EWG's Tap Water Database



Clearwater Water System

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
20100.412 ppm330.0750 ppm - 0.600 ppm
20110.403 ppm330.1000 ppm - 0.590 ppm
20120.210 ppm330.140 ppm - 0.310 ppm
20130.0560 ppm32ND - 0.120 ppm
20140.420 ppm110.420 ppm
20150.205 ppm660.0760 ppm - 0.420 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

EPA Maximum Contaminant
Level (MCL) 4 ppm

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppm = parts per million.

EPA Maximum Contaminant
Level Goal (MCLG)4 ppm

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppm = parts per million.

All test results

Date Result
2010-02-100.0750 ppm
2010-02-100.600 ppm
2010-02-110.560 ppm
2011-02-160.520 ppm
2011-02-160.590 ppm
2011-02-160.1000 ppm
2012-02-100.180 ppm
2012-02-100.310 ppm
2012-02-100.140 ppm
2013-02-010.0480 ppm
2013-02-010.120 ppm
2014-02-130.420 ppm
2015-01-130.420 ppm
2015-01-130.120 ppm
2015-01-130.120 ppm
2015-01-130.420 ppm
2015-05-070.0760 ppm
2015-05-070.0760 ppm