EWG's Tap Water Database — 2021 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
20140.533 ppm13130.210 ppm - 1.10 ppm
20150.770 ppm440.590 ppm - 0.980 ppm
20160.628 ppm440.610 ppm - 0.670 ppm
20170.630 ppm440.580 ppm - 0.670 ppm
20180.643 ppm440.540 ppm - 0.770 ppm
20190.655 ppm440.630 ppm - 0.700 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
2014-01-2214A0680-010.800 ppm
2014-02-2414B1257-040.220 ppm
2014-02-2414B1263-011.000 ppm
2014-02-2414B1257-030.420 ppm
2014-02-2414B1257-020.230 ppm
2014-02-2414B1257-010.360 ppm
2014-02-2414B1254-040.210 ppm
2014-02-2414B1254-030.250 ppm
2014-02-2414B1254-020.290 ppm
2014-02-2414B1254-010.220 ppm
2014-05-0614E0954-010.840 ppm
2014-08-2514H2287-011.10 ppm
2014-10-2814J1573-010.990 ppm
2015-02-2615B1362-010.980 ppm
2015-05-1215E0963-010.890 ppm
2015-07-3015G2528-010.620 ppm
2015-10-0715J0526-010.590 ppm
2016-02-1016B0674-010.610 ppm
2016-05-1616E1352-010.610 ppm
2016-08-2216H2718-010.670 ppm
2016-10-3116K0042-010.620 ppm
2017-01-2417A0747-010.660 ppm
2017-04-1717D1029-010.610 ppm
2017-07-1217G0817-010.580 ppm
2017-11-1417K0673-010.670 ppm
2018-01-3018A1238-010.630 ppm
2018-05-2218E1974-010.630 ppm
2018-08-2118H1888-010.540 ppm
2018-10-1718J0913-010.770 ppm
2019-01-0919A0270-010.640 ppm
2019-05-0619E0460-010.650 ppm
2019-07-1619G1185-010.630 ppm
2019-10-0919J0669-010.700 ppm