All web references are accessed on March 10, 2019
Municipal Fluoridation of Drinking Water
As an example, I’m going to refer to the Regional Municipality of Durham’s “Oshawa Drinking Water System 2017 Annual Report”
(Durham water quality reports can be found here.)
This 2017 document contains three reports: Oshawa (pp 1-13), Whitby (pp 14-25) and Ajax (pp 26-37).
. . . This report has been prepared to satisfy Section 11 of Ontario Regulation (O. Reg.) 170/03. O. Reg. 170/03 sets requirements for drinking water systems . . . Hard copies of this report and the Schedule 22 Summary Report are available . . . Further information on the Drinking Water Regulations can be found on the Ministry of the Environment and Climate Change’s website at www.ontario.ca/ministry-environment-and-climate-change.
The Oshawa Drinking Water System provides potable water to consumers in the City of Oshawa, Municipality of Clarington (Courtice urban area), Town of Whitby, Town of Ajax, and City of Pickering. . . . The treatment and distribution systems are owned and operated by the Regional Municipality of Durham. . . .
The source water for the treatment process is drawn from Lake Ontario. The water supply system includes the following processes:
•Zebra mussel control (chlorine),
•Low lift pumping,
•Coagulation (aluminum sulphate),
•Fluoridation (hydrofluosilicic acid),
•High lift pumping,
•Water storage and distribution
On a political note, according to https://en.wikipedia.org/wiki/Regional_Municipality_of_Durham,
The Region of Durham was established in 1974 as one of several new regional governments in the Province of Ontario
Looking at the other reports (example: https://www.durham.ca/en/living-here/resources/Documents/WaterandSewer/OronoWaterQualityReport2016.pdf), it appears that there are smaller towns in Durham Region which do not have municipal fluoridation. However I suspect the regional ownership of water treatment and distribution systems would make it harder for all municipalities to make independent decisions on water treatment, and I suspect that regionalization generally makes it harder for towns to make independent decisions on many issues.
This form of fluoride, hydrofluosilicic acid, is not the same as sodium fluoride in toothpaste. Compare https://en.wikipedia.org/wiki/Hexafluorosilicic_acid (there are multiple names for H2SiF6) with https://en.wikipedia.org/wiki/Sodium_fluoride (NaF).
Note that the water is treated first in other ways, including disinfection, and then the hydrofluosilicic acid is added as explained on page 2:
. . . The high lift pumps deliver treated water to the distribution system. Disinfection is achieved by the addition of chlorine at multiple application points throughout the plant. . . . Fluoride (hydrofluosilicic acid) is added to the treated water for the prevention of tooth decay.
There is a table on page 4 of Adverse Water Quality Incidents in 2017, Reported to Spills Action Centre in Accordance with Schedule 16-3 and 16-4 of O. Reg. 170/03. There is one involving fluoride:
Incident Date: “March 29”
Parameter: “Fluoride Residual (Plant)”
Result: “Greater than (>) 1.5 mg/L”
Corrective Action: “Stopped feed until residual was within regulatory range“.
Corrective Action Date: “March 29”
There were two of these fluoride incidents in the 2016 report (June 27 and October 16, page 4: https://www.durham.ca/en/living-here/resources/Documents/WaterandSewer/OWAWaterQualityReport2016.pdf).
So, yes, that answers that question. There is such a thing as having too much fluoride.
The 2017 report (page 7) has another chart: Operational Testing Done Under Schedule 7 of O. Reg. 170/03, including one item for fluoride:
Test: “Fluoride – Plant”
Number of Samples: “Continuous”
Range of Results: “0.15-1.67”
Unit of Measure: “Milligram per Litre(mg/L)”
Parameter Description: “Fluoride is added to water to prevent tooth decay.”
I notice that the chart on page 8: “Summary of Treated Water Chemical Parameters Tested Under Schedule 13 and 23 of O. Reg. 170/03” admits that “by-product of chlorination of drinking water” is a “potential source” for two of the chemicals. There is no reference in any of the charts to the fluoridation process as a potential source for any of the chemicals tested.