Groundwater fluoride as a geochemical marker in the etiology of chronic kidney disease of unknown origin in Sri Lanka

The correlation of chronic kidney diseases of unknown etiology (CKDu) in some dry zone areas of Sri Lanka has led to several research investigations into the association of groundwater fluoride with chronic kidney diseases. Environment related kidney diseases in the tropics are clearly multi-factorial with drinking water expected to play a major role in addition to diet, heat stress and severe dehydration. The geochemistry of groundwater in such regions is marked by the presence of fluoride in significant quantities and is receiving increasing attention as a major risk factor in the prevalence of the chronic kidney disease in view of its geographic distribution pattern similar to that of the CKDu, nephrotoxicity and its very high reactivity with other substances. The dual cytoprotective and cytotoxic nature of fluoride depending on the dose and its competitive interactions with Na, Ca and Mg has raised some interesting possibilities for Mg to act as a protective agent for CKDu. This may be applicable, in general, to tropical arid regions with high amounts of Na, Ca, Mg and F in the groundwater. A case study from such regions in Sri Lanka shows that Mg-rich groundwater in the hard water terrains points to a lesser CKDu prevalence. This is indicative of a protective role for Mg against heart ailments caused by CKDu and more detailed investigations on the mechanisms of geo-biochemical interactions of F, Na, Ca and Mg in the etiology of CKD are clearly warranted