Spatial distribution of fluoride in groundwater of Sri Lanka

Abstract

Fluoride ions in drinking water is well known for both beneficial and detrimental effects on health. Millions of inhabitants in the Dry Zone of Sri Lanka are vulnerable to fluorosis due to consumption of high fluoride groundwater. The objective of this study is to upgrade the spatial distribution map of groundwater fluoride levels in Sri Lanka. The map was prepared using nearly 14000 groundwater fluoride data that were collected from primary and secondary sources. The fluoride map of Sri Lanka indicates that the climate and hydrological conditions appear to play a major role in the geochemical distribution of fluoride in groundwater. In some cases, over 25 % of wells have more than 2 mg/L of fluoride, which is much higher than the recommended level for tropical countries. As shown in the map, even within the Dry Zone region, some low fluoride regions can be observed. This may probably be due to the effect of surface water, which contains fairly low levels of fluoride. In general, from among the chemical parameters in groundwater, fluoride stands out as an ion that appears to seriously affect the water quality of the Dry Zone.

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

“…Recent investigations have shown that even within a few years, groundwater wells in the dry zone of Sri Lanka have shown a marked increase of fluoride changing from safe levels to -not recommended‖ levels (Chandrajith et al, 2012). The climate change and the consequent evapotranspiration have been very high in these tropical lands with the resulting elevations of fluoride, Na, Ca and Mg in the groundwater.…”

“…A clear discrimination between the fluoride and Ca/Mg ratios can be observed for the CKDu and nonCKDu drinking water wells (figure 4). Although higher hardness (Ca + Mg) and fluoride is a common factor in most of the dry zone of Sri Lanka (Chandrajith et al, 2012), the Mg-factor is extremely important in the case of CKDu foci in the dry zone of Sri Lanka. While calcium has been given very high prominence, magnesium has been grossly underestimated even though it plays a major role in cardioprotectivity and its calcium antagonistic properties.…”

“…The first Hydro-geochemical Atlas of Sri Lanka was published by Dissanayake and Weerasooriya (1985) and one of their major findings was that high concentrations of groundwater fluoride were distributed in the dry zone and that the wet zone had minimal fluoride. This map was later updated by Chandrajith et al (2012) and the disease pattern of the CKD of unknown etiology coincided with that of the fluoride rich regions. This fact had shown that groundwater fluoride could well be a risk factor in the etiology of the kidney disease.…”

High prevalence of dental fluorosis among schoolchildren in three villages in Vavuniya District: an observational study

“…The community fluorosis index (CFI), based on a 2002 survey among schoolchildren in three schools in high fluoride groundwater areas (>1.5 mg/l up to 10.9 mg/l) of Anuradhapura District, found CFI values in the range 1.85 -2.29 [3] A landmark publication on medical geology in Sri Lanka has noted that dental fluorosis frequently occurs when the fluoride content of drinking water exceeds 1.5 mg/l, and such water is habitually consumed by young children [4]. The findings of this publication have been extended by a later study, which provides a map of Sri Lanka based on fluoride levels of 14,500 samples of groundwater from both shallow and deep wells in 45 locations in seven Provinces, excluding the Central and Northern Provinces [5]. According to this study, vast swathes of the North Central, Eastern and Uva Provinces have groundwater concentrations between 1.0 and 1.5 mg/l, with many areas within them having between 1.5 and 2.0 mg/l, and other locations having over 2.0 mg/l.…”

“…Paper are of particular significance because they define, many localised variations in fluoride content of groundwater within Districts and also within many villages, that would explain the scattered distribution of clinically apparent dental fluorosis among people living in contiguous land areas [4,5,7].…”