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The epidemiology of lung cancer of uranium miners, when projected onto lung cancer of the Japanese survivors of the atomic bombs, shows a Dose Conversion Coefficient (DCC) of 4 mSv per WLM. If, however, the effective radiation dose due to radon progeny, typifying underground uranium mines, is calculated, the DCC is around 15 mSv per WLM. We attempted to resolve the discrepancy, including trying to understand a less serious one, that between calculated DCC's for homes and mines. Our studies included the effects of morphometry models, regional lung deposition models, and the consideration of bifurcation regions of the human tracheo-bronchial tree. (more) |
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The most updated dosimetric lung model is the one published by the International Commission on Radiological Protection (ICRP) in their ICRP66 report. In their approach, the dose is calculated in the layers containing the sensitive cells by assuming that the dose values in the sensitive cells are the same as those in the layers. By using a micro-dosimetric approach in which the energy of alpha particles deposits only in the nuclei of sensitive cells, the DCC has been lowered by about one-third (from 15 mSv/WLM down to approximately 10 mSv/WLM). The most recent attempt was the consideration of killing of target cells through an effect-specific track length model. To focus on the relevant part of the absorbed dose in the cell nuclei, the absorbed dose, which causes cell-killing is discarded in the final calculations of the DCC. Following this approach, the calculated DCC has become 3.4 mSv WLM-1 which is very close to the epidemiologically derived value of ~4 mSv WLM-1. (more) |
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Nuclear Radiation Unit |
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