Radiological risk assessment of environmental radon

Abstract

Measurements of radon gas (222Rn) in the environmental are important to assess indoor air quality and to study the potential risk to human health. Generally known that exposure to radon is considered the second leading cause of lung cancer after smoking. The environmental radon concentration depends on the 226Ra concentration, indoor atmosphere, cracking on rocks and building materials. This study was carried out to determine the indoor radon concentration from selected samples of tin tailings (amang) and building materials in an airtight sealed homemade radon chamber. The radiological risk assessment for radon gas was also calculated based on the annual exposure dose, effective dose equivalent, radon exhalation rates and fatal cancer risk. The continuous radon monitor Sun Nuclear model 1029 was used to measure the radon concentration emanates from selected samples for 96 hours. Five types of tin tailings collected from Kampar, Perak and four samples of building materials commonly used in Malaysia dwellings or building constructions were analysed for radon concentration. The indoor radon concentration determined in ilmenite, monazite, struverite, xenotime and zircon samples varies from 219.6 ± 76.8 Bq m−3 to 571.1 ± 251.4 Bq m−3, 101.0 ± 41.0 Bq m−3 to 245.3 ± 100.2 Bq m−3, 53.1 ± 7.5 Bq m−3 to 181.8 ± 9.7 Bq m−3, 256.1 ± 59.3 Bq m−3 to 652.2 ± 222.2 Bq m−3 and 164.5 ± 75.9 Bq m−3 to 653.3 ± 240.0 Bq m−3, respectively. Whereas, in the building materials, the radon concentration from cement brick, red-clay brick, gravel aggregate and cement showed 396.3 ± 194.3 Bq m−3, 192.1 ± 75.4 Bq m−3, 176.1 ± 85.9 Bq m−3 and 28.4 ± 5.7 Bq m−3, respectively. The radon concentration in tin tailings and building materials were found to be much higher in xenotime and cement brick samples than others. All samples in tin tailings were exceeded the action level for radon gas of 148 Bq m−3 proposed by EPA except monazite 0.15 kg, struverite 0.15 kg and 0.25 kg. Whereas, all building material samples have exceeded the radon concentration in concrete and building materials of 3 to 7 Bq m−3 estimated by ICRP. The annual effective dose, effective dose equivalent, and radon exhalation rates in tin tailings were calculated to be in the range of 2.47 to 11.46 mSv, 5.94 to 1090.56 mSv y−1, and 0.23 to 1.18 mBq kg−1 h−1. For building materials, the calculated risk assessment of the annual effective dose, effective dose equivalent, radon exhalation rates and fatal cancer risk were 0.72 to 10.00 mSv, 1.73 to 24.00 mSv y−1, 0.010 to 0.06 mBq kg−1 h−1 and 40 to 550 chances of persons will suffer the cancer per million (1 × 106), respectively.