Relationships between indoor radon concentrations, thermal retrofit and dwelling characteristics

Indoor radon risk mapping of the Canary Islands using a methodology for volcanic islands combining geological information and terrestrial gamma radiation data

Within the framework of the recent approval of the National Plan Against Radon by the Council of Ministers of the Spanish Government, one of its five axes focuses on the delimitation of priority action areas. In line with this objective, this paper presents the indoor radon risk maps of the Canary Islands. Due to the volcanic origin of the Canary Islands, there is a great deal of geological heterogeneity in the soils on which buildings settle, making it very difficult to delimit radon-risk areas in the process of creating maps. Following a methodology developed in previous works for a study area formed of a set of representative municipalities, this paper presents radon risk maps of the Canary Islands based on lithostratigraphic information and high-resolution terrestrial gamma radiation maps. The goodness of fit of these maps is verified based on a statistical analysis of indoor radon concentration measurements carried out at representative building enclosures. In order to analyse the level of risk to the population, these maps were combined with built up areas (urban fabric) maps and estimations of the annual effective doses due to radon was obtained by applying a dosimetric model. This methodology improves the capability to delimit indoor radon risk areas, with a greater margin of safety. In this respect, it is estimated that areas classified as low risk have indoor radon concentrations 41 % below the current reference level of 300 Bq/m3 established by national regulations in compliance with the precepts laid down in the European EURATOM Directive.

Exploring statistical and machine learning techniques to identify factors influencing indoor radon concentration

Radon is a radioactive gas with a carcinogenic effect. The malign effect on human health is, however, mostly influenced by the level of exposure. Dangerous exposure occurs predominantly indoors where the level of indoor radon concentration (IRC) is, in its turn, influenced by several factors. The current study aims to investigate the combined effects of geology, pedology, and house characteristics on the IRC based on 3132 passive radon measurements conducted in Romania. Several techniques for evaluating the impact of predictors on the dependent variable were used, from univariate statistics to artificial neural network and random forest regressor (RFR). The RFR model outperformed the other investigated models in terms of R2 (0.14) and RMSE (0.83) for the radon concentration, as a dependent continuous variable. Using IRC discretized into two classes, based on the median (115 Bq/m3), an AUC-ROC value of 0.61 was obtained for logistic regression and 0.62 for the random forest classifier. The presence of cellar beneath the investigated room, the construction period, the height above the sea level or the floor type are the main predictors determined by the models used.

Oxidative genomic damage in humans exposed to high indoor radon levels in Northeast Brazil

Radon gas inhalation is the main source of exposure to ionizing radiation by humans. There is still lack in knowledge concerning the chronic and indirect effects of exposure to this carcinogenic factor. Therefore, the aim of this work is to analyze the levels of oxidative genomic damage in inhabitants of a medium-high background radiation area (HBRA) (N = 82) in Northeastern Brazil and compare them with people living in a low background radiation area (LBRA) (N = 46). 8-hydroxy-2-deoxyguanosine (8-OHdG) was quantified in urine, Ser326Cys polymorphism was determined in the hOGG1 gene and indoor radon was measured. HBRA houses had 6.5 times higher indoor radon levels than those from LBRA (p-value < 0.001). The 8-OHdG mean (95% confidence interval) were significantly different, 8.42 (5.98-11.9) ng/mg creatinine and 29.91 (23.37-38.30) ng/mg creatinine for LBRA and HBRA, respectively. The variables representing lifestyle and environmental and occupational exposures did not have a significant association with oxidized guanosine concentrations. On the other hand, lower 8-OHdG values were observed in subjects that had one mutant allele (326Cys) in the hOGG1 gene than those who had both wild alleles (Ser/Ser (p-value < 0.05). It can be concluded that high radon levels have significantly influenced the genome oxidative metabolism and hOGG1 gene polymorphism would mediate the observed biological response.

Lung cancer as adverse health effect by indoor radon exposure in China from 2000 to 2020: A systematic review and meta-analysis

Indoor radon exposure is thought to be associated with adverse health effect as lung cancer. Lung cancer incidences in China have been the highest worldwide during the past two decades. It is important to quantitively address indoor radon exposure and its health effect, especially in countries like China. In this paper, we have conducted a meta-analysis based on indoor radon and its health effect studies from a systematic review between 2000 and 2020. A total of 8 studies were included for lung cancer. We found that the relative risk (RR) was 1.01 (95% CI: 1.01-1.02) per 10 Bq/m³ increase of indoor radon for lung cancer in China. The subgroup analysis found no significant difference between the conclusions from the studies from China and other regions. The health effect of indoor radon exposure is relatively consistent for the low-exposure and high-exposure groups in the subgroup analysis. With a better understanding of exposure level of indoor radon, the outcomes and conclusions of this study will provide supports for next phase of researches on estimation of environmental burden of disease by indoor radon exposures in countries like China.

Radon levels and indoor air quality after application of thermal retrofit measures-a case study

This study was conducted to evaluate the influence of thermal retrofit on radon levels in workrooms, and to determine whether the radon concentration in the building changes after the application of retrofit measures. In the first survey, digital Airthings Corentium Home radon detector was used for 1-month radon measurements during the heating season 2018/19. The daily averaged radon concentrations varied from 37 to 573 Bq/m³ for 10 selected workrooms, while hourly averaged radon measurements showed extreme variations from 6 to 1603 Bq/m³ due to radon fluctuations. In second survey, passive radon technique based on charcoal canister test kit was conducted in all basement workrooms in spring 2021. The averaged radon concentrations grouped according to flooring type in workrooms were 327 Bq/m³ for parquet, 227 Bq/m³ for ceramic tiles, 146 Bq/m³ for vinyl flooring and 71 Bq/m³ for laminate. Besides thermal insulation and airtight windows, noticeable differences in indoor radon concentration within the renovated building are primarily caused by different types of flooring. It includes various types of insulation from the ground/concrete slab: laminate, parquet (wood blocks), vinyl flooring, and ceramic tiles. Detailed analysis point out that laminate is more efficient way for radon protection than other types of flooring. An efficient ventilation system should be installed to avoid increasing occupational radon exposure and to provide healthy and comfortable indoor environment.

Active Monitoring of Residential Radon in Rome: A Pilot Study

We present an overview of the potential of active monitoring techniques to investigate the many factors affecting the concentration of radon in houses. We conducted two experiments measuring radon concentration in 25 apartments in Rome and suburban areas for two weeks and in three apartments in the historic center for several months. The reference levels of 300 and 100 Bq/m³ are overcome in 17% and 60% of the cases, respectively, and these percentages rise to 20% and 76% for average overnight radon (more relevant for residents' exposure). Active detectors allowed us to identify seasonal radon fluctuations, dependent on indoor-to-outdoor temperature, and how radon travels from the ground to upper floors. High levels of radon are not limited to the lowest floors when the use of heating and ventilation produces massive convection of air. Lifestyle habits also reflect in the different values of gas concentration measured on different floors of the same building or in distinct rooms of the same apartment, which cannot be ascribed to the characteristics of the premises. However, the finding that high residential radon levels tend to concentrate in the historic center proves the influence of factors such as building age, construction materials, and geogenic radon.

Assessment of Seasonal Radon Concentration in Dwellings and Soils in Selected Areas in Ga East, Greater Accra Region of Ghana

Seasonal radon levels have been studied in dwellings and soils in selected areas in Ga East, Greater Accra Region of Ghana using LR-115-type II (SSNTDs). This study was conducted to determine the seasonal correlation between soil and dwelling radon concentrations. Detectors were exposed from January to March and April to June, for dry and wet seasons, respectively. Overall, indoor radon was 133.4 ± 6.7 Bqm⁻³ and 72.1 ± 3.6 Bqm ⁻³ for wet and dry seasons. The estimated annual effective dose to the lung received by the occupants at Paraku Estate, Dome, and Kwabenya was 6.9 ± 0.4, 7.2 ± 0.5, and 9.8 ± 0.8 mSvy⁻¹ for the wet season and 3.8 ± 0.2, 4.3 ± 0.2, and 4.6 ± 0.3 mSvy⁻¹ for the dry season. On average, the soil radon concentration was found to be 0.96 ± 0.07 kBqm⁻³ and 2.24 ± 0.01 kBqm⁻³ for wet and dry seasons. To determine the correlation between soil and dwelling radon, a positive Pearson correlation coefficient value R = (0.74) and R = (0.66) was obtained representing the dry and wet seasons. To test the statistical significance between soil and dwelling radon, P < 0.05 was obtained, indicating a statically significant relationship between the two.

INDOOR RADON MONITORING IN SELECTED BUILDINGS IN VYDRNÍK (VIKARTOVCE FAULT, SLOVAKIA)

To test the relation of indoor radon concentration to fault zone, a survey was conducted in selected buildings in Vydrník, situated close to the neotectonically active Vikartovce fault trace. Monitoring was performed using RamaRn track detectors during a period of 1 year. Annual average of indoor radon ranged from 60 to 940 Bq/m3, with an average of 160 Bq/m3. Seasonal variation of indoor radon concentration was confirmed, with minimum in summer (June-August). The results confirmed that radon concentration in rooms above the cellar was lower than in rooms with the direct contact with subsoil. High indoor radon up to 940 Bq/m3 was detected only in one of monitored houses situated close to the generally E-W trending Vikartovce fault and can be attributed to this fault zone used as pathway for radon migration. Influence of nearby situated NW-SE trending crosscutting fault on radon concentration is probable too.

A Systematic Review of Associations between Energy Use, Fuel Poverty, Energy Efficiency Improvements and Health

Energy use in buildings can influence the indoor environment. Studies on green buildings, energy saving measures, energy use, fuel poverty, and ventilation have been reviewed, following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The database PubMed was searched for articles published up to 1 October 2020. In total, 68 relevant peer-reviewed epidemiological or exposure studies on radon, biological agents, and chemicals were included. The main aim was to assess current knowledge on how energy saving measures and energy use can influence health. The included studies concluded that buildings classified as green buildings can improve health. More efficient heating and increased thermal insulation can improve health in homes experiencing fuel poverty. However, energy-saving measures in airtight buildings and thermal insulation without installation of mechanical ventilation can impair health. Energy efficiency retrofits can increase indoor radon which can cause lung cancer. Installation of a mechanical ventilation systems can solve many of the negative effects linked to airtight buildings and energy efficiency retrofits. However, higher ventilation flow can increase the indoor exposure to outdoor air pollutants in areas with high levels of outdoor air pollution. Finally, future research needs concerning energy aspects of buildings and health were identified.

Methodology for determination of radon prone areas combining the definition of a representative building enclosure and measurements of terrestrial gamma radiation

The recommendations of the European Atomic Energy Community (EURATOM) have recently been incorporated into Spanish regulations in the Basic Document of Health Standards of the Technical Building Code (CTE), section HS6, on protection against radon exposure. This further accentuates the need to delimit radon prone areas as a strategy to address measures which minimise the effects of this gas on the population. In this research, measurements of terrestrial gamma radiation and indoor radon of dwellings have been carried out in the same location to delimit these risk areas. A new methodology has been developed including a definition of a Representative Building Enclosure (RBE) and it is proposed a Building Storey Index (I_BS) which allows normalizing measurements of indoor radon activity concentration taken in different levels from the ground to the RBE. The results show the need to consider the type of contact that exists between the building and the ground as a determining factor of radon risk. Terrestrial gamma radiation is used as a proxy for radioisotopic composition of soils to characterise the indoor radon risk at different geological formation.

Mapping indoor radon hazard in Germany: The geogenic component

Indoor radon is considered as an indoor air pollutant due to its carcinogenic effect. Since the main source of indoor radon is the ground beneath the house, we utilize the geogenic radon potential (GRP) and a geogenic radon hazard index (GRHI) for predicting the geogenic component of the indoor Rn hazard in Germany. For this purpose, we link indoor radon data (n = 44,629) to maps of GRP and GRHI and fit logistic regression models to calculate the probabilities that indoor Rn exceeds thresholds of 100 Bq/m³ and 300 Bq/m³. The estimated probability was averaged for every municipality by considering only the estimates within the built-up area. Finally, the mean exceedance probability per municipality was coupled with the respective residential building stock for estimating the number of buildings with indoor Rn above 100 Bq/m³ and 300 Bq/m³ for each municipality. We found that (1) GRHI is a better predictor than GRP for indoor radon hazard in Germany, (2) the estimated number of buildings above 100 Bq/m³ and 300 Bq/m³ in Germany is ~2 million (11.6% of all residential buildings) and ~ 350,000 (1.9%), respectively, (3) areas where 300 Bq/m³ exceedance is greater than 10% comprise only 0.8% of the German building stock but 6.3% of buildings with indoor Rn exceeding 300 Bq/m³, and (4) most urban areas and, hence, most buildings (77%) are located in low hazard regions. The implications for Rn protection are twofold: (1) the Rn priority area concept is cost-efficient in a sense that it allows to find the most buildings that exceed a threshold concentration with a given amount of resources, and (2) for an optimal reduction of lung cancer risk areas outside of Rn priority areas must be addressed since most hazardous indoor Rn concentrations occur in low to medium hazard areas.

Spatial and temporal variations in indoor radon concentrations in Pennsylvania, USA from 1988 to 2018

Indoor radon poses one of the most significant environmental threats to public health as it is the second leading cause of lung cancer in the United States. Developing a more thorough understanding of the factors that affect radon concentrations is key for developing risk maps, identifying where testing should be a priority, and education about indoor radon exposure. The objectives of this study are to investigate seasonal and annual variation of indoor radon concentrations in Pennsylvania, USA from 1988 to 2018, to explore the hotspot areas for high indoor radon concentrations, and to analyze the association with various factors such as weather conditions, housing types, and floor levels. Based on a total of 1,808,294 radon tests conducted from 1988 to 2018, we found that 61% of the area (by zip codes), 557,869 tests conducted in the basement and 49,141 tests conducted on the ground floor in homes in Pennsylvania had higher radon levels than the U.S. EPA action level concentration of 148 Bq/m³ (equivalent to 4 pCi/L). Winter and fall had significantly higher indoor radon concentrations than summer and spring. Case studies conducted in Pittsburgh, Philadelphia, and Harrisburg showed that there was no significant correlation of daily temperature, precipitation, or relative humidity with indoor radon concentration on the day a radon test occurred.

The new Austrian indoor radon survey (ÖNRAP 2, 2013-2019): Design, implementation, results

The delineation of radon prone areas is one of the central requirements of the European Council Directive 2013/59/EURATOM. It is quite a complex task which usually requires the collection of radon data through an appropriate survey as a first step. This paper presents the design and methodology of the recent Austrian radon survey (ÖNRAP 2, 2013-2019) and its implementation. It details the results of the nationwide survey as well as correlations and dependencies with geology and building characteristics. The paper also discusses the representativeness of the survey as well as advantages and disadvantages of the selected approach. For the purpose of establishing a new delineation of radon prone areas in Austria we distributed approximately 75,000 passive long-term radon detectors. They were offered to selected members of the voluntary fire brigades and this resulted in about 50,000 radon measurements. Thus, a return rate of about 67% was achieved. The distribution of the radon results closely follows a log-normal distribution with a median of 99 Bq/m³, a geometric mean of 109 Bq/m³, and a geometric standard deviation factor of 2.29. 11% of the households show a mean radon concentration above the national reference level of 300 Bq/m³. Important data on building characteristics and the location of the measured rooms were collected by means of a specific questionnaire and a measurement protocol that were handed out together with the radon detectors. We were able to identify significant correlations between the indoor radon concentration and geology, the year of construction, and the coupling of the room to the ground (basement yes/no, floor level). Being a geographically-based and not a population-weighted survey, the comparison of building characteristics with the Austrian census data confirms that rural areas are over-represented in this survey. As a summary, the selected approach of conducting passive long-term radon measurements in selected dwellings of members of the voluntary fire brigades proved to be an efficient method to collect reliable data as a basis for the delineation of radon prone areas. The next step was to eliminate factors that influence the measured radon concentration through appropriate modelling. Based on the results predicted by the model radon areas are then be classified. This will be presented in a subsequent publication.

Determination of optimal ventilation rates in educational environment in terms of radon dosimetry

INTRODUCTION

New and renovated energy efficient buildings with minimised ventilation rates together with increased building airtightness are often associated with higher indoor radon concentrations compared to the concentrations in existing buildings. The purpose of our study is to analyse the problem associated with the increased radon concentration and ventilation requirements and recommendations in schools. The radon concentration was critically assessed by varying the design ventilation rates (DVRs) within fifteen cases according to legislative requirements and recommendations. The case study is a branch primary school in western part of Slovenia situated in a radon prone area.

METHODS

Radon (²²²Rn) concentrations were simulated in the classroom, using CONTAM 3.2.

PROGRAM

For validation, measurements were performed on 8 measuring days in September and 6 measuring days in March. The simulated and measured ²²²Rn concentrations are well correlated for all measurement days, with the simulated/measured ratio of 0.85-1.39. In order to define optimal DVRs in terms of dosimetry, the effective dose and its ratio to the worldwide average effective dose at workplace, received by radon progeny in 950 h (expected effective dose, 0.13 mSv/y), were calculated for each case.

RESULTS

Simulations showed that the highest radon concentrations were observed in case 1 with a DVR of 79.6 m³/h (621 Bq/m³) and case 4 with a DVR of 69.4 m³/h (711 Bq/m³), both defined by national regulations. The calculated values in both cases exceeded the national reference value for radon (300 Bq/m³) by 2.1 times and 2.4 times, and the WHO guideline value (100 Bq/m³) by 6.2 times and 7.1 times, respectively. The simulations are in line with the results of radon dosimetry. Both DVRs correspond to the highest effective doses, 1.88 mSv/y (about 14-fold higher than expected effective dose) for case 1 and 2.15 mSv/y (about 17-fold higher than expected effective dose) for case 4. Case 11_Cat I with a DVR of 1999.7 m³/h defined by EN 15251: 2007 resulted in minimal Rn concentration (35 Bq/m³) and corresponds to the lowest effective dose 0.11 mSv/y and its ratio to the expected effective dose 0.8.

CONCLUSIONS

Ventilation is an immediate measure to reduce radon concentration in a classroom and it must be performed in line with other holistic measures to prevent and control radon as a health risk factor.

Radon concentration in conventional and new energy efficient multi-storey apartment houses: results of survey in four Russian cities

During last decades, energy saving in new buildings became relevant within the energy efficiency strategies in various countries. Such energy efficient building characteristics as air tightening and low ventilation can compromise indoor air quality, in particular, increase radon concentration. In Russia, a significant part of the new buildings is the energy efficient multi-storey apartment houses. The aim of this study is to assess the significance of possible radon concentration increase in new energy efficient buildings in comparison with typical conventional multi-storey houses of previous periods. Radon surveys were conducted in Russian cities Ekaterinburg, Chelyabinsk, Saint-Petersburg and Krasnodar. The radon measurements were carried out in 478 flats using CR-39 nuclear track detectors. Energy efficiency index (EEI) was assigned to each house. All buildings were divided into six main categories. The smallest average radon concentration was observed in panel and brick houses built according to standard projects of 1970–1990 (four-city average 21 Bq/m³). The highest average radon concentration and EEI were observed in new energy efficient buildings (49 Bq/m³). The trend of radon increase in buildings ranked with high EEI index is observed in all cities. The potential increase of radiation exposure in energy-efficient buildings should be analyzed taking into account the principles of radiological protection.

The relationship of indoor radon gas concentration with multiple sclerosis: a case-control study

This case-control study aimed to investigate the relationship of indoor radon gas concentration and residential building characteristics with mental health with multiple sclerosis (MS) in Yazd City, Iran. The participants included 45 patients with MS and 100 healthy individuals. The participants' socio-economic status and residential building characteristics were investigated using a questionnaire. The radon gas concentration was also measured by CR-39 detectors over a 6-month period. Furthermore, the participants' mental health data were collected using General Health Questionnaire (GHQ-28). The mean concentrations of radon gas were 66.77 and 65.33 Bq/m³ in the homes of patients with MS and healthy individuals, respectively, but the difference was not significant (p = 0.882). However, the radon gas concentration had a significant relationship with the building's age (p = 0.038), ventilation (p = 0.053), and cooling system (p = 0.021). A significant difference was observed between the two study groups in terms of the mental health (p = 0.018), depression (p = 0.037), somatic symptoms (p ≤ 0.001), and physical activity (p = 0.030). Since the indoor radon gas concentration did not have any significant relationship with MS prevalence, more studies are required in this regard, especially in long-term exposure.

Radon Investigation in 650 Energy Efficient Dwellings in Western Switzerland: Impact of Energy Renovation and Building Characteristics

As part of more stringent energy targets in Switzerland, we witness the appearance of new green-certified dwellings while many existing dwellings have undergone energy efficiency measures. These measures have led to reduced energy consumption, but rarely consider their impact on indoor air quality. Consequently, such energy renovation actions can lead to an accumulation of radon in dwellings located in radon-prone areas at doses that can affect human health. This study compared the radon levels over 650 energy-efficient dwellings in western Switzerland between green-certified (Minergie) and energy-renovated dwellings, and analyzed the building characteristics responsible of this accumulation. We found that the newly green-certified dwellings had significantly lower radon level than energy-renovated, which were green- and non-green-certified houses (geometric mean 52, 87, and 105 Bq/m3, respectively). The new dwellings with integrated mechanical ventilation exhibited lower radon concentrations. Thermal retrofitting of windows, roofs, exterior walls, and floors were associated with a higher radon level. Compared to radon measurements prior to energy renovation, we found a 20% increase in radon levels. The results highlight the need to consider indoor air quality when addressing energy savings to avoid compromising occupants’ health, and are useful for enhancing the ventilation design and energy renovation procedures in dwellings.

In Situ Measurements of Energy Consumption and Indoor Environmental Quality of a Pre-Retrofitted Student Dormitory in Athens

In the following years all European Union member states should bring into force national laws on the energy performance of buildings. Moreover, university campus dormitories are buildings of great importance, due to their architectural characteristics and their social impact. In this study, the energy performance along with the indoor environmental conditions of a dormitory of a university has been analysed. The in situ measurements included temperature, relative humidity, concentrations of carbon dioxide, total volatile organic compounds, and electrical consumption; lastly, the energy signature of the whole building was investigated. The study focused on the summer months, during which significantly increased thermal needs of the building were identified. The ground floor was found to be the floor with the highest percentage of thermal conditions within the comfort range, and the third floor the lowest. Lastly, a significant correlation between electrical consumption and the outdoor temperature was presented, highlighting the lack of thermal insulation. Overall, it was clear that a redesign of the cooling and heating system, the installation of a ventilation system, and thermal insulation are essential for improving the energy efficiency of this building.