The biological effectiveness of radon-progeny alpha particles. III. Quality factors.
Brenner-DJ; Miller-RC; Huang-Y; Hall-EJ
Radiat Res 1995 Apr; 142(1):61-69
A redetermination of quality factors for radon daughters for use in lung cancer risk assessments was performed. Data were taken from a study in which the induction of neoplastic transformations in C3H10T1/2 cells by 11 monoenergetic charged particles having defined linear energy transfers of 4 to 600 kiloelectron volts per micrometer were determined and used to calculate quality factors for polonium-218 (15422749) and polonium-214 (15735678) alpha particles. The quality factors were calculated using an equation that expressed the factors in terms of a lineal energy distribution function scaled for radon progeny. The distribution function varied with the depth of the absorbing tissues and source geometry. Quality factors calculated for smokers and nonsmokers assuming that only basal cells in the bronchial epithelium were target cells were 8.5 and 11.1, respectively. Quality factors were estimated for radon daughter exposed miners and home dwellers assuming that 90% of the miners and 25% of the home dwellers were smokers. These were 8.8 and 10.4, respectively. If target cells were assumed to be distributed uniformly throughout the segmented bronchial epithelium, the quality factors for smokers and nonsmokers were estimated to be 11.8 and 13.7, respectively. Quality factors calculated for exposed miners and home dwellers, again assuming that 90% of the miners and 25% of the home dwellers were smokers, were 12.0 and 13.2, respectively. The authors conclude that the radon daughter quality factors they have calculated using the cell transformation data vary from around 10 to 13. The currently used quality factors of 20 to 25 may be too high. The reason for this is that radon daughter alpha particles deposit most of their energy in regions where the biological effectiveness per unit dose is decreasing. Based on a quality factor of 10, the dosimetrically based estimate of radon (10043922) induced lung cancer mortality in the United States would be approximately 35,000 deaths per year (death/yr), instead of the 70,000death/yr obtained using a quality factor of 20.
Pulmonary-system-disorders; Radon-daughters; Alpha-radiation; Kinetic-energy; In-vitro-studies; Mathematical-models; Risk-analysis; Lung-cancer; Occupational-exposure; Dosimetry; Underground-miners; Environmental-exposure; Cigarette-smoking; Cell-transformation
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