Fluoride is not an industrial waste. That is an urban myth.
The most common fluoride chemical used is hexafluorosilicic acid, with the compound formula H2SiF6, which can be obtained from other industrial processes. One can hardly call it a waste product if it is of commercial value and so a more correct name would be a by-product. Waste also is used because it people generally think of waste as dirty, however this is a refined chemical, not a loaf of bread or chunk of ham left out in the sun.
For instance, sodium chloride, or table salt, can be refined from the ocean, a dry salt lake or even urine. Regardless where one extracts it, it remains sodium chloride. The same is true of hexafluorosilicic acid.
Fluoride is also naturally present is a number of foods and beverages. This fluoride is neither more or less ‘toxic’ than that added to water. Using the table salt analogy, sodium chloride naturally present in foods is no different to sodium chloride added by the salt shaker at the kitchen table. It is the same chemical compound. You can’t say one is different to the other. See USDA (2005). National Fluoride Database of Selected Beverages and Foods, Release 2. for foods and beverages naturally containing fluoride.