Fluoride Levels in Surface and Groundwater in Africa: A Review

Abstract

Fluoride has been reported to be among natural pollutant of water in Africa. High fluoride levels beyond the recommended World Health Organization limit of 1.5 mg/l has been observed in various Africa countries. However, the information is scattered in different publication medium. Therefore, objective of this work was to put together the information on fluoride levels in surface and groundwater in Africa, and describe the status and distribution of fluoride in water among African countries. This study assembled the secondary data of fluoride concentrations in surface and groundwater from the various literatures in African countries. Such countries represent southern, northern, eastern and western Africa. Descriptive statistics was used and results showed that elevated fluoride concentration occurred in countries such as Tanzania, Kenya, Algeria, Nigeria, Ghana, Malawi, Sudan, Uganda, the Republic of South Africa and Ethiopia. The highest fluoride concentration reported was 2,800 mg/l in Lake Nakuru in Kenya. The high fluoride concentrations in water can be linked to volcanic activities, presence of thermal waters especially those with high pH, gases emitted from earth’s crust, granitic and gneissic rocks. The high fluoride in water is severe in countries located in East African Rift Valley like Kenya, Tanzania and Ethiopia. However, all the incidences of highest fluoride levels in water in the Rift Valley countries were found in surface water bodies. This is contrary, as it is expected groundwater to be more concentrated as compared to surface water due to more water rock interaction than in surface water bodies. There was no single study among many studies has reported the long term trend of concentration of fluoride in water with time. Thus, the effort to establish long term trend of fluoride concentration in water should be taken in consideration. This helps to predict future concentration of fluoride and possibility to minimize future risks. Also, fluorosis has also been reported to be endemic in fluoritic areas of Africa though, little is known on other fluoride negative effects. Therefore, more efforts should concentrate on finding appropriate defluoridation techniques to be applied while considering the cost of operation, efficiency, practicability, easy application and environmental friendly.