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ABSTRACT: The bronchial dosimeter for Rn progeny proposed by Yu and Guan in 1998 was employed to survey the bronchial dose from Rn progeny in 30 residences in Hong Kong. An average bronchial deposition fraction of Rn progeny was obtained as 0.0334, which gave an average dose conversion factor (DCF) of 8.5 mSv WLM-1. The mean values of potential alpha energy concentration (PAEC) deposited in the tracheobronchial region (PAECT-B), total PAEC in air (PAECT), annual effective dose (E), concentration of Rn gas (RC) and annual dose conversion factor (ADCF) for all the residential sites combined were 0.11 +/- 0.05, 3.1 +/- 1.4 mWL, 1.2 +/- 0.5 mSv yr-1, 23 +/- 10 Bq m-3 and 0.055 +/- 0.020 (mSv yr-1 per Bqm-3), respectively, with air-conditioned sites (AC sites) and non-AC sites having significantly different mean ADCF values. The indoor relative humidity affected PAECT and RC with high confidence levels (> 95%).
Journal of Environmental Radioactivity 01/2001; 54(2):221-9. · 1.34 Impact Factor
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ABSTRACT: Standardized charcoal canisters with diameters of 4 inch, of a type recommended by the USEPA for passive measurement of radon gas concentrations, have been modified for active air sampling. Simultaneous measurement of the concentrations of radon (Rn) and thoron (Tn) in air can be obtained by counting the areas under gamma-ray peaks. Sample results obtained in a laboratory and in a residence with different conditions are also given. The largest uncertainties are about 2% and 3% for Rn and Tn respectively. The minimum detection limits are around 2.0 Bq/m3 for both gases. If only Rn concentration is required, the measurement time can be significantly shortened.
Applied Radiation and Isotopes 01/1999; 49(12):1691-4. · 1.17 Impact Factor
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ABSTRACT: Variations in a number of radon related properties at places with different ventilation conditions have been investigated. These properties include radon concentration, the total potential alpha energy concentration of radon daughters, the equilibrium factor and the fraction of unattached radon daughters. We have also calculated the resultant dose for the bronchial basal cell layer, the pulmonary region and the total lung. It is found that good air conditioning is an efficient way of mitigating the indoor radon hazard.
Journal of Radiological Protection 12/1998; 15(1):67. · 1.39 Impact Factor
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ABSTRACT: A dosimeter for radon progeny has been proposed consisting of a single sampler with one 400-mesh wire screen and one filter, which is considered as a model for a portable bronchial dosimeter. During the sampling, air is drawn through the screen and the filter at a face velocity of 12.0 cm s(-1). After sampling, measurements of the screen and the filter are made at the same time through gross alpha counting. The annual effective dose (E, in mSv y(-1)) is calculated employing the exposure to radon progenies in the tracheobronchial (T-B) region. The dosimeter can be used in conjunction with an activated charcoal canister for the measurement of the radon gas concentration to yield the effective dose conversion factor (DCF, in mSv y(-1) per Bq m(-3)). These have laid the foundation to the design of a portable bronchial dosimeter. The validity of the dosimeter has been tested through measurements of annual effective dose and the effective dose conversion factor in different environments.
Health Physics 09/1998; 75(2):147-52. · 1.68 Impact Factor
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ABSTRACT: According to the theory and idea of Hopke et al., a bronchial dosimeter consisting of multiple metal screens has been developed to measure the deposition fractions of radon and thoron progeny in the nasal (N) and tracheobronchial (T-B) regions of the human respiratory tract and to give the dose conversion factors in the T-B region in units of mGy WLM(-1) and mSv y(-1) per Bq m(-3). Different air treatments have been performed in a closed laboratory, which include the use of air conditioning and the application of positive and negative ions for the investigation of the change of the dose conversion factors. At the same time, the radon and thoron gas concentrations have also been measured in the laboratory by active sampling using newly designed activated charcoal canisters connected in series with the bronchial dosimeter for the calculation of the resulted annual effective dose under different air treatments. It is observed that the calculated dose conversion factors derived from the bronchial dosimeter have large discrepancies with those computed using existing lung models. It has also been found that the application of negative ions cannot reduce the annual effective dose in the T-B region; the application of positive ions can lead to a reduction, but not as much as the use of air conditioning. The mitigation of radon effects by air conditioning demonstrated using the bronchial dosimeter is more prominent than that shown by using lung models.
Health Physics 09/1998; 75(2):153-8. · 1.68 Impact Factor
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ABSTRACT: The potential alpha energy concentrations of radon and thoron progeny have been surveyed for dwellings in Hong Kong and the mean values are obtained as 3.58 and 2.29 mWL, respectively. The relative importance of the value for thoron is unexpectedly high, which is attributed to the high 232Th content of the building materials used in Hong Kong. It has also been found that the potential alpha energy concentration values for radon progeny changed dramatically with the season due to the different aerosol contents in the air in different seasons. The factors affecting the potential alpha energy concentration values have also been studied. These factors fall into three categories, namely (1) the building characteristics including age of the buildings, wall coverings and floor coverings; (2) the location of sites including nearby environments and the elevation of the sites; and (3) the meteorological parameters including wind speed, atmospheric pressure, air temperature and relative humidity. For categories (1) and (2), all factors seem to affect the potential alpha energy concentration values, although the effects may be different for radon and thoron progeny, which may be due to the very much different half lives of radon and thoron gas and to the different behavior of radon and thoron progeny in the attachment to aerosols. For category (3), only wind speed has been found to have effects.
Health Physics 09/1997; 73(2):373-7. · 1.68 Impact Factor
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ABSTRACT: Tap water, flushing water and drinking water including natural mineral water, artificial mineral water and distilled water have been investigated for their radon concentrations. It has been found that the radon concentration in natural mineral water samples is the highest and that in tap water is the second highest, while other categories have values very near to the detection limit. From these the corresponding annual effective doses for the stomach and the lung are determined. It is found that annual effective dose due to direct consumption of water (mineral and tap water) is far greater than that due to inhalation of radon emanated from tap water and flushing water. Moreover, it is also shown that the annual effective doses due to inhalation of radon emanated from tap water and flushing water is negligible when compared to the total annual effective dose for indoor radon in Hong Kong.
Applied Radiation and Isotopes 08/1994; 45(7):809-10. · 1.17 Impact Factor
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ABSTRACT: The natural radionuclide (238U, 226Ra, 232Th and 40K) contents of soil samples at various locations in Hong Kong, building materials commonly used in Hong Kong and construction materials for roads have been determined by low background gamma-ray spectroscopy using an n-type high purity germanium detector.From the measured radionuclide contents, estimations have been made of the absorbed gamma dose rate in air and the indoor radon concentration in Hong Kong. Both are in good agreement with in-situ measurements. Finally, calculations have been made of the annual individual effective dose equivalent contributed by all kinds of natural background radiations. The total value is 3·2 mSv which is about 60% higher than the global average. Of this total value, 80% comes from the radiation from building materials.The present work suggests that building materials are the primary source of natural background radiation in Hong Kong. Therefore, more extensive studies and perhaps limitation of the radionuclide concentration of building materials in the near future seems necessary.
Journal of Environmental Radioactivity.
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ABSTRACT: Tap water, flushing water and drinking water including natural mineral water, artificial mineral water and distilled water have been investigated for their radon concentrations. It has been found that the radon concentration in natural mineral water samples is the highest and that in tap water is the second highest, while other categories have values very near to the detection limit. From these the corresponding annual effective doses for the stomach and the lung are determined. It is found that annual effective dose due to direct consumption of water (mineral and tap water) is far greater than that due to inhalation of radon emanated from tap water and flushing water. Moreover, it is also shown that the annual effective doses due to inhalation of radon emanated from tap water and flushing water is negligible when compared to the total annual effective dose for indoor radon in Hong Kong.
Applied Radiation and Isotopes.
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ABSTRACT: The bronchial dosimeter for Rn progeny proposed by Yu and Guan in 1998 was employed to survey the bronchial dose from Rn progeny in 30 residences in Hong Kong. An average bronchial deposition fraction of Rn progeny was obtained as 0.0334, which gave an average dose conversion factor (DCF) of 8.5 mSv WLM−1. The mean values of potential α energy concentration (PAEC) deposited in the tracheobronchial region (PAECT−B), total PAEC in air (PAECT), annual effective dose (E), concentration of Rn gas (RC) and annual dose conversion factor (ADCF) for all the residential sites combined were 0.11±0.05, 3.1±1.4 mWL, 1.2±0.5 mSv yr−1, 23±10 Bqm−3 and 0.055±0.020 (mSv yr−1 per Bqm−3), respectively, with air-conditioned sites (AC sites) and non-AC sites having significantly different mean ADCF values. The indoor relative humidity affected PAECT and RC PAECT−B and E with high confidence levels (>95%).
Journal of Environmental Radioactivity.
