EWG's Tap Water Database



Clarksville Waterworks

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
20100.869 ppm13130.750 ppm - 1.06 ppm
20110.876 ppm13130.770 ppm - 1.13 ppm
20120.769 ppm1413ND - 0.920 ppm
20130.783 ppm12120.610 ppm - 0.950 ppm
20140.719 ppm1413ND - 1.05 ppm
20150.823 ppm13130.600 ppm - 0.940 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
2010-01-041000700050.800 ppm
2010-01-041001100370.750 ppm
2010-02-011004200150.970 ppm
2010-03-011006700010.770 ppm
2010-04-061010200150.790 ppm
2010-05-031013000140.850 ppm
2010-06-011015800210.870 ppm
2010-07-131020100380.920 ppm
2010-08-031022100050.990 ppm
2010-09-071025600171.06 ppm
2010-10-041028400260.770 ppm
2010-11-021031200170.950 ppm
2010-12-061034700220.810 ppm
2011-01-041101200170.870 ppm
2011-01-041100600020.790 ppm
2011-02-081104600100.820 ppm
2011-03-071107300260.770 ppm
2011-04-051110100090.920 ppm
2011-05-051112900240.790 ppm
2011-06-071116500260.900 ppm
2011-07-061119200130.890 ppm
2011-08-091122700350.920 ppm
2011-09-061125500031.13 ppm
2011-10-051128300250.900 ppm
2011-11-071131800290.910 ppm
2011-12-071134600330.780 ppm
2012-01-041201000290.850 ppm
2012-01-041200600070.900 ppm
2012-01-04Y1200600070.900 ppm
2012-02-081204500310.710 ppm
2012-03-061207300390.670 ppm
2012-04-031210000230.820 ppm
2012-05-081213500290.820 ppm
2012-06-051216300220.860 ppm
2012-07-141220500220.920 ppm
2012-08-081222700090.840 ppm
2012-09-061226100180.850 ppm
2012-10-021228200300.850 ppm
2012-11-061232400020.780 ppm
2013-01-031300400150.610 ppm
2013-01-081301400440.630 ppm
2013-03-041307000230.790 ppm
2013-04-021309800170.790 ppm
2013-05-061313300160.760 ppm
2013-06-041316100270.830 ppm
2013-07-011319000100.870 ppm
2013-08-061322500330.950 ppm
2013-09-031325300160.900 ppm
2013-10-081328800170.790 ppm
2013-11-051331700080.780 ppm
2013-12-041334400210.690 ppm
2014-01-061400800230.770 ppm
2014-02-111405500020.770 ppm
2014-02-261405800010.700 ppm
2014-03-011406900140.810 ppm
2014-03-101407200210.680 ppm
2014-04-011409700170.820 ppm
2014-05-061413200220.810 ppm
2014-07-161421100021.05 ppm
2014-08-041422300280.820 ppm
2014-09-021425100180.670 ppm
2014-10-13Y1430000170.830 ppm
2014-11-04Y1432100110.660 ppm
2014-12-02Y1434200320.670 ppm
2015-01-12Y1502000240.650 ppm
2015-02-02Y1504000210.770 ppm
2015-02-02Y1503700010.800 ppm
2015-03-04Y1507500010.600 ppm
2015-04-13Y1511100370.780 ppm
2015-05-06Y1513400590.940 ppm
2015-06-04Y1516100180.910 ppm
2015-07-16Y1520800040.830 ppm
2015-08-13Y1523600210.830 ppm
2015-09-09Y1525800470.900 ppm
2015-10-16Y1528900710.900 ppm
2015-11-03Y1531300400.890 ppm
2015-12-07Y1534800480.900 ppm