Study of Worker's Exposure to Thorium,Uranium and Niobium Mineral Dust

The aim of this study is to evaluate worker’s exposure to particles, with special attention to thorium, uranium and niobiumbearing particles. A cascade impactor (CI) with six stages was used to collect particles with aerodynamic diameter in the rangeof 0.64 to 19.4 μm. The elemental mass concentrations impacted in each stage of the CI were determined using the PIXE(Particle Induced X-ray Emission) technique. The Mass Median Aerodynamic Diameter (MMAD) and elemental mass concentration in the fine fraction of aerosol (0.5 to 2.5 μm) were determined.Personal air samplers were used by workers to collect fine particles of aerosol. The concentrations of ²³²Th and ²²⁸Th in these air samplers were measured by the alpha spectrometry technique. Faeces and urine samples from the workersand their wives were analyzed to determine the thorium, uranium and niobium mass concentration (mass spectrometry) and ²³²Th, ²²⁸Th, ²³⁸U and ²³⁴U concentrations (α spectrometry) and then compared to inhabitants of regions with low metal concentrations. The analysis of thefaecesand urine samples from workers and their wives indicated that themain pathway of thorium, uranium and niobium incorporation was byingestion. The observed concentrations of niobium and uranium inurine samples from workers showed a systemic incorporation of niobium and uranium.