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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:15 |
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Conference: Bucharest University Faculty of Physics 2003 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
A comparative Study of the Lung Bio-Kinetic Model
from the Dosimetric and Epidemiologic Approach
Authors:
Vlad C. Tomulescu, Tatiana Angelescu, Mircea Rusu, Octavian Duliu
Affiliation:
Physics Faculty, Atomic and Nuclear Physics Department, University of Bucharest
E-mail
Keywords:
Abstract:
A correct assignment of organs’ weighting factors is of tremendous importance for assessing the effective dose due to inhalation of Radon short lived decay daughters. If for the lung (i.e. the trachea, bronchi, bronchioles and alveoli) there is established a 0.12 organ weighting factor, the other tissues of the respiratory tract (including the naso-oro-pharynx) are not listed. Studies have shown that extra-thoracic airways - as the entrance gate for aerosols - are subject to the highest deposition of solid state Radon progeny, therefore to the highest dose equivalent. Consequently, should we apply the International Commission for Radiological Protection recommendation and assign to the naso-pharynx a tissue weighting factor of 0.025 as half of remainder tissues. However, in such case, the epidemiological studies have shown a lack of correlation to the low incidence of nose and mouth cancers due to Radon progeny inhalation. Therefore, the assumption of a 0.025 weighting factor for the extra-thoracic airways may lead to an overestimate of the effective dose. This work presents comparative graphs of effective doses as function of aerosol size, obtained when considering each separate situation: i) based on the dosimetric conservative recommendation, and ii) on the basis of epidemiological statistics. The ICRP based ModeLung® software for dose calculation following Radon progeny inhalation was used.
When considering the reference worker performing usual labor for a month (i.e. 70 working hours) in an environment where a 0,1kBq/m3 Radon concentration was established at a 0,5 equilibrium factor, and in a classical aerosol distribution, one can obtain the following values for the effective dose coefficient:
YD = 36,88 mSv/WLM (dosimetric case with WET = 0,025 case)
YE = 7,03 mSv/WLM (epidemiologic case WET ~ 0)
It can easily be noticed a 5 times lower value in the epidemiologic case. Though 0,025 is considered a high value for the extra-thoracic compartment weighting factor, there is yet no proposal for a lower non-negative value based on the cancer incidence. The current study is proposing a mean value for the dose conversion coefficient of 19 mSv/WLM, but a weigthing factor value for the extra-thoracic airways remains an opened problem.
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