[Changes in the use of biologically effective fluorides and the consequences].

The nearly 50-year dispute about the usefulness of public water supply fluoridation is basically a dispute about whether the human consumer can be given "optimum" doses of fluorides even in some communities with markedly less than 1 mg/1 F in drinking water. At the very beginning of this dispute, some basically conflicting epidemiological data were found (only seemingly so in our view): around the year 1940 the rate of dental caries in USA children dropped precipitously on drinking water with fluoride concentration growing at an interval of 0.1-0.5 mg/l; at higher concentrations the dental caries rate was declining increasingly less and less (and at concentrations of over 2 mg/l it began picking up again). In contrast to this, in the Federal Republic of Germany in 1950, the interval of 0.1-0.5 mg/l F was related to absolutely no decline in the dental caries rate which was practically as low as in the United States on drinking water containing 2 mg/l. These and other "contradictory" data are put down to man's different intake of fluorides coming from sources other than water. The main cause of different intakes of fluorides from food is apparently in the degree of intensity of field fertilisation with phosphates containing a marked proportion of fluorine, in other words, different intensity of agricultural land fluoridation. In Germany, 23 kg of P2O5 per hectare of arable land was used as early as in 1935, while in the United States this intensity was not reached until 1985.(ABSTRACT TRUNCATED AT 250 WORDS)