Natural radioactivity and radon exhalation in building materials used in Italian dwellings.

Forty-two samples of building materials commonly used in Italian dwellings were surveyed for natural radioactivity. External (gamma), as defined and used by the European Commission, and internal (alpha) hazard indexes were calculated and radon specific exhalation rate and emanation fraction were measured. The accumulation method, by using the E-PERM electret ion chambers, was employed to determine specific exhalation rates of 222Rn. Several of the materials had hazard indexes that exceeded the European Commission limit values. However, it was evident that limit values for internal hazard indexes set based on Rn emanation should take into account the properties and use of the materials. For example, Rn emanation from basalt and glazed tiles was substantially lower than the Rn emanation from other materials with similar hazard indexes. Clearly there is need for improved guidelines and regulations in this area.