EWG's Tap Water Database — 2021 UPDATE



North Harris County Regional Water Authority

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
20140.110 ppm110.110 ppm
20150.1000 ppm110.1000 ppm
20160.160 ppm110.160 ppm
20170.248 ppm4434ND - 0.950 ppm
20180.0800 ppm110.0800 ppm
20190.390 ppm110.390 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
2014-09-15AC668430.110 ppm
2015-09-15AD070160.1000 ppm
2016-11-28AD591360.160 ppm
2018-07-30AE347920.0800 ppm
2019-06-25AE718660.390 ppm