Prevention of bony fluorosis in aluminum smelter workers. Absorption and excretion of fluoride immediately after exposure -- Pt. 1.

1. A program for the prevention of excessive fluoride absorption among aluminum smelter workers is described. This surveillance is based upon knowledge of the portals of entry, distribution, bone deposition and excretory patterns of this element. 2. The control program is based on the thesis that the concentration of fluoride in the urine two to three days after cessation of work-related exposure reflects the bony burden of this element among this occupational group. Further, this program assumes that the concentration of urinary fluoride after three to five days of shift work reflects the extent of work exposure, adequacy of hygienic and engineering controls and work practices. The limitations of such program as it applies to individual samplings of workers is emphasized. 3. A balance between inhaled fluoride and urinary excretion over a 24-hour period (beginning with work exposure) is attempted. An approximate model for aluminum smelter workers in a near equilibrium F balance is constructed. The role of particle size distribution as a determinant of body loading is emphasized. Because of considerable variation in uptake possible with differing particle size distributions, the actual body F loading potential is inadequately determined on the basis of F concentrations in air. These data also suggest that gaseous fluoride is probably adsorbed upon particulates and absorbed at the alveolar level in the same fashion as respirable particulate fluoride. 4. The regression of ambient fluoride on urinary excretion suggests that the present threshold limit value for fluoride might be more appropriately set at 2 mg/M33 for an eight-hour day.