Too toxic for landfills, but good enough to dump into your tap water.
Toxic enough to kill rats yet safe to drink. Really? We don't actually know, as it turns out. What exactly is fluoride? Well, for starters, it’s root element is fluorine, described as:
"Fluorine is a Group 17 element. Fluorine is the most electronegative and reactive of all elements. It is a pale yellow, corrosive gas, which reacts with practically all organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame. Until World War 2, there was no commercial production of elemental fluorine. Atom bomb projects and nuclear energy applications made it necessary to produce large quantities of fluorine since isotopes of uranium can be separated through the gas diffusion of UF6. Reasonably safe handling techniques for fluorine are now available and one can transport liquid fluorine by the ton. Compounds of fluorine with noble gases such as xenon, radon, and krypton are known. Elemental fluorine and the fluoride ion (in quantity) are highly toxic." [2]Fluoride ion is the ionic form of fluorine. Fluorides are organic and inorganic compounds containing the element fluorine. Examples of common fluoride compounds include hydrofluoric acid (HF), and sodium fluoride (NaF).
Fluoride containing compounds are added to toothpaste, drinking water, prescribed treatments, and other commercially available oral hygiene products because fluoride proponents believe they help strengthen the tooth enamel. Sodium fluoride and sodium monofluorophosphate (MFP, SMFP) are common additives.
Many local water municipalities fluoridate their water supplies by adding fluoride in concentrations of less than 4 ppm. Originally, sodium fluoride was used to fluoridate water; however, hexafluorosilicic acid (H2SiF6) and its salt (Na2SiF6) are more commonly used, especially in the United States." [3]
There are many different forms of fluoride, as it turns out. Some are naturally occurring compounds. Indeed, our oceans have roughly 1-1.5 ppm fluoride. Sodium Fluoride is considered 'pharmaceutical grade', and is these have been tested at various times by various agencies, with various relatively consistent results. There are a number of other varieties, and it is in fact one of these that are getting pumped into the water supply: fluorosilicic acid.