EWG's Tap Water Database — 2019 UPDATE



City of Grand Prairie

Fluoride occurs naturally in surface and groundwater and is also added to drinking water by many water systems. Read More.

Fluoride has been promoted as a chemical that reduces dental cavities. Yet it is now well-established that fluoride primarily exerts its protective effects through topical mechanisms, such as sodium fluoride in toothpaste and mouthwash. In contrast, long-term ingestion of fluoride in water increases dental fluorosis, which includes mottling, pitting and weakening of the teeth. EPA's maximum legal limit is set at 4 parts per million (ppm) to prevent skeletal fluorosis, a condition where bones become brittle and more susceptible to fractures, although these effects may occur at lower doses.

Even fluoride levels of 0.7 ppm, the amount of fluoride in drinking water recommended by the U.S. Public Health Service, can result in too much fluoride for bottle-fed babies. EWG recommends that caregivers mix baby formula with fluoride-free water. The National Toxicology Program is investigating the potential for low doses of fluoride to alter thyroid function and childhood brain development.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20121.21 ppm111.21 ppm
20140.619 ppm770.477 ppm - 0.724 ppm
20150.498 ppm110.498 ppm
20170.699 ppm550.663 ppm - 0.734 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 4 ppm

ppm = parts per million

All test results

Date Lab ID Result
2012-08-1312085430061.21 ppm
2014-06-04Q14193310050.724 ppm
2014-06-26Q14240230320.477 ppm
2014-06-26Q14240230150.488 ppm
2014-06-26Q14240230140.666 ppm
2014-06-26Q14240230130.610 ppm
2014-09-10Q14429910100.719 ppm
2014-09-10Q14429910090.651 ppm
2015-06-09Q15210420030.498 ppm
2017-06-27Q17265350060.734 ppm
2017-06-27Q17265350300.723 ppm
2017-06-27Q17265350050.676 ppm
2017-06-27Q17265350290.663 ppm
2017-06-27Q17265350040.700 ppm