Fluorides occur in Earth crust in quantities about 0,3 g/kg and exist in a shape of different minerals. They are finding in CaF2 and in Na2AlF6. Fluor and fluor compounds are using in production of uranium, aluminium and over 100 commercial compounds, including high-temperature plastics.
Origin in water
The most fluorides in water become from nature. In environment they came from phosphate rocks, using for production of phosphate sons. These phosphate deposits consist about 4% of fluor. In areas where the coal is using with high consist of fluorides, it can be important source. In underground water, concentrations change with a type of rock where water comes through, but fluor concentration go to 10 mg/1, 0,3-0,4 mg/1 and for limestone, dolomite, shale and clay high average value from 8,7 mg/1 for alkali rocks, low average value from 0,1 mg/1 for basalts rocks and 9,2 mg/1in granite rocks.
Some studies clearly speak that fluorides have effect on skeletal tissue (bones and teeth).
Low concentrations give protection from caries especially at children. Effects of fluorides (including embed in teeth matrix during formation, which make smaller possibility for decadence and accidence of enamel) are increasing with concentration above 2 mg/l. Fluorides are necessary for bones and teeth construction. Teeth with a fluor have smaller possibilities for caries (many dentifrice consist fluor). Also it is using together with calcium and vitamin D for osteoporosis healing.
Too much fluor can cause teeth hue, and if is using in a long period in organism it can bring to changes in bone structure. High loading of this element can have serious effect on skeleton. There is conclusion that there is clear risk from negative effects after fluor using in quantities bigger then 14 mg/day and very possible risk at loading of 6 mg/day.
Maximal allowable concentrations
According to recommendations of EU (Directive 98/83/EC) limitary value for fluor is 1,5 mg/l and according to our rules for drinking water (Sl. list SRJ 42/98), limitary value for fluor is 1,2 mg/1.