Dose to red bone marrow from natural radon and thoron exposure.

The age-dependent radiation dose to the haematopoietic tissue of bone marrow has been calculated for exposure to radon, thoron and their daughter products. The component of dose due to pure radon is dependent on the fat content of the marrow, since the solubility of radon in fat is about 16 times that in tissue. The mean dose equivalent muSv to the total active marrow is estimated for a range of fat cell diameters from 25 to 200 microns, taking account of the percentage cellularity and distribution of active marrow as a function of age. Similarly, the dose due to the inhalation of short-lived radon daughters was estimated, based on measurements in blood and marrow, modified to allow for the greater deposition of daughter products expected in children. An estimate of the age-dependent dose from long-lived radon daughters was made from uranium miner and natural exposure data. Dose estimates were made for the average UK indoor exposure to radon gas of 20 Bq/m3 and an equilibrium equivalent thoron concentration of 0.3 Bq/m3. The annual radon and thoron derived dose to the active marrow of the newborn was calculated as 30 and 40 muSv, respectively. For a 10-year-old child, the radon and thoron derived annual dose are 70 and 40 muSv, and for a 40-year-old adult 90 and 30 muSv, respectively. The above values exhibit wide range limits due principally to uncertainties in the accumulation of 210Pb in bone, and 210Po in marrow. These data indicate that at the average UK exposure, the alpha-particle dose to active marrow is dominated by that derived from inhaled radon and thoron compared with dietary intake. In infants the dose is dominated by thoron daughters. At the UK radon Action Limit of 200 Bq/m3, the radon and associated thoron derived dose is similar to that from all low LET sources. This work shows that the dose to red bone marrow from radon and thoron is significant, and that the possibility of leukaemia induced by these radiation sources warrants further investigation.     

Radon exhalation rate and uranium estimation in rock samples from Bihar uranium and copper mines using the SSNTD technique.

Widespread uranium mineralization is associated with copper, nickel and other sulphides in the Singhbhum shear zone developed at the northern margin of the Singhbhum craton in the state of Bihar of India. The south-eastern part of the shear zone between Surda-Mosabani-Badia is rich in copper mineralization while the central part between Jaduguda-Bhatin-Nimdih and Narwapahar-Garadih-Turamdih is enriched in uranium. In the present study, trace uranium concentration in geological samples from the Mosabani copper mine and the Narwapahar and Jaduguda uranium mine areas have been determined using fission track registration technique. For the measurement of the radon exhalation rate, the 'can technique' using alpha sensitive LR-115 type II plastic track detectors were used. Uranium concentrations were found to vary from 1.5 to 2097.9 ppm whereas the radon exhalation rate varied from 0.2 to 19.2 Bq m-2 h-1. The values of radon exhalation rate from crushed rock and soil samples are found to correspond with the measured values of uranium in the corresponding samples. A positive correlation has been found between radon exhalation rate and uranium concentration in the samples. The linear coefficients are found to be 0.40, 0.98 and 0.95 in the Mosabani, Narwapahar and Jaduguda mine areas respectively. High values of radon exhalation in subsurface mines like Jaduguda (depth approximately 800 m) and Mosabani (depth > 1000 m) seem to emphasize the need for adequate ventilation for the removal of radon and its progenies from the mines.     

Modelling of cell deaths and cell transformations of inhaled radon in homes and mines based on a biophysical and microdosimetric model

PURPOSE: In this study a biophysical mechanism-based microdosimetric model was applied to predict the biological effects of inhaled radon progenies in homes and in uranium mines. MATERIALS AND METHODS: The radon daughter concentrations of more than 2000 homes were averaged in case of home exposure and the New Mexico uranium mine data were used in case of exposure in mines. The complex microdosimetric model applied in this work was developed by combining a computational fluid and particle dynamics (CFPD) lung model with a lung dosimetry model that quantify the local distribution of radiation burden and the Unit-Track-Length Model, which characterizes the biological outcome of the exposure. RESULTS: Our results show that the inhomogeneity of radon daughter deposition is stronger in the case of mines. Consequently, the numbers of cells which receive multiple hits and the maxima of radiation burdens are significantly higher in mines. In contrast to this, the distributions and maximum values of cell transformation probabilities are very similar in the two cases. CONCLUSIONS: If the same amounts of inhaled progenies are considered then primary cellular consequences are very similar in case of homes and mines, however, the local maxima of radiation burden are higher in mines.     

Radon: is it a problem?

Radon gas is a major source of radiation exposure to the general public. Radon-222 is a product of uranium-238, present in varying concentrations in all soils. Radon enters buildings from soil, water, natural gas, and building materials. Its short-lived breakdown products, termed "radon daughters," include alpha-emitting solids that can deposit in the lungs. Firm evidence links lung cancer risk in miners with high exposure to radon daughters. The amount of risk associated with the much lower but chronic doses received in buildings is difficult to establish. By some extrapolations, radon daughters may be responsible for a significant number of lung cancer deaths. The existence or extent of synergism with smoking is unresolved. Local conditions can cause high levels of radon in some buildings, and measures that reduce indoor radon are of potential value.     

Modelling of cell deaths and cell transformations of inhaled radon in homes and mines based on a biophysical and microdosimetric model

Purpose: In this study a biophysical mechanism-based microdosimetric model was applied to predict the biological effects of inhaled radon progenies in homes and in uranium mines.

Materials and methods: The radon daughter concentrations of more than 2000 homes were averaged in case of home exposure and the New Mexico uranium mine data were used in case of exposure in mines. The complex microdosimetric model applied in this work was developed by combining a computational fluid and particle dynamics (CFPD) lung model with a lung dosimetry model that quantify the local distribution of radiation burden and the Unit-Track-Length Model, which characterizes the biological outcome of the exposure.

Results: Our results show that the inhomogeneity of radon daughter deposition is stronger in the case of mines. Consequently, the numbers of cells which receive multiple hits and the maxima of radiation burdens are significantly higher in mines. In contrast to this, the distributions and maximum values of cell transformation probabilities are very similar in the two cases.

Conclusions: If the same amounts of inhaled progenies are considered then primary cellular consequences are very similar in case of homes and mines, however, the local maxima of radiation burden are higher in mines.     

3D-modelling of radon-induced cellular radiobiological effects in bronchial airway bifurcations: Direct versus bystander effects

Purpose: The primary objective of this paper was to investigate the distribution of radiation doses and the related biological responses in cells of a central airway bifurcation of the human lung of a hypothetical worker of the New Mexico uranium mines during approximately 12 hours of exposure to short-lived radon progenies. Materials and methods: State-of-the-art computational modelling techniques were applied to simulate the relevant biophysical and biological processes in a central human airway bifurcation. Results: The non-uniform deposition pattern of inhaled radon daughters caused a non-uniform distribution of energy deposition among cells, and of related cell inactivation and cell transformation probabilities. When damage propagation via bystander signalling was assessed, it produced more cell killing and cell transformation events than did direct effects. If bystander signalling was considered, variations of the average probabilities of cell killing and cell transformation were supra-linear over time. Conclusions: Our results are very sensitive to the radiobiological parameters, derived from in vitro experiments (e.g., range of bystander signalling), applied in this work and suggest that these parameters may not be directly applicable to realistic three-dimensional (3D) epithelium models.     

Radon exhalation and radiometric prospecting on rocks associated with Cu–U mineralizations in the Singhbhum shear zone, Bihar

The Singhbhum thrust belt is a 200 km long arcuate orogenic belt in Bihar, eastern India. The huge mineral resources, viz. copper, uranium, magnetite, apatite and molybdenite, etc., make it significant from an economic as well as a geological point of view. The belt hosts three types of mineralization: sulphides of copper and other metals, uranium oxides and apatite-magnetite. Several distinct geological episodes are responsible for the evolution of mineralization and the thrust zone itself. Extensive and reliable radiometric prospecting and assaying have been carried out by us for the past 5 years from Dhobani in the east to Turamdih in the west of the Singhbhum shear zone. The present work indicates uranium mineralization in the Pathargora–Rakha area presently being mined for copper and also within areas in the vicinity of Bhatin. Studies on radon emanation have also been undertaken in some parts of the shear zone which indicate reasonably high radon emanation of the soils and rocks studied. This suggests the need for regular monitoring and suitable controls on the mine environment (air quality) and its vicinity. Radon emanation studies coupled with gamma-ray spectrometry and the subsequent modelling of the radiometric and radon measurements will help in the application of radon as a geophysical tracer in exploration of radioactive ore bodies and in radon risk assessment as well as in delineating active and passive faults and even in petroleum exploration.     

氡及其子体辐射诱发的非癌变效应

氡暴露与循环系统疾病的关系以及氡对风湿性疾病的治疗作用已日益受到关注.从铀矿工的流行病学系统回顾中,揭示出氡暴露与冠心病之间存在相关关系.此外,随机对照实验证实,氡浴可以明显改善风湿病的疼痛、晨僵等症状.     

氡及其子体辐射诱发的非癌变效应

氡暴露与循环系统疾病的关系以及氡对风湿性疾病的治疗作用已日益受到关注。从铀矿工的流行病学系统回顾中,揭示出氡暴露与冠心病之间存在相关关系。此外,随机对照实验证实,氡浴可以明显改善风湿病的疼痛、晨僵等症状。