Dosimetric concepts for inhaled radon decay products in the human lung

The primary objective of lung dosimetry is to provide a physical basis in terms of radiation doses for establishing the relationship between airborne radon decay products and lung cancer induction as the most important biological endpoint. In order to accomplish this goal, several dosimetric approaches have been developed which are based on reasonable approximations of the anatomical structure of the respiratory tract, of clearance mechanisms for particles deposited, and of energy deposition at the cellular level. Usually lung cancer risk is correlated with the mean radiation dose to the stem cells in the bronchial epithelium. A different approach is presented here through the application of stochastic models which allow for the biological variability inherent in all anatomical and physiological parameters. Thus, the specific energy distribution in cells or cell nuclei and the number of sensitive targets hit are more appropriate quantities for the interpretation of lung cancer incidence. The relevance of dosimetric approaches at the cellular level is, however, intimately connected with models describing the transformation towards malignancy, and further improvements of lung dosimetry can only be achieved by a more profound insight into the basic biological mechanisms involved in radiation-induced carcinogenesis