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.
Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana
Abstract The most appropriate and widely used source of drinking water for the populations of the upper regions of Ghana is groundwater. In general, groundwater quality is acceptable except for some parts of the Bolgatanga and Bongo Districts, where there are occurrences of elevated levels of natural groundwater fluoride. Concentrations of groundwater fluoride in excess of the World Health Organization (WHO) maximum guideline value (1.5 mg/l) in the Bongo area have been known since 1978. However, the effect of fluoride on people ingesting the water did not receive public and medical attention until October 1993, when health personnel were asked to investigate the cause of stained teeth in school children. The investigation established that 62% of the total population of school children in the Bongo area had dental fluorosis. Against this background, a study was initiated to understand the geochemistry, genesis, and distribution of fluoride in relation to the geology of the area. Groundwater fluoride in the upper regions ranges from 0.11 to 4.60 ppm, with the highest concentrations associated with the fluorine-enriched Bongo coarse-grained hornblende granite and syenite suite. The source of groundwater fluoride within the Bongo granitoids is dissolution of the mineral fluorite and dissolution of and anion exchange with micaceous minerals and their clay products. Applying the WHO recommended guideline values for fluoride in drinking water reveals that 49% of wells in the area deliver water below the optimum level of 0.5 mg/l F–; these populations are thus prone to dental caries. Twenty-eight percent of the wells fall within the optimum interval for good dental health (0.5–1.5 mg/l F–). Twenty-three percent of the wells have concentrations above the recommended maximum guideline limit of 1.5 mg/l F–; this population is susceptible to dental and possibly skeletal fluorosis. Climatic conditions of the area suggest that the individual water consumption is in the order of 3 to 4 l which is higher than the WHO estimate of 2 l/adult/day. In addition, dietary intake for the upper region population is probably higher than WHO baseline values (0.2–0.5 mg/day). This implies that a much higher population is susceptible to developing dental and skeletal fluorosis than originally suspected. Geochemical symbol plot maps help geochemists understand factors controlling the distribution and uptake of fluoride in the upper regions, but they are of minimal value to health officials responsible for planning epidemiological studies and dental health education programs in the region. By casting fluoride data into contoured 'geochemical health-risk maps' using intake interval guidelines more closely aligned to regional climatic and dietary conditions, health officals can better judge the impacts (regional and population based) of fluoride on segments of the population, such as various sex and age groups.
Hydrochemical facies and ground-water flow patterns in northern part of Atlantic Coastal Plain
-----------~-----------------------------A 1 Hydrochemical facies-Continued In troduction ______________________________________ _ 1 Occurrence of hydrochemical facies-Continued Geology __________________________________________ _ 2 Cretaceous sediments _______________________ _ A 15 22 31 Relation of salt water to fresh water _________________ _ 2 Eocene formations ____________________ -___ _ Factors affecting position of the salt-water body ___ _ 2 Miocene formations __________________ --___ _ Factors affecting occurrence of salt water _________ _ 9 Spatial distribution and origin of hydrochemical Ground-water flow patterns _________________________ _ 9 facies ______________________ ---_____ ----__ -_ 37 37 38 39 40 41 Hydrochemical facies _______________________________ _ 11 Concentration of dissolved solids _____________ _ Defintiion _____________________________________ _ 11 Cation facies __________________________ _ Procedures and mapping techniques ______________ _ 14 Anion facies ___________________________ _ Occurrence of hydrochemical facies within stratiSummary and conclusions ___________________________ _ graphic units ________________________________ _ 15 Selected references _________________________________ _