Deposition pattern of inhaled radon progeny size distribution in human lung

One of the important factors controlling the distribution of radiation dose to the different portions of the human respiratory tract is the deposition pattern of radon progeny containing aerosol. Based on the activity size distribution parameters of radon progeny, which were measured in Minia University, the deposition behavior of radon progeny (attached and unattached) has been studied by using a stochastic deposition model. The attached fraction was collected using a low pressure Berner cascade impactor technique. A screen diffusion battery was used for collecting the unattached fraction. Most of the attached activities for 222Rn progeny were associated with aerosol particles of the accumulation mode. The bronchial deposition fraction of particles in the size range of attached radon progeny was found to be lower than those of unattached progeny. The effect of radon progeny deposition by adult male has been also studied for various levels of physical exertion. An increase in the breathing rate was found to decrease the fraction with which inhaled progeny were deposited in the bronchi. As the ventilation rate increases from 0.54 to 1.5 m3 h−1, the average deposition fraction of airway generation 1 through 8 are expected to decrease by 22% for 1.4 nm particles and by 38% for 150 nm particles.