Assessment of the possible radiological hazard caused from marble and granite tails commercially available in Egypt

This paper reports the natural radioactivity and possible radiological hazards in different types of local and imported marble and granite tiles used as covering building materials in Egypt. Gamma-ray spectrometry was used to estimate the 226Ra, 232Th and 40K activity concentrations. The obtained values were found in the ranges 15-73, 29-203, and 50-253 Bq kg−1 in marbles and 23-179, 78-317, 113-1207 Bq kg−1 in granites for 226Ra, 232Th and 40K, respectively. Using indirect methods radon exhalation rates were calculated, the obtained values varied from 2.1 to 9.7 and from 3-23.9 Bq m−2 h−1 for marble and granite samples, respectively. Radon concentrations in the room caused by marble and granite samples were also estimated. Under normal ventilation (0.5 h−1), the obtained values were below reference level (100 Bq m−3) recommended by World Health Organization. Most values of external annual dose and annual doses due to the indoor radon exposure (ERn) were within recommended.