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
20160.499 ppm85ND - 1.06 ppm
20170.683 ppm12120.460 ppm - 1.04 ppm
20180.809 ppm12120.650 ppm - 1.03 ppm
20190.906 ppm11110.640 ppm - 1.22 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
2016-05-266E26068-011.000 ppm
2016-08-186H18074-010.130 ppm
2016-10-206J20044-011.06 ppm
2016-11-176K17050-010.920 ppm
2016-12-216L22052-010.880 ppm
2017-01-307B02057-011.04 ppm
2017-02-227B23047-010.950 ppm
2017-03-237C23040-010.860 ppm
2017-04-067D06079-010.580 ppm
2017-05-247E25036-010.600 ppm
2017-06-287F29077-010.590 ppm
2017-07-277G27070-010.460 ppm
2017-08-247H24058-010.510 ppm
2017-09-277I28041-010.560 ppm
2017-10-267J26049-010.550 ppm
2017-11-157K16044-010.670 ppm
2017-12-207L21074-010.830 ppm
2018-01-248A25037-010.710 ppm
2018-02-21AB22013-010.650 ppm
2018-03-28AC29038-010.720 ppm
2018-04-26AD26026-010.790 ppm
2018-05-17AE17020-010.720 ppm
2018-06-28AF28036-010.740 ppm
2018-07-26AG26021-010.850 ppm
2018-08-30AH30065-010.850 ppm
2018-09-26AI27048-010.830 ppm
2018-10-23AJ25012-011.03 ppm
2018-11-29AK29003-010.800 ppm
2018-12-26AL27057-011.02 ppm
2019-01-30BA31029-010.880 ppm
2019-02-21BB21028-010.690 ppm
2019-03-28BC28013-010.720 ppm
2019-05-29BE30078-010.640 ppm
2019-06-26BF27111-010.850 ppm
2019-07-25BG25051-011.06 ppm
2019-08-28BH29013-010.980 ppm
2019-09-26BI26038-011.22 ppm
2019-10-15BJ17055-010.960 ppm
2019-11-07BK07076-010.950 ppm
2019-12-05BL05085-011.02 ppm