Variations in the fluoride levels of drinking water in South Africa. Implications for fluoride supplementation.

The range of fluoride levels in the drinking-water of cities and villages in South Africa was determined during the transition from a very dry (1983) to a wet (1984/85) period. The combination fluoride ion selective electrode was employed for the determination of the fluoride concentration. It was found that fluoride levels in drinking-water changed for 93% of the cities and villages studied during the period 1983-1985. Furthermore, it became clear that when the water volume of the supplying source increased, the fluoride level decreased significantly (P less than 0.01). Boreholes showed significantly higher fluoride levels (P less than 0.01) than rivers or dams. The impact of the variation in drinking-water fluoride concentrations on supplementary fluoride dosage is discussed and recommendations made.