Table 2 : The average fluoride concentrations in the well water of different provinces of Sri Lanka Province Average Fluoride
Fluorine, the most reactive and electro-negative halogen on the earth, is an element that virtually never occurs naturally in its free, gaseous form In the form of fluorides, however, it is one of the most plentiful and wide spread of elements, standing seventeenth in order of abundance in the earth's crust. Fluorides occur in water, soil, rocks, dusts and the atmosphere. It is also present in most foods, many plants and virtually in all animal tissues. Fluoride is considered as an essential element for the human body for promoting growth of healthy bone and teeth. Although every food stuff contains at least a trace of fluoride, the total intake of fluoride from food is relatively small, and most of it is ingested through drinking water.
Fluoride Problems in Sri Lanka
Argues that excessive fluorides in groundwater are a serious water quality problem in some parts of Sri Lanka. The incidence of dental fluorosis shows a high correlation with the presence of groundwater in certain areas. Tube wells constructed in various rock types have shown different fluoride concentrations, possibly due to the different mineral constituents in these rocks and their relative capability of releasing fluoride ions into groundwater. It has been observed that the tube wells located in the dry zone have higher fluoride concentrations than those in the wet zone. The fluoride contents of groundwater show an inverse relationship with average yields of the tube wells, indicating the inverse relationship of aquifer permeability to the fluoride content in groundwater.
Prevalence of dental fluorosis in four selected schools from different areas in Sri Lanka.
The prevalence of dental fluorosis in four selected schools from different areas in Sri Lanka was investigated by dental examination of 377 school children aged 14 years. In the endemic zone the prevalence of dental fluorosis was 51 to 78% while in a non-endemic area it was 5.4%. There were no significant sex differences in the prevalence of fluorosis. Attention is drawn to the need for using non-fluoridated tooth-paste in areas where dental fluorosis is common. The problem could be further aggravated in the future by the use of water from tube wells in these areas which are known to contain higher concentrations of fluoride than those from shallow wells.