||Carcinogenic Risk of Non-Uniform Alpha Particle Irradiation in the Lungs: Radon Progeny Effects at Bronchial Bifurcations.
Hoffmann, W. ;
Crawford-Brown, D. J. ;
Menache, M. G. ;
Martonen, T. B. ;
||NSI Technology Services Corp., Research Triangle Park, NC. ;Duke Univ. Medical Center, Durham, NC. Center for Extrapolation Modelling. ;North Carolina Univ. at Chapel Hill. Dept. of Environmental Sciences and Engineering. ;Salzburg Univ. (Austria). Dept. of Biophysics.;Health Effects Research Lab., Research Triangle Park, NC.
Pulmonary neoplasms ;
Alpha particles ;
Risk assessment ;
Air pollution effects(Humans) ;
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The combined effect of enhanced deposition and reduced clearance at bronchial bifurcations leads to increased radon progeny doses within branching sites compared to uniformly distributed activity within a given airway generation. A multi-stage carcinogenesis model was used to predict the probability of lung cancer induction at different sites of the bronchial region. For relatively low radon progeny exposures, lung cancer risk is significantly higher in bifurcation zones, particularly at carinal ridges, than along tubular segments. At sufficiently high exposures, however, lung cancer risk is highest in the tubular portions of a generation. This suggests that the common assumption of a uniform dose distribution provides realistic risk estimates for high uranium miner exposures, but may underestimate lung cancer risk at low, environmental exposures. If concomitant exposure to cigarette smoke is factored into the risk analysis in a multiplicative fashion, then the effect related to risk inhomogeneity becomes even more pronounced.