Short-term radon exhalation and dose assessment of marble and granite utilized as construction materials in Saudi Arabia

A rigorous short-term measurement protocol was conducted to assess radon (²²²Rn) radioactivity and its associated radiological parameters in building stones, specifically marble and granite, in Saudi Arabia. In all, three commercial marble types and three types of granite were subjected to extensive analysis. Radon (²²²Rn) exhalation rates were measured by using the closed-chamber method (CCM) combined with a RAD7 detector, model number 716 DURRIDGE Company Inc. (RAD7 Radon Detector User Manual. Boston, MA, DURRIDGE Company Inc. 2019). The measured radon by the CCM was found to be rather low, corresponding to modest surface and mass exhalation rates with ES=0.72±0.23 to 3.13±0.46 Bq.m^–2.h^–1 and EM=14.6±5.80 to 68.8±10.0 Bq.m^–2.h^–1, respectively. These results were utilized to estimate the indoor radon concentration of a standard room with typical global ventilation conditions, the annual inhalation dose, and the associated excess lifetime cancer risk. On the other hand, gamma-ray spectrometric analysis was implemented for measuring ²²⁶Ra concentrations and led to 18.1–21.8 Bq.kg^{–1 226}Ra in the marble and 24.2–75.2 Bq.kg^–1 in the granite. These results are evidently correlated with the observed radon exhalation rates, reinforcing the relationship between radium content and radon release in the studied materials. Consequently, it is noted that radon emanation and attendant risks from the researched marble and granite stones were below international safety stipulations and limits at normal ventilation conditions, with the inherent necessity for good ventilation being emphasized for granite-based interiors.