Modeling radon progeny deposition and dose in human airways using CFD: Effects of respiratory patterns and...

Radon progeny inhalation poses a significant public health risk as radioactive particles deposit throughout the respiratory tract, delivering alpha radiation directly to lung tissues and representing the leading cause of lung cancer among non-smokers. This study presents a three-dimensional computational fluid dynamics (CFD) analysis of radon progeny transport in anatomically realistic human airways with detailed dosimetric calculations. A validated CFD model was developed using SolidWorks and ANSYS Fluent to simulate airflow and particle trajectories from the trachea through the bronchioles. The investigation examined both attached (1-10 μm) and unattached fractions of radon progeny across three breathing intensities: light (15 L/min), normal (30 L/min), and heavy (60 L/min), with temperature effects from 10 °C to 40 °C. The Discrete Phase Model was employed for particle tracking, while the k-ω turbulence model captured flow behaviors. Results show significant breathing rate dependency, with maximum velocities ranging from 2.50 m s^-1 to 8.71 m s^-1 in the tracheal region. Larger particles (5-7 μm) exhibited preferential deposition in upper airways, while smaller particles penetrated deeper regions. Higher ambient temperatures promoted deeper particle penetration due to reduced air density. The calculated dose conversion factors for attached fractions ranged from 6.55 to 10.72 mSv.WLM^-1, aligning with international recommendations (5.4-10.6 mSv.WLM^-1). Regional analysis revealed that bronchial regions receive the highest doses. This computational framework provides valuable insights for radiation protection applications and establishes a methodology for radon exposure assessments.