EWG's Tap Water Database — 2021 UPDATE



East Rio Hondo Water Supply Corporation Arroyo City

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
20140.590 ppm110.590 ppm
20150.360 ppm110.360 ppm
20160.700 ppm110.700 ppm
20170.300 ppm110.300 ppm
20180.350 ppm110.350 ppm
20190.410 ppm110.410 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 Lab ID Result
2014-11-20AC725940.590 ppm
2015-12-01AD148130.360 ppm
2016-09-27AD512890.700 ppm
2017-11-30AE062450.300 ppm
2018-11-29AE472980.350 ppm
2019-07-18AE749450.410 ppm