EWG's Tap Water Database — 2019 UPDATE



St. Louis City

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
20120.560 ppm220.500 ppm - 0.620 ppm
20130.570 ppm220.490 ppm - 0.650 ppm
20140.590 ppm220.580 ppm - 0.600 ppm
20150.595 ppm220.570 ppm - 0.620 ppm
20160.595 ppm220.540 ppm - 0.650 ppm
20170.580 ppm220.540 ppm - 0.620 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
2012-11-14AB873130.500 ppm
2012-11-14AB873140.620 ppm
2013-11-19CRCW111913FSO40.650 ppm
2013-11-19HBBC111913FSO40.490 ppm
2014-05-28AC234350.580 ppm
2014-05-28AC234360.600 ppm
2015-06-11HBCB061115IOC0.620 ppm
2015-06-11CRCW061115IOC0.570 ppm
2016-05-10HBCB051016IOC0.540 ppm
2016-05-10CRCW051016IOC0.650 ppm
2017-08-08CRCW080817IOC0.540 ppm
2017-08-08HBBC080817IOC0.620 ppm