EWG's Tap Water Database — 2019 UPDATE



Osage City, City of

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
20120.686 ppm550.580 ppm - 0.840 ppm
20130.662 ppm550.600 ppm - 0.730 ppm
20140.626 ppm550.580 ppm - 0.690 ppm
20150.622 ppm550.440 ppm - 0.780 ppm
20160.524 ppm550.420 ppm - 0.670 ppm
20170.572 ppm550.450 ppm - 0.810 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
2012-01-30572959BT0.670 ppm
2012-04-09577177BT0.700 ppm
2012-05-15578866WS0.840 ppm
2012-07-25582472BT0.580 ppm
2012-11-07587666BT0.640 ppm
2013-03-15593537BT0.650 ppm
2013-05-14595985WS0.620 ppm
2013-05-16596258BT0.730 ppm
2013-08-12601181BT0.710 ppm
2013-11-25605930BT0.600 ppm
2014-02-03507500.630 ppm
2014-04-19987970.640 ppm
2014-05-051055200.590 ppm
2014-07-281588350.690 ppm
2014-11-102302020.580 ppm
2015-01-192641310.760 ppm
2015-05-063285730.780 ppm
2015-05-183341040.440 ppm
2015-07-223703980.600 ppm
2015-10-284199400.530 ppm
2016-01-104746100.480 ppm
2016-04-125271270.530 ppm
2016-05-025362640.420 ppm
2016-07-065777020.670 ppm
2016-10-246469870.520 ppm
2017-02-146791670.510 ppm
2017-05-117596100.510 ppm
2017-05-167619690.450 ppm
2017-08-158199730.580 ppm
2017-10-108584990.810 ppm