A computational modeling of airflow and radon progeny deposition in human respiratory system

The inhalation of radon and its decay products is the primary source of natural radiation exposure for the general population. The solid particles produced by radon decay are also radioactive and can easily penetrate deep into the lungs, causing damage to the airways. To better understand the harmful effects of inhaling radon decay, we have used a Computational Fluid Dynamics method to model the deposition of radioactive particles in the human respiratory system. This method was used to determine the effective dose resulting from exposure to radon progeny. The simulations have been conducted with representative breathing intensities of light (15 L/min), normal (30 L/min), and heavy (60 L/min) breathing under continuous breathing conditions. The numerical results show that larger particles are deposited more in the bronchi and at higher inhalation rates due to higher inertia. Furthermore, the airflow velocity field and deposition rates were obtained and discussed in detail. The dose conversion factor of radon decay products was calculated for different airflows, taking into account the deposition rates. The calculated dose conversion factor for attached fractions (6.62-11.35 mSv WLM-1) and unattached fractions (3.48-4.68 mSv WLM-1) is above the recommended range of 5.4-10.6 mSv WLM-1 obtained by the International Commission on Radiological Protection and also by the World Health Organization at a level of 10 mSv WLM-1.