Deposition and clearance of inhaled radon progenies in the bronchial airways

Abstract. Majority of lung cancers in the case of former uranium miners were developed in the central airways where the deposition densities of inhaled radon progenies have the highest values. Up to the present no one has compared the radiation burden of primarily deposited radon progenies in the central airways with the radiation burden of radon daughter elements cleared up into the central airways from the more distal bronchial regions. In this paper, this comparison has been realized. Published dosimetric models compute only the primarily deposited fractions and neglect the oncomitant effect of clearance.
In the present work, the deposition distribution of inhaled radon progenies was computed by the Stochastic Lung Model in each bronchial airway generation. A clearance model was developed to compute the mucociliary clearance of deposited particles. In addition, a dosimetric model was elaborated to determine the radiation burden of primarily deposited and the radiation burden of up-cleared radon progenies in each bronchial airway generation.
Based on the results, in the first few airway generations, the burden of the up-cleared radon progenies is about two–three times higher than that of the primarily deposited particles. Thus, the concomitant effect of clearance should not be neglected in this region at the dosimetric and health effects considerations of inhaled radon progenies.