Calculation of lifetime lung cancer risks associated with radon exposure, based on various models and exposure scenarios.

The risk of lung cancer mortality up to 75 years of age due to radon exposure has been estimated for both male and female continuing, ex- and never-smokers, based on various radon risk models and exposure scenarios. We used risk models derived from (i) the BEIR VI analysis of cohorts of radon-exposed miners, (ii) cohort and nested case-control analyses of a European cohort of uranium miners and (iii) the joint analysis of European residential radon case-control studies. Estimates of the lifetime lung cancer risk due to radon varied between these models by just over a factor of 2 and risk estimates based on models from analyses of European uranium miners exposed at comparatively low rates and of people exposed to radon in homes were broadly compatible. For a given smoking category, there was not much difference in lifetime lung cancer risk between males and females. The estimated lifetime risk of radon-induced lung cancer for exposure to a concentration of 200 Bq m(-3) was in the range 2.98-6.55% for male continuing smokers and 0.19-0.42% for male never-smokers, depending on the model used and assuming a multiplicative relationship for the joint effect of radon and smoking. Stopping smoking at age 50 years decreases the lifetime risk due to radon by around a half relative to continuing smoking, but the risk for ex-smokers remains about a factor of 5-7 higher than that for never-smokers. Under a sub-multiplicative model for the joint effect of radon and smoking, the lifetime risk of radon-induced lung cancer was still estimated to be substantially higher for continuing smokers than for never smokers. Radon mitigation-used to reduce radon concentrations at homes-can also have a substantial impact on lung cancer risk, even for persons in their 50 s; for each of continuing smokers, ex-smokers and never-smokers, radon mitigation at age 50 would lower the lifetime risk of radon-induced lung cancer by about one-third. To maximise risk reductions, smokers in high-radon homes should both stop smoking and remediate their homes.

A large and feasible national survey representative of population exposure to outdoor gamma radiation in urban areas.

Background: Although data on outdoor gamma radiation are available for many countries, they have generally been obtained with measurements performed in undisturbed environments instead of in urban areas where most of the population lives. Only one large national survey, with on-site measurements in urban areas, has been identified worldwide, probably due to high costs (e.g., personnel and instrumentation) and difficulties in selecting measuring points. Methods: A campaign of outdoor gamma radiation measurements has been carried out in the entire Italian territory. All measurement points were selected at the infrastructures of an Italian telecommunications company as representatives of all the possible situations of outdoor exposure to gamma radiation for population in urban areas. Ten replicates of portable gamma (X) detectors carried out all the measurements. Results: Approximately 4,000 measurements have been performed. They are distributed across 2,901 Italian municipalities, accounting for 75% of the Italian population. The national population-weighted mean of the gamma ambient dose equivalent rate (ADER) is 117 nSv h-1, and it ranges from 62 to 208 nSv h-1 and from 40 to 227 nSv h-1 for 21 regions and 107 provinces, respectively. The average variability at the municipal level, in terms of the coefficient of variation (CV) is 21%, ranging from 3 to 84%. The impact of land coverage and the distance from a building on the outdoor gamma radiation level was assessed with complementary measurements, leading to differences ranging from -40 to 50% and to 50%, respectively. Conclusion: A representative campaign of outdoor gamma dose rate measurements has been performed in Italy, only in urban areas, to assess the exposure effect due to outdoor gamma radiation on the population. It is the largest national campaign in urban areas worldwide, with a total of 3,876 on-site measurements. The land coverage and the distance from surrounding buildings were recognized to strongly affect outdoor gamma radiation levels, leading to high variability within small areas. The collaboration with a company that owns a network of facilities on a national territory as dense as the residing population made this survey feasible and affordable. Other countries might adopt this methodology to conduct national surveys in urban environments.

Thoron Interference on Performance of Continuous Radon Monitors: An Experimental Study on Four Devices and a Proposal of an Indirect Method to Estimate Thoron Concentration.

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).

Cost-effectiveness analysis to assess the protection of workers from exposure to radon at work: A first application to Italian retail shops.

For the implementation of the requirements in the Council Directive 2013/59/Euratom (2013 EUBSS), the cost-effectiveness analysis (CEA) is generally considered a useful tool to compare different radon policies aimed at reducing radon exposure both at home and at work. In the framework of the EU funded RADPAR project, a methodology to perform CEA analysis of radon control in dwellings was developed - and used also for WHO's radon recommendations of 2009 - and it is based on the evaluation of the health effectiveness in terms of life years and/or QALYs (Quality Adjusted Life Years) gained. In this work, starting from the RADPAR model used for dwellings, a so-called RADPAR4workplaces model was developed to carry out CEA focused on reduction of radon exposure at workplaces. In particular, different radon policies in existing workplaces were considered and their cost-effectiveness were estimated, as a case study, for the Italian retail shops located at ground floor. Main results show that a policy that requires remedial actions where radon concentration is above a certain reference level (RL) and that recommends them also below this RL has a good cost-effectiveness ratio and it is more effective than a policy with no provisions for radon levels below RL. In particular, the further implementation of remediation below RL improves the health effectiveness increasing QALYs gained of 20% while cost per QALY increases of only 14%. Finally, promoting the remediation of workplaces below RL, QALYs gained and cost per QALY increase of about 80% and 20%, respectively, if remediation rate rises from 10% to 50% below RL.

National Radon Action Plans in Europe and Need of Effectiveness Indicators: An Overview of HERCA Activities.

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.

A 10-year follow-up study of yearly indoor radon measurements in homes, review of other studies and implications on lung cancer risk estimates.

Uncertainty on long-term average radon concentration has a large impact on lung cancer risk assessment in epidemiological studies. The uncertainty can be estimated by year-to-year radon concentration variability, however few data are available. In Italy a study has been planned and conducted to evaluate year-to-year radon variability over several years in normally inhabited dwellings, mainly located in Rome. This is the longest study of this kind in Europe; repeat radon measurements are carried out for 10 years using LR-115 radon detectors in the same home in consecutive years. The study includes 84 dwellings with long-term average radon concentration ranging from 28 to 636 Bq/m3. The result shows that year-to-year variability of repeated measurements made in the same home in different years is low, with an overall coefficient of variation of 17%. This is smaller than most of those observed in studies from other European countries and USA, ranging from 15% to 62%. Influencing factors that may explain the differences between this study and other studies have been discussed. Due to the low yearly variability estimated in the present 10-year study, a negligible impact on lung cancer risk estimate for the Italian epidemiological study is expected.

Field experience with soil gas mapping using Japanese passive radon/thoron discriminative detectors for comparing high and low radiation areas in Serbia (Balkan Region).

Based on results of fieldwork in the Balkan Region of Serbia from 2005 to 2007, soil gas radon and thoron concentrations as well as gamma dose rates were measured. Campaigns were conducted in two different geological regions: Niska Banja, considered a high natural radiation area, and Obrenovac around the TentB Thermal Power Plant (TPP), a low natural radiation area. Radon and thoron gas measurements were made by using two types of Japanese passive radon/thoron detectors, which included GPS data and gamma dose rates. The concentrations of soil radon gas in Niska Banja ranged from 1.8 to 161.1 kBq m(-3), whereas the concentrations for soil thoron gas ranged from 0.9 to 23.5 kBq m(-3). The gamma dose rates varied from 70 to 320 nGy h(-1). In the TentB area, radon concentration was found to range from 0.8 to 24.9 kBq m(-3) and thoron from 0.6 to 1.9 kBq m(-3). The gamma dose rate ranged from 90 to 130 nGy h(-1). In addition, the natural radioactivity of the soil was investigated at the low background area. The radium and thorium contents in collected soil samples ranged from 23 to 58 and 33 to 67 Bq kg(-1), respectively. As a result of correlation analyses between the measured values, the highest correlation coefficient (R > 0.95) was found for thorium in the soil and the thoron gas concentration.

The radon issue: considerations on regulatory approaches and exposure evaluations on the basis of recent epidemiological results.

Recent epidemiological results have shown consistent statistically significant increases of lung cancer risk due to exposure to radon in dwellings at moderate levels of exposure, and a strong synergism with cigarette smoking. These results are summarized and discussed in relation to their possible implications for the regulatory control of radon and for future policies for the control of radon risk.

Is high indoor radon concentration correlated with specific activity of radium in nearby soil? A study in Kosovo and Metohija.

This paper presents indoor radon concentrations and specific activities of natural radionuclides measured in soils of Kosovo and Metohija. The measurements of radon concentration were performed during two consecutive 6-month periods in two rooms of 63 houses using CR-39 detectors. The annual radon concentration ranged from 30 to 810 Bq m-3 with the average value of 128 Bq m-3. Almost 15% of the houses had radon concentration higher than 200 Bq m-3. The difference between radon concentrations measured in the two 6-month periods was analyzed, showing, as expected, a slightly higher radon concentration in the "winter period" than in the "summer period". The variation between different rooms of the same houses was also analyzed, showing that 20% of the dwellings had a significantly higher radon concentration (>100 Bq m-3) in one room compared to the other (the coefficient of variation ranged up to 96%). The specific activities of natural radionuclides in the nearby soil were determined by gamma spectrometry. The estimated average value (and standard deviation) of 226Ra, 232Th, and 40K specific activities were 32 (13), 35 (16), and 582 (159) Bq kg-1, respectively. The correlation between indoor 222Rn and 226Ra content in soil was investigated. Only a weak correlation was found (Spearman's rho = 0.220) indicating that other factors might affect diffusion and accumulation of radon indoors, as confirmed also by the high variability between the rooms of the same houses.

Residential radon and lung cancer--detailed results of a collaborative analysis of individual data on 7148 persons with lung cancer and 14,208 persons without lung cancer from 13 epidemiologic studies in Europe.

OBJECTIVES: Studies seeking direct estimates of the lung cancer risk associated with residential radon exposure lasting several decades have been conducted in many European countries. Individually these studies have not been large enough to assess moderate risks reliably. Therefore data from all 13 European studies of residential radon and lung cancer satisfying certain prespecified criteria have been brought together and analyzed. METHODS: Data were available for 7148 persons with lung cancer and 14,208 controls, all with individual smoking histories and residential radon histories determined by long-term radon gas measurements. RESULTS: The excess relative risk of lung cancer per 100 Bq/m3 increase in the observed radon concentration was 0.08 [95% confidence interval (95% CI) 0.03-0.16; P=0.0007] after control for confounding. The dose-response relationship was linear with no evidence of a threshold, and it remained significant when only persons with observed radon concentrations of <200 Bq/m3 were included. There was no evidence that the excess relative risk varied with age, sex, or smoking history. Removing the bias induced by random uncertainties related to radon exposure assessment increased the excess relative risk of lung cancer to 0.16 (95% CI 0.05-0.31) per 100 Bq/m3. With this correction, estimated risks at 0, 100, and 400 Bq/m3, relative to lifelong nonsmokers with no radon exposure, were 1.0, 1.2, and 1.6 for lifelong nonsmokers and 25.8, 29.9, and 42.3 for continuing smokers of 15-24 cigarettes/day. CONCLUSIONS: These data provide firm evidence that residential radon acts as a cause of lung cancer in the general population. They provide a solid basis for the formulation of policies with which to manage risk from radon and reduce deaths from the most common fatal cancer in Europe.

A method to evaluate the contribution of building material to indoor gamma dose rate through outdoor measurements: preliminary results.

Building materials can be an important source of exposure to gamma radiation indoors. In situations in which it is impossible to enter the dwellings to measure indoor gamma dose rate, as can happen in epidemiological studies and in surveys on randomly selected dwellings, it is important to obtain accurate and precise estimates of the indoor gamma dose rate. In this paper, preliminary results of a validation study of a new method, named IN-OUT, to estimate the indoor gamma dose rate attributable to the building materials are presented. This method, which is still in progress, is based on outdoor measurements, performed close to an external wall of a dwelling, and on a 'room model' elaboration, which takes into account geometrical and structural characteristics of the dwelling. The validation was performed using data--relevant to 91 dwellings, at present--collected in Latium and Campania within the framework of 'SETIL', the Italian epidemiological study on the aetiology of childhood leukaemia, lymphoma and neuroblastoma.

Results from time integrated measurements of indoor radon, thoron and their decay product concentrations in schools in the Republic of Macedonia.

As part of a survey on concentrations of radon, thoron and their decay products in different indoor environments of the Balkan region involving international collaboration, measurements were performed in 43 schools from 5 municipalities of the Republic of Macedonia. The time-integrated radon and thoron gas concentrations (CRn and CTn) were measured by CR-39 (placed in chambers with different diffusion barriers), whereas the equilibrium equivalent radon and thoron concentrations (EERC and EETC) were measured using direct radon-thoron progeny sensors consisting of LR-115 nuclear track detectors. The detectors were deployed at a distance of at least 0.5 m from the walls as well as far away from the windows and doors in order to obtain more representative samples of air from the breathing zone; detectors were exposed over a 3-month period (March-May 2012). The geometric mean (GM) values [and geometric standard deviations (GSDs)] of CRn, CTn, EERC and EETC were 76 (1.7), 12 (2.3), 27 (1.4) and 0.75 Bq m(-3) (2.5), respectively. The equilibrium factors between radon and its decay products (FRn) and thoron and its decay products (FTn (>0.5 m)) were evaluated: FRn ranged between 0.10 and 0.84 and FTn (>0.5 m) ranged between 0.003 and 0.998 with GMs (and GSDs) equal to 0.36 (1.7) and 0.07 (3.4), respectively.

The newest international trend about regulation of indoor radon.

On the basis of recent epidemiological findings, many international and national organisations have revised their recommendations and regulations on radon exposure in dwellings and workplaces, or are in the process to do it. In particular, new recommendations and regulations were recently published (or are going to be) by World Health Organization, Nordic Countries, International Commission on Radiological Protection, International, Atomic Energy Agency (and the other international organisations sponsoring the International Basic Safety Standards), European Commission. Although with some differences, these new documents recommend lower radon concentrations in indoor air, especially in dwellings, compared with previous ones. Moreover, preventive measures in all new buildings are more and more considered as one of the most cost-effective way to reduce the radon-related lung cancers, compared with previous approach restricting preventive measures in radon-prone areas only. A comprehensive national action plan, involving several national and local authorities, is generally considered a necessary tool to deal with the many complex actions needed to reduce the risk from radon exposure in an effective way.

Radon in workplaces: first results of an extensive survey and comparison with radon in homes.

Extensive radon surveys have been carried out in many countries only in dwellings, whereas surveys in workplaces are rather sparse and generally restricted to specific workplaces/activities, e.g. schools, spas and caves. Moreover, radon-prone areas are generally defined on the basis of radon surveys in dwellings, while radon regulations use this concept to introduce specific requirements in workplaces in such areas. This approach does not take into account that work activities and workplace characteristics can significantly affect radon concentration. Therefore, an extensive survey on radon in different workplaces have been carried out in a large region of Italy (Tuscany), in order to evaluate radon distribution in workplaces over the whole territory and to identify activities and workplace characteristics affecting radon concentration. The results of this extensive survey are compared with the results of the survey carried out in dwellings in the same period. The workplaces monitored were randomly selected among the main work activities in the region, including both public and industrial buildings. The survey monitored over 3500 rooms in more than 1200 buildings for two consecutive periods of ∼6 months. Radon concentration was measured by means of passive nuclear track detectors.

Residential radon exposure, diet and lung cancer: a case-control study in a Mediterranean region.

We performed a case-control study in Lazio, a region in central Italy characterized by high levels of indoor radon, Mediterranean climate and diet. Cases (384) and controls (404) aged 35-90 years were recruited in the hospital. Detailed information regarding smoking, diet and other risk factors were collected by direct interview. Residential history during the 30-year period ending 5 years before enrollment was ascertained. In each dwelling, radon detectors were placed in both the main bedroom and the living room for 2 consecutive 6-month periods. We computed odds ratios (ORs) and 95% confidence intervals (CIs) for time-weighted radon concentrations using both categorical and continuous unconditional logistic regression analysis and adjusting for smoking, diet and other variables. Radon measurements were available from 89% and 91% of the time period for cases and controls, respectively. The adjusted ORs were 1.30 (1.03-1.64), 1.48 (1.08-2.02), 1.49 (0.82-2.71) and 2.89 (0.45-18.6) for 50-99, 100-199, 200-399 and 400+ Bq/m(3), respectively, compared with 0-49 Bq/m(3) (OR = 1; 0.56-1.79). The excess odds ratio (EOR) per 100 Bq/m(3) was 0.14 (-0.11, 0.46) for all subjects, 0.24 (-0.09, 0.70) for subjects with complete radon measurements and 0.30 (-0.08, 0.82) for subjects who had lived in 1 or 2 dwellings. There was a tendency of higher risk estimates among subjects with low-medium consumption of dietary antioxidants (EOR = 0.32; -0.19, 1.16) and for adenocarcinoma, small cell and epidermoid cancers. This study indicates an association, although generally not statistically significant, between residential radon and lung cancer with both categorical and continuous analyses. Subjects with presumably lower uncertainty in the exposure assessment showed a higher risk. Dietary antioxidants may act as an effect modifier.