Fluorine is the most electronegative element so it is highly reactive. Fluoride is a byproduct of nuclear weapons manufacturing and aluminum production. The ores they mine the aluminum from are radioactive. The stuff they put in the water is literally hazardous waste. They started putting it into the water after WWII claiming it as good for your teeth because the military was getting sued for fluoride causing health problems around nuclear weapons and the industry needed somewhere to dump it cheaply. Now they get paid millions of dollars by communities across the country to put these toxic substances in your water. I'm glad there is an artesian well in my area I get my water from. If you think it is that far-fetched that toxic substances would be put in toothpaste, go look up pictures of the old toothpastes that had radioactive substances in them back in the 30's.