A lot. A whole lot. When the element of fluoride is combined with something else, it becomes a fluoride compound. There is a vast range of fluorine-containing compounds because fluorine has the capability of forming compounds with nearly all the elements. Here are some common forms:
Sodium Fluoride is used in most toothpastes, mouthwashes, dental varnish, dental preparations and nutritional supplements. This same form of fluoride is used as an insecticide and pesticide, as a preservative in glues, as a growth inhibitor for bacteria, fungi and mold. Sodium fluoride is also used in making steel and aluminum products. Added to molten metal, sodium fluoride creates a more uniform metal. Other industrial uses for sodium fluoride include glass frosting and wood preservatives. Sodium Fluoride is also used in the manufacture of chemical and biological weapons. Although this form of fluoride can be used for water fluoridation, the next two forms listed are almost always used due to cost.
Calcium Fluoride (CaF2) is compound of calcium and fluorine which occurs naturally as the mineral fluorite – also called fluorspar. Most of the world’s fluorine comes from calcium fluoride. Fluorides in general are toxic to humans, however CaF2 is considered the least toxic, and even relatively harmless due to its extreme insolubility. Moreover, calcium is a well-known antidote for fluoride poisoning. When an antidote exists in combination with a poison, it makes the poison far less toxic to the body. Calcium fluoride is the form of fluoride commonly found in natural, untreated waters.
Cryolite or Sodium Aluminum Fluoride is commonly used for aluminum smelting, though is also a pesticide often applied directly to field crops, resulting in permitted fluoride residues in and on fresh fruits and vegetables. For more information on cryolite. (For more information on cryolite.)
Fluorosilicic acid (H2SiF6) is commonly used for water fluoridation. This form of fluoride is a toxic liquid by-product, acquired by scrubbing the chimney stacks of phosphate fertilizer manufacture. Other names for it are hexafluorosilicic, hexafluosilicic, hydrofluosilicic, and silicofluoric acid. The CDC approximates that 95% of our water is fluoridated with fluorosilicic acid. (http://www.cdc.gov/fluoridation/fact_sheets/engineering/wfadditives.htm#1)
Sodium Fluorosilicate (Na2SiF6) is primarily added to public drinking water as a fluoridation agent. This same compound is also used as an insecticide and a wood preservative. It is a classified hazardous waste by-product of phosphate fertilizer manufacture which, if not put into our drinking water, must be disposed of at hazardous waste facilities. Other names for it are Sodium Fluosilicate and Sodium Silica Fluoride.
Stannous Fluoride is the popular name given to Tin (II) fluoride. Stannous fluoride is an additive to many toothpastes because it does not become biologically inactive in the presence of calcium, as sodium fluoride does. (http://en.wikipedia.org/wiki/Tin%28II%29_fluoride)
Sulfuryl Fluoride is applied as a gas fumigant to kill insects and rodents. Using sulfuryl fluoride around food products was not allowed due to its toxicity. In 2004 the EPA reversed this policy (following long lobbying efforts by the manufacturer) and allowed its use on food. This opened the doors for food processing companies nationwide to fumigate their facilities with sulfuryl fluoride, leaving high levels of fluoride in and on foods and even food packaging. It has become acceptable for sulfuryl fluoride fumigations to produce fluoride residues of 70 ppm “in or on” processed foods and 130 ppm “in or on” wheat. There have been no labeling requirements for foods treated with sulfuryl fluoride, meaning that consumers have had no way of knowing which foods are treated. (For more information on sulfuryl fluoride.)
In January 2011 this decision was reversed and in about 3 years this fumigation of food reportedly will stop. (Order to cease sulfuryl fluoride fumigation of food products.)