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 and aerosol parameters on human lung dose with regard to a comparison with the corresponding recommended dose values of the International Commission on Radiological Protection (ICRP). The dose conversion factor which gives the relationship between effective dose and potential alpha energy concentration of inhaled short-lived radon decay products (218Po, 214Pb, 214Bi/214Po) 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, simplifying modification of the model were possible. Firstly, the underlying assumptions of the model are described. Secondly, important input parameters of the model are varied to assess the uncertainty of the dose conversion factor due to uncertainty of these parameters. The main emphasis is focused on biological and aerosol parameter variability like variation of breathing rate and breathing mode, clearance rates, critical cells for the induction of lung cancer, particle size and dispersion of the activity size distributions. The possible range of dose conversion factors is discussed both for indoor and mine aerosol conditions in the framework of the presented dose model. The investigation shows that the dosimetric approach leads to a dose conversion convention which is a factor of more than two times higher than the recommended 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 both 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 mode. (author)