EWG's Tap Water Database — 2019 UPDATE



Water District 1 of Johnson County

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
20120.604 ppm14140.220 ppm - 0.720 ppm
20130.592 ppm14140.220 ppm - 0.740 ppm
20140.563 ppm12120.280 ppm - 0.710 ppm
20150.519 ppm14140.190 ppm - 0.680 ppm
20160.378 ppm1514ND - 0.580 ppm
20170.534 ppm14140.430 ppm - 0.630 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
2012-01-17572439BT0.220 ppm
2012-01-17572438BT0.530 ppm
2012-03-06576120WS0.690 ppm
2012-03-06576121WS0.630 ppm
2012-04-17577746BT0.680 ppm
2012-04-17577747BT0.580 ppm
2012-05-29579492BT0.690 ppm
2012-05-29579491WS0.640 ppm
2012-07-23582296BT0.650 ppm
2012-07-23582295BT0.600 ppm
2012-07-23582297BT0.530 ppm
2012-10-22586974BT0.640 ppm
2012-10-22586975BT0.720 ppm
2012-10-22586976BT0.650 ppm
2013-01-22589699BT0.620 ppm
2013-01-22589700BT0.600 ppm
2013-03-05592968WS0.710 ppm
2013-03-05592969WS0.600 ppm
2013-04-22594895BT0.710 ppm
2013-04-22594896BT0.610 ppm
2013-05-14596073WS0.230 ppm
2013-05-14596072BT0.220 ppm
2013-07-22599222BT0.660 ppm
2013-07-22599224BT0.730 ppm
2013-07-22599223BT0.630 ppm
2013-10-22604832BT0.630 ppm
2013-10-22604830BT0.740 ppm
2013-10-22604831BT0.600 ppm
2014-01-21423940.610 ppm
2014-01-21423970.620 ppm
2014-03-04702600.600 ppm
2014-03-04702470.630 ppm
2014-04-07925340.600 ppm
2014-04-07925350.580 ppm
2014-05-071105850.540 ppm
2014-05-131134330.710 ppm
2014-07-221567040.660 ppm
2014-07-221567020.410 ppm
2014-07-221567000.280 ppm
2014-12-102478640.520 ppm
2015-03-162965230.480 ppm
2015-03-162965240.560 ppm
2015-04-243190260.550 ppm
2015-04-273190250.560 ppm
2015-04-273190240.600 ppm
2015-05-043225860.590 ppm
2015-05-043225850.620 ppm
2015-05-043225840.390 ppm
2015-08-033772930.630 ppm
2015-08-033772940.680 ppm
2015-08-033772950.650 ppm
2015-10-194198370.190 ppm
2015-10-194198390.220 ppm
2015-10-204198380.540 ppm
2016-03-145089980.160 ppm
2016-03-145089970.530 ppm
2016-03-145089990.160 ppm
2016-05-175480220.440 ppm
2016-06-205667370.230 ppm
2016-06-205667340.290 ppm
2016-06-205667360.300 ppm
2016-06-205667350.560 ppm
2016-08-236088030.580 ppm
2016-08-236088050.500 ppm
2016-08-236088040.500 ppm
2016-10-136426380.470 ppm
2016-10-136426370.480 ppm
2016-10-136426360.470 ppm
2017-01-046790770.630 ppm
2017-01-046790750.530 ppm
2017-02-136790760.520 ppm
2017-02-147085520.500 ppm
2017-02-147085500.530 ppm
2017-02-147085510.570 ppm
2017-06-127768600.580 ppm
2017-06-127768590.480 ppm
2017-06-127768580.480 ppm
2017-07-187993730.580 ppm
2017-07-187993860.430 ppm
2017-07-187993880.590 ppm
2017-10-098582920.500 ppm
2017-10-098582910.560 ppm