München 2009 – wissenschaftliches Programm
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ST: Fachverband Strahlen- und Medizinphysik
ST 1: Measurements and Effects of Environmental Radiation Exposures
ST 1.3: Vortrag
Dienstag, 10. März 2009, 09:40–10:00, A021
Thoron and its decay products: consequences of increased indoor concentrations for inhalation dosimetry — •Wei Bo Li and Jochen Tschiersch — Helmholtz Zentrum München, Institute of Radiation Protection, D-85764 Neuherberg
Recently, increased concentrations of 220Rn (thoron) and its progeny were measured in traditional residential dwellings in China, India and other countries and gave rise to a reconsideration of their contribution to inhalation dose. A complete assessment of the lung dose is performed, whereas thoron gas and 216Po contribute the least. The effective and organ equivalent doses of the progeny 212Pb and 212Bi in the lungs and in other organs were calculated as a function of activity median diameters in the range 1–10,000 nm, applying the human respiratory tract model and the biokinetic models developed by the ICRP. Taking into account the unattached fraction of 0.03 and a size of 1.5 nm for unattached particles and of 300 nm for attached particles in the indoor air, the dose conversion coefficient was estimated to be 3.8 mSv WLM-1, about 27.5% of the values of 13.8 mSv WLM-1 for 222Rn. This study provides the dose conversion coefficient for thoron decay products. It can be used to assess the inhalation dose for dwellers in areas with a higher thoron concentration.