Use of geochemical data banks in monitoring the natural environment — a case study from Sri Lanka

Abstract

A survey carried out on the incidence of dental diseases and the distribution of fluoride in drinking water wells and also copper in such waters in Sri Lanka showed the influence of the natural environmental factors on the prevalence of certain geographical diseases. In the case of the geographical variation of dental fluorosis and dental caries it was found that in Sri Lanka, more than any artificially created causes, the natural environmental factors such as mineral occurrences containing the elements concerned, climate, topography, geology, structure, soil, etc. play a very significant role in the geographic variations of elements and hence incidence of diseases. The same was found to be true in the case of copper in potable waters. Two cities in the dry zone of Sri Lanka namely Anuradhapura and Polonnaruwa had a natural fluoride concentration ranging from 0.34 to 4.55 ppm. In some of these regions dental fluorosis was as high as 77.5%. Kandy, situated in the wet zone on the other hand, had in its well waters a low fluoride concentration of less than 0.2 ppm and hence only 13% dental fluorosis. Similarly copper in the well waters of Sri Lanka showed a range of concentrations depending on many natural environmental factors and in some areas far removed from any effects of industrialization still had high copper concentrations of the order of 1–3 ppm, due to the occurrence of copper bearing mineral deposits. It is the aim of this paper to illustrate the use of establishing natural geochemical data banks in monitoring the environment as they would provide useful background values. Any attempt at erecting national or international acceptable levels for the chemical elements must necessarily consider those which are natural to defined environments.