Radon exhalation from building materials for decorative use

Assessment of the Radioactivity, Metals Content and Mineralogy of Granodiorite from Calabria, Southern Italy: A Case Study

In this paper, an assessment of the natural radioactivity level, radon exhalation, metal contamination, and mineralogy of a granodiorite rock sample from Stilo, in the Calabria region, Southern Italy is presented as a case study. This rock was employed as a building material in the area under study. The specific activity of 226Ra, 232Th and 40K natural radioisotopes was assessed through high-purity germanium (HPGe) gamma-ray spectrometry. Then, several indices such as the absorbed gamma dose rate (D), the annual effective dose equivalent (AEDE), the activity concentration index (ACI) and the alpha index (Iα), were quantified to determine any potential radiological health risk related to radiation exposure from the analyzed rock. Furthermore, E-PERM electret ion chambers and inductively coupled plasma mass spectrometry (ICP-MS) measurements were carried out to properly quantify the radon exhalation rate and any possible metal pollution, respectively. In particular, to further address metal pollution factors, the geo-accumulation index (Igeo) was calculated to properly address the toxicity levels of the ecosystem originating from the detected metals. Finally, with the aim of successfully discriminating the provenance of such naturally occurring radionuclides, a combined approach involving X-ray diffraction (XRD) and µ-Raman spectroscopy was employed for the identification of the main radioisotope-bearing minerals characterizing the investigated granodiorite. The results achieved in this case study can be taken as the basis for further inquiries into background levels of radioactivity and chemical contamination in natural stone employed as building materials.

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.

Study of the effect of temperature and water content on radon exhalation from phosphate using LR-115 detectors

A study of the influence of moisture content on the radon exhalation rate from phosphate samples (with and without consideration of the back diffusion effect) was performed using the sealed cup technique. The mass exhalation rate was found to increase with an increase in moisture content, reaching a maximum value of 2.414 ± 0.034 Bq kg-1 h-1 with a moisture content of 10%. However, the mass exhalation rate decreased with a continued increase in moisture content above 25%. The mass exhalation rate was also measured at different temperatures between -10 and 50°C. The obtained results show that the mass exhalation rate increases linearly with temperature. We point out that all the obtained values of radon exhalation rate are lower than the world average radon exhalation rate (57.6 Bq m-2 h-1).

Comparison of Indoor Radon Reduction Effects Based on Apartment Housing Ventilation Methods

A lack of ventilation in multi-unit dwellings can affect human health adversely owing to accumulated radon gases; therefore, developing immediate and effective methods to reduce radon gas in indoor living environments is urgently needed. Therefore, this study conducted a basic research study to develop ventilation guidelines for radon through assessments of various ventilation strategies on indoor radon concentration in multiple-unit dwellings, a typical residential type in Korea. Radon measurement was conducted in November 2020 using RAD 7 Radon Detector (Durridge Co., Billerica, MA, USA) for living rooms and rooms of an apartment located in Uijeongbu, Gyeonggi-do, Korea. The radon reduction effect according to the ventilation conditions per hour was compared and evaluated by performing seven natural ventilation scenarios through opening and closing windows leading to the outside and three types of mechanical ventilation with high, middle, and low operating intensity. The concentration ratio (Cr) was estimated to present the indoor radon increase/decrease ratio. Among the natural ventilation scenarios, Case 3 had the highest radon reduction rate in the living room and Case 1 in the room, and Case 2 using natural ventilation equipment showed the lowest reduction rate in both the room and the living room. When ventilated by mechanical ventilation conditions, the radon reduction rate (Pr) was 70% or less under all conditions. Under the natural ventilation measurement condition, when every doors and windows was opened, it showed an effective ventilation in a short time. With high mechanical ventilation, the radon reduction effect in a relatively large space was better. Additionally, with middle and low mechanical ventilation, the reduction effect seems to be good in a relatively narrow space.

Health Hazards Assessment and Geochemistry of ElSibai-Abu ElTiyur Granites, Central Eastern Desert, Egypt

In this paper, a thorough radio- and chem-ecological evaluation of ElSibai-Abu ElTiyur granites located within Egypt’s crystalline basement rocks was conducted for risk and dose assessments. Twenty granitic samples from the study area’s various lithological units were analyzed using high-resolution γ-ray spectrometry to determine the natural radioisotopes (U-238, Th-232, and K-40) concentrations. The average concentrations of U-238, Th-232, and K-40 were 38.72, 38.23, and 860.71 Bq/kg, respectively, exceeding the GAV (global average value) documented by UNSCEAR (Scientific Committee on the Effects of Atomic Radiation, Vienna, Austria). The radiological parameters and indices judging the usage of ElSibai-Abu ElTiyur granites in homes were computed. The obtained results showed that ElSibai-Abu ElTiyur granites are safe to be used by inhabitants as superficial building materials, as per the globally accepted values and the recommended safety limits approved by UNSEAR, WHO (World Health Organization, Geneva, Switzerland), ICRP (International Commission on Radiological Protection, Ottawa, ON, Canada), and EC (European Commission, Luxembourg). Further, the samples were subjected to ICP-MS (inductively coupled plasma mass spectrometry) analysis for quantifying radionuclide variations with chemical composition. Geochemically based on the ICP-MS results, the studied granites proved to be highly evolved A-type granites. They span the metaluminous to peralkaline fields. The REE patterns are characterized by the enrichment of the light rare earths (LREE) over the heavy ones (HREE) where (La/Yb)n = 5.2, (Gd/Yb)n = 1.63 with pronounced negative Eu-anomalies (Eu/Eu*)n = 0.49. The albite granite exhibits the highest concentrations of Ga, Nb, Ta, U, and Y, and REE (Gd, Dy, Ho, Yb) than the Na-metasomatic granites. Finally, the obtained data serve as a valuable future database for finding out the compatibility of the geochemical data with the natural radioactivity levels of granites.

Interaction of MS prevalence, radon gas concentration, and patient nutrition: a case-control study

In general, ecological findings indicate a positive correlation between MS and the intake of certain foods. This study aimed to investigate the relationship between radon (Rn) gas concentration and nutrition of patients in food groups with MS. Demographic information, diet, and building characteristics were collected by a questionnaire. Indoors Rn gas was measured using CR-39 detectors. Three models were used in the study of food intake. The interaction analysis between MS prevalence, diet, residential building characteristics, and Rn gas content was performed using SPSS 2020. The total Rn was significantly associated with cooling devices (P = 0.021). Buildings > 20 years had higher Rn concentrations than buildings < 20 years (P = 0.038). Also, no significant relationship was found between Rn-total and MS concentrations, but the total Rn concentration was higher in people homes with MS. Case group used more processed meat than the control (P < 0.001). The case group consumed more butter than the control, which was significant in Model III (P < 0.04). Tomato consumption in the case group was significantly higher than the control (P < 0.03). According to the results there was no interaction between Rn gas concentration in any of the food groups in each cases. However, future studies with larger sample sizes will be needed prospectively.

MODELING AND EXPERIMENTS TO ESTIMATE RADON EMANATION FACTOR IN SOIL-GRAIN SIZE AND MOISTURE EFFECT

The influence of soil grain size on its radon emanation mechanism was investigated by developing a Monte-Carlo model. The proposed model supplements the previous formulations by accounting for the effect elicited by specific surface area of the sample. The specific surface area of a sample is governed by its grain size and it strongly influences the emanation rate which is a surface phenomenon. The emanation study was further extended to include the moisture effect. Experiments were carried out with two soil samples; Soil-2 and Soil-4 collected from different terrains, to analyze the role played by moisture in the emanation mechanism. The above model was augmented with provisions to include the moisture input. The model could reproduce the experimental results. There is an abrupt increase in the emanation factor when the moisture content changes from 0 to 2%. Thereafter, the increase is gradual and finally becomes steady when the moisture level reaches 10%. Soil-2 and Soil-4 showed sizeable difference in their radon emanation factor values. This could be explained based on the parent226Ra distribution pattern which stems from the mineralogical composition of the samples. Quartz was predominantly found in Soil-2, whereas Soil-4 shows peaks corresponding to minerals namely ilmenite, Rutile and Zircon confirming relatively higher concentration of heavy minerals than Soil-2. The emanation factor values of the individual minerals reported in the literature were used to decide upon the 226Ra distribution depth and with this input the model to ascertain the experimental observations.

A brief radiological survey and associated occupational exposure to radiation in an open pit slate mine in Kashan, Iran

A comprehensive radiological survey was carried out in an open-cut slate stone quarry. The activity of 226Ra, 228Ra and 40 K in the ore samples were measured as 38 ± 5, 41 ± 6 and 869 ± 52 Bq kg1, respectively. Outdoor radon and indoor radon concentrations were measured from 37 ± 7 to 193 ± 11 Bq m−3 (77 ± 8 Bq m−3), and 49 ± 6 to 253 ± 23 Bq m−3 (131 ± 13 Bq m−3), respectively. The average indoor and outdoor gamma dose were measured as 116 and 84 nSv h− 1, respectively. The annual effective doses were estimated between 1.0 ± 0.1 and 3.3 ± 0.3 mSv year−1. The annual lung cancer risks were calculated in the range of 3.3 × 10−2 to 13.12 × 10−2 % (7.72 × 10−2%).

A simple physical-activity-based model for managing children's activities against exposure to air pollutants

Air pollution has been a major health concern worldwide, such that there is an urgent need for exposure assessments of human exposure to air pollutants. As children are more active and may experience more exposure events than adults, it is more challenging to conduct exposure assessments for children. To obtain a general understanding of the impact that children's activity, associated with their respiratory rate (IR), has on estimated exposure risks, we adopted a simple model to narrow down children's exposure behaviors to four categories, which integrated children's regular schedules and the indoor-outdoor ratio (r_I/O) of air pollutants. Although outdoor play only occupies approximately 8.6% of the total weekly time, the results indicate that, in general, outdoor play contributes to over 50% of the total exposure to air pollutants when r_I/O is less than 0.1, which is due to children's relatively large IR during high-intensity activities. When air pollutants mainly originate from indoor sources (i.e., r_I/O=3.0), indoor sitting (28%) and sleeping (36%) account for the major portion of the total exposure due to the longer exposure duration while outdoor events, including playing, walking, and sitting, account for ~15% of the total exposure. In addition, we applied a ratio function (R_M/C) to compare our simple model to a common basic model, revealing that our simulated results are consistent with the basic model, i.e., 0.94≤R_M/C≤1.12, if the r_I/O of air pollutants falls in the range between 0.5 and 1.5. The sensitivity analysis indicates that indoor or outdoor play has a larger impact on the output results than other activity-related variables because of the correspondingly largest IR. We also incorporated weather factors to adjust children's activity schedules for winter and non-winter days showing the change in the contributions of children's activities to total exposure. For example, the contribution differential of outdoor play to the total exposure between winter and non-winter days is ~8% for air pollutants with an r_I/O value of 0.1. Although other factors, such as the activity intensity level and concentration of air pollutant in the microenvironment, must be refined in future studies, our simple model can be applied as a convenient approach to arrange children's activity schedules against possible air pollutant exposure.

A FEASIBILITY TEST FOR QUICK RADON RISK ASSESSMENT BY MEASURING AN IN SITU RADIATION DOSE RATE

Radon concentration was estimated using an accumulation chamber equipped with AlphaGUARD radon monitor. It varies from 12.6 ± 1.20 to 363 ± 19.3 Bq m-3 with a mean value of 180 ± 11.2 Bq m-3. A good correlation between radium content and radon concentrations was obtained of R = 0.754, which suggests that radium is the main reason of releasing radon to the atmosphere. Radon emanation coefficient and exhalation rate were also calculated. Furthermore, the radiation dose rate was measured with a high-pressure ionization chamber detector. The radiation dose rate was strongly correlated with the radon concentration and exhalation rate of R = 0.85 and 0.63. The obtained results support our idea that the radiation dose rate can be a good indicator to the radon level in the atmosphere. In addition, the dependence of radon concentration on the water content was discussed.

Radon and thoron exhalation rate, emanation factor and radioactivity risks of building materials of the Iberian Peninsula

Radon (²²²Rn) and thoron (²²⁰Rn) are radioactive gases emanating from geological materials. Inhalation of these gases is closely related to an increase in the probability of lung cancer if the levels are high. The majority of studies focus on radon, and the thoron is normally ignored because of its short half-life (55.6 s). However, thoron decay products can also cause a significant increase in dose. In buildings with high radon levels, the main mechanism for entry of radon is pressure-driven flow of soil gas through cracks in the floor. Both radon and thoron can also be released from building materials to the indoor atmosphere. In this work, we study the radon and thoron exhalation and emanation properties of an extended variety of common building materials manufactured in the Iberian Peninsula (Portugal and Spain) but exported and used in all countries of the world. Radon and thoron emission from samples collected in the closed chamber was measured by an active method that uses a continuous radon/thoron monitor. The correlations between exhalation rates of these gases and their parent nuclide exhalation (radium/thorium) concentrations were examined. Finally, indoor radon and thoron and the annual effective dose were calculated from radon/thoron concentrations in the closed chamber. Zircon is the material with the highest concentration values of ²²⁶Ra and ²³²Th and the exhalation and emanation rates. Also in the case of zircon and some granites, the annual effective dose was higher than the annual exposure limit for the general public of 1 mSv y⁻¹, recommended by the European regulations.

QUANTIFICATION OF BACK DIFFUSION IN RADON AND THORON EXHALATION RATE MEASUREMENTS

The radon (222Rn) and thoron (220Rn) fluxes from the soil and building materials are the major contributors to their indoor levels. Hence, the measurement of radon and thoron exhalation rates from the source matrix becomes the foremost step in controlling the indoor radon and thoron exposure. It is a challenge to measure the exhalation rates without disturbing the natural conditions. The back-diffusion phenomenon modifies the exhalation rate. The work presented here is to measure the back-diffusion coefficient and takes it into consideration while estimating the exhalation rate. For radon measurements, the back-diffusion coefficient and the free exhalation rates were simultaneously estimated by adopting a novel methodology. The leak rate of the experimental setup measured by this methodology was agreeable with the value measured by adopting the standard technique. In the case of thoron, the back-diffusion effect was found to be negligible for the present experimental conditions and it is duly explained. The above results were obtained by analyzing two soil samples with high 238U and 232Th content collected from monazite-rich coastal area.

INDOOR RADON AND THORON IN THE VICINITY OF PROPOSED URANIUM MINING SITE: A CASE STUDY AT DASARLAPALLY VILLAGE, TELANGANA STATE, INDIA

Studies are being conducted for the past few decades in and around the uranium mining sites across the globe to identify environmental nuclear radiation risk to the common public. The area near Dasarlapally village was identified for uranium exploration by the AMDER, Hyderabad. The present study was carried out to measure the indoor radon and thoron activity concentrations in the dwellings of Dasarlapally village. For this purpose different types of dwellings were chosen randomly across the village. The measured annual average concentration of radon and thoron in dwellings were found to be 141 ± 42 and 139 ± 77 Bqm-3, respectively, and the calculated annual effective inhalation dose due to radon was determined to be 3.5 mSv. Seasonal variation and diurnal variation of radon and thoron activity concentration were investigated. The variation of radon and thoron activity concentration in different types of dwellings was also studied, and the variation was found to be statistically insignificant. The uncertainty propagated in the effective inhalation dose due to thoron was discussed.

Importance of Discriminative Measurement for Radon Isotopes and Its Utilization in the Environment and Lessons Learned from Using the RADUET Monitor

Radon (222Rn) and thoron (220Rn), sources of natural background radiation, have been the subjects of long-standing studies, including research into radon and thoron as major causes of lung cancer at domestic and international levels. In this regard, radon and thoron measurement studies have been widely conducted all over the world. Generally, the techniques used relate to passive nuclear track detectors. Some surveys have shown that passive monitors for radon are sensitive to thoron, and hence some measured results have probably overestimated radon concentrations. This study investigated radon and thoron measurements in domestic and international surveys using the passive radon-thoron discriminative monitor, commercially named RADUET. This paper attempts to provide an understanding of discriminative measurements of radon isotopes and to present an evidence-based roadmap.

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.

EXHALATION OF RADON FROM NATURALLY OCCURRING RADIOACTIVE MATERIALS (NORM) IN NIGERIA

Radon-222 mass exhalation rate, EM, and surface exhalation rate, EA, have been determined for some building materials and fertilizers in Nigeria by accumulation method using AlphaGUARD radon monitor. The building materials include granite, cement, tile, white marble, brick, concrete and sand. The mean EM of the building materials varied from 0.06 ± 0.03 for white marble to 0.23 ± 0.15 Bq kg-1 h-1 for brick. The mean EA ranged between 1.06 ± 0.56 Bq kg-1 h-1 and 3.15 ± 1.52 Bq m-2 h-1 for white marble and brick, respectively. Most of the EM and EA of the building materials were higher than those of other countries. For the fertilizers, the EM and EA ranged from 0.13 ± 0.01 to 0.42 ± 0.03 Bq kg-1 h-1 and 2.11 ± 0.56 to 4.81 ± 1.24 Bq m-2 h-1 with mean values of 0.25 ± 0.07 Bq kg-1 h-1 and 3.24 ± 0.93 Bq m-2 h-1, respectively. The radon mass and surface exhalation rates of the fertilizers were higher than those of the building materials.

A cost effectiveness analysis of interventions to reduce residential radon exposure in Canada

The objective of this analysis is to estimate the incremental cost effectiveness ratios for the 2012 populations in Canada, each province/territory, and 17 census metropolitan areas, for practical radon mitigation scenarios to reduce residential radon exposures. Sixteen intervention scenarios compare radon mitigation implemented at differing rates in new and existing housing relative to preventive measures installed at construction, using three different radon mitigation thresholds. A period life-table analysis was conducted using data derived from two recent Canadian radon surveys, along with Canadian mortality and quality of life data. Analyses adopted a lifetime horizon and a discount rate of 1.5%. It is practical to reduce residential radon and associated lung cancer mortality in Canada, and the most cost effective scenario at each radon mitigation threshold is the combination of the activation of the preventive measures in new housing and mitigation of existing housing.

Comparison of results from indoor radon measurements using active and passive methods with those from mathematical modeling

Computational fluid dynamics (CFD) has been used to simulate the distribution of indoor radon concentration in a naturally ventilated room. Finite volume method was employed in CFD code for the simulation of indoor radon. The simulation results were validated at 34 points in a matrix of two horizontal planes (y = 1.3 m and y = 2.1 m) using passive pinhole dosimeters and at six points using an active scintillation radon monitor. The CFD results were found to exhibit an excellent correlation with the measured values. It is concluded that CFD analysis is a powerful tool to visualize indoor radon distribution.

RADON EXHALATION FROM BUILDING MATERIALS USED IN YEMEN

The present article seeks to determine the annual effective doses of 222Rn exposure, effective radium content and radon exhalation rates in some building materials from the local market of Ibb province, Yemen. A total of 33 samples of building materials were collected from the target area. The radon exhalation rate and effective radium content in these samples were measured using solid-state nuclear track detector, which has become an important tool in every investigation of the radon levels in the surrounding environment. Surface exhalation rate has been found to vary from 178.90 to 1267.6 mBq m-2 h-1, whereas mass exhalation rate has been found to vary from 5.51 to 33.25 mBq kg-1 h-1. All the values of effective radium content in all samples under test were found to be quite lower than the permissible value of 370 Bq kg-1 recommended by Organization for Economic Cooperation and Development. Annual effective doses have also been estimated.

THE SCREENING INDOOR RADON AND PRELIMINARY STUDY OF INDOOR THORON CONCENTRATION LEVELS IN KUWAIT

Indoor measurements of radon and thoron in Kuwait were conducted during the years 2015 and 2016. In this study, 65 dwellings were selected for the long-term radon-thoron survey using passive nuclear track monitors. The monitors (at least one) were used at various locations in the dwellings for 83-306 days. Some measurements were also repeated at the same locations in different seasons. This current study is a preliminary thoron survey with relatively small sample size. The results showed that the range of thoron concentration was from below the lower limit of detection to 35 Bq m-3, whereas the range of radon concentration was within 10-202 Bq m-3. Furthermore, 22% of the radon results exceeded the WHO radon reference level of 100 Bq m-3. The analysis of variance showed a correlation between indoor radon concentration and the season. However, the thoron measurements were rather limited and the values were low. In addition, the relationship was investigated between radon and thoron concentrations involving the floor levels and the type of ventilation systems used.

Numerical modeling of the sources and behaviors of 222Rn, 220Rn and their progenies in the indoor environment-A review

²²²Rn, ²²⁰Rn and their short-lived progenies are well known radioactive indoor pollutants, identified as the leading environmental cause of lung cancer next to smoking. Apart from the conventional measurement methods, numerical modeling methods are developed to simulate their physical and decay processes in ²²²Rn and ²²⁰Rn's life cycle, estimate their levels, concentration distributions, as well as effects of control strategies in the indoor environment. In this article, we summarized the numerical models used to illustrate the physical processes of each source of ²²²Rn and ²²⁰Rn entry into the indoor environment, and the application of Jacobi room models and CFD (Computational Fluid Dynamic) models used to present the behaviors of indoor ²²²Rn, ²²⁰Rn and their progenies. Furthermore, we consider that the development of numerical modeling of ²²²Rn and ²²⁰Rn would have a bright prospect in the directions of stochastic methods based on a steady-state model, the fine simulation of the time-dependent model as well as the multi-dimension model.

Potential factors that impact the radon level and the prediction of ambient dose equivalent rates of indoor microenvironments

This study aimed to measure the equilibrium equivalent radon (EEC_Rn) concentration in an old building (Building-1) and a new building (Building-2) with mechanical ventilation and a natural ventilation system, respectively. Both buildings were located at the campus of University Kebangsaan Malaysia. The concentration of indoor radon was measured at 25 sampling stations using a radon detector model DOSEman PRO. The sampling was conducted for 8 h to represent daily working hours. A correlation of the radon concentration was made with the annual inhalation dose of the occupants at the indoor stations. The equilibrium factor and the annual effective dose on the lung cancer risks of each occupant were calculated at each sampling station. The average equilibrium equivalent radon measured in Building-1 and Building-2 was 2.33 ± 0.99 and 3.17 ± 1.74 Bqm^-3, respectively. The equilibrium factor for Building 1 ranged from 0.1053 to 0.2273, and it ranged from 0.1031 to 0.16 for Building 2. The average annual inhalation doses recorded at Building-1 and Building-2 were 0.014 ± 0.005 mSv y^-1 and 0.020 ± 0.013 mSv y^-1, respectively. The annual effective dose for Building-1 was 0.034 ± 0.012 mSv y^-1, and it was 0.048 ± 0.031 mSv y^-1 for Building-2. The values of equilibrium equivalent radon concentration for both buildings were below the standard recommended by the International Commission on Radiological Protection (ICRP). However, people may have different radon tolerance levels. Therefore, the inhalation of the radon concentration can pose a deleterious health effect for people in an indoor environment.

Indoor radon concentration in Korea residential environments

The purpose of this study is to provide basic data for the evaluation and management of health effects with respect to exposure to radon within residential environments in South Korea. It is part of a case-control study to develop a management plan based on indoor radon exposure levels and assess their impact on health. To investigate the long-term cumulative concentration levels of radon, 599 patients who have respiratory diseases were recruited in South Korea, and alpha track detectors were installed in their residences for a period of 3 months from mid-2015 to late 2016. A survey was then conducted to determine the factors affecting the radon concentration. The radon concentration levels were analyzed in conjunction with the survey results. The results show that the arithmetic mean of the radon concentrations in domestic residences was in the range of 70.8 ± 65.2 Bq/m³. An analysis of covariance (ANCOVA) was performed to identify the environmental factors affecting the radon concentration and contributing to variations in the residential radon concentration based on the height of the residence. The results show that the contribution of the local environmental factor to the variation in radon concentration (p < 0.05) was greater than that of other environmental factors. Although no statistically significant difference was found with regard to the construction year of the building before the control (p > 0.05), the same was found with regard to the construction year after the control (p < 0.05).

The use of gamma-survey measurements to better understand radon potential in urban areas

Accounting for as much as 14% of all lung cancers worldwide, cumulative radon progeny exposure is the leading cause of lung cancer among never-smokers both internationally and in the United States. To understand the risk of radon progeny exposure, studies have mapped radon potential using aircraft-based measurements of gamma emissions. However, these efforts are hampered in urban areas where the built environment obstructs aerial data collection. To address part of this limitation, this study aimed to evaluate the effectiveness of using in situ gamma readings (taken with a scintillation probe attached to a ratemeter) to assess radon potential in an urban environment: DeKalb County, part of the Atlanta metropolitan area, Georgia, USA. After taking gamma measurements at 402 survey sites, empirical Bayesian kriging was used to create a continuous surface of predicted gamma readings for the county. We paired these predicted gamma readings with indoor radon concentration data from 1351 residential locations. Statistical tests showed the interpolated gamma values were significantly but weakly positively related with indoor radon concentrations, though this relationship is decreasingly informative at finer geographic scales. Geology, gamma readings, and indoor radon were interrelated, with granitic gneiss generally having the highest gamma readings and highest radon concentrations and ultramafic rock having the lowest of each. Our findings indicate the highest geogenic radon potential may exists in the relatively undeveloped southeastern part of the county. It is possible that in situ gamma, in concert with other variables, could offer an alternative to aerial radioactivity measurements when determining radon potential, though future work will be needed to address this project's limitations.

USE OF COMMERCIAL RADON MONITORS FOR LOW LEVEL RADON MEASUREMENTS IN DYNAMICALLY OPERATED VOC EMISSION TEST CHAMBERS

Compared to the intended EU reference level of 300 Bq m-3 for indoor radon concentrations, the contribution of building materials appears to be low. Considering the recommended limit of 100 Bq m-3 by WHO, their contribution is supposed to be relevant, especially at low air exchange rates. This study as part of a two-part research project investigated the suitability of direct low level 222Rn measurement under simulated indoor conditions with commercial radon monitors and dynamically operated emission test chambers. Active measuring devices based on ionisation or scintillation chambers with 1-σ uncertainties below 8.6% at 20 Bq m-3 were found to be best suitable for a practical test procedure for the determination of radon exhalation rates of building materials. For the measurement of such low concentrations, the knowledge of the accurate device background level is essential.

Phosphogypsum recycling in the building materials industry: assessment of the radon exhalation rate

Phosphogypsum can be classified as a Naturally Occurring Radioactive Material (NORM) residue of the phosphate fertilizer industry. One of the main environmental concerns of its use as building material is the radon exhalation. The aim of this study is to measure the radon exhalation rate from plates and bricks manufactured with phosphogypsum from three installations of the main Brazilian producer, Vale Fertilizantes, in order to evaluate the additional health risk to dwellers. A simple and reliable accumulator method involving a PVC pipe sealed with a PVC pipe cover commercially available with CR-39 radon detector into a diffusion chamber was used for measuring radon exhalation rate from phosphogypsum made plates and bricks. The radon exhalation rate from plates varied from 0.19 ± 0.06 Bq m^-2 h^-1, for phosphogypsum from Bunge Fertilizers, from 1.3 ± 0.3 Bq m^-2 h^-1, for phosphogypsum from Ultrafertil. As for the bricks, the results ranged from 0.11 ± 0.01 Bq m^-2 h^-1, for phosphogypsum from Bunge Fertilizers, to 1.2 ± 0.3 Bq m^-2 h^-1, for phosphogypsum from Ultrafertil. The results obtained in this study for the radon exhalation rate from phosphogypsum plates and bricks are of the same order of magnitude than those from ordinary building materials. So, it can be concluded that the recycling of phosphogypsum as building material is a safe practice, since no additional health risk is expected from the radiological point of view.

An analysis of the radioactive contamination due to radon in a granite processing plant and its decontamination by ventilation

This work focuses on studying concentration distribution of ²²²Rn radioisotope in a granite processing plant. Using Computational Fluid Dynamic Techniques (CFD), the exposure of the workers to radiation was assessed and, in order to minimise this exposure, different decontamination scenarios using ventilation were analysed. Natural ventilation showed not sufficient to maintain radon concentration below acceptable limits, so a forced ventilation was used instead. Position of the granite blocks also revealed as a determining factor in the radioactive level distribution. Thus, a correct layout of the stored material and an adequate ventilation system can guarantee free of exposure to radiation zones within the studied workshop. This leads to a drastic fall in the exposure of the workers and consequently minimises their risk of developing aggressive illness like lung cancer.

Environmental impact of CO2, Rn, Hg degassing from the rupture zones produced by Wenchuan M s 8.0 earthquake in western Sichuan, China

The concentrations and flux of CO2, (222)Radon (Rn), and gaseous elemental mercury (Hg) in soil gas were investigated based on the field measurements in June 2010 at ten sites along the seismic rupture zones produced by the May 12, 2008, Wenchuan M s 8.0 earthquake in order to assess the environmental impact of degassing of CO2, Rn and Hg. Soil gas concentrations of 344 sampling points were obtained. Seventy measurements of CO2, Rn and Hg flux by the static accumulation chamber method were performed. The results of risk assessment of CO2, Rn and Hg concentration in soil gas showed that (1) the concentration of CO2 in the epicenter of Wenchuan M s 8.0 earthquake and north end of seismic ruptures had low risk of asphyxia; (2) the concentrations of Rn in the north segment of seismic ruptures had high levels of radon, Maximum was up to level 4, according to Chinese code (GB 50325-2001); (3) the average geoaccumulation index I geo of soil Hg denoted the lack of soil contamination, and maximum values classified the soil gas as moderately to strongly polluted in the epicenter. The investigation of soil gas CO2, Rn and Hg degassing rate indicated that (1) the CO2 in soil gas was characterized by a mean [Formula: see text] of -20.4 ‰ and by a mean CO2 flux of 88.1 g m(-2) day(-1), which were in the range of the typical values for biologic CO2 degassing. The maximum of soil CO2 flux reached values of 399 g m(-2) day(-1) in the epicenter; (2) the soil Rn had higher exhalation in the north segment of seismic ruptures, the maximum reached value of 1976 m Bq m(-2) s(-1); (3) the soil Hg flux was lower, ranging from -2.5 to 18.7 n g m(-2) h(-1) and increased from south to north. The mean flux over the all profiles was 4.2 n g m(-2) h(-1). The total output of CO2 and Hg degassing estimated along seismic ruptures for a survey area of 18.17 km(2) were approximately 0.57 Mt year(-1) and 688.19 g year(-1). It is recommended that land-use planners should incorporate soil gas and/or gas flux measurements in the environmental assessment of areas of possible risk. A survey of all houses along seismic ruptures is advised as structural measures to prevent the ingress of soil gases, including CO2 and Rn, were needed in some houses.

STUDY ON RADON CONCENTRATION AT THE WORK PLACES OF MYSURU, BENGALURU AND KOLAR DISTRICTS OF KARNATAKA STATE, SOUTH INDIA

Concentrations of radon, thoron and their progeny inside the working place depend on the activity of radionuclides in the soil, building materials, atmospheric conditions, construction of the building, type of work and ventilation condition. Radon is a radioactive noble gas, and it is emanated from ²²⁶Ra present in earth crest and building material. Based on the type of work, construction of the building and ventilation condition, concentrations of radon, thoron and their progeny have been measured in 60 workplaces at 10 locations of Mysuru, Bengaluru and Kolar districts of Karnataka state using Solid-State Nuclear Track Detector technique. From the study, variations of radon, thoron and their progeny have been observed with the nature of work.

Assessement of doses to members of the public arising from the use of ornamental rocks in residences

The main pathways to human exposure associated with naturally occurring radionuclides in ornamental rocks are external irradiation and the inhalation of radon. Usually, external doses and risks are assessed by using generic approaches in which the specific properties and use of the material are not considered. Moreover, limited information on radon inhalation dose due to the use of rock is available. The radionuclide concentrations in 180 rock samples reached a wide range of values: for ²²⁸Ra from  <2 to 530 Bq kg^-1, for ²²⁶Ra between  <5 and 600 Bq kg^-1and for ⁴⁰K varied between 190 and 2797 Bq kg^-1. Considering the rock properties, mathematical models, a residential scenario and radionuclide concentrations in the rocks, ²²²Rn concentrations and inhalation and external doses were estimated to range from 0.1 to 13 Bq m^-3, from 0.01 and 0.26 mSv yr^-1 and from 0.01 and 0.61 mSv yr^-1, respectively. The ventilation and the emanation rates are key parameters for the Rn dose, whereas the location of the receptor significantly affects the external dose. The overestimations of doses and risks by the generic approaches highlight the necessity of considering the properties and use of the materials for those estimations.

A comparison of the dose from natural radionuclides and artificial radionuclides after the Fukushima nuclear accident

Due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the evacuees from Namie Town still cannot reside in the town, and some continue to live in temporary housing units. In this study, the radon activity concentrations were measured at temporary housing facilities, apartments and detached houses in Fukushima Prefecture in order to estimate the annual internal exposure dose of residents. A passive radon-thoron monitor (using a CR-39) and a pulse-type ionization chamber were used to evaluate the radon activity concentration. The average radon activity concentrations at temporary housing units, including a medical clinic, apartments and detached houses, were 5, 7 and 9 Bq m(-3), respectively. Assuming the residents lived in these facilities for one year, the average annual effective doses due to indoor radon in each housing type were evaluated as 0.18, 0.22 and 0.29 mSv, respectively. The average effective doses to all residents in Fukushima Prefecture due to natural and artificial sources were estimated using the results of the indoor radon measurements and published data. The average effective dose due to natural sources for the evacuees from Namie Town was estimated to be 1.9 mSv. In comparison, for the first year after the FDNPP accident, the average effective dose for the evacuees due to artificial sources from the accident was 5.0 mSv. Although residents' internal and external exposures due to natural radionuclides cannot be avoided, it might be possible to lower external exposure due to the artificial radionuclides by changing some behaviors of residents.

Theoretical modeling of indoor radon concentration and its validation through measurements in South-East Haryana, India

A three dimensional semi-empirical model deduced from the existing 1-D model has been used to predict indoor radon concentration with theoretical calculations. Since the major contributor of radon concentration in indoors originates from building materials used in construction of walls and floor which are mostly derived from soil. In this study different building materials have been analyzed for radon exhalation, diffusion length along with physical dimensions of observation area to calculate indoor radon concentration. Also calculated values have been validated by comparing with experimental measurements. The study has been carried out in the mud, brick and cement houses constructed from materials available locally in South-East region of Haryana. This region is also known for its protruding land structure consisting volcanic, felsite and granitic rocks in plane. Further, exhalation (Jw) ratio from wall and floor comparison has been plotted for each selected village dwelling to identify the high radon emanating source (building material) from the study region. All those measured factors might be useful in building construction code development and selection of material to be used in construction.

Characteristics of indoor radon and its progeny in a Japanese dwelling while using air appliances

Characteristics of radon and its progeny were investigated in different air conditions by turning four types of indoor air appliances on and off in a two-story concrete Japanese dwelling. The four appliances were air conditioner, air cleaner, gas heater and cooker hood. The measurements were done using two devices: (1) a Si-based semiconductor detector for continuous measurement of indoor radon concentration and (2) a ZnS(Ag) scintillation counting system for equilibrium-equivalent radon concentration. Throughout the entire experiment, the cooker hood was the most effective in decreasing indoor radon concentration over a long period of time and the less effective was the air conditioner, while the air cleaner and gas heater did not affect the concentration of radon. However, the results measured in each air condition will differ according to the lifestyles and activities of the inhabitants. In this study, indoor radon and its progeny in a Japanese dwelling will be characterised by the different air conditions.

An overview of radon research in Canada

Based on new scientific information and broad public consultation, the Government of Canada updated the guideline for exposure to indoor radon and launched a multi-year radon programme in 2007. Major achievements in radon research accomplished in the past 7 y are highlighted here.

Radon exhalation rates from some building materials used in Sudan

Measurements of radon concentration, surface and mass exhalation rates were made for 12 types (264 measurements) of building material samples frequently used in Sudan. In this survey, we used the can technique, containing CR-39, to estimate the radon exposure from building materials. The results of radon concentrations in the selected building materials ranged from 506 ± 79 Bq.m−3 in mud bricks of Aroma area to 128 ± 39 Bq.m−3 in ceramic material. The surface and mass exhalation rates ranged from 949 ± 70 mBq.m−2.h−1, 11.25 ± 1.76 mBq.kg−1 h−1 to 240 ± 35 mBq.m−2 h−1, 2.84 ± 0.87 mBq.kg−1.h−1, respectively. The effective dose was calculated that ranged from 3.59 ± 1.10 mSv.y−1 to 14.21 ± 2.23 mSv.y−1, for ceramic and mud materials, respectively. These results agreed with similar findings that mud contributes in a higher indoor concentration than the other investigated materials, mud was found to constitute an effective dose above the action level as quoted by the International Commission on Radiological Protection (ICRP).