Radon progeny microdosimetry in human and rat bronchial airways: the effect of crossfire from the alveolar region

Abstract

The objectives of the present study were (1) to present a comprehensive analysis of the microdosimetric quantities in both human and rat bronchial airways and (2) to assess the contribution of the crossfire alpha particles emitted from the alveolar region to bronchial absorbed doses. Hit frequencies, absorbed doses and critical microdosimetric quantities were calculated for basal and secretory cell nuclei located at different depths in epithelial tissue for each bronchial airway generation for defined exposure conditions. Total absorbed doses and hit frequencies were slightly higher in rat airways than in corresponding human airways. This confirms the a priori assumption in rat inhalation experiments that the rat lung is a suitable surrogate for the human lung. While the contribution of crossfire alpha particles is insignificant in the human lung, it can reach 33% in peripheral bronchiolar airways of the rat lung. The latter contribution may even further increase with increasing alveolar 214Po activities. Hence, the observed prevalence of tumors in the bronchiolar region of the rat lung may partly be attributed to the high-linear energy transfer crossfire alpha particles.