Water Quality in the Dry Zone of Sri Lanka - Some Interesting Health Aspects

Abstract

Dental fluorosis and kidney diseases are commonly observed in many parts of the dry zone of Sri Lanka, notably in the North Central Province. Chronic Renal failure (CRF) ,has recently shown a marked increase in some areas in the Anuradhapura and Polonnaruwa districts. Geochemically , the groundwater in these areas is generally of the Na/K type with the C1- sub-type predominating possibly due to the increasing drought conditions and salt build up. The Total Dissolved Solids (TDS) and the electrical conductivity are also correspondingly high. A unique feature of the dry zone is that in a large number of areas, the fluoride levels in the groundwater are higher than the recommended danger levels of the World Health Organization (WHO), and in some wells values as high as 10 mg/l F- have been recorded. The WHO stipulates that a F - concentration of 1.5 rnd is the upper limit. The abundance of fluoride in the groundwater and the higher intake of water have resulted in dental fluorosis being largely prevalent in children. It is also presumed that skeletal fluorosis is more common than hitherto believed. Though the incidence of CRF is increasing, the exact cause of the disease is not known to any degree of certainty. Since the affected people are mostly from the farming community, the contamination of drinking water possibly by agrochemicals is considered a possibility. Among the other possibilities are: (a) the use of inferior quality aluminium vessels which may react with fluoride (b) genetic factors (c) alcohol consumption (d) deficiency of some essential trace nutrients (e) excess of a toxic trace element (0 some organic matter in the water. The abundance of high fluoride in all areas and total dissolved solids in the groundwater, and the high saline nature of the water may well turn out to be a major factor in the incidence of CRF. Studies carried out on the health effects of excess fluoride in drinking water have indicated the detrimental effect it could have on the kidneys. However, this needs further investigations before any firm conclusions can be drawn. in contrast to the dry zone where evaporation and accumulation of salts on the surface have resulted in differing hydrogeochemical characteristics. These features are illustrated in figure 2. Approximately 75% of the population of Sri Lanka live in a rural environment with a close association with the immediate physical environment, obtaining their drinking water directly from the ground. The chemistry of the groundwater must therefore, have an important bearing on the health of the population.