The role of individual characteristics of human subjects on the radiation burden of the bronchial airways from radon progeny.

Variability in radiation-related health risk and genetic susceptibility to radiation effects within a population is a key issue for radiation protection. Besides differences in the health and biological effects of the same radiation dose, individual variability may also affect dose distribution and its consequences for the same exposure. As exposure to radon progeny affects a large population and has a well-established dose-effect relationship, investigating individual variability upon radon exposure may be particularly important. Using the Stochastic Lung Model combined with mucociliary clearance and alpha-particle microdosimetry models, deposition rates and absorbed dose rates were determined for a healthy adult, a 5-year-old child, and an adult with severe asthma. The results show that children receive significantly higher absorbed dose rates in basal and secretory cell nuclei than healthy adults, despite lower deposition rates, due to smaller airways and thinner mucus layers. For individuals with severe asthma, both deposition rates and dose rates are higher due to airway contraction and slower mucus clearance, although increased mucus thickness reduces absorbed dose rates. These findings demonstrate that anatomical and physiological differences significantly influence absorbed doses in the lungs upon radon exposure and highlight the importance of accounting for individual variability in radiation protection and risk assessment.