The health risks to workers in the Florida phosphate industry resulting from chronic inhalation of radionuclide-containing aerosols have not been adequately addressed. The present study establishes a database of information on the particle size distribution, density, shape, chemical composition, and radioactivity concentration for six phosphate facilities in the northern and central regions of the state. A seven-stage cascade impactor was employed to sample aerosols at various processing areas in these plants. Aerosol mass loadings are lowest mainly at shipping areas where they are approximately one order of magnitude less than at granulator areas within equivalent particle size intervals. Aerosol mass concentrations increase as the aerosol size increases for the majority of the plants and operational areas. The aerosol loading at each area varies widely depending on plant, and the variance is largest at the storage areas due to the variability of mechanical operations and patterns of building ventilation...