Determination of Water Fluoride Concentration and the Influence of the Geographic Coordinate System and Time

Abstract

The upper limit of fluoride concentration in water for human consumption is 1.5 ppm. A great amount of studies have been carried out concerning the water fluoride concentration in wide areas around the world, but none have studied the change of fluoride concentration as a function of geographical coordinates and through time. This paper describes ?microvariation? of fluoride concentration among wells separated by less than 500 meters and during a month. On the other hand, a ?macrovariation? is also studied describing changes among cities that are separated by more than 10 kilometres and compared with fluoride concentrations measured 65 years ago. Fluoride concentration was measured in a wide geographical area of Argentina, which is 133000 km2. Samples of water were collected from different regions. Macrovariation: Differences in fluoride concentration in well water among regions were found, as well as an increase in water fluoride concentration during 7 decades. Microvariation: Daily water fluoride concentration in a specific area displayed a great variation in the measurements through time. In addition, wells with no more than 500 m of separation were measured at the same time and were significantly different. These results indicate that in order to determine the fluoride concentration of a region, different samples of the same area should be obtained and a sampling through time should also be done.