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Radon ( 222 Rn) and thoron ( 220 Rn) were reported as the highest contributors to natural radiation received by humans. Furthermore, radon has been stated as the second-highest cause of lung cancer. The concentrations of 238 U and 232 Th (the parent nuclide of radon and thoron, respectively) in nature vary with geological conditions and can be enhanced by human activities. Bangka Island in Indonesia is one such case with tin mining, where the environment contains a high amount of 232 Th due to the island's granite bedrock. This study assesses the public's exposure to radon and thoron inhalation on Bangka Island by conducting measurements using a continuous radon-thoron monitor and a time-integrated monitor for radon, thoron, and thoron progeny concentrations. From those measurements, their diurnal and seasonal variation in the dwellings on Bangka Island were analyzed. From 135 dwellings on Bangka Island, the estimated annual effective dose derived from the inhalation of radon, thoron, and their progenies reaches 4.3 mSv at the highest and a mean of 1.7 ± 0.8 mSv in which thoron contributes more than two times higher than radon. Note that the public exposure to radon and thoron inhalation in Bangka was within the reference level for the existing exposure situation., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: The study is not related to any ethical issues such as research involving animals and the protection of human subjects. Consent to participate: All authors have agreed to participate and contribute to the published version of the manuscript., (© 2024. The Author(s).)

This study focuses on public exposure to natural radioactivity caused by the inhalation of radon and thoron progeny in homes in Franceville, Moanda and Mounana in Gabon. The equilibrium factor (F Tn ) between thoron and its progeny was determined experimentally for a proper estimate of the effective dose. In order to assess internal exposure due to radon and thoron progeny, 150 passive radon-thoron discriminative detectors (RADUET) and thoron progeny monitors were deployed for about 3 months in the above-mentioned towns. The results of the measurements obtained showed that the average concentrations of thoron progeny (EETC) were 1.54 ± 0.08 Bq m -3 , 3.05 ± 0.09 Bq m -3 and 1.84 ± 0.11 Bq m -3 in Franceville, Moanda and Mounana, respectively. The ranges of the measured thoron equilibrium factors were 0.004-0.710, 0.005-0.750, and 0.006-0.794 in Franceville, Moanda and Mounana, respectively. The arithmetic and geometric mean values were, respectively, 0.183 and 0.117 in Franceville, 0.184 and 0.122 in Moanda, and 0.221 and 0.140 in Mounana. The experimentally determined equilibrium factor (F Tnexp ) allowed us to compare the value of the experimentally determined effective dose with the theoretically determined one calculated using the equilibrium factor proposed by United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2000 report. F Tnexp values were around 6-11 times greater than the UNSCEAR typical value. The ranges, arithmetic and geometric mean EERC values determined were 30.40-55.60 Bq m -3 , 24.00 ± 0.90 Bq m -3 and 41.68 (1.00) in Franceville, 36.40-62.50 Bq m -3 , 45.30 ± 0.70 Bq m -3 and 44.72 (1.00) in Moanda, and 35.00-90.00 Bq m -3 , 50.00 ± 2.00 Bq m -3 and 48.50 (1.00) in Mounana. The mean values of the annual effective inhalation dose due to thoron progeny determined using F Tnexp were 0.32 mSv (compared to 0.049 mSv), 0.63 mSv (compared to 0.103 mSv), and 0.39 mSv (compared to 0.055 mSv) in Franceville, Moanda and Mounana, respectively. The main conclusion of this study is that indirect estimations of thoron progeny concentrations considerably underestimate the estimation of the annual effective inhalation dose., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

222Rn is recognized as a matter of international concern for human health risk. Because 220Rn as well as 222Rn coexist in the natural environment, thoron sometimes influences the experiment for radon measurement. It is important to measure radon and thoron separately to evaluate the risk of the exposure to 222Rn. As a discriminative measurement method for 222Rn and 220Rn, a simple technique with a single scintillation cell is well known. However, in recent years, the influence of atmospheric environment on the geometrical efficiency of the scintillation cell has not yet been investigated. In this study, environmental dependence of geometrical efficiency for the scintillation cell in 222Rn and 220Rn measurement was investigated using the Lucas type scintillation cell and Monte Carlo particle simulation. It was found that the influence of temperature and pressure on the geometrical efficiencies were larger than that of relative humidity., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Passive radon monitors with CR-39s are widely used in major epidemiological surveys. However, the conventional CR-39 track density determining strategy makes it difficult to accurately estimate the concentration because of the heterogeneity of tracks on CR-39s. This study introduced a stochastic method, Latin hypercube sampling, to improve the track density determining strategy and provide the probability distribution of 222Rn concentration and equilibrium equivalent thoron concentration. The first 222Rn and 220Rn discriminated survey was conducted in Wuhan, China, in 2018 using RADUET® and deposition-based passive 220Rn progeny monitors and applying the stochastic method to the measurement. The results indicate that the stochastic method could decrease the effects of the track heterogeneity on the CR-39s and provide reliable results. The 220Rn progeny contributed more than 40% of the total inhalation dose in the survey, which cannot be ignored in urban family dwellings., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The World Health Organization (WHO) recommends that countries adopt the reference level of 100 Bq m-3 for indoor radon gas. Adopting the reference level requires a preliminary assessment of the indoor radon concentration. In the preliminary investigation, a cut-off value is useful, which is a value for selecting samples that can be reliably determined to be below the reference level (in this paper, the WHO reference level) using a straightforward method. If the true value was the WHO reference level, then the cut-off value of the PicoRad collector for selecting samples was determined as 80 Bq m-3 through the analysis of the 95% prediction interval., (© The Author(s) 2024. Published by Oxford University Press.)

The National Metrology Institute of Japan plan to use an inner-through-type ionization chamber (IC) as a working standard to calibrate radon monitors. Novel methods to calibrate the IC were described, and the calibration factor, CF [Bq m -3 A-1], of the IC with its expanded uncertainty (k = 2) was evaluated to be (2.0 ± 0.2) × 1016 Bq m-3 A-1 in the order of 10-13 A in the IC output current. In this study, the CFs, evaluated under sampling conditions between continuous gas flowing and stationary gas filled inside the IC, were in agreement within the uncertainty., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

To assess public exposure to radon, thoron, and their progeny, measurements were conducted in 50 dwellings within the bauxite-rich area of Fongo-Tongo in western Cameroon. Passive integrating radon-thoron discriminative detectors (specifically RADUET) were employed for radon and thoron measurements. Additionally, concentrations of short-lived radon and thoron progeny were estimated using Direct Radon Progeny Sensors (DRPSs) and Direct Thoron Progeny Sensors (DTPSs) based on LR-115 detectors. The findings revealed indoor radon concentrations ranging from 31 to 123 Bq m -3 with a geometric mean (GM) of 62 Bq m -3 , and indoor thoron concentrations ranging from 36 to 688 Bq m -3 with a GM of 242 Bq m -3 . The Equilibrium Equivalent Radon Concentration (EERC) ranged from 3 to 86 Bq m -3 with a GM of 25 Bq m -3 , while the Equilibrium Equivalent Thoron Concentration (EETC) ranged from 1.2 to 12.5 Bq m -3 with a GM of 7.6 Bq m -3 . Notably, all dwellings recorded radon concentrations below 100 Bq m -3 . Arithmetic means of radon and thoron equilibrium factors were calculated as 0.47 and 0.04, respectively. To assess annual effective doses from radon and thoron inhalation, equilibrium factors were used along with direct measurements of EERC and EETC. The differences observed in annual effective doses were 4.5% for radon and 42.5% for thoron. Furthermore, the contribution of thoron and its decay products to the annual effective dose from radon, thoron, and their progeny ranged from 12 to 94%, with an average contribution of 58%. Thus, this study found that the effective dose due to thoron inhalation in the study area exceeded that due to radon inhalation. It is concluded that, when evaluating radiation doses and health risks, it is crucial to consider both thoron and its progeny alongside radon and its progeny. This underscores the importance of considering direct measurements for accurately estimating radiation doses., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this study, the activity concentrations of radon (222Rn), thoron (220Rn) and thoron progeny were measured simultaneously in Djeno (Pointe-Noire, Republic of Congo) using RADUET detectors to evaluate the air quality and the radiological risks due to the inhalation of these radionuclides. Activity concentrations of radon progeny were calculated from those of radon. Indoor radon, thoron and progenies followed a lognormal distribution ranging between 20 and 40, 6 and 62, 8 and 17.6 and 0.4 and 19.6 Bq m-3 for radon, thoron, radon progeny and thoron progeny, respectively. Mean values for radon were lower than the worldwide values estimated by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are 40 Bq m-3 (arithmetic mean) and 45 Bq m-3 (geometric mean). Radon concentrations in the dwellings under study were below the World Health Organization and the International Commission on Radiological Protection recommended reference levels, which are, respectively, 100 and 300 Bq m-3. The mean concentration of thoron was twice the world average value of 10 Bq m-3 estimated by UNSCEAR. Thoron progeny mean concentration was sharply greater than the typical value (0.3 Bq m-3) for indoor atmosphere provided by UNSCEAR. Annual effective dose ranges were 0.40-0.87 mSv (arithmetic mean, 0.57 ± 0.11 mSv) for radon and 0.10-4.14 mSv (arithmetic mean, 0.55 ± 0.77 mSv) for thoron. The mean value for radon was lower than the value (1.15 mSv) estimated by UNSCEAR, while the mean value for thoron was five times higher than the UNSCEAR value (0.10 mSv). The study showed that the use of the typical equilibrium factor value given by UNSCEAR to compute effective dose led to an error above 80%. Finally, the results of this study showed that the excess relative risk of radon-induced cancer was low, below 2% for the population under 55 y. The results presented in the present study prove that the population of Djeno is exposed to a relatively low potential risk of radon- and thoron-induced cancer., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Site-specific Dose Conversion Factors (DCFs) for radon progeny were estimated based on the aerosol measurement results in an outdoor environment and a tourist cave. The Activity Median Diameter (AMD) and unattached fraction were measured and used to calculate the effective dose per unit intake of radon progeny. The AMDs in the outdoor environment was in the range of 0.24-0.71 μm with the unattached fraction of 0.17. In the tourist cave, two peaks were found in the aerosol size distribution at nucleation and accumulation modes and the unattached fraction was measured to be 0.69 with a range of 0.36-0.85. The DCFs at the outdoor environment did not differ from those from the publication of the International Commission on Radiological Protection; however, the DCF in the tourist cave was significantly higher due to the discrepancy in the unattached fraction and the aerosol size distribution. It was found that these two factors would significantly affect the DCF so that we should be aware of it., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Portable-type electrostatic-collection radon monitors (RAD7) are often used for in-situ measurements of radon in water. In this study, we evaluated the calibration factors and their uncertainties for two RAD7 monitors based on comparative measurements with the liquid scintillation counting method. In the first experiment, we found that both RAD7 monitors had relatively large uncertainties due to leakage of radon gas that bubbled from the gaps between the lids of the desiccant container and the glass vial. Therefore, for the second experiment, these gaps were closed as much as possible using parafilm and clay, respectively. As a result, the relative uncertainties for both RAD7 monitors were significantly decreased. Furthermore, we collected spring water samples to confirm the reliability of radon concentrations. After closing the leakage point, the uncertainty of radon concentrations in spring water we measured using the typical protocol of the RAD7 were significantly lower, which improves the measurement., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The radon-prone area of the Adamawa region in Cameroon is characterized by high natural radiation background resulting from the high concentrations of radium-226, thorium-232, and indoor radon. To produce a radon-risk map, radon measurements in soil were carried out in the city of Ngaoundere. The radon activity concentration in soil gas ranged from 256 to 166 kBq m -3 with a mean of 80 kBq m -3 and a standard deviation of 38 kBq m -3 . The area is mostly classified as high risk (80%) according to the Swedish classification, and 20% as medium risk. A low-risk area was not observed. Granite-like geology sites were characterized by higher radon concentration. A ratio of about 295:1 was obtained for soil radon gas to indoor radon concentrations, with a positive correlation (R = 0.40), and a transfer factor of 3 per mil. These results demonstrate that in situ measurements of radon concentration in soil can provide accurate information on the level of indoor radon concentrations. Geostatistical and deterministic interpolation techniques have been used to obtain a radon map by comparing the suitability of ordinary kriging and inverse-distance-weighted (IDW) interpolation methods. It turned out that there is not much difference in the prediction errors of the two techniques (Root Mean Square Error = 34.4 for ordinary kriging and 34.3 for IDW). It is concluded that both methods give acceptable results. In situ measurements and geostatistical analysis allow assessment of expected indoor radon exposure in a given area at reduced costs and time required. However, for the investigated area, more research is needed to produce reliable radon-risk maps., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Researchers have used various methods to obtain the exhalation rates of radon and thoron from soil and building materials. One of the typical methods for radon exhalation rate is the circulation method using an accumulation container, an external or internal sampling pump and a continuous radon monitor. However, it is necessary to consider sampling flow rate if this method is applied to exhalation rate measurement for thoron due to its short half-life. Based on a calibration experiment, the measured thoron concentrations obtained by an electrostatic collection type radon and thoron monitor (RAD7) were found to be influenced strongly by the sampling flow rate. It was also found that the thoron exhalation rate from a soil sample depended on the pressure difference which was proportional to the increasing sampling flow rate. The thoron exhalation rate measured at the generally used sampling flow rate of the internal sampling pump of the RAD7 was overestimated compared with the value at 0 L min-1., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

222 Rn and 226 Ra concentrations of less than a few to several thousands of Bq L - 1 have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these internationally recognized regulatory values have also been observed in Japan. In this study, concentrations in spring water in the northern part of Japan were measured and the effective dose from intake of the water was evaluated. 222 Rn concentrations were measured using a liquid scintillation counter, and 226 Ra concentrations were measured using a high purity germanium detector after chemical preparation. The measured 222 Rn concentrations (=12.7 ± 6.1 Bq L -1 ) and 226 Ra concentrations (<0.019-0.022 Bq L -1 ) did not exceed the reference values set by international and European/American organizations. A conservative estimate of the annual effective ingestion dose of 8 μSv for 222 Rn and 226 Ra obtained in this study is much smaller than the estimated overall annual effective dose of 2.2 mSv from natural radiation to the Japanese population. However, this dosage accounts for 8% of the WHO individual dosing criteria of 0.1 mSv/year for drinking water.

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and long-term measurements of radon and thoron exhalation rates were conducted for four years in Gifu Prefecture. The ventilated type accumulation chamber (0.8 × 0.8 × 1.0 m 3 ) with an open bottom was embedded 15 cm into the ground. The vertical distributions of radon and thoron activity concentrations from the ground were obtained using passive type radon-thoron discriminative monitors (RADUETs). The RADUETs were placed at 1, 3, 10, 30, and 80 cm above the ground inside the accumulation chamber. The measurements were conducted from autumn 2014 to autumn 2018. These long-term results were found to be in good agreement with the values obtained by another methodology. The radon exhalation rates from the ground showed a clearly seasonal variation. Similar to findings of previous studies, radon exhalation rates from summer to autumn were relatively higher than those from winter to spring. In contrast, thoron exhalation rates were not found to show seasonal variation.

In this study, to get a better understanding in characterizing groundwater and ensure its effective management, the radon concentrations in water samples were measured through Ryukyu limestone in southern Okinawa Island, Japan. Water samples were collected from a limestone cave (Gyokusendo cave, dropping water) and two springs (Ukinju and Komesu, spring water), and the radon concentrations were measured by liquid scintillation counters. The radon concentrations in the samples from the Gyokusendo cave, and Ukinju and Komesu springs were 10 ± 1.3 Bq L -1 , 3.2 ± 1.0 Bq L -1 , and 3.1 ± 1.1 Bq L -1 , respectively. The radon concentrations showed a gradually increasing trend from summer to autumn and decreased during winter. The variation of radon concentrations in the dripping water sample from the Gyokusendo cave showed a lagged response to precipitation changes by approximately 2-3 months. The estimated radon concentrations in the dripping water sample were calculated with the measured radon concentrations from the dripping water obtained during the study period. Based on our results, groundwater in the Gyokusendo cave system was estimated to percolate through the Ryukyu limestone in 7-10 days, and the residence time of groundwater in the soil above Gyokusendo cave was estimated to be approximately 50-80 days. This work makes a valuable contribution to the understanding of groundwater processes in limestone aquifers, which is essential for ensuring groundwater sustainability.

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon measurements in tourism natural hot spring water in Indonesia as part of radiation protection for public health. The purpose of this paper is to study the contribution of radon doses from natural hot spring water and thereby facilitate radiation protection for public health. A total of 18 water samples were measured with an electrostatic collection type radon monitor (RAD7, Durridge Co., USA). The concentration of radon in natural hot spring water samples in the West Java region, Indonesia ranges from 0.26 to 31 Bq L -1 . An estimate of the annual effective dose in the natural hot spring water area ranges from 0.51 to 0.71 mSv with a mean of 0.60 mSv for workers. Meanwhile, the annual effective dose for the public ranges from 0.10 to 0.14 mSv with an average of 0.12 mSv. This value is within the range of the average committed effective dose from inhalation and terrestrial radiation for the general public, 1.7 mSv annually.

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h -1 and 1109 nGy h -1 . Indoor radon concentrations ranged from 124 Bq m -3 to 1015 Bq m -3 . That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m -3 recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

An improved passive CR-39-based direct 222 Rn/ 220 Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both 222 Rn and 220 Rn without the equilibrium factor. A theoretical model was established to calculate the EEC with optimization. Subsequently, an exposure experiment was carried out to test the performance of this detector, and we compared the chamber experiment and the theoretical model by estimating and measuring various parameters. The deposition flux of progeny derived from the prediction agreed well with the value measured in the exposure chamber. The energy-weighted net track density (NTD) measured by this detector is much more reliable to reflect the linear relation between NTD and time-integrated EEC. Since the detector is sensitive to the exposure environmental condition, it is recommended to apply the detector to measure the EEC after its calibration in a typical indoor environment.

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small container for storing contact lenses and its performance was evaluated. The conversion factor for radon ( 222 Rn), the effect of thoron ( 220 Rn) concentration and the air exchange rate were evaluated using the calibration chamber at Hirosaki University. The minimum and maximum detectable radon concentrations were calculated. The conversion factor was evaluated as 2.0 ± 0.3 tracks cm -2 per kBq h m -3 ; statistical analyses of results showed no significant effect from thoron concentration. The minimum and maximum detectable radon concentrations were 92 Bq m -3 and 231 kBq m -3 for a measurement period of three months, respectively. The air exchange rate was estimated to be 0.26 ± 0.16 h -1 , whose effect on the measured time-integrated radon concentration was small. These results indicate that the monitor could be used as a wearable monitor for radon measurements, especially in places where radon concentrations may be relatively high, such as mines and caves.

Radon ( 222 Rn) and thoron ( 220 Rn), sources of natural background radiation, have been the subjects of long-standing studies, including research into radon and thoron as major causes of lung cancer at domestic and international levels. In this regard, radon and thoron measurement studies have been widely conducted all over the world. Generally, the techniques used relate to passive nuclear track detectors. Some surveys have shown that passive monitors for radon are sensitive to thoron, and hence some measured results have probably overestimated radon concentrations. This study investigated radon and thoron measurements in domestic and international surveys using the passive radon-thoron discriminative monitor, commercially named RADUET. This paper attempts to provide an understanding of discriminative measurements of radon isotopes and to present an evidence-based roadmap.

Air exchange through a porous medium depends partly on a pressure gradient induced in it, i.e., air-flow conditions of the outer air. Consequently, response of diffusion-type detectors to radon and thoron may vary with air-flow conditions surrounding the detectors. This effect may be significant for thoron measurement because thoron has a shorter half-life than radon. The present study examined response of diffusion-type detectors (RADUETs and one AlphaGUARD) to thoron with respect to wind speed using a thoron calibration chamber. Response of RADUETs to thoron increased with wind speed. Response of the AlphaGUARD increased with wind speed, but it became constant at a high wind speed. Different response trends to thoron between the RADUETs and the AlphaGUARD could be qualitatively explained by flow states induced by the pressure gradient in the filter or the sponge of these detectors. For RADUETs, laminar (Darcy) flow was induced in the sponge in the examined wind speed range, which meant that thoron entry into the detector increased with wind speed. For the AlphaGUARD, laminar flow was induced in the filter in the low wind speed range, whereas flow was changed to turbulent (non-Darcy) flow at a high wind speed for which thoron entry into the detector did not depend on wind speed.

Radon (Rn), thoron (Tn), and thoron progeny (TnP) were measured in seven inhabited areas of the uranium and thorium bearing region of Lolodorf, located in southwestern Cameroon. Then the equilibrium factor (F Tn ) between thoron and its progeny was determined in order to show the importance of direct progeny measurements for correct estimation of effective dose due to radon, thoron and their progenies. A total of 220 RADUET detectors were used to measure indoor radon and thoron and 130 TnP monitors for thoron progeny indoors. The arithmetic and geometric mean concentrations of Rn, Tn, and TnP were 103 and 89 Bq m -3 , 173, and 118 Bq m -3 , 10.7, and 7.4 Bq m -3 , respectively. Total effective dose determined from radon, thoron, and their progenies was estimated at 4.2 ± 0.5 mSv y -1 . Thoron equilibrium factor varied according to seasons, the type of dwelling, building materials and localities. Thoron (Tn and TnP) contribution to effective dose ranged between 3 and 80% with the average value of 53%. Total effective dose estimated from the world average equilibrium factor of 0.02 given by UNSCEAR was 2.7 ± 0.2 mSv y -1 . The effective dose due to thoron varied greatly according to the different values taken by F Tn and was different from that determined directly using TnP concentrations. Thus, effective dose due to thoron determined from the equilibrium factor is unreliable. Therefore, the risk of public exposure due to thoron (Tn and TnP) may therefore be higher than that of radon (Rn and RnP) in many parts of the world if F Tn is no longer used in estimating total effective dose. This is not in contradiction with the UNSCEAR conclusions. It is therefore important to directly measure the radon and thoron progeny for a correct estimate of effective dose., (Copyright © 2020 Bineng, Saïdou, Tokonami, Hosoda, Tchuente Siaka, Issa, Suzuki, Kudo and Bouba.)

Indoor radon (Rn), thoron (Tn) and thoron progeny (TnP) were simultaneously measured in the gold mining areas of Betare-Oya using RADUET detectors and TnP monitors. Rn and Tn concentrations range between 88-282 and 4-383 Bq m-3, respectively, with the arithmetic means of 133 ± 39 and 93 ± 76 Bq m-3. The 76% of houses for Rn and 25% for Tn exceed the WHO reference level of 100 Bq m-3 and 3% of the houses exceed the ICRP threshold of 300 Bq m-3. The equilibrium equivalent thoron concentration ranges between 1 and 19 Bq m-3 with a mean value of 6 ± 4 Bq m-3. The thoron equilibrium factor ranges between 0.01 and 0.55 with arithmetic mean of 0.11, higher than the world average value of 0.02 given by UNSCEAR. The total inhalation dose due to Rn, Tn and their progeny ranges between 1.8 and 6.2 mSv y-1 with the arithmetic mean of 3.8 ± 1.1 mSv y-1., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The World Health Organisation (WHO) recommends that the concentration of radon in water should be no more than 100 kBq m-3 (100 BqL-1) and the Codex Alimentarius Commission states that the limit of quantification (LOQ) of a method should be no more than one-fifth of this value. In this study, a degassing method with an RAD7 device was used to measure radon concentrations in water, compared to a liquid scintillation counter (LSC) method used as the reference, to investigate whether the numerical value of the LOQ of this method was more than 1/5 (20 kBq m-3) of 100 kBq m-3. The degassing method with leak prevention was shown to reach a target value of 20 kBq m-3 or less under a relative humidity of 6% or lower in the chamber of the RAD7 device. Accordingly, the RAD7 degassing method with leak prevention can be used to accurately measure radon concentrations in water within the guidance level set out by the WHO., (© The Author(s) 2019. Published by Oxford University Press.)

Radon, thoron and associated progeny measurements have been carried out in 71 dwellings of Douala city, Cameroon. The radon-thoron discriminative detectors (RADUET) were used to estimate the radon and thoron concentration, while thoron progeny monitors measured equilibrium equivalent thoron concentration (EETC). Radon, thoron and thoron progeny concentrations vary from 31 ± 1 to 436 ± 12 Bq m -3 , 4 ± 7 to 246 ± 5 Bq m -3 , and 1.5 ± 0.9 to 13.1 ± 9.4 Bq m -3 . The mean value of the equilibrium factor for thoron is estimated at 0.11 ± 0.16. The annual effective dose due to exposure to indoor radon and progeny ranges from 0.6 to 9 mSv a -1 with an average value of 2.6 ± 0.1 mSv a -1 . The effective dose due to the exposure to thoron and progeny vary from 0.3 to 2.9 mSv a -1 with an average value of 1.0 ± 0.4 mSv a -1 . The contribution of thoron and its progeny to the total inhalation dose ranges from 7 to 60 % with an average value of 26 %; thus their contributions should not be neglected in the inhalation dose assessment.

Within the framework of a joint research project on natural radiation exposure and its health effects in Cameroon from 2014 to 2017, the Institute of Geological and Mining Research and the Hirosaki University worked together to carry out natural radiation survey in mining and ore bearing regions of Cameroon. Air kerma rates were measured using car-borne survey method. In-situ gamma spectrometry was used to determine activity concentrations of 238U, 232Th and 40K in soil. A total of 450 RADUET detectors and 350 thoron progeny monitors were deployed in dwellings of the study areas for 2-3 months, collected and analysed. Although natural radioactivity level seems to be normal in most of the surveyed areas, there are many points where activity concentrations of natural radionuclides are largely above the world average values. Indoor radon, thoron and thoron progeny results show the importance to put in place the national radon plan in Cameroon. It was also pointed out that thoron cannot be neglected when assessing inhalation dose., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Long-term exposure to radon has been determined to be the second leading cause of lung cancer after tobacco smoking. However, an in-depth study of this topic has not been explicitly carried out in Chiang Mai (Thailand). This paper presents the results of an indoor radon level measurement campaign in dwellings of Chiang Mai using total of 110 detectors (CR-39) during one year. The results show that the average radon levels varied from 35 to 219 Bq/m³, with an overall average of 57 Bq/m³. The finding also shows that the average value is higher than the global average value of 39 Bq/m³. In addition, to examine the cause of lung cancer development among people with risk of chronic exposure to radon during their lifetime, 35 non-smoker lung cancer patients and 33 healthy nonsmokers were analyzed for telomere length. As expected, telomere length was significantly shorter in lung cancer patients than in healthy nonsmokers. Among healthy nonsmokers, the telomere length was significantly shorter in a high radon group than in an unaffected low radon group. To the best of our knowledge, our research provides the first attempt in describing the shortened telomeres in areas with high levels of environmental radon that might be related to lung cancer development.

222 Rn, 220 Rn and their short-lived progenies are well known radioactive indoor pollutants, identified as the leading environmental cause of lung cancer next to smoking. Apart from the conventional measurement methods, numerical modeling methods are developed to simulate their physical and decay processes in 222 Rn and 220 Rn's life cycle, estimate their levels, concentration distributions, as well as effects of control strategies in the indoor environment. In this article, we summarized the numerical models used to illustrate the physical processes of each source of 222 Rn and 220 Rn entry into the indoor environment, and the application of Jacobi room models and CFD (Computational Fluid Dynamic) models used to present the behaviors of indoor 222 Rn, 220 Rn and their progenies. Furthermore, we consider that the development of numerical modeling of 222 Rn and 220 Rn would have a bright prospect in the directions of stochastic methods based on a steady-state model, the fine simulation of the time-dependent model as well as the multi-dimension model., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Twenty-five beauty products known to contain natural radionuclides were collected, and their 222 Rn mass exhalation rates were measured. The effective doses to workers due to 222 Rn exhaled from these products were estimated. The 222 Rn mass exhalation rates of these products were below 177 μBq kg -1 s -1 and were almost identical to those of natural rocks in Japan. The maximum effective dose of 222 Rn exhaled from these products was 71 μSv y -1 ., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In order to evaluate internal exposure to radon and thoron, concentrations for radon, thoron, and thoron progeny were measured for 259 dwellings located in high background radiation areas (HBRAs, outdoor external dose: 3-5 mGy y -1 ) and low background radiation areas (control areas, outdoor external dose: 1 mGy y -1 ) in Karunagappally Taluk, Kerala, India. The measurements were conducted using passive-type radon-thoron detectors and thoron progeny detectors over two six-month measurement periods from June 2010 to June 2011. The results showed no major differences in radon and thoron progeny concentrations between the HBRAs and the control areas. The geometric mean of the annual effective dose due to radon and thoron was calculated as 0.10 and 0.44 mSv, respectively. The doses were small, but not negligible compared with the external dose in the two areas.

The radon exhalation rate can be obtained quickly and easily from the evolution of radon concentration over time in the accumulation chamber. Radon monitoring based on the electrostatic collection method is not interfered with by (220)Rn. In this paper, we propose that the difference between radon and (218)Po concentrations in the measurement cell of this kind of radon exhalation monitor is the main system error, and it changes with time and different effective decay constants. Based on the results of simulation experiments, we propose that the calibration factor obtained from the suitable experiment cannot completely correct the system error, even if it is useful to reduce the measurement error. The better way for reducing measurement error is to use the new measurement model which we have proposed in recent years., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This study examined correlations between radon, thoron and thoron progeny concentrations based on surveys conducted in several different countries. For this purpose, passive detectors developed or modified by the National Institute of Radiological Sciences (NIRS) were used. Radon and thoron concentrations were measured using passive discriminative radon-thoron detectors. Thoron progeny measurements were conducted using the NIRS-modified detector, originally developed by Zhuo and Iida. Weak correlations were found between radon and thoron as well as between thoron and thoron progeny. The statistical evaluation showed that attention should be paid to the thoron equilibrium factor for calculation of thoron progeny concentrations based on thoron measurements. In addition, this evaluation indicated that radon, thoron and thoron progeny were independent parameters, so it would be difficult to estimate the concentration of one from those of the others.

In Japan, many dwellings have decorative wall coverings made from granite, andesite, tuff, gabbro, and marble. However, information regarding activity concentrations and radon (Rn) and thoron (Rn) exhalation rates for such rocks is very scarce. Therefore, samples of the granite, andesite, tuff, and marble that are used as wall coverings in Japan were collected from mining companies, and their activity concentrations and Rn and Rn exhalation rates were measured. Dose estimations for inhabitants living in houses built with these materials were also carried out. The activity concentration of natural radionuclides in all the materials was lower than the critical values described by the International Atomic Energy Agency (IAEA) (10,000 Bq kg for K and 1,000 Bq kg for all other radionuclides of natural origin). The maximum values of Rn and Rn mass exhalation rates for the granite samples were 0.12 and 430 mBq kg s, and those for the area exhalation rates were 1.8 and 6300 mBq m s, respectively; these values are higher than those for other samples. The maximum value of effective doses to inhabitants was 0.68 mSv y, which is lower than the intervention exemption level (1 mSv y) given in the International Commission on Radiological Protection (ICRP) Publication 82.

Radon diffusion through soil is strongly affected by the degree of water saturation of the soil pores. Methods have been developed by many researchers to measure radon diffusion coefficient. We developed an updated experimental system to estimate radon diffusion coefficients for typical types of soil in Japan and applied it to a typical loam with different water saturation levels (0-0.82). The system consists of a passive-type scintillation cell, soil column, accumulation tank, and radon source. The radon concentration in the accumulation tank is kept stable, and radon diffused through the soil column is continuously measured with the passive-type scintillation cell. We found the radon diffusion coefficients vary from 9.60 × 10(-6) m(2) s(-1) to 1.27 × 10(-7) m(2) s(-1) for the loam samples. Generally, the diffusion coefficients are almost constant for a water saturation range of 0-0.4 and decrease with increasing water saturation from 0.4 to 0.82.

We simultaneously measured radon and thoron exhalation rates in areas of weathered acid rocks in Japan to investigate the relationship between them and between measured and calculated radon exhalation rates. To calculate the radon exhalation rate, we used an equation proposed by UNSCEAR. Our analysis showed that both the radon and thoron exhalation rates measured at one location in a natural environment fluctuated widely, even within one day. We found a strong correlation between the radon and thoron exhalation rates. The measured radon exhalation rates tended to be lower than the calculated values: the mean ratio of the measured exhalation rate to the calculated rate was 0.65. We concluded that the UNSCEAR equation is applicable under a controlled environment (temperature, humidity, etc.), but not where there are artificial underground structures that may influence the transportation of radon in soil.

The effective diffusion coefficient of radon is a very important factor in estimating the rate of radon exhalation from the ground surface. In this study, we developed an experimental system that overcomes technical problems in previous studies to accurately evaluate the effective diffusion coefficient. The radon source used for this system was the National Institute of Radiological Sciences radon chamber. This chamber is a calibrated international standard facility that can produce stable radon concentrations for long periods of time. Our tests showed that leakage of radon from the system was negligible. After the leakage test, we evaluated the effective diffusion coefficient in free-space and in dry porous materials at porosities of 35% and 45%. To ensure that the porous material in the column was as homogeneous as possible, we filled the column with an artificial soil with controlled grain size and grain composition. The measured values and theoretical calculations agreed well, which indicate that the proposed system can be used to accurately and quickly evaluate the effective diffusion coefficient.

The exposure from radon, thoron, and thoron progeny was measured for 45 dwellings in high background radiation area in Takandeang, Indonesia with ambient dose equivalent rate ranging from 0.34 μSv h−1 to 1.90 μSv h−1. The measurement was taken using passive radon and thoron discriminative detector and thoron progeny detector. This measurement was taken from November 2018 to October 2019, and within one month the detector would be replaced with a new detector. The concentrations of radon, thoron, and thoron progeny were calculated as 42–490 Bq m−3, 20–618 Bq m−3, and 4–40 Bq m−3, respectively. The concentrations for outdoor were 49–435 Bq m−3, 23–457 Bq m−3, and 4–37 Bq m−3, respectively, and the annual effective dose was 9.8–28.6 mSv y−1. Based on the result of Spearman’s correlations analysis between the indoor radon and thoron concentrations and between the indoor thoron progeny and thoron concentrations, we suggest that exposure to thoron cannot be predicted from exposure to radon, and the equilibrium equivalent thoron concentration has a large uncertainty when it is estimated from thoron concentration assuming a single thoron equilibrium factor.

To assess public exposure to radon, thoron, and their progeny, measurements were conducted in 50 dwellings within the bauxite-rich area of Fongo-Tongo in western Cameroon. Passive integrating radon-thoron discriminative detectors (specifically RADUET) were employed for radon and thoron measurements. Additionally, concentrations of short-lived radon and thoron progeny were estimated using Direct Radon Progeny Sensors (DRPSs) and Direct Thoron Progeny Sensors (DTPSs) based on LR-115 detectors. The findings revealed indoor radon concentrations ranging from 31 to 123 Bq m−3 with a geometric mean (GM) of 62 Bq m−3, and indoor thoron concentrations ranging from 36 to 688 Bq m−3 with a GM of 242 Bq m−3. The Equilibrium Equivalent Radon Concentration (EERC) ranged from 3 to 86 Bq m−3 with a GM of 25 Bq m−3, while the Equilibrium Equivalent Thoron Concentration (EETC) ranged from 1.2 to 12.5 Bq m−3 with a GM of 7.6 Bq m−3. Notably, all dwellings recorded radon concentrations below 100 Bq m−3. Arithmetic means of radon and thoron equilibrium factors were calculated as 0.47 and 0.04, respectively. To assess annual effective doses from radon and thoron inhalation, equilibrium factors were used along with direct measurements of EERC and EETC. The differences observed in annual effective doses were 4.5% for radon and 42.5% for thoron. Furthermore, the contribution of thoron and its decay products to the annual effective dose from radon, thoron, and their progeny ranged from 12 to 94%, with an average contribution of 58%. Thus, this study found that the effective dose due to thoron inhalation in the study area exceeded that due to radon inhalation. It is concluded that, when evaluating radiation doses and health risks, it is crucial to consider both thoron and its progeny alongside radon and its progeny. This underscores the importance of considering direct measurements for accurately estimating radiation doses. [ABSTRACT FROM AUTHOR]

Chiang Mai province of Thailand is known for having the highest natural background radiation in the country, as well as being recognized as one of the world's most polluted cities for air quality. This represents the major contributor to the development of lung cancer. This research aims to estimate the comprehensive dose of both internal and external exposure due to natural background radiation and related health perspectives in the highly polluted area of Chiang Mai. The average values of indoor radon and thoron concentrations in 99 houses over 6 months were 40.8 ± 22.6 and 17.8 ± 16.3 Bq/m3, respectively. These results exceed the worldwide value for indoor radon and thoron (40 and 10 Bq/m3), respectively. During burning season, the average values of indoor radon (56.7 ± 20 Bq/m3) and thoron (20.8 ± 20.4 Bq/m3) concentrations were higher than the world-wide averages. The radon concentration in drinking water (56 samples) varied from 0.1 to 91.9 Bq/L, with an average value of 9.1 ± 22.8 Bq/L. Most of the drinking water samples (87%) fell below the recommended maximum contamination limit of 11.1 Bq/L. The average values of natural radionuclide (226Ra, 232Th and 40K) in 48 soil samples were 47 ± 20.9, 77.9 ± 29.7 and 700.1 ± 233 Bq/kg, respectively. All values were higher than the worldwide average of 35, 30 and 400 Bq/kg, respectively. The average value of outdoor absorbed gamma dose rate (98 ± 32.5 nGy/h) exceeded the worldwide average of 59 nGy/h. Meanwhile, the average activity concentrations of 226Ra, 232Th and 40K in 25 plant food samples were 2.7 ± 0.1, 3.2 ± 1.6 and 1000.7 ± 1.9 Bq/kg, respectively. The 40K concentration was the most predominant in plant foods. The highest concentrations of 226Ra, 232Th and 40K were found in Chinese cabbage, celery and cilantro, respectively. The total annual effective dose for residents in the study area varied from 0.6 to 4.3 mSv, with an average value of 1.4 mSv. This indicates a significant long-term public health hazard due to natural background radiation and suggests a heightened radiation risk for the residents. The excess lifetime cancer risk value (5.4) associated with natural background radiation was found to be higher than the recommended value. Moreover, the number of lung cancer cases per year per million average of 25.2 per million persons per year was in the limit range 170–230 per million people. Overall, our results will be used for future decision making in the prevention of lung cancer risk associated with natural background radiation. [ABSTRACT FROM AUTHOR]

Indoor radon, thoron and thoron progeny concentrations, along with the equilibrium factor for thoron progeny and soil gas radon concentrations, have been measured to assess radiological risks in the centre and south regions of Cameroon. Indoor radon and thoron concentrations were estimated using radon–thoron discriminative detectors (RADUET), while thoron progeny monitors measured the equilibrium equivalent thoron concentration (EETC). Radon concentrations in the soil were determined using a MARKUS 10 detector. It was found that radon, thoron and thoron progeny concentrations range between 19 and 62 Bq m−3, 10 and 394 Bq m−3 and 0.05 and 21.8 Bq m−3, with geometric means of 32 Bq m−3, 98 Bq m−3 and 4.9 Bq m−3, respectively. The thoron equilibrium factor ranges between 0.007 and 0.24, with an arithmetic mean of 0.06 ± 0.03; this is higher than the world average value of 0.02 provided by the United Nations Scientific Commission on the Effects of Atomic Radiation(UNSCEAR, New York, USA). The level of the soil radon concentration ranges from 4.8 to 57.3 kBq m−3, with a geometric mean of 12.1 kBq m−3 at a depth of 0.7 m. Of the sampling points, 66% fall within normal radon risk areas, and 3% of the sampling areas are high radon risk areas exceeding 50 kBq m−3. The annual effective dose was found to be 0.03 ± 0.01 mSv for radon, 0.08 ± 0.05 mSv for thoron, 0.63 ± 0.12 mSv for radon progeny and 1.40 ± 0.84 mSv for thoron progeny. The total dose is estimated to be 2.14 mSv y−1. The mean estimated indoor excess lifetime cancer risk values due to radon, thoron, radon progeny and thoron progeny are 0.12 × 10−3, 0.31 × 10−3, 2.51 × 10−3 and 5.58 × 10−3, respectively. Thoron progeny contributed 60% to the effective dose. Thus, thoron progeny cannot be neglected in dose assessments, in order to avoid biased results in radio-epidemiological studies. [ABSTRACT FROM AUTHOR]

Some areas around the world have anomalies with high natural radiation that may affect public health due to chronic-low-dose radiation exposure. In the paper, we summarized several studies that find Mamuju, Indonesia, a unique high natural radiation area. The majority of the relevant papers are about monitoring, main sources, and influential factors for the enhancement of radon and dose assessments. Under these circumstances, the Mamuju region is regarded as a promising area for conducting epidemiological studies, and it will provide a unique opportunity for improving and expanding low-dose-rate data on human health effects. [ABSTRACT FROM AUTHOR]

Indoor radon (Rn), thoron (Tn) and thoron progeny (TnP) were simultaneously measured in the gold mining areas of Betare-Oya using RADUET detectors and TnP monitors. Rn and Tn concentrations range between 88–282 and 4–383 Bq m−3, respectively, with the arithmetic means of 133 ± 39 and 93 ± 76 Bq m−3. The 76% of houses for Rn and 25% for Tn exceed the WHO reference level of 100 Bq m−3 and 3% of the houses exceed the ICRP threshold of 300 Bq m−3. The equilibrium equivalent thoron concentration ranges between 1 and 19 Bq m−3 with a mean value of 6 ± 4 Bq m−3. The thoron equilibrium factor ranges between 0.01 and 0.55 with arithmetic mean of 0.11, higher than the world average value of 0.02 given by UNSCEAR. The total inhalation dose due to Rn, Tn and their progeny ranges between 1.8 and 6.2 mSv y−1 with the arithmetic mean of 3.8 ± 1.1 mSv y−1. [ABSTRACT FROM AUTHOR]

A pilot study to measure ambient gamma dose rate and radon and thoron progeny concentrations was made for eight dwellings selected in Yangjiang, China. Indoor and outdoor ambient gamma dose rates were 110-370 and 100-220 nGy h, respectively. Doses received from indoor terrestrial radiation were estimated to be 0.6-1.8 mSv year. Radon, thoron and thoron progeny concentrations were 19-98, 18-1120 and 0.4-10.3 Bq m, respectively. This pilot study showed that the position of passive-type monitors to be placed and the deployment period should be carefully determined for estimating reliable annual average concentrations. [ABSTRACT FROM AUTHOR]

Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan's 2011 Tohoku earthquake [11 March 2011, moment magnitude ( M) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an AlphaGUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems. [ABSTRACT FROM AUTHOR]

A continuous measurement system, with a ventilation-type accumulation chamber, was developed for radon exhalation rate determination. A reasonable sampling flow rate for the measurement system was determined by comparing the values obtained by the system with those obtained by a grab sampling method. The sampling flow rate of passage through the scintillation cell from the accumulation chamber was varied from 0.05 to 2.0 l min-1. The difference in pressure between the inside and outside of the accumulation chamber increased as the sampling flow rate became large, and the estimated radon exhalation rate also increased with the sampling flow rate. From these results, a reasonable sampling flow rate was estimated to be less than 0.2 l min-1. [ABSTRACT FROM AUTHOR]