Fluoride
Montara Water and Sanitary District
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
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 0.879 ppm | 15 | 15 | 0.290 ppm - 1.90 ppm |
| 2015 | 0.638 ppm | 13 | 9 | ND - 1.60 ppm |
| 2016 | 1.14 ppm | 14 | 14 | 0.170 ppm - 1.90 ppm |
| 2017 | 1.10 ppm | 16 | 16 | 0.310 ppm - 1.70 ppm |
| 2018 | 1.19 ppm | 14 | 14 | 0.250 ppm - 1.70 ppm |
| 2019 | 0.720 ppm | 1 | 1 | 0.720 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 |
|---|---|---|
| 2014-01-20 | 1233-032-1110 | 0.780 ppm |
| 2014-01-20 | 1233-031-1140 | 1.10 ppm |
| 2014-01-20 | 1233-030-1150 | 1.10 ppm |
| 2014-03-18 | 5810-008-1050 | 0.780 ppm |
| 2014-04-21 | 1233-032-1100 | 0.860 ppm |
| 2014-04-21 | 1233-031-1030 | 1.000 ppm |
| 2014-04-21 | 1233-030-1050 | 1.40 ppm |
| 2014-08-27 | 5810-011-0900 | 0.720 ppm |
| 2014-10-20 | 1233-032-1025 | 0.820 ppm |
| 2014-10-20 | 1233-031-1010 | 0.970 ppm |
| 2014-10-20 | 1233-030-1020 | 1.90 ppm |
| 2014-12-08 | 5810-012-1035 | 0.290 ppm |
| 2014-12-08 | 5810-003-1110 | 0.650 ppm |
| 2014-12-08 | 5810-014-1030 | 0.510 ppm |
| 2014-12-08 | 5810-015-1100 | 0.310 ppm |
| 2015-01-19 | 1233-032-1000 | ND |
| 2015-01-19 | 1233-031-1110 | ND |
| 2015-01-19 | 1233-030-1055 | 1.60 ppm |
| 2015-04-20 | 1233-032-1045 | ND |
| 2015-04-20 | 1233-031-1035 | ND |
| 2015-05-18 | 1233-030-1040 | 1.30 ppm |
| 2015-07-20 | 1233-031-1100 | 0.970 ppm |
| 2015-07-20 | 1233-032-1120 | 0.770 ppm |
| 2015-07-20 | 1233-030-1110 | 1.000 ppm |
| 2015-08-17 | 5810-001-0920 | 0.200 ppm |
| 2015-10-19 | 1233-030-0850 | 1.10 ppm |
| 2015-10-19 | 1233-031-1050 | 0.760 ppm |
| 2015-10-19 | 1233-032-1015 | 0.600 ppm |
| 2016-01-18 | 1233-032-1030 | 0.170 ppm |
| 2016-01-18 | 1233-030-1020 | 1.40 ppm |
| 2016-01-18 | 1233-031-1110 | 0.710 ppm |
| 2016-01-28 | 5810-011-0930 | 0.780 ppm |
| 2016-05-18 | 5810-032-1215 | 0.960 ppm |
| 2016-05-18 | 5810-031-1150 | 1.30 ppm |
| 2016-05-18 | 5810-030-1200 | 1.70 ppm |
| 2016-05-19 | 5810-010-1030 | 0.650 ppm |
| 2016-09-15 | 5810-030-1035 | 1.90 ppm |
| 2016-09-15 | 5810-032-1045 | 1.10 ppm |
| 2016-09-15 | 5810-031-1015 | 1.40 ppm |
| 2016-12-01 | 5810-032-1035 | 1.000 ppm |
| 2016-12-01 | 5810-031-1015 | 1.20 ppm |
| 2016-12-13 | 5810-030-1158 | 1.70 ppm |
| 2017-01-25 | 5810-008-0930 | 0.540 ppm |
| 2017-01-25 | 5810-031-0900 | 1.30 ppm |
| 2017-01-25 | 5810-030-0915 | 1.60 ppm |
| 2017-01-25 | 5810-032-0930 | 0.970 ppm |
| 2017-04-13 | 5810-032-1040 | 1.10 ppm |
| 2017-04-13 | 5810-031-1000 | 1.10 ppm |
| 2017-04-13 | 5810-030-1020 | 1.70 ppm |
| 2017-08-10 | 5810-032-0905 | 0.970 ppm |
| 2017-08-10 | 5810-031-0845 | 1.20 ppm |
| 2017-09-06 | 5810-030-1110 | 1.70 ppm |
| 2017-11-08 | 5810-003-0940 | 0.650 ppm |
| 2017-11-08 | 5810-012-1025 | 0.310 ppm |
| 2017-11-08 | 5810-014-0920 | 0.500 ppm |
| 2017-11-09 | 5810-032-1130 | 0.980 ppm |
| 2017-11-09 | 5810-031-1040 | 1.30 ppm |
| 2017-11-09 | 5810-030-1120 | 1.70 ppm |
| 2018-02-07 | 5810-032-1400 | 1.50 ppm |
| 2018-02-07 | 5810-031-1305 | 1.20 ppm |
| 2018-02-07 | 5810-030-1315 | 1.60 ppm |
| 2018-05-01 | 5810-032-1145 | 1.10 ppm |
| 2018-05-01 | 5810-031-1020 | 1.20 ppm |
| 2018-05-01 | 5810-030-1050 | 1.70 ppm |
| 2018-07-23 | 5810-001-1130 | 0.250 ppm |
| 2018-07-23 | 5810-015-1120 | 0.340 ppm |
| 2018-07-26 | 5810-030-1100 | 1.70 ppm |
| 2018-07-26 | 5810-032-1110 | 1.000 ppm |
| 2018-07-26 | 5810-031-1140 | 1.30 ppm |
| 2018-11-15 | 5810-031-0815 | 1.20 ppm |
| 2018-11-15 | 5810-030-0900 | 1.60 ppm |
| 2018-11-15 | 5810-032-0835 | 0.990 ppm |
| 2019-04-16 | 5810-010-1020 | 0.720 ppm |