The main chemicals used to fluoridate drinking water are known as “silicofluorides” (i.e., hydrofluorosilicic acid and sodium fluorosilicate). Silicofluorides are not pharmaceutical-grade fluoride products; they are unprocessed industrial by-products of the phosphate fertilizer industry. Since these silicofluorides undergo no purification procedures, they can contain elevated levels of arsenic — moreso than any other water treatment chemical. In addition, recent research suggests that the addition of silicofluorides to water is a risk factor for elevated lead exposure, particularly among residents who live in homes with old pipes.