Indoor Radon Levels in Selected Houses in Isfahan, Central Iran

The highest concentration of radon (222 Rn) and thoron (220 Rn) in indoor environment is a major health hazard for man (1) as a result many researchers (2–4) are interested to estimate indoor radon concentration in many countries. In this study, a survey of radon and its daughters has been done to provide data on the hourly, daily and seasonal average indoor radon in Isfahan city dwellings and to estimate the effective dose to the general public. The overall average radon concentration in the surveyed area was 73.32 Bqm-3. All of the season was having a concentration of radon less than the action level (200Bqm-3) as recommended by the International Commission on Radiation Protection (ICRP) (5) and the activity level of 400 Bqm-3 given by the Turkish Atomic Energy Commission. The annual effective dose (ERn, mSv) due to the indoor radon and its progeny was calculated as (6), where C R is the indoor radon concentration (Bqm-3), F the equilibrium equivalent concentration factor which is 0.4 for inhabitants, O the indoor occupancy factor which is 0.8 showing that 80% of time is spent indoors and D the dose conversion factor which equal 9 nSv h-1 per Bqm-3 (4). The radon content of air in the lungs has been calculated by assuming the air volume in the lungs to be 3.2 × 10-3 m 3 for the 'Reference Man' and assuming further that the short-lived decay products will stay in the lungs, the dose rate due to alpha radiation was determined as The effective dose equivalent rate was calculated by taking a quality factor of 20 for alpha-radiation and applying a weighting factor of 0.12 and 0.88 for the lungs other tissues, respectively, by Equilibrium-equivalent radon concentration (EECRn) using the following equation was used to more express the indoor radon concentration, EEC Rn =FC R , where F is the equilibrium factor (= 0.45) and C R is the measured indoor radon activity. The equivalent dose received by bronchial pulmonary regions of human lungs has been calculated using a conversion factor 1.0 × 10-5 mSv/Bq h m 3 (7). An average value of the equilibrium-equivalent radon concentration (EEC Rn) and the annual effective dose were calculated for each season and hours. All the results were listed in Table 1 and it shows also a variation of dose relationship from indoor radon measurements from dwellings in Isfahan area. Radon has been classified …