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An account is given of the behaviour of thoron and its progeny in the indoor environment. Emphasis is placed on the spatial distribution of these radionuclides in room air and on their interactions with indoor aerosols. How these aspects of thoron and progeny behaviour give rise to special problems for measuring them and assessing their radiological impact are described. Descriptions and comparisons are given of a range of thoron and progeny measurement techniques both passive and active. Recent progress in thoron dosimetry is described as well as compared with radon dosimetry. The results of some indoor thoron and progeny surveys carried out in different countries in recent years are given. As an example of this a summary account is presented of a recently concluded survey of thoron and its airborne progeny in over 200 houses in Ireland.

A roundtable discussion was made at the end of the workshop. All the presentations were summarised in this discussion. It involved measurement techniques, quality assurance and dose assessment and health effects of thoron and its progeny. In particular, major epidemiological studies may be affected by thoron interference in radon measurements. Since their data are not sufficient when compared with that of radon, further efforts in thoron studies will be needed.

Previous studies have demonstrated that kappa opioid receptor (KOR) antagonists reduce stress- and depression-like behaviors. We hypothesized that administration of a novel opioid mixed agonist/antagonist capable of antagonist activity at the KOR would attenuate forced-swim stress (FSS)-induced immobility, an animal model of depression-like behavior. C57Bl/6J mice were exposed to antinociceptive and repeated FSS testing after pretreatment with a graded dose of a novel bivalent morphinan compound, bis(N-cyclobutylmethylmorphinan-3-yl) sebacoylate dihydrochloride (MCL-144B). MCL-144B demonstrated dose- and time-dependent antinociception and KOR-mediated antagonism. In support of the hypothesis, pretreatment with MCL-144B dose-dependently attenuated stress-induced antinociception and immobility in the forced-swim test.

Radon exposure assessment in case–control studies on radon and lung cancer is generally based on contemporary radon concentration measurements, which can be affected by significant changes in the building structures or in living habits. Another method to estimate the radon exposure of the subjects is the recently developed retrospective dosimetry technique based on the 210 Po surface activity from glass objects. In order to compare the results obtained by the two methods, a study has been carried out in a sample of 26 dwellings in Rome, with radon concentration values ranging from 28 to 623 Bq m −3 . Retrospective detectors based on CR-39 and LR 115 were exposed on 50 glass objects in bedrooms and living rooms. The correlation factor between the two sets of data, after removing six extreme values, is 0.67, which is similar to results obtained in other validation studies of similar sample size. The correlation increases to 0.83 if the 21 objects exposed in non-smoky dwellings are selected, while it vanishes to −0.01 for the 23 objects exposed in smoky dwellings, suggesting quite larger variations of plate-out in presence of environmental tobacco smoke.

Background: In epidemiological studies investigating radon-related health risk, the radon exposures are often derived from contemporary short-term radon measurements. Recent radon measurements, taken over a period of 1 year in dwellings, are often casually extrapolated and taken to be representative for periods spanning several decades. By simply considering the well-known variability of radon concentrations in dwellings and its sensibility to trivial factors such as living habits or minor changes in the dwelling itself, an amount of skepticism concerning the reliability of this practice should arise. In mining areas, this variability is already well acknowledged since mining conditions, such as ventilation of mine shafts, flooding of mine galleries, etc., are known to be able to change radon concentrations in dwellings built on top of mine shafts for over more than one decade. Methods: This study was conducted in stable rural communities in Yugoslavia. Present radon concentrations were compared to an indicator of past radon concentrations, that is the 210Po activity, fixed on glass surfaces or in the bulk of voluminous materials. Results: In less than 50% of the cases, the past and present radon concentrations agree within a factor of 2. Conclusions: This comparison indicates that even in stable rural communities, deriving past radon concentrations by extrapolating present ones is not a particularly good practice.

The principal objective of the work reported here was to investigate the influence of electric fields from high voltage power lines on the behaviour of short-lived, alpha particle emitting radon progeny in outdoor air Active and passive measurement of short-lived radon progeny were made at one metre above ground level, at various distances from a 400 kV power line, both when the line was energised and during a period when it was switched off for engineering modifications. Within the limitations of the measurement techniques used no effect at ground level on short-lived radon progeny behaviour due to the power line could be detected. Elevated levels of the long-lived radon decay product 210 Po were measured on 36 year old glass insulators taken from a 110 kV power line indicating that electric fields from power lines may remove radon progeny from the air. Radon progeny detection techniques employed were based on the use of solid state nuclear track detectors.

An account is given of the need to obtain estimates of indoor radon exposures in past decades as a necessary support for radon epidemiological studies. Retrospective radon exposure assessment procedures based on the measurement of the alpha recoil implanted long-lived radon decay product 210 Po are critically described. Particular emphasis is placed on the CR-LR Difference Method in which surface implanted 210 Po is measured using the alpha track detectors CR-39 and LR-115 mounted side by side on glass surfaces. The results are presented of a series of retrospective radon measurements made both in the Schneeberg-Schlema former uranium mining district and in an adjacent non-mining district of the east of Germany. In Schneeberg-Schlema, due to the complex effects of mining, indoor radon levels in the past are estimated in some cases to have been above fifty times contemporary levels.

Results from epidemiological studies on lung cancer and radon exposure in dwellings and mines led to a significant revision of recommendations and regulations of international organizations, such as WHO, IAEA, Nordic Countries, European Commission. Within the European project RADPAR, scientists from 18 institutions of 14 European countries worked together for three years (2009–2012). Among other reports, a comprehensive booklet of recommendations was produced with the aim that they should be useful both for countries with a well developed radon program and countries with little experience on radon issues. In this paper, the main RADPAR recommendations on radon programs and policies are described and discussed. These recommendations should be very useful in preparing a national action plan, required by the recent Council Directive 2013/59/Euratom., JRC.I.1-Chemical Assessment and Testing

The results of measurements of 210Po surface activities on glass in dwellings in a number of European countries and the USA are presented. A description of a new CR-39 based α-track detector configuration and methods of α-track energy identification used in this work are given. While the primary function of the detector was to measure 210Po on surfaces, it was also designed to measure contemporary 222Rn levels and 214Po on surfaces. The results obtained are interpreted using a model which is based on the Jacobi-Porstendorfer room model and on Samuelsson's recursive implementation of the Bateman equations for serially transforming radionuclides applied in conjunction with the implantation model of Cornelis. The ages of the glass investigated ranged from 2 y to 75 y. The dwellings investigated included 10 in the former uranium mining district of Schneeberg, Germany where large variations in indoor 222Rn levels in the recent past decades have taken place.

Many radon detectors exist in the form of a planar disc shaped alpha particle detector mounted in one end of a small cylindrical chamber. Models have been developed to determine the sensitivity of such detectors to radon exposure. A model, adapted from the Jacobi-Porstendorfer room models, is used to determine the partitioning of short-lived radon progeny between airborne and surface deposited states within the detecting volume. This is used in conjunction with Monte Carlo simulation to obtain the radon sensitivity. The use of these models with passive alpha track detectors is highlighted although they are of general applicability to passive detectors using other alpha detecting media. Using these models it is possible to design passive detectors with dimensions such that the alpha track densities may be optimised to a chosen radon exposure range. Validation of the modelling is presented in the form of comparisons between predicted and experimentally determined sensitivities of CR-39 alpha track detectors.

Long-term (circa 3 months) simultaneous measurements of indoor concentrations of thoron gas, airborne thoron progeny and radon were made using passive alpha track detectors in 205 dwellings in Ireland during the period 2007-09. Thoron progeny concentrations were measured using passive deposition monitors designed at the National Institute of Radiological Sciences (NIRS), Japan, whereas thoron gas concentrations were measured using Raduet detectors (Radosys, Budapest). Radon concentrations were measured in these dwellings by means of NRPB/SSI type alpha track radon detectors as normally used by the Radiological Protection Institute of Ireland (RPII). The concentration of thoron gas ranged from

A radon survey has been carried out around the town of Niska Banja (Serbia) in a region partly located over travertine formations, showing an enhanced level of natural radioactivity. Outdoor and indoor radon concentrations were measured seasonally over the whole year, using CR-39 diffusion type radon detectors. Outdoor measurements were performed at 56 points distributed over both travertine and alluvium sediment formations. Indoor radon concentrations were measured in 102 living rooms and bedrooms of 65 family houses. In about 50% of all measurement sites, radon concentration was measured over each season separately, making it possible to estimate seasonal variations, which were then used to correct values measured over different periods, and to estimate annual values. The average annual indoor radon concentration was estimated at over 1500 Bq/m(3) and at about 650 Bq/m(3) in parts of Niska Banja located over travertine and alluvium sediment formations, respectively, with maximum values exceeding 6000 Bq/m(3). The aver age value of outdoor annual radon concentration was 57 Bq/m(3), with a maximum value of 168 Bq/m(3). The high values of indoor and outdoor radon concentrations found at Niska Banja make this region a high natural background radiation area. Statistical analysis of our data confirms that the level of indoor radon concentration depends primarily on the underlying soil and building characteristics. (c) 2006 Elsevier Ltd. All rights reserved.

Publisher Summary A new and simple technique to measure the variability of radon progeny deposition onto room surfaces, using a dual detector configuration of CR-39 and LR-115, is described. While this technique may find use in basic studies of radon progeny behavior in enclosed spaces and exposure chambers, its main application may prove to be in the retrospective assessment of radon exposure using surface trap detectors. Here the dual detector technique can be used to determine the variability of radon progeny deposition in rooms so that corrections may be applied to the glass surface trap measurements. In surface trap fieldwork, the biggest cost is that of survey personnel visiting dwellings. The additional cost involved in using the dual detector technique described here will be small in comparison but should considerably improve the quality of the estimated radon exposure data.

Approximately 200 volume traps were retrieved from dwellings in various radon prone areas in Europe. They were analysed for the purpose of retrospective radon assessment. Emphasis is put on specific problems encountered when using field samples as opposed to laboratory exposed samples. It was seen that in very dusty circumstances, direct penetration of radon decay products from the outside to the centre of the volume traps calls for extra caution. Rinsing the samples is proposed as a solution and was tested in field and laboratory conditions, showing good results. An attempt was made to give an assessment of the achievable accuracy of the method. Where possible, the volume trap retrospective results were compared with contemporary measurements or to retrospective results from surface traps. The overall impression is that although volume traps are sometimes hard to find in the field, the high reliability of the results makes it well worth the effort. (C) 2001 Elsevier Science B.V. All rights reserved. Scientific Workshop on Radon in the Living Environment, Apr, 1999, Athens, Greece

In recent years, 210 Po implanted in glass artefacts has been used as an indicator of the mean radon gas concentration in dwellings in the past. Glass artefacts have been selected in many dwellings and the α-recoil implanted 210 Po concentration has been measured using various techniques. Some of these retrospective techniques use a model to estimate the retrospective radon gas on the basis of this surface 210 Po activity. The accumulation of 210 Po on glass surfaces is determined by the deposition regime over the exposure period. The 210 Po activity is determined not only by the radon progeny deposition velocities, but by other room parameters such as ventilation rate, aerosol conditions and the surface to volume ratio of the room. Up to now in using room models, a nominal or ‘base-case’ scenario is used, i.e. a single value is chosen for each input parameter. In this paper a Monte–Carlo analysis is presented in which a probability distribution for each parameter is chosen, based on measurements quoted in the literature. A 210 Po surface activity is calculated using a single value drawn from each of the parameter distributions using a pseudo-random number generator. This process is repeated n times (up to 20 000), producing n independent scenarios with corresponding 210 Po values. This process permits a sensitivity analysis to be carried out to see the effect of changes in inputs on the model output.

In 2003, arising from the unusual occurrence of two cases of lung cancer in a non-smoking household in a karstic limestone region of Ireland, a medical specialist suggested that radon in the dwelling be measured. The whole-house average radon concentration was found to be 49 kBq/m 3 , which is the highest radon level detected to date in an Irish dwelling. After remediation had taken place, measurements of surface alpha-recoil implanted 210 Po activities were made on glass objects throughout the dwelling by means of a standard passive alpha-track method. Surface activities of 210 Po on glass ranging up to 2500 Bq/m 2 were found. Using a modified Jacobi room model, it was estimated that the mean radon concentrations in different parts of the dwelling over the past 8–22 years ranged from 59 kBq/m 3 to as high as 212 kBq/m 3 . Samples of dust were also taken for analysis from the surface of a 70-year-old mirror covered in a thick layer of dust. Using gamma and alpha spectrometry, it was found that the dust contained between 0.88 and 1.10 MBq/kg of 210 Po/ 210 Pb.

The loss in vacuo of RaB atoms by alpha recoil from radon daughter deposits collected with membrane filters was investigated. Experimentally determined values of the recoil loss efficiency range from less than 20 to approx. 100% for the different filter types examined. Factors influencing the loss efficiency and also the significance of such losses in radon daughter measurements are discussed.

The principal results of a preliminary study made on indoor radiation levels in Ireland are presented. During the period 1983–1984 measurements were made in over 250 houses. Most measurements were made using passive devices: TLDs for penetrating radiation and CR-39 alpha track plastic detectors for radon measurements. The median value of the doses from penetrating radiation was 0.78 milligray/year with a maximum value of 1.47 m Gy/year detected. The radon concentrations showed a large degre of variability with a median value of 43 Bq/m 3 . About 10% of the houses had radon air concentrations in excess of 100 Bq/m 3 with a maximum of 700 Bq/m 3 being recorded. A tentative analysis of the data with regard to the geological situation is presented.

The possibility of using filtration and electric fields both separately and in combination to reduce the indoor air concentrations of radon daughters is described in theoretical terms and with reference to investigations in experimental rooms. For energy conservation considerations these investigations were carried out without reducing the radon concentration by ventilation or other means. The importance of aerosols to the effectiveness of these methods is also described. It is demonstrated that it is possible by use of filtration rates of 3 – 4 times per hour to reduce the potential alpha energy concentration by a factor of 4 – 5. In case of low aerosol concentration the corresponding reduction in lung dose may be much smaller, depending upon the dose-exposure model used, due to the filtration-caused change in the partitioning of the radon daughters between the attached and un-attached states.