Occurrence of Fluoride in Groundwater

Geographical belts of high fluoride concentrations in groundwater extend from Syria through Jordan, Egypt, Libya, Algeria, Morocco and the Rift Valley of Western Africa through the Sudan and Kenya.  Another belt stretches from Turkey through Iraq, Iran and Afghanistan to India, northern Thailand and China.  The highest natural fluoride concentration ever found in water (2,800 mg/L) was recorded in Lake Nakuru in the Rift Valley in Kenya.   High groundwater fluoride concentrations are associated with igneous and metamorphic rocks such as granites and gneisses, volcanic rocks, and salt deposits of marine origin.