CONICET | Buscador de Institutos y Recursos Humanos

Assessment of the health hazards from natural radioactivity in indoor environments by calculating the main conventional radiological hazardous parameters, based on the activity concentrations of uranium, thorium, and potassium present in building materials were performed. The specific activities of 232Th, 226Ra, and 40K in an extensive selection of Brazilian commercial granite samples were measured using gamma-ray spectrometry. The external gamma dose rate due to natural radionuclides in covered sites with granite was evaluated using a portable survey meter. Although a good agreement between calculated and experimentally measured dose rates was obtained (the values were below the average worldwide exposure of 2.4 mSv/y due to natural sources), the traditional radiological hazard indices were unable to reliably evaluate the contribution of building materials to external and internal dose in indoor environments. Several granites present, for instance, radium equivalent activities above the limit of 370 Bq/kg recommended for the safe use of building materials for dwellings by Organization for Economic Cooperation and Development. On the other hand, radon exhalation rates were theoretically calculated from the measured values of 226Ra specific activities and allowed a good understanding of indoor radon behavior, since was took into account important parameters, such as the volume of the room, the exhaling surface area of the granite, and especially, the air exchange rate. For a room, adequately ventilated (0.3 1/h), which has its floor and walls decorated with any of the analyzed granites, the indoor radon concentration will be lower than 100 Bq/m3. Level deemed safe by the World Health Organization. These results confirm that the radon emanation rate indoors is the main parameter to fully understand the effect of the materials in dwelling constructions.