And, I am not so sure that calcium fluoride, by itself, is harmful but may be beneficial. Now to the unobvious, and there is much literature on this including Senate testimony. Fluorine, when mixed with an organophosphate, becomes something quite hideous. Roundup is an organophosphate substance that comes to mind, which is a commonly used product and finding it's way into the food web. Roundup, by itself, is not too awfully toxic, but as it is metabolized an organophosphorus is released, which is even less toxic than the mother chemical Roundup.
Fluorine combines with phosphorus quite readily.
Organophosphorous compounds are cumulative. This is so whether the chemical industry wants to admit it or not, the cumulative action of organophosphrous compounds is well established by the National Academy of Sciences. Therefore, a person's body begins to be hit by cumulative organophosphate action. Organophosphates are also bio-cumulative. That is to say, they cause damage in successive generations.