EWG's Tap Water Database — 2019 UPDATE



Waterloo Water Works

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
20120.737 ppm2120ND - 1.10 ppm
20130.626 ppm10100.530 ppm - 0.810 ppm
20140.717 ppm770.610 ppm - 1.000 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
2012-01-0318788330.660 ppm
2012-02-0118835850.730 ppm
2012-03-0118891310.710 ppm
2012-03-2118941350.900 ppm
2012-03-2118941400.800 ppm
2012-03-2118941330.600 ppm
2012-03-2118941341.10 ppm
2012-03-2118941360.900 ppm
2012-03-2118941370.600 ppm
2012-03-2118941381.000 ppm
2012-03-2118941391.000 ppm
2012-04-0218955010.590 ppm
2012-05-0119010600.870 ppm
2012-06-0419069920.550 ppm
2012-07-1119147840.850 ppm
2012-08-0119198060.850 ppm
2012-09-0419278760.840 ppm
2012-10-0219361330.790 ppm
2012-11-0119413490.550 ppm
2012-12-0419478640.590 ppm
2013-01-0219523090.610 ppm
2013-02-0519578010.590 ppm
2013-04-0219695260.530 ppm
2013-05-0219748210.540 ppm
2013-06-0519816190.540 ppm
2013-07-1119883160.810 ppm
2013-08-0819947030.610 ppm
2013-09-0520020700.730 ppm
2013-10-0220082220.680 ppm
2013-12-0420208230.620 ppm
2014-01-0820263070.640 ppm
2014-02-0520319410.610 ppm
2014-03-0620380940.630 ppm
2014-04-0220427800.710 ppm
2014-05-0120479700.630 ppm
2014-07-0920655520.800 ppm
2014-08-1320719581.000 ppm