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
20130.395 ppm660.210 ppm - 0.750 ppm
20140.442 ppm990.200 ppm - 0.740 ppm
20150.437 ppm330.200 ppm - 0.630 ppm
20160.268 ppm550.200 ppm - 0.360 ppm
20170.359 ppm15150.180 ppm - 0.590 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
2013-06-253F25067-030.750 ppm
2013-06-253F25067-020.460 ppm
2013-06-253F25067-010.330 ppm
2013-09-283I30025-020.270 ppm
2013-11-253K26108-020.350 ppm
2013-12-173L17097-040.210 ppm
2014-03-134C14011-080.430 ppm
2014-03-134C14011-050.440 ppm
2014-08-114H12133-060.250 ppm
2014-08-114H12133-010.390 ppm
2014-08-114H12133-020.430 ppm
2014-08-114H12133-040.740 ppm
2014-11-184K21010-020.200 ppm
2014-11-184K21010-010.570 ppm
2014-12-044L05007-030.530 ppm
2015-12-225L22085-060.630 ppm
2015-12-225L22085-020.200 ppm
2015-12-225L22085-010.480 ppm
2016-02-226B23061-030.200 ppm
2016-02-236B23061-040.360 ppm
2016-04-286D29012-080.290 ppm
2016-04-286D29012-070.220 ppm
2016-04-286D29012-040.270 ppm
2017-05-157E16017-050.300 ppm
2017-09-117I12038-050.590 ppm
2017-09-117I12038-040.310 ppm
2017-09-117I12038-030.180 ppm
2017-10-037J03118-080.460 ppm
2017-10-037J03118-010.390 ppm
2017-10-037J03118-020.400 ppm
2017-10-037J03118-030.250 ppm
2017-10-037J03118-040.290 ppm
2017-10-037J03118-050.360 ppm
2017-10-037J03118-060.390 ppm
2017-10-037J03118-070.510 ppm
2017-10-317K01144-050.380 ppm
2017-10-317K01144-020.350 ppm
2017-12-147L15016-020.230 ppm