Fluoride
City of Louisville
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.
Testing results - average by year
Year | Average result | Samples taken | Detections | Range of results |
---|---|---|---|---|
2014 | 0.771 ppm | 2 | 2 | 0.761 ppm - 0.781 ppm |
2015 | 1.10 ppm | 2 | 2 | 1.05 ppm - 1.14 ppm |
2016 | 0.662 ppm | 13 | 13 | 0.540 ppm - 0.790 ppm |
2017 | 0.610 ppm | 4 | 4 | 0.560 ppm - 0.690 ppm |
2018 | 0.632 ppm | 9 | 9 | 0.470 ppm - 0.740 ppm |
2019 | 0.649 ppm | 7 | 7 | 0.550 ppm - 0.700 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 | Result |
---|---|
2014-02-11 | 0.761 ppm |
2014-02-11 | 0.781 ppm |
2015-05-05 | 1.14 ppm |
2015-05-05 | 1.05 ppm |
2016-01-05 | 0.790 ppm |
2016-02-09 | 0.720 ppm |
2016-04-07 | 0.690 ppm |
2016-06-22 | 0.670 ppm |
2016-06-22 | 0.640 ppm |
2016-08-03 | 0.680 ppm |
2016-08-03 | 0.650 ppm |
2016-09-14 | 0.630 ppm |
2016-09-14 | 0.640 ppm |
2016-10-06 | 0.640 ppm |
2016-10-07 | 0.540 ppm |
2016-11-01 | 0.690 ppm |
2016-12-07 | 0.620 ppm |
2017-01-30 | 0.570 ppm |
2017-08-10 | 0.560 ppm |
2017-08-10 | 0.620 ppm |
2017-12-21 | 0.690 ppm |
2018-02-07 | 0.610 ppm |
2018-03-07 | 0.470 ppm |
2018-04-04 | 0.660 ppm |
2018-06-06 | 0.740 ppm |
2018-06-06 | 0.650 ppm |
2018-10-31 | 0.643 ppm |
2018-11-07 | 0.700 ppm |
2018-12-13 | 0.631 ppm |
2018-12-25 | 0.580 ppm |
2019-01-11 | 0.668 ppm |
2019-06-20 | 0.550 ppm |
2019-06-21 | 0.700 ppm |
2019-06-21 | 0.667 ppm |
2019-07-10 | 0.688 ppm |
2019-08-07 | 0.617 ppm |
2019-09-11 | 0.650 ppm |