EWG's Tap Water Database



Owensboro Municipal Utilities

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
20100.736 ppm550.160 ppm - 0.981 ppm
20110.750 ppm440.620 ppm - 0.878 ppm
20120.658 ppm330.210 ppm - 0.887 ppm
20130.860 ppm220.840 ppm - 0.880 ppm
20140.768 ppm440.720 ppm - 0.820 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 Lab ID Result
2010-10-22000082140.981 ppm
2010-10-22000082170.847 ppm
2010-10-25L485622050.160 ppm
2010-11-01L486734010.840 ppm
2010-11-01L486734020.850 ppm
2011-06-14L521085010.630 ppm
2011-06-14L521080010.620 ppm
2011-06-24000109950.878 ppm
2011-06-24000109980.872 ppm
2012-07-03000154360.887 ppm
2012-07-03000154350.876 ppm
2012-07-05L583643050.210 ppm
2013-09-26L659980010.840 ppm
2013-09-26L659980020.880 ppm
2014-06-10L703928010.820 ppm
2014-06-10L703928020.800 ppm
2014-06-10L704382020.720 ppm
2014-06-10L704382010.730 ppm