Determination of the radon progeny activity size distribution at different types of workplaces

Inhalation of radon and its short-lived progeny is one of the most significant contributors to the total effective dose from natural sources of ionising radiation. Exposure to radon progeny represents a substantial health risk, primarily due to its established link to lung cancer. Dose coefficients are derived from biokinetic models describing the behaviour of radon decay products in the respiratory tract, combined with dosimetric models that account for energy deposition from emitted radiation. Given the variability of environmental and working conditions at different workplaces, obtaining site-specific aerosol data to support more accurate and tailored dose coefficient calculations is beneficial. The key parameters influencing effective dose include the equilibrium equivalent activity concentration (EEAC), total aerosol concentration, and the size distribution of radioactive aerosol particles. Additional factors such as work activity, relative humidity, and ventilation type significantly affect aerosol characteristics and, consequently, the equilibrium factor (F) and the unattached fraction (f_p), which can vary considerably between sites. This study presents field measurements of the activity size distribution of short-lived radon progeny at several workplaces, using the Dekati ELPI + cascade impactor and the Graded Screen Array Diffusion Battery (GSA DB). The measurements were conducted primarily at underground workplaces with natural ventilation, including former mining excavations and tourist caves. For comparison, the study also includes one site with forced ventilation-a facility for disposing of low-level radioactive waste-and one outdoor location influenced by radon exhalation from a uranium mining waste rock dump.