The Estimated Annual Effective Dose Caused By Radon and Thoron Gases in the Vicinity of Active Faults in the North East of Iran

Active faults are actually the most important factor in the entry of radon and thoron to the surface of Earth. The location of residential areas on these faults is one of the main reasons for increasing the concentration of these radioactive gases in them.
By using RTM1688, the concentration of Radon and Thoron was measured in 200 houses in rural residential areas placed on the active faults in Northern Khorasan in the north-east of Iran.
Radon measurements range was registered from 12Bqm-3 and 188 Bqm-3 with an average of 75.43 Bqm-3. The highest annual effective dose in samples was 5.45 mSv and the lowest was 0.35 mSv with an average of 2.187mSv. The range of Thoron was registered between 0.0 Bqm-3 and 840Bqm-3 with an average of 325.48 Bqm-3. The highest annual effective dose in samples was 21.17 mSv and the lowest was 0 mSv with an average of 8.20 mSv.
The results show that in close areas to active faults of north-east of Iran the concentration of Thoron and Radon is two to three times more than the safe level. It was found that 20 percent of residential areas are subject to annual effective dose greater than the limit for radon and 54 percent for Thoron. The high concentration of Thoron and Radon in these areas show that the active faults play the main role of producing of these gases which may increase of lung diseases.