EWG's Tap Water Database — 2021 UPDATE



Blooming Prairie

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
20140.812 ppm660.290 ppm - 1.20 ppm
20150.975 ppm440.810 ppm - 1.10 ppm
20160.588 ppm440.540 ppm - 0.630 ppm
20170.570 ppm330.540 ppm - 0.590 ppm
20180.772 ppm550.690 ppm - 0.910 ppm
20190.733 ppm440.710 ppm - 0.750 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
2014-02-1214B0793-020.290 ppm
2014-02-1214B0859-011.10 ppm
2014-02-1214B0793-010.290 ppm
2014-04-2914D1940-011.10 ppm
2014-08-1814H1904-011.20 ppm
2014-11-0414K0224-010.890 ppm
2015-02-2315B1228-011.10 ppm
2015-04-1415D1192-011.000 ppm
2015-07-2015G1928-010.990 ppm
2015-10-2715J1464-010.810 ppm
2016-02-0816B0572-010.630 ppm
2016-05-0416E0613-010.620 ppm
2016-08-1516H1698-010.560 ppm
2016-12-2716L0906-010.540 ppm
2017-01-3117B0001-010.540 ppm
2017-04-0317D0202-010.580 ppm
2017-08-2917H2408-010.590 ppm
2018-01-3118B0079-010.910 ppm
2018-04-2518D1508-010.780 ppm
2018-08-1418H1379-010.780 ppm
2018-10-2518J1364-010.690 ppm
2018-11-0818K0462-010.700 ppm
2019-01-1419A0467-010.710 ppm
2019-04-0919D0711-010.740 ppm
2019-08-2719H2495-010.730 ppm
2019-10-2919J1713-010.750 ppm