Where Do the Fluoridation Additives Come From?
Fluoride additives used in the United States for water fluoridation (sodium fluoride, sodium fluorosilicate, and fluorosilicic acid) are derived from apatite which is a type of limestone deposit used in the production of phosphate fertilizers. Apatite contains 3-7% fluoride and is the main source of fluoride used in water fluoridation. (1)
During processing, apatite is ground up and treated with sulfuric acid, producing phosphoric acid (the main ingredient in the production of phosphate fertilizer [also utilized in soda pop]) plus a solid and two gases. The solid, calcium sulfate (also known as gypsum) is the material used to form drywall or sheetrock. The two gases, hydrogen fluoride and silicon tetrafluoride, are captured in water to form fluorosilicic acid which today is the most commonly used fluoride additive in the United States. (2)
The two remaining fluoride additives (sodium fluoride and sodium fluorosilicate) are derived from fluorosilicic acid. Sodium fluoride is produced when fluorosilicic acid is neutralized with caustic soda. Fluorosilicic acid is neutralized with sodium chloride or sodium carbonate to produce sodium fluorosilicate. (1)
(1) US Dept. of Health and Human Services, Centers for Disease Control, Dental Disease Prevention Activity. Water fluoridation: a manual for engineers and technicians. Atlanta, September 1986.
(2) American Water Works Association. AWWA standard for sodium fluoride (ANSI/AWWA B701-99), March 1, 2000: AWWA standard for sodium fluorosilicate (ANSI/AWWA B702-99), March 1, 2000 and AWWA standard for fluorosilicic acid (ANSI/AWWA B703-00), September 1, 2000.