Annual effective dose assessment for natural and fallout radionuclides due to intake of drinking water in Bangladesh

Full text: A study of the natural and fallout radioactivity in drinking water due to gamma-ray emitters have been performed in Bangladesh, as part of the national programme for environmental surveillance. A total of 60 drinking water samples from Chittagong, Dinajpur and Sylhet regions were collected and analysed by using an HPGe detector coupled to a 4096 channel analyser. All water samples were processed as per standard procedures. All of these samples were used for detailed analysis of radioactivity for a range of naturally occurring and anthropogenic radionuclides; potassium-40, caesium-134, caesium-137, radon-222, radium-226, uranium-238 and thorium-232. The results of these analyses have been used to assess the potential dose to the member of the public in Bangladesh. The average activity of 238U, 232Th, 226Ra, 222Rn and 40K in the water samples of the three regions is found to be 121.70 mBq.L-1, 225.30 mBq.L-1, 176.30 mBq.L-1, 129.38 mBq.L-1 and 1156.26 mBq.L-1, respectively. These values are comparable with the world values. The average (based on the data of three regions) annual intake of radioactivity by a Bangladeshi adult due to the radionuclides was found to be 66.26 Bq, 2123.35 Bq, 96.50 Bq, 70.84 Bq and 633.05 Bq, respectively for 238U, 232Th, 226Ra, 222Rn and 40K radionuclides. The effective dose to an individual from an intake of a radionuclide via ingestion of drinking water is calculated by the formula Ding = CR x IF x ED Where, Ding = annual effective dose to an individual due to ingestion of radionuclide (Sv.y-1); CR= concentration of radionuclide in ingested drinking water (Bq.L-1); IF= annual intake of drinking water containing radionuclide (L.y-1); and ED= ingestion dose conversion factor for radionuclide (Sv.Bq-1). The maximum estimated annual effective doses for natural radionuclides due to intake of drinking water were determined to be 70.21 μSv. No fallout radionuclide due to 137Cs and 134 Cs was found in the drinking water samples. Naturally occurring radionuclide account for the entire dose received. The assessed doses to the public based on the levels of radioactivity measured in the drinking water included in this study are very low compared to the average total dose received by members of the Bangladesh population due to natural background radiation of 2300 μSv. (author)