Impact of temporal variability of radon concentration in workplaces on the actual radon exposure during working hours

For workplaces where significant diurnal variations in radon concentrations are likely, measurements to evaluate average radon concentration during working hours could be useful for planning an optimized protection of workers according to the 2013/59/Euratom Directive. However, very few studies on this subject, generally limited to periods of few weeks, have been published. Therefore, a study has been conducted to evaluate the actual long-term radon exposure during working hours for a sample of 33 workplaces of four different types (postal offices, shops, restaurants, municipal offices), mainly located at the ground floor, and with expected considerable air exchange rate occurring during working hours due to frequent entrance/exit of persons or mechanical ventilation. The results show that the difference between the average radon level during working hours and that one during the whole day is about 20% on average and ranges from 0 to 50%. These observed differences, generally smaller compared with those found in other similar studies, are nearly the same if the analysis is restricted to workplaces with annual radon level higher than 300 Bq m-3, and therefore natural or mechanical ventilation normally present during working hours of the monitored workplaces cannot be considered an effective mitigation measure. However, the costs and time-response characteristics of the active monitors, as those used for the present study, will probably allow using more frequently a similar measurement strategy in workplaces.

Building material radon emanation and exhalation rate: Need of a shared measurement protocol from the european database analysis

In this paper the authors present a collection of radon emanation and exhalation rate data of about 2000 samples of building materials used in Europe. The data analysis highlighted some critical issues, such as the use of different units to express radon exhalation rate, the use of different measurement techniques and the general lack of information about density and thickness of samples. In many cases these differences of type and amount of information make difficult a reliable comparison of the obtained data. In the light of these considerations, the need arises to start, at both national and European level, a research activity aimed to develop a shared protocol for measuring the radon exhalation rate based on widely used and reliable measurement techniques. At European level, this protocol could support in forthcoming EU Member States national radon action plans, to take into account the contribution of building materials to the indoor radon concentrations.

Increased glucocorticoid concentrations in early life cause mitochondrial inefficiency and short telomeres

Telomeres are DNA structures that protect chromosome ends. However, telomeres shorten during cell replication and at critically low lengths can reduce cell replicative potential, induce cell senescence and decrease fitness. Stress exposure, which elevates glucocorticoid hormone concentrations, can exacerbate telomere attrition. This phenomenon has been attributed to increased oxidative stress generated by glucocorticoids ('oxidative stress hypothesis'). We recently suggested that glucocorticoids could increase telomere attrition during stressful periods by reducing the resources available for telomere maintenance through changes in the metabolic machinery ('metabolic telomere attrition hypothesis'). Here, we tested whether experimental increases in glucocorticoid levels affected telomere length and mitochondrial function in wild great tit (Parus major) nestlings during the energy-demanding early growth period. We monitored resulting corticosterone (Cort) concentrations in plasma and red blood cells, telomere lengths and mitochondrial metabolism (metabolic rate, proton leak, oxidative phosphorylation, maximal mitochondrial capacity and mitochondrial inefficiency). We assessed oxidative damage caused by reactive oxygen species (ROS) metabolites as well as the total non-enzymatic antioxidant protection in plasma. Compared with control nestlings, Cort-nestlings had higher baseline corticosterone, shorter telomeres and higher mitochondrial metabolic rate. Importantly, Cort-nestlings showed increased mitochondrial proton leak, leading to a decreased ATP production efficiency. Treatment groups did not differ in oxidative damage or antioxidants. Hence, glucocorticoid-induced telomere attrition is associated with changes in mitochondrial metabolism, but not with ROS production. These findings support the hypothesis that shortening of telomere length during stressful periods is mediated by glucocorticoids through metabolic rearrangements.

Updated database on natural radioactivity in building materials in Europe

The paper presents the latest collection of activity concentration data of natural radionuclides (²²⁶Ra, ²³²Th and ⁴ K) in building materials. This database contains about 24200 samples of both bulk materials and their constituents (bricks, concrete, cement, aggregates) and superficial materials used in most European Union Member States and some European countries. This collection also includes radiological information about some NORM residues and by-products (by-product gypsum, metallurgical slags, fly and bottom ashes and red mud) which can be of radiological concern if recycled in building materials as secondary raw materials. Moreover, radon emanation and radon exhalation rate data are reported for bricks and concrete.

AN INTERNATIONAL COOPERATION BY USING AN ALL-ENCOMPASSING PASSIVE RADON MONITOR

The recently developed radon film-badge makes it possible to measure radon indoors, in soil, in water and/or in aqueous media (e.g. mud). As a result of its wide response linearity, this monitor has been successfully used to measure radon in-water with concentrations from 10 to ~10 000 Bq/L. By exploiting the unique characteristics of this badge, a mini-survey has been carried out by Health Canada in which radon in water was measured from 12 private wells, as well as in tap water originating from the Ottawa River. Due to the widespread interest of different laboratories in using these passive monitors, laboratories were provided with plastic films to construct their own badges by using in-house CR-39 detectors. Monitors were then irradiated by a known radon concentration at the National Institute of Radiation Metrology (ENEA)'s radon chamber and sent back to each laboratory for processing and counting. Even though these laboratories have been using different etching- and counting-procedures, the film-badge responses varied only within ~12%.

Radiological characterization of the ancient Roman tuff-pozzolana underground quarry in Orvieto (Italy): A natural laboratory to revisit the interactions between radionuclides and aerosols

Orvieto (Italy) has a large network of underground tunnels quarried to extract tuff and pozzolana by Etruscans and Romans. One of these tunnels was chosen as natural laboratory to compare different radiation measurement and dose assessment methods. Indeed, tuff and pozzolana are very rich in natural radioactivity and are interesting from the radiation protection point of view since they are still used as building materials. In order to characterize this site an in situ experimental procedure was followed. It consisted in measurements carried out with different instruments: two portable gamma ray spectrometers, two gamma dose rate meters, two radon monitors and one two channel working level monitor. Samples of tuff and pozzolana stones were also collected to be measured with gamma spectrometry in laboratory. Due to the high content of ²³⁸U, ²³²Th (more than 200 Bq kg^-1 for both radionuclides) and ⁴⁰K (more than 2000 Bq kg^-1) of tuff and pozzolana, elevated levels of exposure to natural radioactivity were found: indeed, with different instruments and approach, a gamma dose rate of about 1 μGy h^-1 and an average radon concentration of about 10,000 Bq m^-3, with a Potential Alpha Energy Concentration (PAEC) of 288 MeV cm^-3, were measured. The radiological characteristics of Orvieto underground quarry make it a perfect site for "in field" intercomparisons of different measurement and dose assessment methods.

A comparison of radon and its decay products' behaviour in indoor air

The inhalation of short-lived radon decay products (RDP) yields the greatest contribution to the natural radiation exposure. This paper deals with a study carried out to improve the knowledge of the behaviour of RDPs, their interaction with particulates and the plateout during the time. The tests confirmed that a high aerosol particle concentration increases the probability that an ion sticks to aerosol and remains long in the air, leading to both an increase of F and a decrease of fp, as reported in the literature. The same experimental protocol applied in a small radon chamber showed a strong reduction of the equilibrium factor (an average of ∼10 %), because in a small environment the plateout phenomenon prevails on the attachment to particulate.

Natural radioactivity in building material in the European Union: robustness of the activity concentration index I and comparison with a room model

Using a wide database collected in the last 10 years, the authors have calculated the activity concentration index I for many building materials in the European Union. Suggested by a European technical guidance document, the index I has recently been adopted as a screening tool in the proposal for the new Euratom basic safety standards directive. The paper analyses the possible implications of the choice of different parameters for the computation of index I, i.e. background to be subtracted, dose criteria, etc. With the collected data an independent assessment of gamma doses was also made with an ISS room model, choosing reasonable hypotheses on the use of materials. The results of the two approaches, i.e. index I and a room model, were compared.

Natural radioactivity in building materials in the European Union: a database and an estimate of radiological significance

The authors set up a database of activity concentration measurements of natural radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) in building material. It contains about 10,000 samples of both bulk material (bricks, concrete, cement, natural- and phosphogypsum, sedimentary and igneous bulk stones) and superficial material (igneous and metamorphic stones) used in the construction industry in most European Union Member States. The database allowed the authors to calculate the activity concentration index I--suggested by a European technical guidance document and recently used as a basis for elaborating the draft Euratom Basic Safety Standards Directive--for bricks, concrete and phosphogypsum used in the European Union. Moreover, the percentage could be assessed of materials possibly subject to restrictions, if either of the two dose criteria proposed by the technical guidance were to be adopted.

Development of a framework of quality assurance practices for a radon passive dosemeter service

Etched track detectors are widely used for the detection of radon and its decay products. The reliability of radon measurement performed with such devices requires that laboratories producing analytical data are able to provide results of the required quality. The need for uniform results from laboratories at an international level therefore requires the implementation of a quality assurance programme, the harmonization of criteria, sampling procedures, calculations and the reporting of results, agreed on the basis of fundamental principles and international standards. The quality assurance programme described here is the first step on the way to ISO/IEC 17025 certification for the RI-RN (ISPESL) laboratory.

Radiometric characterisation of more representative natural building materials in the province of Rome

Natural building materials, characterised by middle-low-activity concentrations of primordial radionuclides ((40)K, (232)Th and (238)U series) are widely used in Italy. Since natural materials reflect the geological variability of their sites of origin, a systematic study was carried out in the province of Rome and the results are reported in this paper. In the present work, in order to evaluate average, minimum and maximum contents of primordial radionuclides, more representative lithologies outcropping on the territory of the province of Rome were identified and around 150 samples were collected. Also, these lithologies were characterised from a radioprotection point of view, by means of the evaluation of the index, I, when they are used as building materials. The results confirm the high-primordial radionuclide content within some materials used in Latium (central Italy). Although the study was carried out in a limited area, the results confirm considerable variation in the primordial radionuclide content depending on the sites of origin.

A passive radon dosemeter suitable for workplaces

The results obtained in different international intercomparisons on passive radon monitors have been analysed with the aim of identifying a suitable radon monitoring device for workplaces. From this analysis, the passive radon device, first developed for personal dosimetry in mines by the National Radiation Protection Board, UK (NRPB), has shown the most suitable set of characteristics. This radon monitor consists of a diffusion chamber, made of conductive plastic with less than 2 cm height, containing a CR-39 film (Columbia Resin 1939), as track detector. Radon detectors in workplaces may be exposed only during the working hours, thus requiring the storage of the detectors in low-radon zones when not exposed. This paper describes how this problem can be solved. Since track detectors are also efficient neutron dosemeters, care should be taken when radon monitors are used in workplaces, where they may he exposed to neutrons, such as on high altitude mountains, in the surroundings of high energy X ray facilities (where neutrons are produced by (gamma, n) reactions) or around high energy particle accelerators. To this end, the response of these passive radon monitors to high energy neutron fields has been investigated.