High Radon Concentrations Research Articles

A Summary of Residential Radon Surveys and the Influence of Housing Characteristics on Indoor Radon Levels in Canada.

Based on community and nationwide radon surveys with long-term radon measurements in a total of 21,818 homes, radon distribution characteristics in Canada have been reassessed with the population-weighted arithmetic mean radon concentration of 82 Bq m−3, geometric mean radon concentration of 55 Bq m−3, and geometric standard deviation of 2.45. The major pathway for the influx of radon into Canadian homes is from the surrounding soil. Statistical analysis has shown that radon levels in houses with a basement are, on average, about twice the radon levels in houses without a basement, and houses with private wells also tend to have higher radon concentrations than houses with municipal water supply.

Monitoring of radionuclides in the natural waters of Novosibirsk, Russia

Results of the investigation of 238U, 232Th, 226Ra and 222Rn content in the natural waters of Novosibirsk city and adjacent territories are presented for the first time. Hydraulic interrelations between the aquifer systems of Quaternary, Neogene and Paleogene sediments, Upper Devonian – Lower Carboniferous sediments and Upper Paleozoic granites predetermined the features of hydrogeological structure. Twenty-five chemical types of water were established, with the domination of HCO3 Mg–Ca, HCO3 Na–Mg–Ca and SO4–HCO3 Na–Mg–Ca. The amount of total dissolved solids varies from 127 to 1848 mg l−1, pH from neutral to alkaline (6.9–9.5). The values of Eh vary from reductive −157 mV (O2dissolved = 0.3 mg l−1) to oxidative +280 mV (O2dissolved = 19.4 mg l−1). Silicon content varies from 0,14 to 11,77 mg l−1. The ranges within which the concentrations of radioactive elements vary in natural waters are: radon (222Rn) 0–1216 Bq.l−1, uranium (238U) 9.75∙10−8 – 0.098 mg l−1, thorium (232Th) 2.2∙10−7 – 2.1∙10−3 and radium (226Ra) 1.6∙10−12 – 3,5∙10−7 mg l−1. The maximal content of these elements in the waters of boundary territories reach 222Rn – 43,764 Bq.l−1, 238U–6.5 mg l−1 and 226Ra – 3.7∙10−7 mg l−1. The 232Th/238U ratio is 4.20∙10−5 – 2.96. The concentrations of uranium and thorium in the geological objects of Novosibirsk vary within the ranges (mg.kg−1): 238U = 1.6–3.6 and 232Th = 5.55–13.6 for sedimentary rocks, and 238U = 0.2–47.2 and 232Th = 0.8–44.1 in intrusive formations. It is established that waters with high radon content relate to the aquiferous zones of Upper Devonian - Lower Carboniferous shale rocks and hornfels, as well as Upper Paleozoic granites. The highest concentrations of radionuclides are characteristic of the aqueous scattering halos of the uranium ore deposit.

Origin of the chemical composition of São Francisco ultra-fresh thermal water (Itabira region, Minas Gerais, Brazil)

Geochemical studies documented the composition of ultra-fresh thermal water in the Fazenda Giráu, near Itabira (Minas Gerais state, Brazil) for the first time. The studied water is characterized by temperature of 35 °C, very low electric conductivity (approx. 20 μS/cm), uncommon Mg–Ca–HCO3–NO3 hydrochemical type, and an elevated radon concentration (about 500 Bq/L). The presence of tritium suggests the modern age of studied water, contained in highly resistant quartzite-dominated aquifer rocks. Application of a geothermometric approach gave an estimation of the equilibrium temperature in the geothermal system at about 42 °C. Inverse geochemical modelling quantified water-rock reactions responsible for the observed groundwater chemistry. Decomposition of soil organic matter and decay of primary (feldspars, biotites, muscovite) and secondary (montmorillonites, illite) aluminosilicate minerals accompanied by kaolinite and gibbsite formation are the dominant processes forming chemical composition of water. The investigated water has balneotherapeutic potential due its elevated temperature and high concentrations of radon and silicic acid.

Radon transport events associated with the impact of a NORM repository in the SW of Europe

Two radon measurement stations located to the north and south of a NORM (Naturally Occurring Radioactive Materials) repository of phosphogypsum (southwest of Europe) were used to monitor radon behavior during 2018. The stations are located at opposing sides of the repository, one in Huelva City to the north and other one in a rural area to the south. This setup aimed to identify the influence of the NORM repository on each station and use radon levels as a marker of atmospheric transport in the local area. To achieve this, a comparison was carried out with other coastal stations in the south of Spain, finding higher average concentrations in Huelva City, ~3.3 Bq m−3. Hierarchical clustering was applied to identify days with different radon patterns at each Huelva station, detecting possible local radon transport events from the repository. Three events were investigated with WRF (Weather Research and Forecasting) and FLEXPART-WRF (FLEXible PARTicle dispersion model). It was found that both sampling sites required atmospheric stagnant conditions to reach high radon concentration. However, under these conditions the urban station showed high radon regardless of wind direction while the rural station also required radon transport from the repository, either directly or indirectly.

General Overview of Radon Studies in Health Hazard Perspectives.

The adverse human health effects due to ionizing radiation are well known. Radon is the major source of background radiation among those that are of natural origin. It contributes about 55% of the natural radiation dose to humans. It is a colorless, odorless, and tasteless radioactive noble gas that comes from the natural radioactive decay series of uranium. Radon can be found everywhere in the atmosphere and become attached to aerosols in the air. The aerosols carrying radon and its progeny can be inhaled and deposited in different regions of the human respiratory tract. The deposited radioactive aerosols continue to decay and exposing the lung to ionizing radiation can destroy sensitive cells in the lung, causing a mutation that turns to be cancerous. Different countries and international and national organizations put their action levels to reduce radon lung cancer risk. The Environmental Protection Agency recommends 148 Bq/m3 as the action level. On the other hand, International Commission for Radiation Protection (ICRP) recommends 200 Bq/m3 as the action level. The main objective of this review is to focus on how radon is established as a health hazard, ways of radon detection and measurements, methods of reducing and controlling high indoor radon concentration, and what are the recommended international action levels of radon concentrations. It mainly focuses on the health perspective of radon studies because it is now a crucial and hot issue in the world. In most developing countries like our country Ethiopia, radon studies are not well investigated.

Assessment of radon exhalation rates in mineral rocks used in building decoration in Nigeria

The recent interest in the applications of mineral rocks for interior building decoration has been a major concern from the radiological perspective because the breaking down of rocks into various shapes and sizes releases radioactive gaseous element that is harmful to human health. Hence, this study assessed the radon exhalation rates of different rock types in Nigeria and their implications on human health. A total of 45 samples comprising five samples per rock type were prepared, packed, and sealed inside a modified closed can and thereafter subjected to radon concentration measurement using a RAD7 detector. The results of the study showed that granite and limestone rock types had high radon concentrations and exhalation rates as compared to other rock samples assessed. The radon concentration for granite and limestone rockfalls within the action level limit. Thus, effort should be made to ensure adequate ventilation of any building that uses these rock types in building decoration. The results obtained can be used as baseline data for future investigation of the rock types in any locality.

Inhalation dose in the indoor environment of Eloor industrial area, Kerala, India

Radon (222Rn) and Thoron (220Rn), the members of Uranium and Thorium decay series respectively, are ubiquitous in nature. Being airborne alpha active radioisotopes, they are the major contributors of inhalation dose especially in the indoor environments. This study measures the Potential Alpha Energy Concentration (PAEC) of radon/thoron progenies in the dwellings of Eloor industrial region in Kerala and thereby evaluate the internal/inhalation dose to the population. Aerosol samples were collected from 100 locations in the study area using high volume air sampler and gross particulate activity measurement was done using ZnS(Ag) alpha counter. The PAEC of radon progeny in the study area varied from 0.13 to 2.94 and that of thoron progeny varied from 0.3 to 7.7. It has been observed that the dwelling with marble floor possesses relatively higher concentration of radon and thoron progenies while lower concentrations were observed in dwellings with tile floors. Taking the mean concentrations of 222Rn and 220Rn progeny levels of 100 samples collected, the inhalation dose was 0.14 mSvy-1 for radon and 0.09 mSv y-1 for thoron, which delivers a total inhalation dose of 0.23 mSv y-1 to the population residing in that area. Measured data show below compared to the ICRP recommended action level of 3–10 mSvy-1 for general populace. Although measured data requires no immediate action to reduce the hazardous radon and thoron level in the studied area, however the radiation risk from such hazardous gas is not completely discarded. Since human spent more than 80% of time in indoor and the radiation hazards follows linear no threshold model, therefore the indoor environment should be well ventilated to reduce any unexpected health hazards.

Radiological survey on radon entry path in an underground mine and implementation of an optimized mitigation system

BackgroundThe European Union council has introduced the basic safety standards (EU-BSS) for protection against the dangers arising from exposure to ionizing radiation by laying down a new radon reference level at workplaces. In this regard, all European state members must establish a national reference level based on all pre-defined requirements. After implanting the directive 2013/59/Euratom by European state members, new challenges have been revealed to mitigate radon appropriately in underground workplaces due to the exciting limitations (e.g., ventilation system, dust dispersion, air injection, etc.). Therefore, a conceptual design of an environmental radiological survey was defined and implemented by examining the hypothesis to find practical solutions following EU-BSS. The main objectives of this study were to identify the potential radon entry paths, utilize an optimized ventilation system, and carry on long-term radon monitoring in an operational underground manganese mine.ResultsThe mullock rocks (the geological structure of the mine walls) contained a small amount of Ra-226 (2–4 Bq kg−1). On the other hand, the mine ore (black shale, underlayer black shale, and carbonate ore) has shown the highest concentration of Ra-226 (12–16 Bq kg−1) and the highest radon exhalation (1.2–1.6 mBq s−1 m−2). The surface radon exhalation from the mine walls was in the range of 0.7 ± 0.1 and 1.5 ± 0.2 mBq m−2 s−1. It was found that shortly after mining activity was undertaken, radon concentration increased dramatically with an average of about 5900 ± 420 Bq m−3 near the freshly broken walls. The optimized mobile mitigation system reduced radon concentration to 250 ± 41 Bq m−3 on average.ConclusionApart from the fact that aged walls were involved in the radon accumulation, considering the mine ventilation performance and the total active surface area, the exhaled radon from the aged walls could not be the primary potential source of high radon concentration when mining activity was undertaken. According to the obtained results, the ores, recently fragmented during the course of mining operations, were the primary path. Therefore, after successfully identifying the radon entry path, radon concentration could be reduced to meet the EU-BSS requirement by implementing the developed mitigation system.

General model for estimation of indoor radon concentration dynamics.

A known relationship exists between high radon concentrations and lung cancer, and therefore, the indoor radon quantification is important, and it is beneficial to have a model to estimate indoor concentration. The work is focused on the development of an INDORAD (INDOor RAdon Dynamic) model for estimation of indoor radon dynamics, with time-dependent meteorological parameters and adjustable soil and building properties being considered. This model is based on a systemic approach, where the flows of material between compartments are considered, without a spatial resolution. This approach allowed to simplify the mathematical processing and enabled to consider together all known sources of indoor radon. The developed model was put in use in a laboratory building where soil constitutes major source of radon. The results (radon concentrations) from the model were compared to an existing data set from Saelices el Chico in a soil with high concentration of 226Ra. The outcome of the validation implies that INDORAD could predict radon concentrations satisfactorily. Suggestions for future updates of the model to improve indoor radon estimations are provided.

Residencial radon and small cell lung cancer: A case control study.

e20566 Background: Residential radon is the second most important risk factor for lung cancer. We aim to asses the effect of residential radon exposure on the risk of SCLC in general population. Methods: A multicentric hospital-based case-control study was designed including 10 hospitals from Spain and Portugal. Incident cases with pathological diagnosis of SCLC were prospectively recruited. Controls consisted in patients undergoing non-complex surgery unrelated to tobacco consumption. All study participants were sent a radon detector. Results: A total of 375 cases and 902 controls were recruited. 24.5% of cases were women. The median age at diagnosis was 66 for cases. 6.4% of the cases were younger than 50 years. Tobacco consumption was higher in cases compared to controls. Residential radon concentrations were higher than 147 Bq/m3 in 161 SCLC cases (42.9%). Median residential radon concentration was also higher in SCLC cases compared to controls (152.5 Bq/m3 vs 142 Bq/m3). Those people exposed to more than 147 Bq/m3 and heavy smokers showed an OR of 72,62 (95%CI 17.95 - 499.41) compared to never-smokers with less than 50 Bq/m3. Conclusions: radon exposure seems to increase the risk of small cell lung cancer. There is a significant lung cancer risk departing from 148 Bq/m3 and there is also a linear dose-response pattern. Tobacco consumption may also produce an important effect modification for radon exposure. Those individuals exposed to high radon concentrations and heavy smokers can have a very high risk of this cancer type compared with their low exposed and never-smoking counterparts. It is necessary to increase radon awareness among citizens and administrations in order they can establish the necessary protective and mitigation measures against residential radon. Effect modification between residential radon exposure and tobacco consumption on the risk of small cell lung cancer.[Table: see text]

A Quantitative Assessment of Indoor Radon Level and Its Annual Effective Dose in Buildings of Gachin Rural District in Hormozgan Province, Iran

Introduction: Measurement of indoor radon concentration and its determining factors is crucial for improving public health and developing proper methods that can reduce indoor radon concentrations. This study aimed to measure the indoor radon concentration and to examine its variations in relation to variables, such as the construction materials, ventilation, and age of buildings. Material and Methods: Indoor radon concentrations were measured using solid-state nuclear track detectors (SSNTDs) during winter. Each detector was mounted 50-90 cm above the surface flooring of bedrooms and living rooms. After three months of exposure, the detectors were collected and transferred to a laboratory. They were then etched in 6.25 N NaOH solution in a bath at a constant temperature of 90°C for 240 minutes. Next, the detectors were washed with distilled water and dried. The alpha particle tracks were counted using an automatic alpha track counting system. Results: The mean radon concentration was 53.20 Bq/m3,and 94% of the samples had a radon concentration 3, which is the action level proposed by the World Health Organization (WHO). The annual effective dose varied from 0.25 mSvy-1 to 3.05 mSvy-1, with a mean dose of 0.91 mSvy-1. The results showed that the type of constructed materials and ventilation influence the indoor radon concentration in winter. Conclusion: The annual effective dose in the study area was below the global average of 1.15 mSvy-1. Therefore, local residents must be informed about the health risks of high radon concentrations and understand the role of improved ventilation in reducing the indoor radon levels.

Calibration of Solid State Nuclear Track Detectors CR-39 for radon study in a high concentration underground mines

The Brazilian National Commission for Nuclear Energy (CNEN) establishes a reference level of 1000 Bq m-3 of radon concentration in underground mines. Solid State Nuclear Track Detectors – SSNTD is considered the main method of analysis in radon research. The methods and instrumentation used to determine radon concentration needs to be validated by calibration to ensure reliable results. This work aims to determine the calibration factor of CR-39 detectors exposed to well known radon concentrations produced in closed systems by sources of Ra-226 with activities of 3.379 kBq and 0.483 kBq, which are NISTS sources of activities and emanation factors. The detectors were exposed to six different levels of exposure. The conversion factor between tracks density and exposure obtained was K = 52.028 ± 0.752 [(tracks density.cm-2)/(kBq.d.m-3)]. As object of application of this work, mines were chosen with high radon concentrations reported by Santos (2015) in special a pegmatite mine located in the northwest of Minas Gerais. This mine presented radon concentration much higher than the recommended by the Brazilian national standard NN.CNEN.4.01, up to 7384 ± 517 Bq m-3.

Occupational radiation dose for medical workers at the University Hospital Center “Mother Theresa” in Tirana

The exposure to environmental and “artificial” radiation sources was investigated in the University Hospital Center “Mother Theresa” in Tirana. The concentration of indoor radon exceeds the reference level of 300 Bq m−3 in some 50% of workplaces, accounting for an average effective dose rate of 3.7 mSv y−1. The average dose rate due to external gamma radiation was measured to be 0.12 mSv y−1. While, the occupational exposure of medical workers was found to be 0.67 mSv y−1 on average. The high radon concentrations account for approximately 83% of worker radiation dose, indicating the need for adopting mitigation actions.

Study of the possibility of using radon potential maps for identification of areas with high indoor radon concentration

In this study, five different methods for determining the geogenic radon potential are compared in the Mochovce region, Slovakia. Based on these methods, maps of radon potential were made and localities with suspected elevated indoor radon levels were identified. Subsequently, indoor radon concentrations measurements were performed there. Based on the measurements in six municipalities, an approximately linear relationship was found between the values of geogenic radon potential and indoor radon concentrations. These results confirm the usability of radon potential maps as valuable tools for characterizing radon-prone areas.

Radon risk mapping: A new geostatistical method based on Lorenz Curve and Gini index

In confined spaces such as living environments and workplaces, the concentration levels of radon (Rn222) can be very high as compared to the external environment. Since Rn has been classified as the second leading cause of lung cancer after cigarette smoking, to apply efficient locally based risk reduction actions, dense maps of indoor radon concentration are needed. These maps would provide information about the areas prone to high radon concentrations and therefore more dangerous to human health. The soil is the primary source of the Rn, hence the risk assessment and reduction for the radon exposure cannot disregard the identification of the local geology. In this regard, we propose an innovative method, based on the Gini index computation, for the realization of interpolated maps (kriging) to describe the distribution of concentration of Rn. To validate the method, a tool that simulates sets of radon concentrations is used, whose variability is, to the first order, controlled by a priori imposed different lithologies. A systematic comparison is made between the results achieved by means of a classically used geostatistical method and the proposed Gini-based tool. We show how, by using this latter tool, the kriging solutions appear to be more robust to resolve the different geogenic radon sources independently from the number of the available measurements.

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

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. Radon (222Rn) concentrations were simulated in the classroom, using CONTAM 3.2. 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 950h (expected effective dose, 0.13mSv/y), were calculated for each case. Simulations showed that the highest radon concentrations were observed in case 1 with a DVR of 79.6m3/h (621 Bq/m3) and case 4 with a DVR of 69.4m3/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 1999.7m3/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. 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.

Overlapping correction suitable for an LR-115 detector located inside a diffusion chamber

A simulation program based on Monte Carlo methods was developed to study the behaviour of the overlapping effect in the LR-115 nuclear track detectors located inside a diffusion chamber. The relation between the non-overlapped tracks and the radon exposure level that the detector was exposed was adopted. This study focuses on very high radon concentration levels found in soil gas, uranium mines, or underground places. These anomalous levels can influence the radiological risk related to inhalation of indoor radon or the spontaneous increases in thermal neutron background. LR-115 detector exposed to anomalous levels can register a large number of latent tracks on its surface. After an etching treatment, some visible tracks can be placed covering one or more visible tracks altering the LR-115 response. In order to develop this work and be more realistic, visible tracks were simulated taking into account radon exposure level, geometry and dimensions of the diffusion chamber, dimensions of the detector, the V function, the etching process and the reading process. Results show that the overlapping effect in the LR-115 inside a cylindrical diffusion chamber exposed to very high levels can be solved with an uncertainty of 5%. The same methodology can also be applied when considering other detectors and geometry and dimensions of a diffusion chamber.

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.

Assessment of radon radiological hazards in some ophiolite rocks, North Eastern Desert, Egypt

The natural stones are commonly used as interior and exterior building material. The accessory minerals of some rocks can generate a high amount of radon in the atmosphere. Ophiolitic rocks including serpentinites, metagabbros, gabbros metabasalts, metabasaltic-andesites, meta-andesites, Dokhan andesites, dacites, rhyolites, quartz diorites, tonalites, granodiorites, monzogranites and syenogranites. From the Eastern Desert of Egypt were analyzed for radon. The annual effective dose values of all studied rocks are higher than the world average due to the high radon content in the samples. The studied rocks are not recommended to be used as construction material.

Evaluation of occupational radon exposure and comparison with residential radon exposure in Canada—a population-level assessment

Radon is a naturally occurring radioactive gas and presents everywhere on the Earth at varying concentration in workplaces and at homes. With Canadian labour statistics, time statistics and more than 7600 long-term radon measurements in workplaces, occupational radon exposure is evaluated for all 20 job categories based on North American Industry Classification System. Results are compared with residential radon exposure based on more than 22 000 long-term radon tests conducted in Canadian homes. The average annual effective dose due to radon exposure in workplaces is 0.21 mSv, which is lower than the average annual effective dose of 1.8 mSv from radon exposure at home by a factor of eight. Due to relatively higher radon concentration in residential homes and longer time spent indoors at home, exposure at home contributes to 90% of workers’ total radon exposure (on average 1692 h in workplaces and 5852 h at homes). The analysis presented here is based on province-wide average radon exposures in various indoor and outdoor environments. Since the risk of developing lung cancer increases proportionally with increasing radon exposure, this evaluation indicates that on average reduction of radon levels in homes is very important and an effective way to reduce radon-induced lung cancers in Canada.