| Abstract |
Measuring background radiations (BR) and risk assessment due to the radiation exposure is very important, in terms of different perspectives, especially in view of health threat to public due to its carcinogenic nature. Human beings are always exposed to environmental radiations. The terrestrial component of the BR is reliant on the compositions of soils and rocks. Usually radionuclides present in three naturally occurring radioactive series, viz. the thorium-232, uranium-238 and actinium-235 series, and fourth one an artificially produced neptunium-237 series, are responsible for radiation exposure. Exposure of public to ionizing radiation may lead to stochastic effects. Many computational stochastic models, developed for simulated cells irradiation, utilize probabilities and probability distribution functions to describe biophysics of cells. Such models have established a sigmoidal connection between carcinogenic risk and radiation exposure.
This study has been accomplished in different parts. In first part of study an extensive review of literature have been carried out. In 2nd part of study ambient concentrations of indoor/outdoor radon and gamma dose rates (GDR) were measured, using RTM 1688-2 and Ludlum micrometer 19, in the Muzaffarabad city. For indoor radon measurements, radon concentrations varied in the range of 16 to 150 Bq m-3 whilst, for outdoor environment from 7 to 31 Bq m-3. Average values of indoor and outdoor radon concentrations were found as 46.9 and 13.3 Bq m-3 respectively. For indoor measurements, GDR ranges from 419 to 1486 µGy y-1 with mean value of 846 µGy y-1. Whilst outdoor GDR varied from 495 to 1029 µGy y-1 with mean value 777 µGy y-1. For indoor measurements, annual effective dose (E_Rn) due to radon exposure ranges from 0.4 to 3.78 mSv y-1 with average value of 1.18 mSv y-1. Radon doses delivered to lungs varied from 0.97 to 9.08 mSv y-1 with an average value of 2.84 mSv y-1. Excess lifetime cancer risk (ELCR) varied from 1.49 ×10-3 to 14.01×10-3 with mean value 4.38×10-3. Data of current study shows that lung cancer cases per year per million person (〖Lung〗_(cancer cases)) ranges between 7.26 to 68.1 per million persons per year with mean value of 21.2 per million persons per year. Present study results reported for 〖Lung〗_(cancer cases) are lower than ICRP recommended values viz. 170–230 per million persons. Average value of indoor radon value viz. 46.9 Bq m-3 for the current study is found to be less than the reference value of 100 Bq m-3 proposed by the world health organization (WHO). Whilst, average value of outdoor gamma absorbed dose rate viz. 88.7 nGy h-1 for the current study is found to be greater than the world average value of 54 nGy h-1 for outdoor gamma absorbed dose rate in air due to terrestrial sources.
In 3rd part of study, the specific activities of primordial radionuclides, gross alpha and gross beta activities in soil samples collected from 29 locations of Azad Kashmir were estimated. Soil samples were analyzed, for possible radionuclide contents and relevant health implications, by high-resolution γ-ray spectroscopy and α/β counter ASC-950-DP Protean instrument. The alpha activity varied from 77.31 ± 9.95 to 440.08 ± 16.48 Bq kg-1 with an overall average value of 234.88 ± 1.69 Bq kg-1. While beta activity varied from the minimum detection level, i.e., |
