Track structure predictions of radon-induced biological effects in human bronchial epithelium

Abstract

The formalism of track structure theory was used to predict the probabilities of different cellular radiation effects in basal and secretory cells of the bronchial epithelium exposed to radon progeny alpha particles. Cellular radiosensitivity data applicable to the prediction of carcinogenic response consists of in vitro data on oncogenic transformation and survival in C3H10T1/2 cells, mutation and survival in V79 Chinese hamster cells, and chromatid aberrations and survival in CH2B 2 cells. Energy spectra of 218Po and 214Po alpha particles were computed for cell nuclei located at varying depths in the bronchial epithelium of different airway generations. Applying track structure theory, the number of observable inactivations, chromatid aberrations, transformations, and mutations can be calculated for a given alpha particle energy spectrum. The computed effect probabilities are then weighted by the depth-density distributions of basal and secretory cells. The track structure predictions for airway generation 4 suggest that cellular radiation effects are rather uniformly distributed within the bronchial epithelium and that the lung cancer risk per unit exposure at low exposure levels is either constant or increases slightly, and then decreases at high cumulative exposures.