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
20120.622 ppm16160.270 ppm - 3.05 ppm
20130.456 ppm13130.290 ppm - 0.700 ppm
20140.417 ppm770.280 ppm - 0.610 ppm
20150.452 ppm550.300 ppm - 0.780 ppm
20160.360 ppm990.190 ppm - 0.600 ppm
20170.288 ppm1817ND - 0.530 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
2012-02-13I12043220.610 ppm
2012-02-13I12043180.400 ppm
2012-04-09I12098970.520 ppm
2012-04-09I12098660.330 ppm
2012-04-09I12098940.300 ppm
2012-04-10I12101060.270 ppm
2012-05-30I12156520.390 ppm
2012-05-30I12156460.430 ppm
2012-05-30I12156500.350 ppm
2012-06-20I12183530.530 ppm
2012-06-21I12185250.380 ppm
2012-06-21I12185300.340 ppm
2012-07-16I12213730.480 ppm
2012-07-16I12213703.05 ppm
2012-07-17I12216490.420 ppm
2012-07-17I12216501.15 ppm
2013-03-11I13103300.390 ppm
2013-05-20I13215680.580 ppm
2013-06-05I13239130.290 ppm
2013-06-05I13239120.380 ppm
2013-06-05I13239140.540 ppm
2013-06-05I13239210.380 ppm
2013-06-18I13260170.470 ppm
2013-06-18I13260190.340 ppm
2013-07-10I13295870.700 ppm
2013-07-11I13298160.480 ppm
2013-07-11I13298120.560 ppm
2013-07-11I13298100.450 ppm
2013-08-07I13337810.370 ppm
2014-06-09I14207720.280 ppm
2014-06-10I14210750.330 ppm
2014-06-10I14210740.580 ppm
2014-06-17I14223350.610 ppm
2014-06-17I14223300.310 ppm
2014-07-30I14291120.420 ppm
2014-07-30I14291130.390 ppm
2015-03-09I15088650.360 ppm
2015-05-27I15204790.300 ppm
2015-06-16I15234550.460 ppm
2015-06-24I15253010.360 ppm
2015-07-24I15302300.780 ppm
2016-06-23I16276470.200 ppm
2016-06-24I16278400.440 ppm
2016-06-24I16278390.600 ppm
2016-06-27I16281250.430 ppm
2016-06-27I16281240.370 ppm
2016-06-27I16281270.410 ppm
2016-06-28I16284410.190 ppm
2016-06-28I16284400.210 ppm
2016-06-29I16286570.390 ppm
2017-03-13I17099010.310 ppm
2017-03-14I17101400.410 ppm
2017-03-14I17101370.170 ppm
2017-03-14I17101370.170 ppm
2017-05-30I17225740.530 ppm
2017-05-31I17227530.450 ppm
2017-05-31I17227590.450 ppm
2017-05-31I17227630.190 ppm
2017-06-19I17261090.470 ppm
2017-06-19I17261070.330 ppm
2017-07-06I17293250.260 ppm
2017-07-20I17322150.200 ppm
2017-07-25I17328110.180 ppm
2017-07-25I17328130.350 ppm
2017-08-03I17345650.170 ppm
2017-08-14I17364760.320 ppm
2017-08-17I17373290.220 ppm