EWG's Tap Water Database — 2019 UPDATE



Metropolitan Water District

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
20150.195 ppm220.132 ppm - 0.258 ppm
20160.185 ppm220.170 ppm - 0.200 ppm
20170.246 ppm330.220 ppm - 0.299 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
2015-01-050.258 ppm
2015-09-140.132 ppm
2016-01-050.200 ppm
2016-06-210.170 ppm
2017-01-030.299 ppm
2017-01-060.220 ppm
2017-06-060.220 ppm