Radioactivity in building materials

All building materials have a small but not negligible amount of natural radioactivity; since they come from the earth’s crust, this radioactivity is due to the radioactive families of Uranium (U-238), Thorium (Th-232), and Potassium (K-40), in varying concentrations depending on the type and origin of the original rocks. Some granites and some tuffs can sometimes record significant concentrations of radioisotopes, while in marbles and carbonate stones radioactivity is rarely present unless they are settled in lagoon environments (i.e., Lecce, Italy limestones). Also building products fabricated with naturally occurring radioactive materials (NORM) can exhibit residual radioactivity, such as in various types of sand, ceramics, or cements. The radioactive content in the materials used to build is therefore of a certain importance because it can significantly affect the annual effective dose equivalent absorbed due to the long residence time of people inside the buildings. In Italy the reference regulatory device in the field of work activities involving the presence of natural sources is Legislative Decree 230/95 (including subsequent amendments and additions), while the radioactive content of construction materials is regulated by the Legislative Decree 101/2020. In order to avoid excessive alarms or, on the contrary, to underestimate the problem, a cognitive investigation was carried out on the radioactivity content in ornamental and structural building materials, in order to possibly identify critical radioactivity concentration. The natural stones analyzed are granite rocks sampled in Sardinia (Ornamental Stones District of Gallura). The analyses were done in the ENEA’s Environmental Traceability and Radiometry Laboratory specialized in low and very low activity concentration of radioisotopes in the environment. The gamma spectrometry analyses were carried out on the samples reduced to grains, to which, following the EC guidelines, the criteria on the criticality of the materials were applied, calculating three parameters: the activity concentration index (I), the gamma absorbed dose rate (Da) and the annual effective dose (He). The results indicate low concentrations of Uranium and Thorium and therefore compliance with the legislation limits concerning the radio-exposure from minerals, so that they can be used for ornamental purpose in buildings