EWG's Tap Water Database — 2019 UPDATE




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
20120.900 ppm220.720 ppm - 1.08 ppm
20130.635 ppm220.390 ppm - 0.880 ppm
20140.825 ppm220.790 ppm - 0.860 ppm
20150.285 ppm21ND - 0.570 ppm
20160.655 ppm220.640 ppm - 0.670 ppm
20170.570 ppm330.490 ppm - 0.640 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
2012-03-28AB675840.720 ppm
2012-03-28AB675851.08 ppm
2013-03-29AB934960.880 ppm
2013-03-29AB934970.390 ppm
2014-03-24AC200800.790 ppm
2014-03-25AC200810.860 ppm
2015-03-26AC438440.570 ppm
2016-03-30AC678570.640 ppm
2016-03-30AC678580.670 ppm
2017-03-27AC923310.490 ppm
2017-03-27AC923300.640 ppm
2017-05-17AC979790.580 ppm