[Ⅱ ]

Objective: To investigate the role and related mechanism of ubiquitin-like protein FAT10 in the angiotensin Ⅱ (AngⅡ)-induced endothelial cell inflammatory responses. Methods: The Western blot was used to detect the protein expression of FAT10 in 16-weeks old WKY rat carotid artery, thoracic aorta artery, renal artery and vascular smooth muscle cells (VSMC), human umbilical vein endothelial cells (HUVEC) and human breast cancer cells (MDA-MB-231). The optimal concentration and stimulation time of AngⅡ on inducing the highest FAT10 in HUVEC were determined. The following plasmids were constructed: control plasmid, overexpression FAT10 plasmid (Flag-FAT10), invalid interference plasmid, and interference FAT10 plasmid (sh-FAT10). These plasmids were then transfected into HUVEC cells and divided into following groups: control group, Flag-FAT10 group, invalid interference group, and sh-FAT10 group. After culturing with 100 nmol/L AngⅡ for 36 h, the control group and the Flag-FAT10 group were treated with reactive oxygen species scavenger N-acetyl-L-cysteine ​​(NAC), the protein expression levels of the inflammatory factor monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) were measured. Laser confocal microscopy was used to detect the generation levels of reactive oxygen species in the cells of vrious groups. Results: FAT10 was expressed in carotid artery, thoracic aorta, and renal artery of normal blood pressure rats and expressed in HUVEC, VSMC, MDA-MB-231. The expression level of FAT10 gradually increased in proportion to the increase of the time and concentration of AngⅡ stimulation in HUVEC, and the expression level of FAT10 was the highest when the HUVEC was treated with 100 nmol/L AngⅡ for 36 h (P<0.01). The protein expression level of MCP-1 (P<0.001) and TNF-α (P<0.01) was higher in AngⅡ treated HUVEC with FAT10 overexpression, while the expression level of MCP-1 and TNF-α protein was lower in AngⅡ treated HUVEC with FAT10 knockdown (all P<0.01). The level of intracellular reactive oxygen species (ROS) production was significantly increased with FAT10 overexpression (P<0.001), and the level of ROS was decreased when the expression of FAT10 was interfered (P<0.05). The increased level of MCP-1 and TNF-α proteins in FAT10 overexpressed HUVEC was reversed by NAC (all P<0.05). Conclusion: FAT10 promotes the release of inflammatory factors induced by AngⅡ in endothelial cells by increasing the level of intracellular ROS production.

AN EXPERIMENTAL CHAMBER FOR TESTING ABATEMENT EFFECTS OF RADON EXPOSURE WITH DIFFERENT MEASURES

For more effective testing the abatement effects of radon exposure with different counter measures, an air-conditioned laboratory room was reformed as an experimental chamber. Based on the well control and real time monitoring of concentrations of 222Rn, its attached and unattached progeny and their size distributions, the chamber could provide three modules corresponding to ventilation, source reduction and filtration for abating radon exposure. Preliminary results showed that the chamber was useful for testing the abatement effect of indoor radon exposure.

INFLUENCE OF STATIC ELECTRICITY ON RADON MEASUREMENT USING PASSIVE DETECTORS

In order to investigate the influence of the static electricity on the measurement using passive radon detector, detectors were charged at the surface of chamber and its CR-39 elements respectively on purpose before the exposure in this study. The results of in-chamber experiments revealed that the static electricity would lead to critical influence on measurement especially when the CR-39 elements were negatively charged. The static charge would remain for several ten hours, which result in more significant influence on the short-term measurement.

OCCUPATIONAL EXPOSURE TO RADON IN DIFFERENT KINDS OF NON-URANIUM MINES

For more accurate assessments of the occupational exposure to radon for miners, the individual monitoring was conducted by using an improved passive integrating (222)Rn monitor. A total of 120 miners in 3 different kinds of mines were monitored throughout a year. The results showed that the individual exposure to radon significantly varied with types of mines and work. Compared with the exposure to coal miners, the exposure to copper miners was much higher. Furthermore, it was found that the exposure might be overestimated if the environmental (222)Rn monitored by the passive integrating monitors was used for assessment. The results indicate that the individual monitoring of radon is necessary for an accurate assessment of radon exposure to miners, and radon exposure to non-uranium miners should also be assessed from the viewpoint of radiation protection.

Ras-association domain family 10 acts as a novel tumor suppressor through modulating MMP2 in hepatocarcinoma

Ras-Association Domain Family 10 (RASSF10) is the last identified member of the RASSF family. The functional characteristics of this new gene in human cancers remain largely unclear. Here, we examined RASSF10 for the biological functions and related molecular mechanisms in hepatocellular carcinoma (HCC). We found that RASSF10 is expressed in normal human liver tissue, but is silenced or down-regulated in 62.5% (5/8) of HCC cell lines. The mean expression level of RASSF10 was significantly lower in primary HCCs compared with their adjacent normal tissues (P<0.005, n=52). The promoter methylation contributes to the inactivation of RASSF10 as demonstrated by bisulfite genomic sequencing and demethylation treatment analyses. Transgenic expression of RASSF10 in silenced HCC cell lines suppressed cell viability, colony formation and inhibited tumor growth in nude mice (QGY7703, P<0.01; HepG2, P<0.05). Furthermore, RASSF10 was shown to induce the cell accumulation in G1 phase with the increase of p27, as well as the decrease of cyclinD1 and CDK2/CDK4. Over-expression of RASSF10 also inhibited HCC cells migration (P<0.01) or invasion (P<0.05). Adhesion genes array revealed that Matrix Metalloproteinase 2 (MMP2) was a downstream effector of RASSF10. RASSF10 acting as a tumor suppressor to inhibit HCC invasion partially mediated by Focal Adhesion Kinase or p38 MAPK to decrease the accumulation of MMP2. Our study suggests that RASSF10 acts as a tumor suppressor for HCC.

Terrestrial gamma radiation dose rate in Ryukyu Islands, subtropical region of Japan

In order to explain the distribution of natural radiation level in the Asia, in situ measurements of dose rate in air due to terrestrial gamma radiation have been conducted in a total of 21 islands that belong to Ryukyu Islands (Ryukyu Archipelago), subtropical rejoin of southwest Japan. Car-borne surveys have also been carried out in Okinawa-jima, the biggest island of the archipelago. Based on the results for these measurements, arithmetic mean, the maximum and the minimum of the dose rates at 1 m in height from the unpaved soil ground in the archipelago were estimated to be 47, 165 and 8 nGy h(-1), respectively. A comparative study of car-borne data obtained prior to and subsequent to the 2011 Fukushima nuclear accident, as for Okinawa-jima, indicated that the nuclear accident has no impact on the environmental radiation at the present time.

Assessment of gamma dose rate in dwellings due to decorative stones

For more accurate assessment of the enhanced external exposure to dwellers caused by decorative stones, based on a model room and different decorative conditions, the 3-D distributions of indoor gamma dose rates were computed by the Monte Carlo simulations, and a new model was established to estimate the extra gamma dose rate at the centre of the room in this study. For verification of the simulation results, the gamma radiation was both instantaneously and cumulatively measured in a test room. The results showed that both the gamma dose rate at the centre of the room and the distribution of indoor gamma radiation were in general agreement with the simulated ones.

Estimation of the front-to-total activity ratio for wire screens using CFD simulation

Wire screens are widely used for sampling radioactive aerosols. The front-to-total activity ratio is a critical factor in describing the self-shielding effect of the wire screens. In this study, computational fluid dynamic method was applied to simulate the deposition of aerosols on the surface of the wire screens. Four different types of screens were investigated for particle size varying from 1 nm to 10 µm. Experimental verification was carried out in a radon chamber. The results showed good agreement between experimental data interception and the simulation. Significant differences on the front-to-total activity ratio for the different types of screens were observed when the size of particle was <20 nm.

An improved electrostatic integrating radon monitor with the CR-39 as alpha-particle detector

In this study, based on the electrostatic integrating radon monitor (EIRM) developed by Iida et al., a new type of EIRM with the allyl glycol carbonate (CR-39) as alpha-particle detector was developed for outdoor radon measurements. Besides using the CR-39 to replace the cellulose nitrate film as alpha-particle detector, the electrode and the setting place of the CR-39 were also optimally designed based on the simulation results of the electric field and the detection efficiency. The calibration factor of the new EIRM was estimated to be 0.136±0.002 tracks cm(-2) (Bq m(-3) h)(-1), with the lower detection limit of 0.6 Bq m(-3) for a 2-month exposure. Furthermore, both the battery and the dry agent were also replaced to protect the environment. The results of intercomparison and field experiments showed that the performances of the new EIRM were much better than the original one. It suggests that the new type of ERIM is more suitable for large-scale and long-term outdoor radon surveys.

Long Noncoding RNA: its partners and their roles in cancer

RNA transcripts, which do not encode proteins, have received considerable attention in recent years. These non-coding RNAs are classified into two groups: small non-coding RNAs and long non-coding RNAs (lncRNAs). Increasing evidence suggests that lncRNAs are emerging as key regulators in many biological processes. However, knowledge of the underlying mechanisms whereby they act is still limited. Here, we try to elucidate the way that lncRNAs function in the context of DNA, RNA and protein interaction networks. It is noteworthy that lncRNA and another type of non-coding RNA microRNA (miRNA) may 'talk' to each other more frequently than ever expected. Additionally, lncRNAs display aberrant expression profiles in different kinds of cancers, with their potential roles in carcinogenesis and cancer metastasis. We summarize the effect of some cancer related lncRNAs upon tumor biological events, including cell proliferation, apoptosis, invasion and metastasis. Finally, we focus on the clinical value of lncRNAs, considering their potential application in cancer diagnosis, prognosis and therapeutic intervention.

ICRP Publication 126: Radiological Protection against Radon Exposure

In this report, the Commission provides updated guidance on radiological protection against radon exposure. The report has been developed considering the latest ICRP recommendations for the system of radiological protection, all available scientific knowledge about the risks of radon, and the experience gained by many organisations and countries in the control of radon exposure. The report describes the characteristics of radon exposure, covering sources and transfer mechanisms, the health risks associated with radon, and the challenges of managing radon exposure. The Commission recommends an integrated approach for controlling radon exposure, relying as far as possible on the management of buildings or locations in which radon exposure occurs, whatever the use of the building. This approach is based on the optimisation principle, and is graded reflecting the responsibilities of key stakeholders, notably in workplaces, and the intent of the national authorities to control radon exposure. The report also provides recommendations on managing radon exposure when workers’ exposures are considered as occupational, and the appropriate requirements of the Commission should be applied.

Effects of atmospheric parameters on radon measurements using alpha-track detectors

The calibration factors of alpha-track radon detectors (ATDs) are essential for accurate determination of indoor radon concentrations. In this paper, the effects of atmospheric parameters on the calibration factors were theoretically studied and partially testified. Based on the atmospheric thermodynamics theory and detection characteristics of the allyl diglycol carbonate (CR-39), the calibration factors for 5 types of ATDs were calculated through Monte Carlo simulations under different atmospheric conditions. Simulation results showed that the calibration factor increased by up to 31% for the ATDs with a decrease of air pressure by 35.5 kPa (equivalent to an altitude increase of 3500 m), and it also increased by up to 12% with a temperature increase from 5 °C to 35 °C, but it was hardly affected by the relative humidity unless the water-vapor condensation occurs inside the detectors. Furthermore, it was also found that the effects on calibration factors also depended on the dimensions of ATDs. It indicated that variations of the calibration factor with air pressure and temperature should be considered for an accurate radon measurement with a large dimensional ATD, and water-vapor condensation inside the detector should be avoided in field measurements.

Efficiency of endovenous versus arterial administration of mesenchymal stem cells for ischemia-reperfusion-induced renal dysfunction in rats

BACKGROUND

Ischemia followed by reperfusion leads to acute renal failure in both native kidneys and a renal allograft. Our previous study found that transplantation of mesenchymal stem cells (MSCs) ameliorated ischemia-reperfusion (I/R)-induced kidney dysfunction by increasing the activities of antioxidant enzymes. The purpose of this study was to evaluate whether intra-arterial versus intravenous administration was more effective.

METHODS

Renal ischemia was induced by clamping the right renal vessels for 60 minutes after removal of the left kidney. MSCs (1 × 10(6)) were administered through either the tail vein (TV) or the renal arter (RA), followed by reperfusion. We evaluated kidney function as well as tissue activities of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Histopathologic and immunohistochemical examinations were performed. To tracking MSCs in vivo, they were transfected with firefly luciferase and monomeric red fluorescent protein reporter genes (fluc-mrfp). MSC retention and survival were assessed using bioluminescence imaging. We observed the effects of MSCs (1 × 10(6), 2 × 10(6), and 5 × 10(6)) on IR injury.

RESULTS

MSC infusion via either the tail vein or the renal artery significantly improved kidney function at days 1, 3, and 5 as indicated by lower urea and creatinine levels compared with vehicle controls (P < .05). I/R induced a reduction in renal tissue SOD activity but GSH-PX was significantly improved by MSCs (P < .05) on day 1. Treatment with MSCs also significantly reduced renal tissue MDA levels that had been otherwise increased by renal I/R injury (P < .05). The above parameters were similar between the TV and the RA groups. Histological examination revealed kidneys from MSC-treated rats to show fairly normal morphology. The percentages of proliferating cell nuclear antigen (PCNA)-positive cells were higher in the MSC groups: 16.83 ± 4.62%, 19.17 ± 6.21%, and 2.17 ± 1.16% for the TV, RA, and control groups, respectively. There was no significant dose-related difference among MSC groups. Bioluminescence imaging demonstrated most MSCs to be lost within 7 days after either intravenous or intra-arterial infusion.

CONCLUSIONS

MSCs ameliorated I/R-induced acute renal failure in rats with similar efficiency whether infused either through the TV or the RA. There was no dose-dependent responses.

A new technique for measuring the concentrations of airborne radon progeny by using an imaging plate

A new technique was developed for measuring the concentrations of airborne radon progeny by using an imaging plate (IP). The concentrations of radon progeny collected on the sampling filter were measured with the IP at 2-5-, 6-20- and 21-30-min intervals after sampling, and the alpha disintegrations were automatically counted by a self-developed image analysis software. To reduce the overlapping impact on alpha counts, a plastic separator with a 0.5-mm thickness was set between the sampling filter and the IP. The lower limit of detection for the equilibrium equivalent concentration of radon was estimated to be ∼3.5 Bq m(-3) for a 10-min sampling at 10 l min(-1). Comparison experiments showed that results measured with the new technique were well consistent with those measured with the alpha spectrometer. It indicates that the new technique is a useful method for accurate measurements of airborne radon progeny concentrations.

Preparation and emanation properties of an ion-exchanged solid thoron source

For the calibration purpose of thoron ((220)Rn) measurements, solid sources with constant (220)Rn emanation are generally desired. In this study, Th(4+) in the thorium nitrate powder was successfully exchanged to the surfaces of sodium benzenesulphonate resins with a bead diameter of ∼0.5 mm by using the ion-exchange method. Tests of (220)Rn emanating from the ion-exchanged resin indicated that the emanation rates were nearly constant, provided both the air humidity and air temperature were controlled. As the resin can be easily prepared to be of various sizes and activities of sources, the ion-exchanged resin is considered as a promising standard source for calibrations of (220)Rn measurements.

An optimal measuring timetable for thoron measurements by using Lucas scintillation cell

Up to now, several different timetables have been proposed for thoron ((220)Rn) measurements by using the Lucas scintillation cell. In this study, based on the measuring principle, the uncertainty of the measurements was theoretically studied by using a self-developed simulation program. The results showed that a measuring timetable of 1-min consecutive counting lasted for 10 times was an optimal routine for (220)Rn measurements. Compared with the previously proposed timetables, the new measuring timetable could reduce the uncertainty of (220)Rn measurements by >19 %.

Comparison of discrimination methods for alpha radiation signals using imaging plates

The discrimination of different radiation signals is important for quantitative measurements of naturally occurring radionulides by using the technique of imaging plates (IPs). In this study, four discrimination algorithms previously proposed for discriminating and counting the incident alpha signals were experimentally compared from the view points of linearity response, the discrimination capability of alpha signals from beta signals and the detection uncertainty. The results showed that all the methods had a good linearity response and could discriminate alpha signals from beta signals. In general, a larger region of interest (ROI) has a higher detection efficiency, but the discrimination capability of alpha signals from beta signals is worse. By taking into account both the detection efficiency and the uncertainty of detection, the algorithm using an ROI of 5 × 100 μm × 100 μm was considered to be the most appropriate method for quantitative measurements of alpha radiation.

Measurement of the (212)Pb particle size distribution indoors

A new device has been developed for the measurement of the (212)Pb particle size distribution indoors. This device consists of two wire screens and a back-up filter with a diameter of 2.0 cm. The sampling flow rate is typically 3.0 l min(-1). After 3-h sampling time and 6-h waiting time, a CR-39 detector is used for the registration of the alpha particles from the (212)Pb, deposited on the wire screens and the filter, respectively. It appears clear from field measurements that there are no appreciable differences among the particle size distributions from different dwellings within the same location and under the same climate conditions. However, the (212)Pb particle size distributions from the countryside dwellings have different results from those of the city dwellings.

A theoretical study on accurate measurements of thoron with airflow-through scintillation cell method

For accurate measurements of (220)Rn concentration with airflow-through scintillation cell method, a theoretical study was performed for discussing the influences of sampling flow rate, volumes of sampling tube and scintillation cell on the measurements. It is found that a high flow rate and a large inner volume of scintillation cell as well as a small inner volume of sampling tube are not only preferable for measuring low levels of (220)Rn, but also helpful for enhancing the measurement accuracy. In calibration experiments, both the sampling flow rate and the sampling tube volume should be noted. The variations of the flow rate and tube volume should be considered for accurate measurements in the fields.

Estimation of indoor (220)Rn progeny concentrations with (220)Rn measurements

For estimating indoor thoron ((220)Rn) progeny concentrations with (220)Rn measurements, both theoretical studies and field measurements were carried out in this work. Based on the theoretical study, it was found that the exhalation rate of (220)Rn (E(Tn)) could be optimally assessed with the (220)Rn concentration measured at a point of 50 cm far from the source wall, and the equilibrium equivalent thoron concentration (EETC) could be further estimated with the E(Tn) and the area of wall surface as well as the room volume. Field measurements testified that the estimated EETCs were in general agreement with the directly measured results with an average ratio of 0.87 ± 0.12. The new method developed in this study is thought to be preferable for long-term and large-scale surveys of indoor EETC.

Characteristic and performance of a simple thoron chamber

For calibration and intercomparison experiments, a thoron chamber with an inner volume of 300 l was designed based on a programmable constant temperature and humidity testing device in this work. The commercial lantern mantles enriched with (232)Th were used as the (220)Rn source and the mantles were set in 3×3×3 points of lattice style inside the chamber. Experimental studies showed that (220)Rn concentrations in the chamber could be easily controlled and adjusted from about 0.5 to 80 kBq m(-3) through manual settings of the relative humidity and temperature, and the spatial distribution of (220)Rn in the chamber was fairly homogeneous.

TP53 codon 72 polymorphisms and breast carcinoma susceptibility: A meta-analysis

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Background: Previously, TP53 codon 72 polymorphisms have been implicated as risk factors for various cancers. Several studies have conducted on the association of TP53 codon 72 polymorphisms with susceptibility to breast carcinoma and have yielded inconclusive results. The aim of the present study was to assess possible associations of breast cancer risk with TP53 codon 72 polymorphisms. Methods: We conducted a search in the Medline, EMBASE, OVID, Sciencedirect, and Chinese National Knowledge Infrastructure (CNKI) without a language limitation, covering all papers published up to Dec 2008. The associated literature was acquired through deliberate searching and selected based on the established inclusion criteria for publications. Results: Consequently, fifteen studies, including 3436 cases and 4394 controls, met the included criteria and thus were selected. Ultimately, the relevant data were extracted and further analyzed using systematic meta- analyses. The results showed that individuals carrying homozygote Arg/Arg genotype have a significant increased risk of breast cancer compared with those carrying Pro/Pro genotype (OR: 1.58, 95%CI:1.10–2.28). For Arg allele, no evidence indicated that individuals with Arg/Arg genotype have an increased risk of breast cancer compared with those with a combined Pro genotype (Arg/Pro+Pro/Pro) (OR: 1.68, 95%CI:1.24–2.29). For Pro allele, individuals with homozygote Pro/Pro genotype have a marked decreased susceptibility to breast cancer relative to those with a combined Arg genotype (Arg/Pro+Arg/Arg) (OR: 0.84, 95%CI:0.73–0.98). Conclusions: The results of the present study suggest that TP53 codon 72 polymorphisms might be a risk factor for breast cancer. Homozygote Arg allele genotype could significantly increase susceptibility to breast cancer, while Pro/Pro allele markedly decreases breast risk.

No significant financial relationships to disclose.

Instrument performance of a radon measuring system with the alpha-track detection technique

An instrument performance test has been carried out for a radon measuring system made in Hungary. The system measures radon using the alpha-track detection technique. It consists of three parts: the passive detector, the etching unit and the evaluation unit. A CR-39 detector is used as the radiation detector. Alpha-track reading and data analysis are carried out after chemical etching. The following subjects were examined in the present study: (1) radon sensitivity, (2) performance of etching and evaluation processes and (3) thoron sensitivity. The radon sensitivity of 6.9 x 10(-4) mm(-2) (Bq m(-3) d)(-1) was acceptable for practical application. The thoron sensitivity was estimated to be as low as 3.3 x 10(-5) mm(-2) (Bq m(-3) d)(-1) from the experimental study.

Simulation of the concentrations and distributions of indoor radon and thoron

The technique of computational fluid dynamics (CFD) was used to study the concentrations and distributions of indoor radon (222Rn) and thoron (220Rn) as well as their progeny in three dimensions. According to the simulation results, in a naturally ventilated room, the activity distribution of 222Rn is homogeneous except for the places near air diffuser (supply and exhaust) locations. The concentration of 220Rn exponentially decreases with the distance from the source wall which is considered independently. However, as the ventilation rate increased, the concentrations of both 222Rn and 220Rn decreased and their activity distributions become complicated due to the effect of turbulent flow. It suggests that the impact factors of monitoring conditions (sampling site, airflow characteristics, etc.) should be taken into account in obtaining representative concentrations of 222Rn/220Rn for dose assessment. Both the simulation results of activities and their distributions agreed well with the experimental results in a laboratory room. It suggests that the CFD models may be applicable for the estimation of indoor 222Rn and 220Rn as well as their progeny.

Occurrence of 222Rn, 226Ra, 228Ra and U in groundwater in Fujian Province, China

222Rn, 226Ra, 228Ra and U were determined in a total of 552 groundwater samples collected throughout Fujian Province of China. The geometric mean concentrations of 222Rn, 226Ra, 228Ra and total U in the groundwater were 147.8 kBq m-3, 12.7 Bq m-3, 30.2 Bq m-3 and 0.54 microgram kg-1, respectively. High groundwater 222Rn was explained by the predominantly granitic rock aquifers in Fujian. A lifetime risk of 1.7 x 10(-3) was estimated for the ingestion of groundwater 222Rn. High ratios of 228Ra to 226Ra contents (geometric mean of 2.4) and their disproportion suggest that 228Ra should also be measured in the assessment of population doses from drinking water in the regions of high rock or soil 232Th. No significant correlation between the 222Rn concentrations in groundwater and air was found.

Estrogen activates telomerase

Telomerase activity is present in most malignant tumors and provides a mechanism for the unlimited potential for division of neoplastic cells. Although telomerase is known to be a regulated enzyme, the factors and mechanisms involved in telomerase regulation are not well understood. In the present study, we examined the effects of estrogen on telomerase activity. Telomerase activity in estrogen receptor (ER)-positive MCF-7 cells was up-regulated by the treatment with 17beta-estradiol. This activation accompanied up-regulation of the telomerase catalytic subunit, hTERT mRNA. Gel shift assays revealed that the imperfect palindromic estrogen-responsive element in the hTERT promoter specifically binds to ER. Transient expression assays using luciferase reporter plasmids containing various fragments of hTERT promoter showed that this imperfect palindromic estrogen-responsive element is responsible for transcriptional activation by ligand-activated ER. We also found that estrogen activates c-Myc expression in MCF-7 cells and that E-boxes in the hTERT promoter that bind c-Myc/Max play additional roles in estrogen-induced transactivation of hTERT. Estrogen thus activates telomerase via direct and indirect effects on the hTERT promoter. These findings may help elucidate the mechanisms of hormonal control of telomerase activity and aid understanding of the roles of sex steroids in cellular senescence and aging as well as estrogen-induced carcinogenesis.

An instrument for measuring equilibrium-equivalent 222Rn and 220Rn concentrations with etched track detectors

To simultaneously measure both 222Rn and 220Rn progeny concentrations, a new type of portable integrating monitor with allyl diglycol carbonate (CR-39) plastic detectors was developed. The monitor gives the average equilibrium-equivalent 222Rn and 220Rn concentrations (EEC(RN) and EEC(Tn)) during sampling intervals. The detection efficiencies of the alpha particles were calculated by Monte Carlo method. The lower limits of detection for EEC(Rn) and EEC(Tn) are estimated to be 0.57 Bq m(-3) and 0.07 Bq m(-3) for 24 h continuously sampling at a flow rate of 0.8 L min(-1). The measuring results with the new type monitors were confirmed through intercomparison experiments. In a small survey, a rather high 220Rn progeny concentration with an average of 1.73 Bq m(-3) was observed in traditional Japanese dwellings with soil/mud plastered walls. On the other hand, a very high 232Th concentration in soil was reported in China. They suggested that there is a possibility of high 220Rn progeny concentration in both Japan and China.