Occupational exposure to mineral dust of thorium

The results of workers' exposure to mineral dust containing thorium and uranium, in two Brasilian mine and processing plant, are shown. The mineral dust samples were collected using a personal sampler and a cascade impactor. The faces samples were analysed to estimate the workers' incorporation. At installation A 232 Th concentration in the respirable fraction of aerosol are lower then detection limit (1 mBq/m3) and the 232 Th concentration in faces are in range of detection limit up to 23 mBq/g. At installation B the mineral dust samples were collected with a cascade impactor to determine the MMAD (Mass Median Aerodynamic Diameter) and the elemental mass concentration. The particles containing Nb, Th, U Sr, Zr and Y are in the respirable fraction of aerosol. The particle size are in the range of 1,6 up to 2,2 μm 232 Th in the respirable fraction of aerosol are lower then detection limit (1 mBq/m3) and the 232 Th concentration in faces are in range of detection limit up to 23 mBq/g. At installation B the mineral dust samples were collected with a cascade impactor to determine the MMAD (Mass Median Aerodynamic Diameter) and the elemental mass concentration. The particles containing Nb, Th, U, Sr, Zr and Y are in the respirable fraction of aerosol. The particle size are in the range of 1,6 up to 2,2 μm 232 Th in the respirable fraction are lower then detection limit. The 232 Th concentration in faeces are in range of detection limit up to 10,8 mBq/g. In both installations, incorporation occurs due mineral inhalation and ingestion. (author)