Endemic fluorosis in the Ethiopian Rift Valley.

Between 1977 and 1985, the fluoride content of drinking water and the incidence of endemic fluorosis were assessed and correlated in 16 large farms, villages and towns in the Ethiopian Rift Valley. The fluoride level of drinking-water collected from wells there ranged from 1.2 mg/litre to 36.0 mg/l (mean 10.0 mg/l). Dental fluorosis was observed in more than 80% of sampled children resident in the Rift Valley since birth, with maximum prevalence in the age-group 10-14 years; 32% of the children showed severe dental mottling. Males were affected more than females. Three areas, Wonji-Shoa, Alemtena and Samiberta, were identified as having cases of skeletal fluorosis. The highest incidence was at Wonji-Shoa sugar estates, where a linear relationship was observed between the development of crippling fluorosis, fluoride concentration of drinking-water, and period of exposure to it. The first cases of skeletal fluorosis there appeared among workers (98% males) who had been consuming water with fluoride content of more than 8ppm for over 10 years. Among 30 workers with crippling skeletal fluorosis, cervical radiculo-myelopathy was found to be the commonest incapacitating neurologic complication. As a preventive measure, low-fluoride surface water should be supplied for drinking wherever feasible; if this is not possible, the development of partial defluoridation should be considered.