There is confusion about the difference between fluoride and fluorine. Fluoride is related to fluorine, but the two chemicals are not the same. Fluorine is a chemical element, while fluoride is either the ion of that element or else a compound containing it. The symbol F stands for fluorine, while fluoride is F– or else contained in a compound (e.g., NaF).
Pure fluorine is a pale yellow gas that occurs in the Earth’s crust and dissolved in seawater. But, fluorine is a reactive element, so it rarely occurs in pure form. It forms the ion F– and combines with other elements, forming compounds and minerals.
Fluoride examples include the ion and the compounds containing fluorine as an anion:
- Fluoride ion – F–
- Sulfur hexafluoride – SF6
- Calcium fluoride – CaF2
- Sodium fluoride – NaF
- Sodium fluorosilicate – Na2SiF6
The most familiar use of fluoride is in cavity prevention, but it has other applications.
- Cavity prevention (sodium fluoride, sodium monofluorophosphate)
- Osteoporosis treatment
- Aluminum smelting (cryolite, Na3AlF3)
- Steel making (fluorite, CaF2)
- Fluorocarbon productions (hydrogen fluoride, HF)
- Biochemical assays
- Fluoride-ion batteries
Fluorine and Fluoride Health Effects and Risks
Elemental fluorine is highly toxic to humans and other living organisms. Its effects are comparable to those of pure chlorine, irritating eyes and mucous membranes and damaging the liver and kidneys. Some fluorides are also extremely dangerous, such as hydrogen fluoride, which is more commonly known as hydrofluoric acid.
But, in tiny amounts, fluoride is likely a micronutrient. The daily recommended amount depends primarily on age and ranges from 0.6 mg/day to 4.0 mg/day. Fluoride deficiency increases the risk of tooth cavities. Topical application of a fluoridated compound, such as sodium fluoride, helps prevent cavities while resulting in minimal ingestion of fluoride. Ingesting too much fluoride leads to dental fluorosis, a condition that ranges from harmless white marks on teeth to brown, weakened teeth. Excessive fluoride ingestion also leads stomach ulcers and skeletal fluorosis, which is a chronic bone and joint disease. While beneficial in minute doses, fluoride becomes lethal at levels between 32 to 64 mg/kg body weight. The safe upper limit of fluoride consumption is 7 mg/day (European Union) or 10 mg/day (United States) for adults or 0.10 mg/kg per day for infants and children up to 8 years old.
Dietary Sources of Fluorine and Fluoride
There are several common sources of fluorine and fluoride in the diet:
- Fluoridated water
- Black tea
Of these sources, tea contains the highest fluoride levels. One cup of black tea provides about 0.884 milligrams of fluoride.
- Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, René; Cuer, Jean Pierre (2000). “Fluorine Compounds, Inorganic”. Ullmann’s Encyclopedia of Industrial Chemistry. ISBN 978-3527306732. doi:10.1002/14356007.a11_307
- IPCS (2002). Environmental health criteria 227 (Fluoride). Geneva: International Programme on Chemical Safety, World Health Organization. ISBN 978-92-4-157227-9.
- Malinowska, E.; Inkielewicz, I.; Czarnowski, W.; Szefer, P. (2008). “Assessment of fluoride concentration and daily intake by human from tea and herbal infusions”. Food Chem. Toxicol. 46 (3): 1055–61. doi:10.1016/j.fct.2007.10.039
- Yeung, C.A. (2008). “A systematic review of the efficacy and safety of fluoridation”. Evidence-Based Dentistry. 9 (2): 39–43. doi:10.1038/sj.ebd.6400578