Fluoride
San Luis Obispo Water Department
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 | 0.669 ppm | 13 | 13 | 0.500 ppm - 0.900 ppm |
2015 | 0.592 ppm | 13 | 13 | 0.400 ppm - 0.800 ppm |
2016 | 0.562 ppm | 13 | 13 | 0.400 ppm - 0.700 ppm |
2017 | 0.423 ppm | 13 | 11 | ND - 0.700 ppm |
2018 | 0.538 ppm | 13 | 13 | 0.400 ppm - 0.600 ppm |
2019 | 0.529 ppm | 14 | 14 | 0.200 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 | Lab ID | Result |
---|---|---|
2014-01-22 | 5867-011-0750 | 0.600 ppm |
2014-02-11 | 5867-011-1015 | 0.500 ppm |
2014-03-05 | 5867-011-1130 | 0.600 ppm |
2014-04-22 | 5867-011-1025 | 0.700 ppm |
2014-05-12 | 5867-011-1100 | 0.700 ppm |
2014-06-10 | 5867-011-0835 | 0.800 ppm |
2014-07-28 | 5867-011-1015 | 0.600 ppm |
2014-08-14 | 5867-011-0945 | 0.600 ppm |
2014-09-16 | 5867-011-1320 | 0.700 ppm |
2014-09-22 | 5867-011-0940 | 0.700 ppm |
2014-10-08 | 5867-011-1120 | 0.700 ppm |
2014-11-13 | 5867-011-1230 | 0.900 ppm |
2014-12-15 | 5867-011-1235 | 0.600 ppm |
2015-01-12 | 5867-011-1025 | 0.800 ppm |
2015-02-12 | 5867-011-1105 | 0.600 ppm |
2015-03-23 | 5867-011-1410 | 0.600 ppm |
2015-04-27 | 5867-011-1254 | 0.700 ppm |
2015-05-14 | 5867-011-0930 | 0.500 ppm |
2015-06-23 | 5867-011-0945 | 0.600 ppm |
2015-07-28 | 5867-011-1020 | 0.600 ppm |
2015-08-11 | 5867-011-0730 | 0.600 ppm |
2015-09-14 | 5867-011-1010 | 0.600 ppm |
2015-09-29 | 5867-011-1315 | 0.700 ppm |
2015-10-15 | 5867-011-0920 | 0.400 ppm |
2015-11-11 | 5867-011-0925 | 0.500 ppm |
2015-12-14 | 5867-011-1000 | 0.500 ppm |
2016-01-13 | 5867-011-0940 | 0.500 ppm |
2016-02-10 | 5867-011-0930 | 0.600 ppm |
2016-03-15 | 5867-011-0920 | 0.500 ppm |
2016-04-12 | 5867-011-0950 | 0.500 ppm |
2016-05-03 | 5867-011-0830 | 0.600 ppm |
2016-06-09 | 5867-011-1005 | 0.500 ppm |
2016-07-05 | 5867-011-0900 | 0.400 ppm |
2016-08-02 | 5867-011-0845 | 0.700 ppm |
2016-09-20 | 5867-011-0940 | 0.600 ppm |
2016-09-20 | 5867-011-0955 | 0.600 ppm |
2016-10-11 | 5867-011-0930 | 0.700 ppm |
2016-11-03 | 5867-011-0920 | 0.600 ppm |
2016-12-20 | 5867-011-0920 | 0.500 ppm |
2017-01-05 | 5867-011-0910 | 0.400 ppm |
2017-02-07 | 5867-011-0920 | 0.600 ppm |
2017-03-13 | 5867-011-0905 | 0.500 ppm |
2017-04-11 | 5867-011-0940 | 0.600 ppm |
2017-05-09 | 5867-011-0810 | 0.600 ppm |
2017-06-06 | 5867-011-0925 | 0.600 ppm |
2017-07-11 | 5867-011-1015 | 0.600 ppm |
2017-08-16 | 5867-011-1055 | 0.400 ppm |
2017-09-11 | 5867-011-1302 | 0.1000 ppm |
2017-09-11 | 5867-011-0900 | ND |
2017-10-17 | 5867-011-0930 | ND |
2017-11-02 | 5867-011-0922 | 0.700 ppm |
2017-12-07 | 5867-011-0925 | 0.400 ppm |
2018-01-16 | 5867-011-0950 | 0.500 ppm |
2018-02-01 | 5867-011-0840 | 0.500 ppm |
2018-03-07 | 5867-011-0950 | 0.600 ppm |
2018-04-06 | 5867-011-0830 | 0.500 ppm |
2018-05-09 | 5867-011-0935 | 0.500 ppm |
2018-06-05 | 5867-011-1020 | 0.600 ppm |
2018-07-09 | 5867-011-0930 | 0.600 ppm |
2018-08-02 | 5867-011-1315 | 0.500 ppm |
2018-09-06 | 5867-011-1100 | 0.600 ppm |
2018-09-06 | 5867-011-1420 | 0.600 ppm |
2018-10-04 | 5867-011-1130 | 0.500 ppm |
2018-11-01 | 5867-011-0810 | 0.600 ppm |
2018-12-06 | 5867-011-1100 | 0.400 ppm |
2019-01-10 | 5867-011-0900 | 0.500 ppm |
2019-02-06 | 5867-011-1130 | 0.500 ppm |
2019-03-07 | 5867-011-1030 | 0.500 ppm |
2019-04-10 | 5867-011-0800 | 0.600 ppm |
2019-05-09 | 5867-011-0945 | 0.500 ppm |
2019-05-16 | 5867-006-1330 | 0.200 ppm |
2019-06-01 | 5867-011-0730 | 0.500 ppm |
2019-07-01 | 5867-011-0815 | 0.600 ppm |
2019-08-05 | 5867-011-0900 | 0.600 ppm |
2019-09-09 | 5867-011-1347 | 0.700 ppm |
2019-09-09 | 5867-011-0950 | 0.600 ppm |
2019-10-08 | 5867-011-0915 | 0.500 ppm |
2019-11-07 | 5867-011-0845 | 0.500 ppm |
2019-12-11 | 5867-011-0930 | 0.600 ppm |