Fluoride (F-) is an ion of the element fluorine, and is a natural component in most water resources. According to Hem (1989), fluoride concentrations in fresh water are generally less than 1 mg/L (milligrams per liter), and the concentration of fluoride in the world's oceans is about 1.3 mg/L. The source of most fluoride in natural fresh-water resources is various rocks and minerals in bedrock and sediments.
Information Circular 1
Digital Object Identifier (DOI)
Conrad, Philip G.; Carey, Daniel I.; Webb, James S.; Dinger, James S.; Fisher, R. Stephen; and McCourt, Matthew J., "Ground-Water Quality in Kentucky: Fluoride" (1999). Kentucky Geological Survey Information Circular. 3.