Radon-thoron and their progeny dosimetry in multi-storeyed malls in Delhi NCR (India) using plastic track detectors

Environmental radioactivity due to radon, thoron and their progenies in the ambient air in the multi-storeyed malls situated in Delhi National Capital Region (NCR) including district Faridabad, Haryana (India) was evaluated using LR-115 (type-II) SSNTDs. The average value of activity in different seasons due to radon and thoron varied from 18.45 ± 1.95 Bqm−3 to 45.37 ± 4.69 Bqm−3 and 10.64 ± 0.94 Bqm−3 to 22.91 ± 1.88 Bqm−3 respectively. The collective annual exposure and annual effective dose due to radon and thoron varied from 45.37 × 10−3 WLM to 295.67 × 10−3 WLM with an average value of (159.88 ± 3.66) × 10−3 WLM, and 0.17 mSv to 1.13 mSv with an average value of 0.61 ± 0.01 mSv respectively during the four seasons of the year. Owing to poor ventilation in basement of malls, the annual effective dose is high compared with upper floors of the malls where proper ventilation is provided.