Browsing by Author "Maheso, Abbey Matimba"
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- ItemRadon levels in South African homes - design elements for a national survey and initial results from directed sampling(Stellenbosch : Stellenbosch University, 2021-03) Maheso, Abbey Matimba; Newman, Richard T.; Lindsay, R.; Stellenbosch University. Faculty of Science. Dept. of Physics.ENGLISH ABSTRACT: Radon (222Rn) is an inert, colourless, odourless radioactive gas that is generated by the alpha decay of radium (226Ra), a radionuclide in the uranium (238U) decay series. Radon (222Rn) is the primary source of environmental radiation exposure posing significant risks to human health. The World Health Organization (WHO) estimates that between 3 and 14% of lung cancers are attributable to radon and its progeny. There are a number of factors contributing in a multiplicative manner to the radon levels inside dwellings (e.g. underlying soil and geology, building materials, building construction). An overview of existing data on indoor radon levels across South Africa and national radon surveys conducted around the world is presented. The approach strategies adopted to achieve public acceptance of radon detectors in dwellings is presented and discussed. An investigation into the most appropriate technology to use for short- and long-term indoor radon measurements was undertaken. As part of this, results from measurements with track-etch, electret ion-chamber and Airthings™ detectors were critically compared. Radon measurements were carried in workplaces, homes and schools. The radon concentration recorded in workplaces (offices and laboratories) ranged from 32.2 5.2 Bqm3 to 87.0 10.1 Bqm3. The levels recorded in Gauteng homes ranged from 2.4 0.3 Bqm3 to 102.5 11.7 Bqm3. The levels recorded in schools and homes in Western Cape ranged from 12.3 2.8 Bqm3 to 143.7 17.0 Bqm3 and from 0.0 0.0 Bq m3 to 126.9 14.6 Bqm3, respectively. Results of the surveys showed that radon concentration levels in most of the dwellings were low, whilst in areas close to granite outcrops the levels were found to be relatively high. The overall annual mean effective dose rate from radon and its decay progenies was estimated to be 0.6 0.4 mSvy1 which yields an excess lifetime cancer risk of around 1.7 1.1 x 103. These values are below the recommended action levels. The study recommends that the highly populated areas, especially those close to granite outcrops, should be prioritised for the future indoor radon survey. The radon measurements should preferably be made during the winter seasons using electret ion-chamber and track-etch detectors. Access to homes can be gained through the door-to-door approach, invitations and school outreach.