EWG's Tap Water Database — 2019 UPDATE



City of Columbia

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
20120.645 ppm220.620 ppm - 0.670 ppm
20130.620 ppm220.590 ppm - 0.650 ppm
20140.540 ppm220.520 ppm - 0.560 ppm
20150.540 ppm220.530 ppm - 0.550 ppm
20160.545 ppm220.540 ppm - 0.550 ppm
20170.610 ppm330.580 ppm - 0.630 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
2012-02-06AD023070.620 ppm
2012-02-06AD023080.670 ppm
2013-01-30AD190880.650 ppm
2013-01-30AD190890.590 ppm
2014-01-15AD345350.560 ppm
2014-01-15AD345360.520 ppm
2015-01-15AD503480.550 ppm
2015-01-15AD503470.530 ppm
2016-01-13AD691920.540 ppm
2016-01-13AD691910.550 ppm
2017-01-17AD883560.630 ppm
2017-03-07AD907170.580 ppm
2017-08-02AD983920.620 ppm