Petr S. Miklyaev

The artilcle presents comments on the manuscript by A.S. Vasiliev et al. “A review of approaches to assessment of potential radon hazard of land plots”. The manuscript does not fully reflect some features of the existing regulations for assessment of potential radon hazard of territories. In addition, important results of modern research in the field have not been considered, and single science-based approach in Russia to assess the potential radon hazard of building sites, which has been implemented in practice and tested in the industry of engineering and environmental surveys, is ignored.

An analysis of the international radon regulatory framework identified actual challenges for the design and conduct of indoor radon surveys, though there is little discussion on this issue in the radon community. The main challenges hindering the development of radon regulation on an international scale, particularly in indoor radon surveys include the following: (i) responsibility for indoor radon testing and mitigation, (ii) excessive focus on Radon Priority Areas, (iii) the role of temporal uncertainty in indoor radon testing, (iv) the standardization of indoor radon measurements, and (v) the standardization of thoron EEC measurements and indoor testing. To address these gaps and inconsistencies, actual needs for design and conduct of indoor radon surveys are proposed, covering the aforementioned challenges. The needs statement, including a discussion of solutions, addresses the following key aspects of radon regulation: (1) legislation, (2) radon measurements, (3) awareness, and (4) building protection. The focus remains on the radon measurement aspect, detailing the strategy and tools for conducting indoor radon surveys within a rational approach. This includes the main research activities necessary for the sustainable development of global radon regulation. The final part of the article presents a Rational Method (protocol) of indoor radon measurements serving as a detailed guideline for standardizing indoor radon testing at the international level. This ensures the decision-making reliability of at least 95% and harmonizes relevant national approaches considering traditional measurement protocols using both short-term and long-term measurements. The proposed solutions aim to achieve the goal of a modern design and conduct of indoor radon surveys that are consistent with large-scale (mass) testing and effectively identify hazardous buildings. These solutions are based on a rational approach with convenient tools and active voluntary participation of the population to be implemented within the framework of national radon regulation.

An analysis of the international radon regulatory framework identified actual challenges for design and conduct of indoor radon surveys, though there is little discussion on this issue in the radon community. The main challenges hindering the development of radon regulation on an international scale, particularly in indoor radon surveys include: (i) Responsibility for indoor radon testing and mitigation, (ii) Excessive focus on Radon Priority Areas, (iii) Role of temporal uncertainty in indoor radon testing, (iv) Standardization of indoor radon measurements, and (v) Standardization of thoron EEC measurements and indoor testing. To address these gaps and inconsistencies, actual needs for design and conduct of indoor radon surveys are proposed, covering the aforementioned challenges. The needs statement, including a discussion of solutions, addresses the following key aspects of radon regulation: (1) Legislation, (2) Radon measurements, (3) Awareness, (4) Building protection. The focus remains on the radon measurement aspect, detailing the strategy and tools for conducting indoor radon surveys within a rational approach. This includes the main research activities necessary for the sustainable development of global radon regulation. The final part of the article presents a rational method (protocol) of indoor radon measurements serving as a detail guideline for standardizing indoor radon testing at the international level. This ensures decision-making reliability of at least 95% and harmonizes relevant national approaches considering traditional measurement protocols using both short-term and long-term measurements. The proposed solutions aim to achieve the goal of modern design and conduct of indoor radon surveys, which consists in the large-scale (mass) testing and effectively identify hazardous buildings. These solutions are based on a rational approach with convenient tools and active voluntary participation of the population, to be implemented within the framework of national radon regulation.

The uranium mines both developed and abandoned appear to be one of the most significant sources of radon exhalation in the world. Therefore, the study of radon exposure of the population in the areas around rehabilitated uranium mines is very important. This article presents the results of the radon release studies at the rehabilitated Beshtaugorsky uranium mine site, which is now used by local people for hiking and picnicking. A dose assessment is also provided. The following parameters were measured: (i) radon flux density from the soil by the open charcoal chamber method using the beta radiometer “Camera-01”; (ii) concentration of radon and its progeny in the air using the radiometer “Alpha-AERO” based on a semiconductor detector; (iii) radon in groundwater by accumulation of radon in charcoal using the “Camera-01” equipment; (iv) content of natural radionuclides in soils and rocks by NaI(Tl) spectrometry; and (v) gamma dose rate using the Geiger-Muller counter. Measurements were taken at 38 points along the Beshtaugorskaya ring road, as well as at the mouths of abandoned adits. The measurements showed significant radon release at the mouths of the former adits and in some sections of tectonic faults. In our opinion, the abnormal radon release is due to convective thermally induced air convection in permeable zones of the mountain massif; radon transport by groundwater does not affect surface radon emissions. The most important source of radiation risk is the incompletely sealed mine openings, which periodically blow out radon-enriched air. In places around the mouth of these mines, the equivalent equilibrium concentration of radon progeny in the open air reaches 35,000–45,000 Bq/m³, and the gamma dose rate also exceeds 10 µSv/h, which is more than 30 times the permissible level. A person resting for 4 h in such an area may, in the worst case, receive a dose of more than 2 mSv. It is advisable to implement measures to prevent or reduce the time people spend in the area around the former mine openings.

The article presents the results of the radon release studies at the rehabilitated uranium mine and an assessment of doses received by the population when using the territory for recreational purposes (the case of the former Beshtaugorsky uranium mine). The measurements of radon flux density from the ground surface, radon concentration in the atmospheric air and groundwater, as well as the gamma dose rate and content of natural radionuclides in soils and bedrocks were performed. It is established that abnormally high radon release associated with both a former uranium adits and natural factors such as tectonic faults. The abnormally high radon release is due to advective radon transport, mainly associated with convective thermally induced air convection in permeable zones of mountain massif; radon transport by groundwater does not affect radon emissions from the surface. The most significant source of radiation risk is the incompletely blocked adit mouths, from which mine air is periodically blown out. Radon concentration and gamma dose rate values many times exceed permissible levels in these locations. A person resting in such an area for 4 hours can lead to a dose exceeding 2 mSv. This is advisable to take measures to prevent or reduce the time people spend in the areas of former adit mouths.

Among the many accumulated challenges, radon mitigation measures for existing buildings are not still carried out in Russia that, combined with the use of an inadequate method for indoor radon measurements, has led to stagnation and crisis of the radon regulation system. To overcome the crisis, a ranking of buildings and responsibility distribution in radon control, including theses on updating the national norms and regulations for ensuring radiation safety, as well as nine priority activities of the radon action plan are proposed in accordance with IAEA requirements.

Recent years have seen increased attention given to radon from two scientific directions. After neglecting radon as an earthquake precursor in the 1990s, it has become the subject of discussions in earthquake-forecast papers due to growing networks of radon monitoring in different countries, particularly the technologies of real-time radon measurements where gamma spectrometers are of great interest as sources of ²²²Rn identification. The second fast-developing direction involves radon in Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) models as a source of boundary layer ionization. Here we address the second topic, which is not connected with the earthquake forecast problems, namely, the role of air ionization by radon as a source of the Global Electric Circuit (GEC) modification. In this publication, we try to unite all of these problems to present a more complex view of radon as an important element in our environment. Special attention is paid to the dependence of radon variability on environmental conditions.

Recent years demonstrate the increased attention to radon from two scientific directions. After neglecting radon as earthquake precursors in 1990-th it becomes again the subject of earthquake-forecast papers discussions due to growing networks of the radon monitoring in different countries, especially, the technologies of real-time radon measurements where the gamma-spectrometers become the leader of interest as the sources of 222Rn identification. The second fast developing direction is including the radon in the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) models as a source of the boundary layer ionization. And here we encounter with second direction which is not connected with the earthquake forecast problems. It is the role of air ionization by radon as a source of the Global Electric Circuit (GEC) modification. In this publication we try to unite all these problems to present more complex view on radon as important element of our environment.

Significant temporal variations in radon are observed in any buildings, including unoccupied buildings with limited ventilation. This fact causes serious difficulties in radiation monitoring to assess the compliance of premises with the requirements of the normative, which limits the annual average level of radon in buildings. Therefore, neither at the national nor at the international level has yet been solved the problem of standardizing the indoor radon measurement if the test duration is less than a year. An analysis of approaches to radon measurement, including an assessment of the effectiveness of regulation, shows very significant differences between practices established in different countries. For example, in Russia, rapid (no more than 20 min) measurements are mainly used and mitigation measures to protect existing buildings from radon are practically not carried out. In European countries, mainly long-term (at least two months) measurements are used, while mitigation measures are still relatively rare, with the exception of the UK and Sweden. In the USA, short-term (2–7 days) measurements are widely used, which are not only carried out, but also paid for by residents themselves, including mitigation measures. However, despite the established approaches to indoor radon monitoring in Russia and the USA, there is a persistent distrust among specialists in the results of shortterm and, especially, rapid measurements. In this regard, a compromise approach is proposed to standardize radon measurements based on a rational criterion by applying fundamental ISO/IEC concepts such as “measurement uncertainty” and “conformity assessment”. The rational criterion for conformity assessment allows using measurements of different durations, providing a given reliability when making a decision. It also proposes a rationale for optimizing indoor radon monitoring through the participation of not only professional inspectors, but also the population itself due to the possibility of introducing simple methods and inexpensive radon devices within the rational criterion.