RESUMO
While in the open air the amount of radon gas is very small and does not pose a health risk, in confined spaces, radon can accumulate to relatively high levels and become a health hazard. Exposure to high levels of radon has been associated with an increased risk of lung cancer, depending on the time length of exposure. Radon level in dwelling of Shiraz with 1,200,000 populations has been sampled and analyzed in this study. Our study could be considered the largest radon study in Iran both time and area wise. In this study, radon [222Rn] concentration in residential dwellings in Shiraz-Iran was sampled and measured during two consecutive six month periods in 2009-2010. We used Solid State Nuclear Track Detectors [SSNTD], CR-39 polycarbonate films. The survey parameters of radon concentrations were floor types, construction materials and dwelling's age. Annual average indoor radon concentration for the survey period was 94 +/- 52 Bq/m3. The calculated mean annual effective doses in basements and different floors were less than the lowest limit recommended action level of 3 mSv by ICRP. High radon concentrations are measured in basements and old dwellings; however, due to rapidly changing housing structures and ventilation practices with no intervention, lower levels of radon concentration has been expected in Shiraz