Estimation of the Indoor Radon and the Annual Effective Dose from Granite Samples

Inhalation of radon and radon daughters increases the risk of lung cancer. The main sources of indoor radon are the building materials especially granite. The aim of this research is to estimate the indoor radon and the annual effective dose from the building materials. Eighteen granite samples bought from the market in Thailand were measured using an ionization chamber (ATMOS 12 DPX) for the radon concentration in air. Radon exhalation rates were calculated using the radon concentration in air. And then the indoor radon and the annual effective dose were estimated from the granite samples using radon exhalation rates. The radon exhalation rates ranged from 0.05-15.55 Bq m^-2 h^-1 with an average of 5.87 Bq m^-2 h^-1. The indoor radon concentration ranged from 10.00-59.33 Bq m^-3 with an average of 28.53 Bq m^-3. The annual effective dose ranged from 0.25-1.49 mSv y^-1 with an average of 0.72 mSv y^-1. A good correlation between the radon exhalation rate and the indoor radon concentration was observed. Six samples showed the annual effective dose higher than the annual exposure limit for the general public (1 mSv y^-1) recommended by the International Commission on Radiological Protection (ICRP).