Implications of the ICRP Task Group's proposed lung model for internal dose assessments in the mineral sands industry

摘要

The ICRP Task Group on Respiratory Tract Models for Radiological Projection is proposing a model to describe the deposition, clearance, retention and dosimetry of inhaled radionuclides for dose-intake calculations and interpretation of bioassay data. The deposition model takes into account new data on the regional deposition of aerosol particles in human lung and the inhalability of large particles. The clearance model treats clearance as competition between mechanical transport, which moves particles to the gastro-intestinal tract and lymph nodes, and the translocation of material to blood. This provides a realistic estimate of the amount of a given material (such as mineral sand) that is absorbed systemically, and its variation with aerosol size. The proposed dosimetry model takes into account the relative sensitivities of the various tissue components of the respiratory tract. A new treatment of dose received by epithelia in the tracheo-bronchiolar and extrathoracic regions is proposed. This paper outlines the novel features of the task group model, and then examines the impact that adoption of the model may have on the assessment of doses from occupational exposures to mineral sands and thoron progeny. 39 refs., 15 figs., 6 tabs.