Francesco Bochicchio

Radon concentration data originating from different surveys can be combined for several purposes: epidemiological analyses, aimed at estimating radon‐related health risks; mapping applications, intended to identify radon‐prone areas; but also for population exposure assessment, by making optimal use of the information contained in the different datasets. Although individual surveys often have limited sample sizes, the increasing availability of survey radon data since the 1980s offers an opportunity to improve knowledge of radon distribution. However, this requires a robust methodology capable of comparing surveys with differing designs and objectives, and of appropriately combining their results while accounting for the specific objectives of the data combination. This paper specifically tackles the inherent challenge of comparing and subsequently combining such heterogeneous datasets in order to achieve a more comprehensive and robust assessment of population radon exposure. To this end, a step‐by‐step procedure designed to facilitate the combination of data from various radon surveys is proposed. A practical application of this methodology has been carried out for the city of Rome, Italy, where data originating from five distinct surveys, carried out since approximately 1990, have been compiled, compared, and (four of them) combined to obtain a better evaluation of the exposure of the population of Rome and its 12 administrative units ( municipi ). As a key outcome of this application, the study will produce a radon “expected burden” map for the different municipi (administrative divisions) of the city of Rome. This map will account for both the estimated radon concentration within each municipio —derived from the combined analysis of the diverse survey data—and the corresponding population size, thereby providing a population‐weighted spatial assessment of radon exposure in the general population, crucial for evaluating health impacts and guiding mitigation strategies.

Population exposure to indoor radon has been proven to increase the risk of lung cancer, and it is considered a leading cause after tobacco smoking. Due to the relatively low outdoor activity concentration, most of the exposure to radon occurs indoors. Radon is generated mostly by the rocks that contain radium-226 either in the soil or in the building materials. Once generated, it enters the buildings directly, due to the activity concentration gradient, or indirectly via a radon carrier. The magnitude and the relative contribution of the entry patterns depend mainly on the building characteristics, the geology, and the living habits of occupants.

Protection of the population and of workers from exposure to radon is a unique challenge in radiation protection. Many coordinated actions and a variety of expertise are needed. Initially, a National Radon Action Plan (NRAP) has been developed and implemented by some countries, while it is currently recommended by international organizations (e.g., World Health Organization) and required by international regulations, such as the European Council Directive 2013/59/Euratom and the International Basic Safety Standards on Radiation Protection and Safety of Radiation Sources, cosponsored by eight international organizations. Within this framework, the Heads of the European Radiological Protection Competent Authorities (HERCA) have organized activities aimed at sharing experiences to contribute toward the development and implementation of effective NRAPs. Two workshops were held in 2014 and 2015, the latter on radon in workplaces. As a follow-up to these, an online event took place in March 2021, and a second specific workshop on NRAP is planned for June 2022. These workshops were attended by experts from the competent authorities of European countries, relevant national and international organizations. The experience of several countries and the outcomes from these workshops have highlighted the need for adequate indicators of the effectiveness and progress of the actions of NRAPs, which could also be useful to implement the principle of optimization and the graded approach in NRAPs. In this paper, the activities of HERCA to support the development and implementation of effective NRAPs are described and some examples of effectiveness indicators are reported, including those already included in the NRAP of some European countries.

The performance of continuous radon monitors (CRMs) is usually evaluated under controlled conditions in a radon chamber during calibrations or intercomparison exercises. The impact of thoron on CRMs response is rarely evaluated; in case the evaluation is performed, it is carried out in a controlled atmosphere with relatively constant, homogeneous, and generally high thoron concentrations and very low radon levels. In a real indoor environment, both radon and thoron concentrations are extremely variable, so the thoron interference evaluations reported in the literature are generally not applicable to CRMs used to measure radon concentration indoors. For this reason, an experimental study was carried out with four different CRMs in an indoor environment (an office room) where medium-to-high concentrations of both radon and thoron were expected. Thoron concentration has been separately evaluated throughout two different active monitors. Three CRMs resulted in overestimations of radon concentration by about 10% due to thoron interference, whereas such interference results were negligible for the fourth CRM. However, the thoron interference can also be used to assess thoron concentration by using CRM not specifically designed to do so. Based on the results of this study, an indirect method to assess thoron concentration is indeed proposed, relying on the combination of two identical monitors (one placed right close to the wall and the other one far enough from there).

Electrostatic precipitation is a well-known technology to reduce public exposure to radon daughters. A custom electrostatic precipitator (ESP) prototype has been designed and built to study the effectiveness of such a removal technique in specific workplaces having low-to-zero air exchange rates with external environments. An appropriate mathematical model has been set up in order to simulate the behavior of environmental and nuclear data throughout the ESP operation, to optimize the design for the prototype to be built, to estimate its effectiveness in terms of effective dose reduction. Reference detectors have been used to measure both the radon concentration and the potential alpha energy concentration of its decay products. After a full calibration procedure, two main experiments have been performed in a room satisfying the requirements of very low ventilation rate and high radon concentration. The effective dose rate after an ESP continuous working period of either 3 h or 5 h turned out to be 50% lower than the value measured before ESP switching ON. The main contribution to dose reduction was found to be given by the first 2 hours of operation.

Protection from radon exposure in workplaces and dwellings, as included in the latest relevant international regulations and recommendations, is based on the new concept of ‘reference level’ whose meaning is significantly different from that of previous ‘action level’ concept. In fact, whereas remedial actions had to be considered only for radon concentrations above the action level, actions to optimise radon exposure are requested with priority above reference level but optimisation should be applied also for radon concentrations below reference level. Similar considerations can be applied to the usually called ‘Rn-prone’ areas, which are here proposed to be regulated as ‘priority’ areas. The main implication of these new challenging concepts is a substantial increase of avertable lung cancer deaths, as it will be shown using Italian data. Some practical examples of possible policy actions fitting an approach based on these new concepts will also be given, which could be useful for the implementation of the Council Directive 2013/59/Euratom.

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 organisations, such as WHO, IAEA, Nordic Countries, European Commission. Within the European project RADPAR, scientists from 18 institutions of 14 European countries worked together for 3 y (2009–12). 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 programme and for countries with little experience on radon issues. In this paper, the main RADPAR recommendations on radon programmes 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.

In recent years, international organisations involved in radiation protection and public health have produced new guidance, recommendations and requirements aiming better protection from radon exposure. These organisations have often worked in close collaboration in order to facilitate the establishment of harmonised standards. This paper deals with such standards and specifically with the new European Council Directive of 5 December 2013 on basic safety standards for protection against the dangers arising from exposure to ionising radiation (2013/59/Euratom). This new Directive has established a harmonised framework for the protection against ionising radiations, including protection from radon exposure. Requirements for radon in workplace are much more tightening than in previous Directive, and exposures to radon in dwellings are regulated for the first time in a Directive. Radon-related articles of this Directive are presented and discussed in this paper, along with some comparisons with other relevant international standards.

In order to optimize the design of a national survey aimed to evaluate radon exposure of children in schools in Serbia, a pilot study was carried out in all the 334 primary schools of 13 municipalities of Southern Serbia. Based on data from passive measurements, rooms with annual radon concentration >300 Bq/m(3) were found in 5% of schools. The mean annual radon concentration weighted with the number of pupils is 73 Bq/m(3), 39% lower than the unweighted 119 Bq/m(3) average concentration. The actual average concentration when children are in classrooms could be substantially lower. Variability between schools (CV = 65%), between floors (CV = 24%) and between rooms at the same floor (CV = 21%) was analyzed. The impact of school location, floor, and room usage on radon concentration was also assessed (with similar results) by univariate and multivariate analyses. On average, radon concentration in schools within towns is a factor of 0.60 lower than in villages and at higher floors is a factor of 0.68 lower than ground floor. Results can be useful for other countries with similar soil and building characteristics. On average, radon concentrations are substantially higher in schools in villages than in schools located in towns (double,on average). Annual radon concentrations exceeding 300 Bq/m3 were found in 5% of primary schools (generally on ground floors of schools in villages). The considerable variability of radon concentration observed between and within floors indicates a need to monitor concentrations in several rooms for each floor. A single radon detector for each room can be used provided that the measurement error is considerable lower than variability of radon concentration between rooms.