EWG's Tap Water Database — 2019 UPDATE



Herington, City of

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
20120.426 ppm550.390 ppm - 0.490 ppm
20130.384 ppm550.340 ppm - 0.410 ppm
20140.388 ppm550.350 ppm - 0.460 ppm
20150.384 ppm550.250 ppm - 0.460 ppm
20160.274 ppm550.170 ppm - 0.350 ppm
20170.308 ppm550.250 ppm - 0.350 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
2012-01-17572607BT0.390 ppm
2012-04-11577392BT0.400 ppm
2012-05-08578569WS0.390 ppm
2012-07-16581495BT0.490 ppm
2012-10-15586625BT0.460 ppm
2013-01-22589692BT0.410 ppm
2013-05-06595580WS0.390 ppm
2013-05-14596079BT0.410 ppm
2013-09-09602676BT0.370 ppm
2013-11-12605511BT0.340 ppm
2014-01-13368650.350 ppm
2014-04-08934040.360 ppm
2014-04-221002300.360 ppm
2014-07-071466470.410 ppm
2014-10-202162060.460 ppm
2015-01-202642900.430 ppm
2015-04-203158030.450 ppm
2015-04-203158020.460 ppm
2015-07-073621670.250 ppm
2015-10-194217330.330 ppm
2016-01-114746150.170 ppm
2016-04-185295960.350 ppm
2016-04-185295600.350 ppm
2016-07-115801090.290 ppm
2016-10-036344900.210 ppm
2017-01-036800160.320 ppm
2017-04-037334080.310 ppm
2017-04-177431070.250 ppm
2017-07-107946060.310 ppm
2017-10-028512030.350 ppm