Vanadium in ground water from Mt. Fuji: Does it have health effect on habitants around the mountain?

Abstract

A study was carded out in the Nathenje area in order to determine fluoride concentrations in groundwater and to investigate the occurrence of dental fluorosis in school children. From a fluoride distribution map, it was observed that the central part of Nathenje had high fluoride concentration of between 2 mg/L and 7.02 mg/L. The southern and western parts had less than 1 mg/L. About 52% of the groundwater supplies had fluoride concentrations are above the Word Health Organization maximum permissible limit of 1.5 mg/L. Fluoride concentrations for the rainy season varied from <0.5 to 6.984-0.01 mg/L with 52.9% of the boreholes above the 1.5 mg/L. Fluoride for dry season ranged from <0.5 to 7.024-0.02 mg/L with 50.8% of the boreholes above 1.5 mg/L. Fluoride concentrations remained almost constant during the two seasons of the study period. A social survey revealed that 68.5% of children had dental fluorosis from areas with greater than 4.95 mg/L fluoride. About 25% were affected in areas with an average content of 1.85 mg/L. No occurrence of dental fluorosis was detected in children from areas with less than 1 mg/L fluoride. It was therefore concluded that fluoride is a serious contaminant of groundwater in Nathenje where most of the groundwater contains fluoride higher than World Health Organization acceptable levels. These high fluoride values seem to be associated with the weathered basement complex containing biotite that is a probable source of fluoride. The other suspected sources of fluoride in Nathenje groundwater could be due to the dissolution of hornblende, fluorite and amphibole, which are reported to occur in rocks and soils. The fluoride concentrations in Nathenje groundwater vary from less than 0.5 mg/L to 7.02 mg/L probably due to varying concentrations of fluoride-bearing minerals and their dissolution rate. It was observed that the central part of the Nathenje area where groundwater contains high fluoride content, about 68.5% of children has suffered dental fluorosis. This shows that excess fluoride occurrence in groundwater supplies causes dental fluorosis among children in this area. Based upon the results of this study, it was recommended that further studies should be done on the genesis of fluoride in groundwater. It was also recommended that water quality analyses should be carried out during borehole construction, and monitoring of boreholes should be done after the boreholes have been handed over to the communities.