Drinking water in South Africa: implications for fluoride supplementation.

During the extremely heavy rainfall period in the first half of 2000 in certain summer rainfall regions of South Africa a similar investigation as in 1983-1984/1985 was done but on a smaller scale, and compared to the previous results. A greater reduction (P < 0.05) of the fluoride levels in the drinking water than previously recorded has recently been demonstrated, thus strongly accentuating the effect of heavy rains. Presently, for fluoride prescription we recommend that the prescriber should decide whether it is a dry or wet period for his area and then read the fluoride content for that area, from the higher or lower end of the water fluoride content range from the tables published in 1988, 1991 or 1994. When in doubt the higher fluoride level should be used as a measure of safety against overprescribing. If only one value exists it should be used until further notification. An extended study is in process to set a single table for South Africa.