDATE



Stockton Town Water System

Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. 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
20140.500 ppm110.500 ppm
20150.700 ppm54ND - 1.000 ppm
20160.925 ppm440.800 ppm - 1.000 ppm
20170.782 ppm440.600 ppm - 0.900 ppm
20180.785 ppm330.695 ppm - 0.895 ppm
20190.803 ppm110.803 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

The EWG Health Guideline of 0.14 ppm for nitrate was defined by EWG . This health guideline protects against cancer and harm to fetal growth and development.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The legal limit for nitrate, established in 1962, was developed to protect infants from acute methemoglobinemia, a life-threatening disorder of oxygen transport in the body. This limit does not fully protect against the risk of cancer and harm to the developing fetus.

ppm = parts per million

All test results

Date Result
2014-06-080.500 ppm
2015-01-080.900 ppm
2015-04-200.800 ppm
2015-06-010.800 ppm
2015-07-061.000 ppm
2016-01-051.000 ppm
2016-04-200.800 ppm
2016-07-111.000 ppm
2016-10-040.900 ppm
2017-01-090.900 ppm
2017-04-030.600 ppm
2017-10-020.789 ppm
2017-11-140.837 ppm
2018-01-020.895 ppm
2018-04-020.764 ppm
2018-07-170.695 ppm
2019-01-070.803 ppm