It's funny, but the person who wrote the bogus research that made it "established science" that fluoride is good for you HAPPENED to be related to the founder of Alcoa, the biggest producer of aluminum at that time.
Fluoride was a major toxic waste byproduct of the aluminum smelting process, and it was so toxic that it could cost a fortune to dispose of it by conventional means. The cost of waste disposal threatened to make aluminum prohibitively expensive, which would make it uncompetitive in the markets.
So some fiendish mind hatched the plot of dissolving this toxic waste in THE ENTIRE MUNICIPAL WATER SUPPLY OF THE USA at a "safe" dosage level. By fudging scientific data, the son-in-law created bogus research that it was actually GOOD FOR YOU at that level.
VOILA another scam that Al Gore would be proud of.
Today sodium fluoride is obtained by hauling away the toxic dust from the smokestack scrubbers at fertilizer plants. The scrubbers had to be installed because the smoke was killing livestock downwind from the plant. So they scrub out the toxic crud from the smokestack, then dump the ENTIRE CONTENTS of the scrubbed emissions bins into the municipal water supplies. ALL OF IT, because purifying it and sorting out only the "pure" fluoride would be prohibitively expensive, so the municipal water gets ALL of the toxic chemicals in it along with the toxic fluoride.
But don't worry, if people start gettting sick they will cut back the dose until the water supply returns to tolerable levels of toxic chemicals in it.