ISSN 2348-313X (Print) International Journal of Life Sciences Research ISSN 2348-3148 (online) Vol. 8, Issue 2, pp: (74-83), Month: April - June 2020, Available at: www.researchpublish.com
Measurement of Indoor Radon (Rn-222) and Determination of Annual Effective Dose to Dwellers of Rijau, North-central, Nigeria Salihu Mohammed a*, Mohammed Ahmeda a)
Department of Physical Sciences, Niger State Polytechnic, Zungeru, Nigeria Corresponding Author’s Email: salmedangle@yahoo.co.uk
Abstract: In the present work, a total of ninety seven (97) randomly selected residential buildings across sixteen (16) linked villages of Rijau city were investigated. Solid track detectors; CR-37 were each exposed for a period of twelve (12) months after which they were etched and analyzed to determine their respective track densities. The detectors were etched in a 6.25 M solution of NaOH at 90 oC for 3 hours. The concentrations were used to compute exposures to dwellers and other radiological parameters per dwelling. Result of the survey yielded least, average and peak radon concentrations of 158.00±28.38 at Gyalle Area, 125.61±24.10 and 87.67±16.26 Bqm -3 at Low-cost Area respectively. This translated to least, average and peak Annual Effective Dose of 2.66, 3.13 and 3.99 mSvy -1 respectively. When compared with the standards set by International Centre for Ionizing Radiation (ICRP), both the measured Concentration and consequent Annual Effective Dose were within safe limit. The result from this work shall serve as a baseline radon data in the study area. Keywords: Radon gas, CR-37, Annual Effective Dose, Rijau.
1. INTRODUCTION Radon gas is significantly influenced by geological bed rock, topography, house construction type, soil Radium content, soil density, radioactivity of building materials, ventilation conditions, meteorological conditions and human activities (Ursulean, 2013, Fahiminia et al., 2016) which differs from place to place. More than two third of the approximately 200,000 population of Rijau dwellers are predominantly farmers living in the interior villages. The houses they dwell in are mostly the local hut type usually built with red mud. In addition to poor ventilation, the huts are almost always without flooring of any form other than the same mud compressed locally in a process traditionally referred to as dabe. The dabe flooring which is a condensed soil-on-soil flooring system renders the dwellers potentially exposed to Rn-222 gas due to infiltration arising from geological bed rock and soil radium (Ra-226) content. Measurement is the only means of ascertaining the radiological exposure risk posed to dwellers by Radon gas and other Natural Occurring radioactive Materials (NORMS) for a given residential building or area. Indoor Radon exposure is responsible for approximately 60% of the total natural background radiation. Surveys to directly measure radon concentration in a significant and representative sample of dwellings are generally used to estimate the distribution of indoor radon concentration. According to the United States Environmental Protection Agency (USEPA), radon is the second most frequent cause of lung cancer, after cigarette smoking, accounting for some 21,000 lung cancer deaths per year in the United States (USEPA; UNSCEAR, 2000; Shoeib and Thabayneh, 2014).
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