Fluoride in groundwater from high-fluoride areas of Ghana and Tanzania

Naturally high concentrations of fluoride are found in groundwater from many parts of the world, including Africa, and can have an important impact on human health. Chronic ingestion of high concentrations gives rise to dental fluorosis and in extreme cases, skeletal fluorosis. While not life-threatening, these can impair quality of life and affect livelihoods, particularly in rural areas. They also pose a considerable constraint on groundwater development. As donors become increasingly concerned over groundwater-quality issues, groundwater-development projects may be halted through concerns over excessive fluoride concentrations. Fluoride problems tend to be more prevalent in the more arid parts of the world, where water is already a scarce resource. Groundwater fluoride concentrations have been investigated in two study areas in Africa: the Bolgatanga area of northern Ghana (Upper East Region) and the Tabora-Singida areas of central Tanzania. Both study areas have notable groundwater fluoride problems, with Tanzania being particularly badly affected. Fluoride concentrations were found to exceed 20 mg L–1 in central Tanzania and 4 mg L–1 in northern Ghana. Both these extremes are in excess of the WHO guideline value for fluoride in drinking water of 1.5 mg L–1. In Ghana, 23% of samples analysed exceeded the WHO guideline value, while in Tanzania 57% were in excess. Dental fluorosis is common in both areas, particularly in children, and is clearly related to the water supply.