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[[Image:defluoridation unit.jpg|thumb|right|300px|Household defluoridation unit (HDU). Photo: ADDIS ABABA UNIVERSITY.]]

High levels of fluoride in groundwater has been reported parts of in Ethiopia, Malawi, Kenya and Tanzania and can lead to health problems including dental fluorosis, osteosclerosis, thyroid problems, growth retardation and even kidney failure. WHO report shows excessive fluoride intake (3-6 mg/L) can lead to severe and permanent bone and joint deformations of skeletal fluorosis and the consumption of drinking water with even higher fluoride concentrations (10 mg/L) can lead to crippling fluorosis, which causes the hardening and calcifying of the bones.