Indoor 222Rn Research Articles

Measurement of indoor radioactivity and dose derived from 222Rn, 220Rn and EECs by using SSNTD based technique.

Alpha flux radiated from 222Rn, 220Rn and progeny is the primary contributor of natural radioactivity to the inhabitants in the ambient atmosphere. The annual indoor 222Rn and 220Rn concentrations were found to be 85±43 and 84±36Bq m-3, respectively. The estimated annual indoor 222Rn and 220Rn concentration is below to reference value of 100Bq m-3 suggested by WHO. The calculated annual inhalation dose due to exposure to the alpha flux of 222Rn, 220Rn and their progeny is well below the recommended reference level given by UNSCEAR and ICRP. The data were further checked for normalisation and found that 222Rn and Effective Equilibrium Radon Concentration (EERC) data are not normally distributed.

Lithological Impact on Radon Levels: A Study of Indoor and Soil Gas Radon in the Centre Region of Cameroon

AbstractThe objectives of the current study are to carry out soil gas radon (Rn) measurements, to evaluate the total inhalation effective dose, to determine risk levels over the lithological formations of the study area. The behavior investigation of Rn activity concentration distributions in dwellings and soils, and soil Rn mapping were also conducted. Soil gas Rn measurements were made at 102 sampling points by Markus 10 instrument. This data was combined with previously reported results from 140 indoor Rn RADTRAK dosimeters to determine the total inhalation effective dose and to conduct a statistical analysis. Overall, the Rn activity concentrations in soil and dwellings range from 4 to 66 kBq m−3 and from 15 to 140 Bq m−3, with averages of 31 ± 15 kBq m−3 and 41 ± 24 Bq m−3 respectively. The corresponding total inhalation effective dose ranges from 0.35 to 3.53 mSv y−1, with a mean value of 1.37 ± 0.58 mSv y−1. For soil gas Rn, the chlorite schist lithology showed the highest average concentration level. Which could be justified by the possible presence, within chlorite minerals, highly emitting zones of alpha particles, leading to the formation of radioactive halos. Normal and high‐risk level of Rn were found for about 82% and 11% of the total area surveyed respectively. These findings highlight the need for preventive measure against Rn exposure in homes within the investigated areas. This study contributes valuable insights into Rn distribution patterns and risk assessment, offering a basis for targeted interventions in the region.

Seasonal variation of background counting rates in liquid scintillation counting

A liquid scintillation background sample was measured daily in a custom-built TDCR counter for more than 17 months. The double and triple coincidence counting rates exhibit an annual sinusoidal fluctuation with a maximum in winter and a minimum in summer. Possible correlations with air temperature, air humidity, radon concentration and secondary cosmic radiation were investigated. The observation of a correlation with the ambient dose equivalent rate H˙*(10)SCR originating from the charged component of secondary cosmic radiation and an anti-correlation with the effective atmospheric temperature Teff suggest that the seasonal fluctuations in the background counting rate may be primarily driven by temporal variations in the muon flux at ground level. Additionally, a correlation was found with the indoor 222Rn concentration in air.

Study on the effect of Fresh Air Ventilation system for reducing indoor 222Rn

ObjectiveTo explore the reduction effect for the indoor 222Rn (Rn) by Fresh Air Ventilation (FAV) system, a novel commercial ventilation device in China. MethodsThe indoor concentrations of Rn and its decay products (RnD) in three residential rooms, two in Beijing and one in Hefei city, Anhui province, before and after FAVS functioned were measured using an active continuous method. The air exchange rate was monitored by measuring CO2 concentration using the tracer gas method. ResultsIn the three rooms, the FAVS reduced the Rn concentrations from (162 ​± ​80) Bq/m3 to (63 ​± ​22) Bq/m3 and decreased the RnD concentrations from (64 ​± ​35) Bq/m3 to (13 ​± ​6) Bq/m3 on average, a decrease of (59 ​± ​25)% in the Rn concentrations and a drop of (77 ​± ​18)% in the RnD concentrations. Considering dose conversion factors of Rn and RnD, FAVS decreased the exposure dose by (76 ​± ​20)%. Besides, FAVS increased the air exchange rates from 0.17 h−1 to 0.56 h−1 on average. ConclusionsFAVS can effectively reduce indoor Rn and RnD concentrations by improving the air exchange, serving as a valuable supplement to existing radon mitigation methods, especially in extreme climates.

222Rn and progeny concentrations and equilibrium factor (F) in different types of dwellings typical of the west coast region of India

Monitoring of 222Rn, its progeny concentrations, and their diurnal variations in living environments are important for inhalation dose assessment. In this study, the indoor 222Rn and progeny concentrations were measured in dwellings constructed with different types of flooring, walls, and roofing materials. The ionization-chamber-based AlphaGuard and DRPS-based flow mode integrated samplers were used for the 222Rn and its progeny measurements respectively. Higher 222Rn concentration values were recorded in the dwelling with marble floor and the lower in the dwelling constructed using concrete blocks. The equilibrium factors (F) for different dwellings ranged from 0.28 to 0.54. The study highlights the importance of evaluating the specific value of the equilibrium factor for accurate dose assessment.

Preliminary Population Exposure to Indoor Radon and Thoron in Dhaka City, Bangladesh

Radon, an element of natural radiation, is considered one of the leading causes of lung cancer worldwide. In Bangladesh, radon has been clarified as a foremost source of radiation exposure. Potential natural-radiation-induced elevated cancer risks were estimated in Bangladesh previously for the population. In this survey, as a very preliminary study in the country, comparative indoor radon (222Rn, Rn) and thoron (220Rn, Tn) concentration/population exposure was determined for the multistoried dwellings of south-western areas of Dhaka city. RADUET was used to assess annual Rn and Tn concentrations in determining the primary inhalation dose for the population. The annual effective dose of Rn and Tn was evaluated in this study for dwellings at 0.3 mSvy−1, constituting a Tn dose contribution of an average of 40% with a dwelling-based wide range of 10–96%. Thus, Tn should not be neglected for Bangladesh while estimating radiological inhalation dose from the indoor environment. Again, the equilibrium factors, F of Rn and Tn, were determined by short-term measurement at averages of 0.6 and 0.02, respectively. Furthermore, using questionnaire estimation by principal component analysis, PCA following the dwelling characteristics, human lifestyles, and estimated long-term indoor Rn and Tn concentrations, this paper discussed indoor atmospheric/Rn factors for the investigated multistoried dwellings in Dhaka city.

Estimation of Indoor 222Rn Concentration in Lima, Peru Using LR-115 Nuclear Track Detectors Exposed in Different Modes

Radon is the main source of natural radioactivity, and its measurement is considered extremely important in radioprotection, given its relationship with the occurrence of lung cancer. In the last two years, measurements of this radioactive gas were carried out in Lima considering a grid of 5 km2 and the population density to determine the number of measurements to be carried out. Cellulose nitrate nuclear track detectors exposed in bare mode and diffusion chamber mode were used to estimate 222Rn concentrations. In diffusion chamber mode, non-commercial monitors and commercial monitors were used. The monitoring results are presented for 43 districts of the Lima Province whose population is approximately ten million inhabitants occupying a total area of 2655.15 km2. Measurements were made obtaining an average concentration of 49 Bq·m−3 using bare detectors and 66 Bq·m−3 using non-commercial diffusion chambers. Average concentrations obtained by both detector exposure modes were below the maximum concentration recommended by the WHO. A radon (222Rn) map was also obtained as a visual representation of the 222Rn levels in the Lima province using inverse distance weighting (IDW) interpolation.

Evaluation of indoor 222Rn and 220Rn concentrations in Dakshina Kannada, Karnataka, India

Naturally occurring radioactive gases which tend to build up (radon and thoron) in indoor environs can cause deleterious health effects including the development of lung cancer. The present study aims to measure 222Rn and 220Rn levels in dwellings in different seasons in the environs of Dakshina Kannada region of India. The 222Rn and 220Rn concentrations were measured in the monsoon, autumn, winter, and summer seasons using Solid State Nuclear Track Detector (SSNTD, LR-115 type II) films fixed in single-entry pinhole cylindrical twin-cup dosimeters. The higher 222Rn levels in indoors were observed during winter with an average concentration of 38.8Bqm-3 and lower during summer with an average of 14.1Bqm-3. The average indoor thoron concentration was also highest in winter with an average value of 25.5Bqm-3 and lowest in summer with 8.8Bqm-3. The annual inhalation dose ranged from 0.44 to 1.06mSvyear-1 with a mean value of 0.66mSvyear-1. The annual effective dose varied from 1.03 to 2.57mSvyear-1 with an average value of 1.59mSvyear-1. The assessed values have been contrasted with the limit suggested by the UNSCEAR and the ICRP and were found to be within the permissible level. The normality of frequency distribution curves of 222Rn and 220Rn concentrations was assessed by the Kolmogorov-Smirnov test.

Understanding Seasonal Indoor Radon Variability from Data Collected with a LoRa-Enabled IoT Edge Device

The long-term assessment of radon (Rn) is a critical factor in evaluating the exposure risk faced by building occupants, and it plays a significant role in determining the implementation of Rn remediation strategies aimed at enhancing indoor air quality (IAQ). Meteorological parameters, such as temperature, relative humidity, and atmospheric pressure, as well as geological factors, such as soil properties, uranium content, rock formations, parent rock weathering, and water content, can significantly impact the assessment of Rn exposure risk and the selection of appropriate mitigation measures. A continuous monitoring campaign of a National Architectural Heritage building serving as a museum open to the public for a period of 546 consecutive days was conducted. The results of the in situ investigation revealed a broad range of seasonality in indoor Rn emission, with a negative correlation observed between Rn concentration and air temperature. The data indicated that indoor Rn concentration increases in the winter months as a result of reduced indoor air temperature and decreased air exchange, while it decreases in the summer months due to increased air temperature and enhanced natural ventilation. However, the implementation of high ventilation rates to improve IAQ may result in significant heat losses, thereby affecting the thermal comfort of building occupants during the winter months. Therefore, it is imperative to achieve a balance between ventilation practices and energy efficiency requirements to ensure both IAQ and thermal comfort for building occupants.

Long-term vs. short-term measurements in indoor Rn concentration monitoring: Establishing a procedure for assessing exposure potential (RnEP)

Radon (Rn-222 or Rn) is a naturally occurring chemical element that belongs to the progeny of U-238 released from soil and rocks into the atmosphere, whose impact on organisms is not negligible when it occurs inside confined spaces, such as mine shafts or low-ventilated buildings. The current methodologies for indoor radon assessment are based on passive and active detection. If passive detectors are mainly designed for long-term assessment, active detectors are electronic equipment that can allow on-time visualization of results and, therefore, faster decision-making on risk mitigation measures implementation. However, despite offering a prompt and informed decision, the uncertainty associated with active detector results may cast doubt on the quality of the measurements, which especially arises from the duration of the monitoring campaign. Since radon emanation from soils and rocks depends on a set of variables related to meteorological parameters and soil structure, the seasonal variation of these parameters impacts indoor radon concentration assessment, both on short-term and long-term measurements. Therefore, short-term monitoring campaigns lasting a month, a week, or a day may not produce a statistically representative description of indoor radon exposure for the monitored building. Accordingly, the study compares the reliability of short-term and long-term indoor radon measurements. It proposes a procedure for assessing the indoor Radon Exposure Potential (RnEP) based on in situ measurements through the analysis of the frequency of occurrence of results divided into three classes of potential exposure (low, moderate and high) to reduce occupants' radon risk exposure.

High Indoor Rn Concentration Mitigation in a Heritage Building: Case Study Analysis of the Applied Constructive Measures

Indoor radon (Rn) concentration is pointed out by the World Health Organization (WHO) as the second leading cause of lung cancer. Adopting mitigation measures based on ventilation procedures is an effective solution for most cases. However, the occurrence of abnormal concentrations of indoor Rn in heritage buildings, where most interventions are restricted, may lead to alternative remediation techniques. In these cases, constructive mitigation measures, such as the use of barrier membranes on the floor or specific coating mortars on the walls, can be adequate solutions. In the current investigation, two constructive measures were applied and analyzed sequentially. The preliminary long-term monitoring campaign registered extremely high indoor Rn concentration measurements. The application of a barrier membrane covering the floor of the test compartment allowed a 90% reduction in the average Rn concentration, but it nevertheless remained substantially above the recommended value of 300 Bq·m−3. Subsequently, a coating mortar was applied on the walls. The combined measures contributed to a total reduction of 94% in the average indoor Rn concentration, which remains slightly above the recommended exposure limit. Despite the verified reduction and the apparent effectiveness of the measures, it is still necessary to carry out more monitoring campaigns to test their general applicability.

Study of correlation between radon (222Rn) gas in soil and indoor radon with dose assessment in the bauxite bearing area of Fongo-Tongo, Western Cameroon

ABSTRACT The aim of the current work is to study the correlation between 222Rn gas in soil and indoor 222Rn concentrations. Markus 10 and RADTRAK detectors were used to measure 222Rn concentrations at 1 m depth in soil 30 points and 50 dwellings respectively. These concentrations varied from 35 kBq m−3 to 255 kBq m−3 with a geometric mean of 67 (18) kBq m−3, and from 85 Bq m−3 to 410 Bq m−3, with a geometric mean of 152 (26) Bq m−3 respectively in the soil gas and dwellings. In additional, 99% of the measurement points had concentrations higher than the limit value of 40 kBq m−3 according to the Swedish criterion for risk levels; 94% of the houses had radon concentrations higher than 100 Bq m−3, the reference value of the World Health Organization (WHO). When there was not a good air flow between the outside and the inside of the dwelling, the correlation coefficients were R2 = 0.82 and R2 = 0.73 respectively for the earthen and concrete dwellings. Under the best natural ventilation conditions, these correlation coefficients decrease significantly. Their values were R2 = 0.54 and R2 = 0.34 respectively for the earthen and concrete dwellings. Furthermore, a RadonEye +2 detector revealed a daily 222Rn accumulation reaching values of 800 Bq m−3 in some dwellings when all doors and windows were closed. Architecturally, dwellings built with sealed materials such as cement and concrete, whose do not facilitate 222Rn diffusion and transport, have lower 222Rn concentrations and effective dose than others These results show that 222Rn gas in soil and in confined air in dwellings are strongly correlated.

Investigation of indoor 222Rn, 220Rn and their progeny in Punjab, northwestern India

Investigation of indoor 222Rn, 220Rn and their progeny in Punjab, northwestern India

Radon and thoron concentrations in the southwest region of Angola: dose assessment and implications for risk mapping.

Indoor radon (222Rn) and thoron (220Rn) are the most important natural sources of ionizing radiation to the public. Radiological studies that assess simultaneously 222Rn and 220Rn, and their controlling factors are particularly scarce in African countries. Hence, we conducted a survey of indoor 222Rn and 220Rn in buildings located in the SW region of Angola. Bedrock samples were also collected, and a borehole was executed to assess 226Ra and 224Ra activity concentration, 222Rn and 220Rn exhalation and emanation potential in the surface and at depth. The aim of this study was to determine the factors (geological and anthropogenic) that may influence the annual inhalation dose (AID) received by the population. Overall, the sum of indoor radon and indoor thoron concentrations, labelled the total indoor radon concentration (TIRC), was higher than 300Bq/m3 in only 5% of the buildings studied. The contribution of 220Rn to the TIRC averaged 35% but may reach 95%, demonstrating the relevance of discriminating radon and thoron in indoor radon surveys. Indoor 222Rn and 220Rn were not correlated, indicating both must be estimated to properly assess the AID. Indoor 220Rn concentrations were statistically different according to the building materials and type of usage. Higher 222Rn and 220Rn concentrations were observed in dwellings compared to workplaces. The median AID estimated for dwellings was 1.50mSv/y compared to 0.26mSv/y for workplaces, which are lower than the estimated average radiation exposure due to natural sources of 2.4mSv/y. AID values higher than 1mSv/y effective dose threshold established in the Council Directive 2013/59/EURATOM for the purpose of radiation protection in workplaces were observed in 12% of the workplaces studied suggesting the need for mitigation measures in those buildings. The analysis of bedrock samples revealed statistically significant correlations between 224 and 226Ra activity concentration, and 220Rn and 222Rn exhalation and emanation potential. The borehole samples indicated a strong influence of weathering processes in the distribution of radioisotopes. The highest 226Ra and 224Ra activity concentration, and 222Rn and 220Rn exhaled per unit mass, TIRC and AID were observed in association with A-type red granites and porphyries. We conclude that both geological and anthropic factors, such as the type of building usage and building materials, must be considered in dose assessment studies and for the development of risk maps.

On harmonization of radon maps

Background: Maps are important tools for geographic visualization of the state of the environment with respect to resources as well as to hazards. One of the hazards is indoor radon (Rn), believed to be the most important cause of lung cancer after smoking. In particular, as part of Rn mitigation policy and in compliance with the European Basic Safety Standards, EU Member States have to declare areas with elevated indoor Rn concentration levels. However, as this is done by national authorities according to individually chosen criteria, the resulting maps are not easily comparable.
 Objective: We aim to identify causes for the lack of compatibility of maps and suggest solutions for the problem.
 Design: This study draws from experiences of recent research projects, literature, and personal involvement of the authors in the discussions.
 Results: An overview is given on causes and effects of lack of compatibility between maps. Existing experiences are reported. Options for defining lack of compatibility and for identifying it are discussed. Methods for harmonization, that is, remediating lack of compatibility, are addressed.
 Conclusions: The difficulty of harmonization increases with the aggregation level of data which support maps. Harmonization is the more difficult, the higher aggregated the data are which support maps. In particular, harmonization of radon priority area maps is technically non-trivial, and theoretical efforts as well as practical tests will have to be undertaken.

Radiation exposure due to 222Rn, 220Rn and their progenies in three metropolises in China and Japan with different air quality levels

Radiation exposure due to radon contributes most of the ionizing radiation exposure to people among natural radiation sources. This research measured the 222Rn, 220Rn by the RADUET and their progeny concentrations by the improved deposition based 222Rn and 220Rn progeny monitor, and the contribution of outdoor PM2.5 concentrations to indoors by a modified steady-state mass balance model in Beijing, Changchun, China and Aomori, Japan. Based on these results, we preliminarily explored the relevance between the city level outdoor PM2.5 exposure and indoor 222Rn, 220Rn inhalation exposure in these three metropolises with different air quality levels. The average equilibrium equivalent radon concentration (EERC) and equilibirum equivalent thoron concentration (EETC) indoor were 17.2 and 1.1 Bq m−3 in Beijing, 19.4 and 1.3 Bq m−3 in Changchun, and 10.8 and 0.9 Bq m−3 in Aomori, respectively. The indoor EERC and EETC in Beijing showed 1.4 and 2.2 times as high as that measured in 2006. The indoor radiation dose due to inhalation presented in a descending order as Changchun, Beijing and Aomori, which were in accordance with their outdoor 222Rn concentrations. The indoor radiation doses due to 220Rn contributed 30% of the total dose in the three cities, indicating that 220Rn cannot be neglected when evaluating indoor radiation dose. It should be noted that, the indoor PM2.5 concentrations of outdoor origin presented strong correlation (r = 0.772) with indoor EETC and moderate correlation (r = 0.663) with indoor EERC, indicating that the PM2.5 of outdoor origin can break the concentration balance of the indoor PM2.5, then affect the indoor 222Rn and 220Rn behaviors, and further affect the inhalation exposure of radon.

Radon Hazard in Central Italy: Comparison among Areas with Different Geogenic Radon Potential.

Radon (222Rn) is a natural radioactive gas formed in rocks and soil by the decay of its parent nuclide (238-Uranium). The rate at which radon migrates to the surface, be it along faults or directly emanated from shallow soil, represents the Geogenic Radon Potential (GRP) of an area. Considering that the GRP is often linked to indoor radon risk levels, we have conducted multi-disciplinary research to: (i) define local GRPs and investigate their relationship with associated indoor Rn levels; (ii) evaluate inhaled radiation dosages and the associated risk to the inhabitants; and (iii) define radon priority areas (RPAs) as required by the Directive 2013/59/Euratom. In the framework of the EU-funded LIFE-Respire project, a large amount of data (radionuclide content, soil gas samples, terrestrial gamma, indoor radon) was collected from three municipalities located in different volcanic districts of the Lazio region (central Italy) that are characterised by low to high GRP. Results highlight the positive correlation between the radionuclide content of the outcropping rocks, the soil Rn concentrations and the presence of high indoor Rn values in areas with medium to high GRP. Data confirm that the Cimini–Vicani area has inhalation dosages that are higher than the reference value of 10 mSv/y.

Measurement of indoor 222Rn, 220Rn and decay products along with naturally occurring radionuclides in some monuments and museums of Punjab, India

Measurement of indoor 222Rn, 220Rn and decay products along with naturally occurring radionuclides in some monuments and museums of Punjab, India

Estimation of natural gas contribution in indoor 222Rn concentration level in residential houses

Estimation of natural gas contribution in indoor 222Rn concentration level in residential houses

Predictors of indoor radon levels in the Midwest United States

ABSTRACT Radon (Rn) is a natural and toxic radioactive gas that accumulates indoors, mainly in low-ventilated underground floors and basements. Several factors make prediction of indoor Rn exposure in enclosed spaces challenging. In this study, we investigated the influence of soil, geology, topography, atmospheric variables, radiation, urbanization, community economic well-being, and monthly and yearly variations on indoor Rn concentrations. We analyzed 7,515 monthly indoor Rn measurements in 623 zip codes from two U.S. States (Michigan and Minnesota) during 2005–2018 using a random forest model. Using Shapley Additive exPlanations (SHAP) values we investigated the contribution of each factor using variable importance and partial dependence plots. Factors that predict indoor Rn differed between states, with topographical, geological and soil composition being most influential. Cross-validated Pearson correlation between predictions and measurements was 0.68 (RMSE = 47.8 Bq/m3) in Minnesota, and 0.67 (RMSE = 52.5 Bq/m3) in Michigan. Our results underline the importance of soil structure for radon exposure, presumably due to strapped Rn in soil. The differences across states also suggest that Rn studies performing model development should consider geographical variables, along with other factors. As indoor Rn levels are multifactorial, an understanding of the factors that influence its emanation and build up indoors will help better assess spatial and temporal variations, which will be useful to improve prevention and mitigation control strategies. Implications: Radon exposure has become a year-round problem as people spend most of their time indoors. In North America, radon exposure is increasing over time and awareness related to its health effects remains low in the general population. Several factors make prediction of indoor radon exposure in enclosed spaces challenging. In this study, we used random forest to investigate the influence of factors on indoor radon in the Midwest United States. We found that topography, geology, and soil composition were the most influential factors on indoor radon levels. These results will help better assess spatial and temporal variations, which will further help better prevention and mitigation control strategies.