the influence of internal wall and floor covering materials and ventilation type on indoor radon and thoron levels in hospitals of kermanshah, iran

results in terms of radon and thoron emissions, travertine and plaster were found to be the most appropriate and inappropriate covering for walls, respectively. furthermore, granite and travertine were discovered to be inappropriate materials for flooring, while plastic floor covering was found suitable. natural ventilation performed better for radon, while artificial ventilation worked better for thoron. background building materials and the ventilation rate of a building are two main factors influencing indoor radon and thoron levels (two radioactive gases which have the most important role in human natural radiation exposure within dwellings). objectives this analytical descriptive study was intended to determine the relationship between indoor radon and thoron concentrations and the building materials used in interior surfaces, as well as between those concentrations and the type of ventilation system (natural or artificial). materials and methods 102 measurements of radon and thoron levels were taken from different parts of three hospital buildings in the city of kermanshah in the west of iran, using an rtm-1688-2 radon meter. information on the type of building material and ventilation system in the measurement location was collected and then analyzed using stata 8 software and multivariate linear regression. conclusions internal building materials and ventilation type affect indoor radon and thoron concentrations. therefore, the use of proper materials and adequate ventilation can reduce the potential human exposure to radon and thoron. this is of utmost importance, particularly in buildings with a high density of residents, including hospitals.