Assessement of doses to members of the public arising from the use of ornamental rocks in residences.

The main pathways to human exposure associated with naturally occurring radionuclides in ornamental rocks are external irradiation and the inhalation of radon. Usually, external doses and risks are assessed by using generic approaches in which the specific properties and use of the material are not considered. Moreover, limited information on radon inhalation dose due to the use of rock is available. The radionuclide concentrations in 180 rock samples reached a wide range of values: for (228)Ra from  <2 to 530 Bq kg(-1), for (226)Ra between  <5 and 600 Bq kg(-1)and for (40)K varied between 190 and 2797 Bq kg(-1). Considering the rock properties, mathematical models, a residential scenario and radionuclide concentrations in the rocks, (222)Rn concentrations and inhalation and external doses were estimated to range from 0.1 to 13 Bq m(-3), from 0.01 and 0.26 mSv yr(-1) and from 0.01 and 0.61 mSv yr(-1), respectively. The ventilation and the emanation rates are key parameters for the Rn dose, whereas the location of the receptor significantly affects the external dose. The overestimations of doses and risks by the generic approaches highlight the necessity of considering the properties and use of the materials for those estimations.