EWG's Tap Water Database — 2019 UPDATE



South-Central Service Area

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
20120.460 ppm220.450 ppm - 0.470 ppm
20130.454 ppm220.394 ppm - 0.514 ppm
20140.481 ppm440.421 ppm - 0.543 ppm
20150.617 ppm220.511 ppm - 0.722 ppm
20160.565 ppm220.550 ppm - 0.580 ppm
20170.785 ppm440.670 ppm - 0.900 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 Result
2012-09-040.450 ppm
2012-09-040.470 ppm
2013-08-060.514 ppm
2013-08-060.394 ppm
2014-07-210.538 ppm
2014-07-210.543 ppm
2014-07-210.423 ppm
2014-07-210.421 ppm
2015-08-040.511 ppm
2015-08-040.722 ppm
2016-09-140.580 ppm
2016-09-140.550 ppm
2017-08-090.900 ppm
2017-08-090.670 ppm
2017-08-090.900 ppm
2017-08-090.670 ppm