Natural radioactivity and radon exhalation rate of Sardinian dimension stones

Due to the ever-growing public concern about radon risk arising from building materials, the radon exhalation rates and the natural radioactivity of eighteen dimension stones mostly used in Sardinia and widely exported worldwide have been estimated by means of laboratory tests. Some of the quarrying companies that operate within the Sardinian territory provided the samples to be tested, which include twelve granitoids, four pyroclastic rocks and two basalts. The Activity Concentration Index (Iɤ), the External Radiation Hazard Index (Hex) and the Radium equivalent activity (Raeq) were calculated for each rock sample under investigation, based on the estimated values of 222Rn exhalation rate and 226Ra, 232Th and 40K radioactivity concentration. A poor correlation between radon release rates and 226Ra radioactivity concentrations was found. The contribution to indoor radon accumulation was also simulated for the stone with the highest 222Rn exhalation rate and the resulting concentration compared with the limit value establish by the 2013/59/Euratom Directive. These findings can be extended to rocks formed in similar geodynamic settings that are likely to produce igneous rocks with similar petrographic and geochemical features.