THE INFLUENCE OF BIOLOGICAL AND AEROSOL PARAMETERS OF INHALED SHORT-LIVED RADON DECAY PRODUCTS ON HUMAN LUNG DOSE

The purpose of this article is to assess the influence of biological a nd aerosol parameters on human lung dose with regard to a comparison w ith the corresponding recommended dose values of the International Com mission on Radiological Protection (ICRP). The dose conversion factor which gives the relationship between effective dose and potential alph a energy concentration of inhaled short-lived radon decay products (Po -218, Pb-214, Bi-214/Po-214) is calculated with a dosimetric approach. The calculations are based on a lung dose model with a structure that is related to the recently recommended ICRP respiratory tract model. Because of the short half-lives of the investigated nuclides, simplify ing modifications of the model were possible. Firstly, the underlying assumptions of the model are described. Secondly, important input para meters of the model are varied to assess the uncertainty of the dose c onversion factor due to the uncertainty of these parameters. The main emphasis is focussed on biological and aerosol parameter variability l ike variation of breathing rate and breathing mode, clearance rates, c ritical cells for the induction of lung cancer, particle size and disp ersion of the activity size distributions. The possible range of dose conversion factors is discussed both for indoor and mine aerosol condi tions in the framework of the presented dose model. The investigation shows that the dosimetric approach leads to a dose conversion conventi on which is a factor of more than two times higher than the recommende d epidemiological values of the ICRP of 3.9 mSV.WLM(-1) for the public and 5.1 mSv.WLM(-1) at working places. The dosimetric results yield b ath for indoor and mine aerosol conditions dose conversion factors in the range of 10 mSV.WLM(-1) to 15 mSV.WLM(-1) depending on breathing m ode.