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Radon
Published in William H. Hallenbeck, Radiation Protection, 2020
The mean outdoor concentration of Rn-222 in the contiguous U.S. is 0.25 pCi/liter (Nazaroff, 1990). The mean indoor concentration in the U.S. is 1.5 pCi/liter (Nero, 1986), and the mean exposure rate of the U.S. public is estimated at 0.25 WLM/year (Nazaroff, 1990). Also, thoron (Rn-220; halflife = 55.6 sec) produced by the decay of Ra-224 (halflife = 3.66 days) infiltrates dwellings along with Rn-222. Ra-224 and Rn-220 are members of the naturally occurring thorium-232 decay series.
The Contemporary Earth
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
232Th is the parent nuclide of the thorium family. Its decay products include a radioactive gas, thoron. Like radon, thoron is also a chemically inert substance, but it has a much shorter half-life (only 54 seconds) and, hence, has less time to diffuse from its site of origin.
Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
Revati Phalkey, Naima Bradley, Alec Dobney, Virginia Murray, John O’Hagan, Mutahir Ahmad, Darren Addison, Tracy Gooding, Timothy W Gant, Emma L Marczylo, Caryn L Cox
Radon-220 (thoron) is part of the decay chain of the primordial radionuclide, thorium-232 (half-life 14 billion years). Radon-220 has a half-life of 56 seconds and has numerous short-lived, solid, chemically active decay products, some of which are also alpha-emitters.
Seasonal variation of indoor radon–thoron levels in dwellings of four districts of Haryana, India
Published in Science and Technology for the Built Environment, 2019
Amanjeet Panghal, Ajay Kumar, Suneel Kumar
Thoron (220Rn), whose immediate parent is 224Ra, is a member of the 232Th decay series. In contrast to radon (half-life 3.82 days), the short half-life (55.6 s) of thoron severely limits its migration distance from its source and, as a consequence, thoron in indoor air almost exclusively comes from the materials of the internal surfaces of rooms in buildings. In contrast to the extensive database on indoor radon, that of thoron gas and in particular of its airborne progeny in dwellings is very limited (United Nation Scientific Committee on the Effects of Atomic Radiation [UNSCEAR] 2000). Thoron progeny doses are indeed smaller than those from radon, but in a comparative context, they cannot be considered negligible. Thoron, however, has been gaining attention only during the last few years. Increased thoron concentrations have been measured, for example, in Italian tuff and pozzolana buildings (Sciocchetti et al. 1992), Japanese traditional mud houses (Doi et al. 1992; Guo et al. 1992), and Chinese traditional clay dwellings (Shang et al. 2005; Tschiersch et al. 2007); the source of thoron in these buildings is the building material.
Comparative study of 222Rn/220Rn progeny concentration and estimation of age-dependent dose due to inhalation of radon progeny for different body organs
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Manpreet Kaur, Ajay Kumar, Rohit Mehra, Rosaline Mishra
The radiation dose received by human beings due to the inhalation of radon, thoron, and their progeny present in the indoor environment contribute about half of the average radiation dose from all natural sources of radiation (UNSCEAR 2000). Based on the results of recent case control studies in Europe (Krewski et al.2005) and North America (Darby et al.2005), the World Health Organization (WHO 2009) indicated that exposure due to radon, thoron, and their decay products in dwellings could be the second most important cause of lung cancer, next to smoking. Several epidemiological and assessment of lung cancer risk studies have established the fact that not only the mine workers but also the general public living in the dwellings with high radon concentration may be effected by radon and its progenies (Mustafa and Vasisht 1987). The radon nuclides and its daughters usually enter the houses due to pressure gradient created within indoors and outdoors by temperature difference. These nuclides are trapped by walls of houses; therefore, in houses the radon concentration is observed high, but due to seasonal changes the concentration level may changes. Hence the importance of measuring the decay products of radon and thoron is being realized by researchers (Bangotra et al.2015; Kaur et al.2017; Ramola et al.2016) as these are the major inhalation dose givers to the general population.
Study of radon/thoron exhalation rate, soil-gas radon concentration, and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Manpreet Kaur, Ajay Kumar, Rohit Mehra, Rosaline Mishra
The radon mass exhalation and thoron surface exhalation rate in collected soil samples has been assessed using SMART Rn Duo Monitor, designed and calibrated by Gaware et al. (2011). The principle is based on the detection of alpha particles, emitted from the sampled radon/thoron and its decay products formed inside the detector volume (153 cm3), by scintillation with ZnS:Ag. The monitor has a sensitivity factor of 1.2 counts h−1 Bq m−3 and measurement range of 8 Bq m−3 to 10 MBq m−3.