Fluoride
City of Lewiston
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 |
---|---|---|---|---|
2013 | N/A | 0 | 0 | N/A |
2014 | 0.553 ppm | 6 | 6 | 0.340 ppm - 0.897 ppm |
2015 | 0.493 ppm | 6 | 6 | 0.288 ppm - 0.929 ppm |
2016 | 0.552 ppm | 4 | 4 | 0.342 ppm - 0.789 ppm |
2017 | 0.715 ppm | 5 | 5 | 0.321 ppm - 0.923 ppm |
2018 | 0.609 ppm | 2 | 2 | 0.339 ppm - 0.879 ppm |
2019 | 0.297 ppm | 5 | 4 | ND - 0.640 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 |
---|---|---|
2014-02-25 | I140226039-002 | 0.897 ppm |
2014-02-25 | I140226039-001 | 0.512 ppm |
2014-06-03 | I140604041-001 | 0.458 ppm |
2014-06-03 | I140604041-002 | 0.475 ppm |
2014-08-13 | I140814054-005 | 0.633 ppm |
2014-08-13 | I140814054-004 | 0.340 ppm |
2015-01-21 | I150122025-001 | 0.348 ppm |
2015-04-21 | I150422037-001 | 0.929 ppm |
2015-06-10 | I150611032-001 | 0.460 ppm |
2015-06-10 | I150611032-002 | 0.398 ppm |
2015-07-22 | I150723044-003 | 0.532 ppm |
2015-07-22 | I150723044-001 | 0.288 ppm |
2016-02-09 | I160209050-001 | 0.789 ppm |
2016-02-09 | I160209050-002 | 0.406 ppm |
2016-04-06 | I160407008-003 | 0.670 ppm |
2016-04-06 | I160407008-001 | 0.342 ppm |
2017-03-28 | I170328050-002 | 0.897 ppm |
2017-03-28 | I170328050-001 | 0.923 ppm |
2017-10-25 | I171026026-001 | 0.568 ppm |
2017-10-25 | I171026026-002 | 0.867 ppm |
2017-10-25 | I171026026-003 | 0.321 ppm |
2018-02-21 | I180221045-001 | 0.339 ppm |
2018-02-22 | I180223004-001 | 0.879 ppm |
2019-01-24 | I190124017-001 | 0.307 ppm |
2019-04-23 | I190423067-002 | 0.240 ppm |
2019-04-23 | I190423067-001 | 0.640 ppm |
2019-05-15 | I190516039-001 | 0.300 ppm |
2019-08-14 | I190814075-003 | ND |