Prevention of bony fluorosis in aluminum smelter workers. A 15-year retrospective study of fluoride excretion and bony radiopacity among aluminum smelter workers -- Pt. 4.

1. Fifty six aluminum smelter workers with 10 to 43 years' occupational exposure, and who had been previously studied medically, were re-x-rayed. Average urinary fluoride concentrations since 1960 were estimated to range from 2.78 mg/liter preshift and 7.71 mg/liter postshift. 2. Roentgenographic studies in 1960-66 and 1974 failed to reveal any evidence of fluoride associated bony change. 3. Although these workers represent a self-selected group, their magnitude and duration of exposure far outweighs any other group working at present or in the past at this plant. The implication that they have uniformly self-selected as fluoride resistant individuals is improbable. 4. These data indicate that group post-shift ur a long period is not associated with enhanced risk of bony fluorosis. If preshift urinary fluoride concentrations are less than 4 mg/l, the same results appears to apply.