Study of radioactivity and radiation levels in Bangladesh for assessment of population exposure

Abstract

Thc indoor-outdoor radiation dosc Icvels, and radioactivity Icvels of natural radionuelidcs in soil and watcr samplcs of 56 locations of Bangladcsh wcrc measurcd. Thc radiation dosc Icvcls at thc scabcachcs of Bangladcsh and thc conccntrations of naturally occurring radionuelidcs in thc sand samplcs of Cox's Bazar sea-beach' ~nd Kuakata sea-beach were also measurcd. Thc radiation dose Icvels wcre measured' by a calibrated portable radiation dose ratc survcy-meter PDR I Sv. The assessment of radioactivity levels in soil, sand, and water sa.mples were pcrformcd by a high-rcsolution low background HPGe dctcctor. Radiatioil dose due to radioactivity insoi! samples and intake of water samples werc also assesscd. 111eavcrage indoor dose levels at kntcha-houses, new-buildings, and old-buildings werc found to be 0.23 :t 0.04 IlSv.hr", 0.25. :t 0:04 IlSv.hr", and 0.27 :t 0.04 IlSv.hr" respectively. The weightcd . average indoor dose levels in all kinds of houses was found to be 0.24 :t 0.04 ,.Sv.hr'l. Thc average outdoor dose level was fonnd to be 0.20 :t 0.07 IlSv.hr". The ratio of average indoor dose level to avcrage outdoor dose level was found to be 1.2. The total average effective dose cquivalcnt due to external natural radiation was estimated to be :...2 mSv.y". The average conceJitrations of 2J2Th, mU, 40K, and 137CSin soil samples were found to be 83.56:t '17.96 Bq.kg", 44.35 :t 12.65 Bq.kg'l, 630.89:t 173.85 Bq.kg",. and 5.37 :t 4.87 Bq.kg,l respectively. TIle average activities of the mentioned radionuelides in water sanlplcs were found to be 249.59:t 51.67 mBq.L,I, 156.77:t 30.46 mBq.L'I, 9.08 . :t 3.36 Bq.L,I, and 1.17 :t 1.80 Bq.L,1 respectively. TIlc average al\llual effcctivc dose equivalcnt duc to ingestion of water was fonnd to be 74.01 :t 21.41 IlSv ranging between 24.20 :t 5.57 IlSvand 134.04 :t 16.10 flSV. The average allllual effective dose equivalent due to terrestrial radiation was found to bc J .26 :t 0.27 mSv with a range from 0.56 :t 0.08 to 1.88 :t 0.09 mSv. TIle average dose levcl in the shiningbrown colonred smidy area.s in Cox's Bazar sea-beach was found to be 8.94 :t 3.15 mSvfl ranging betwecn 6.39 :t 2.28 mSvf' and 11.91 :t 4.29 mSvf' whilc !he average dose level in shining-brown 'coloured sandy areas of Kuakata sea-beach was found to be 4.20 :t 0.88 mSvfl ranging from 2.98 :t 0.70 mSv.y,1 to 5.87:t 0.18 mSvf'. The average radiation dose levels in public areas of Cox's Bazar sea-beach, Potenga sea-beach, and Kuakata sea-bcach were fonnd to be 1.49 :t 0.18 mSvfl, 1.58 :t 0.2'6 mSvf', and 1.58 :t 0.35 mSvf' respectively. By plotting the cumulativc frcqucncy plots for thc avcrage conccntrations of radionuelides and average radiation dose levels, the geometric mean and geomctric standard deviation for each type of data were estimated and compared with the corresponding aritlnnetic mean and standard deviation. Exccpt the 137Csconcentration in water samples, all data were found tt? be distribnted nonnally. A good correlation between the corresponding concentrations of radionuelides in soil and water smnples of the smnc placc was found .. Thc average fatalcancer.risk was found'to be 101 per 106 people with a range from 78 to 144 . cases per million peoplc, based on thc measured average dose levcl.