EWG's Tap Water Database — 2021 UPDATE



Minong Waterworks

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
20140.641 ppm26260.0670 ppm - 0.830 ppm
20150.691 ppm24240.629 ppm - 0.770 ppm
20170.0665 ppm220.0610 ppm - 0.0720 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
2014-01-131160980010.657 ppm
2014-01-131160980010.830 ppm
2014-02-111194170010.636 ppm
2014-02-111194170010.700 ppm
2014-03-241246500010.636 ppm
2014-03-241246500010.770 ppm
2014-04-221290070010.800 ppm
2014-04-221290070010.645 ppm
2014-05-201342080010.710 ppm
2014-05-201342080010.661 ppm
2014-06-241413580010.730 ppm
2014-06-241413580010.673 ppm
2014-07-281479560010.600 ppm
2014-07-281479560010.703 ppm
2014-08-271540440010.640 ppm
2014-08-271540440010.661 ppm
2014-09-168185470.0670 ppm
2014-09-168185440.0710 ppm
2014-09-251600450010.600 ppm
2014-09-251600450010.666 ppm
2014-10-271656760010.695 ppm
2014-10-271656760010.630 ppm
2014-11-181692810010.660 ppm
2014-11-181692810010.740 ppm
2014-12-151728550010.691 ppm
2014-12-151728550010.800 ppm
2015-01-141758680010.629 ppm
2015-01-141758680010.710 ppm
2015-02-241809460010.730 ppm
2015-02-241809460010.644 ppm
2015-03-171840750010.646 ppm
2015-03-171840750010.770 ppm
2015-04-211893140010.652 ppm
2015-04-211893140010.720 ppm
2015-05-261960790010.710 ppm
2015-05-261960790010.678 ppm
2015-06-232016640010.720 ppm
2015-06-232016640010.697 ppm
2015-07-272080430010.690 ppm
2015-07-272080430010.703 ppm
2015-08-202131340010.667 ppm
2015-08-202131340010.730 ppm
2015-09-152179210010.670 ppm
2015-09-152179210010.674 ppm
2015-10-202249570010.670 ppm
2015-10-202249570010.692 ppm
2015-11-232300110010.670 ppm
2015-11-232300110010.668 ppm
2015-12-032311030010.694 ppm
2015-12-032311030010.740 ppm
2017-09-1210175790.0610 ppm
2017-09-1210175820.0720 ppm