Annual Average Radon Concentration Research Articles

Coherent long-term average indoor radon concentration estimates obtained by electronic and solid state nuclear track detectors

Despite the rapid development of consumer-grade electronic radon monitors, their capabilities to assess long-term average radon concentrations are not systematically investigated. We present the results of a year-long measurement campaign in 32 dwellings and workplaces in two areas with typical and high radon concentrations in Bulgaria. A systematic comparison was made between electronic monitors and the gold standard – solid-state nuclear track detectors (SSNTDs). RadonEye Plus2 (RE) monitors were used, calibrated and metrologically tested at the three participating laboratories. Two SSNTD-based detectors were utilized: passive radon detectors (PRDs) developed by UKHSA, and CDs/DVDs, developed at SU. Two PRDs for quarterly radon measurements, a RE, a CD and a DVD were placed at each location. Additional old CDs/DVDs were collected for retrospective radon estimates. The results for the annual average radon concentrations, estimated by the four methods are presented. The average difference between the REs and PRDs estimate was 8% (median 4%), between the REs and CDs was 5% (median 0.4%) and between REs and DVDs was -10% (median-12%). The Z-score, representing the difference normalized to its uncertainty, in most cases fell within -1 and 1, indicating excellent agreement. The retrospective estimates also demonstrated excellent agreement with the other data. However, in some cases, small but statistically significant biases were identified between REs and SSNTDs or between different SSNTDs, requiring an inclusion of a reference instrument in future studies. Overall, the results imply that with sound metrological assurance, RadonEye Plus2 monitors can assess long-term average radon concentrations with sufficient accuracy.

On the identification of radon areas as defined in art. 103 of Council Directive 2013/59/EURATOM.

Radon maps are one of the key tools for implementing a graded approach to reduce exposure due to radon. The Council Directive 2013/59/Euratom indicated how to identify the geographical areas of the country most exposed to indoor radon. Using annual average radon concentrations in 5000 dwellings in the Lazio region, located in central Italy, the expected number of dwellings with annual average radon concentrations above the reference level of 300Bq per m3 within the 6km grid squares was estimated. For the purpose of application, radon areas were identified by arbitrarily selecting grid squares with at least 10 expected dwellings per square kilometer above 300Bq per m3. Since comprehensive measurements surveys must be conducted within the radon areas to identify all dwellings exceeding the reference level for the purpose of reducing radon concentration, quantitative economic considerations are reported.

Rock-avalanche deposit causes extreme high indoor radon concentrations in Kinsarvik, Ullensvang municipality, Western Norway

The radon problem in Kinsarvik, Ullensvang municipality in Western Norway, is among the most severe in the world. Annual average indoor radon concentrations as high as 56,000 Bq/m3 have been measured. The problem affects >100 houses, where average yearly indoor radon concentrations of 4340 Bq/m3 has been reported. Indoor radon concentrations vary during the year, which has been explained by thermally induced flows of radon-bearing air through a porous ice-margin deposit.Updated geological knowledge and new mapping methods (LIDAR data) have allowed for a re-examination of the problem. There is significant evidence that does not fit with the established geological understanding that classifies the Kinsarvik deposit to be an ice-marginal moraine. Instead, the landforms and internal structures of the deposit are characteristic of a rock-avalanche deposit. The LIDAR data suggests a rockslide deposit of approximately 50 million m3.Airborne and ground gamma-ray spectroscopy show elevated uranium content in the granitic bedrock north and east of Kinsarvik. These uranium-bearing rocks are also found in an open pit in the Kinsarvik deposit.Terrestrial cosmogenic nuclide dating of four surface boulders shows an average age of 10,900 ± 600 years. This suggests the rock avalanche fell immediately after the last deglaciation of Western Norway.Our results support that the radon problem in Kinsarvik is caused by uranium bearing bedrock and a porous rock-avalanche deposit that emanates radon, which in turn exhibits an alternating, temperature driven flow direction.

Extreme reverse seasonal variations of indoor radon concentration and possible implications on some measurement protocols and remedial strategies

Indoor radon levels in dwellings are typically higher in cold months than in warm ones. The indoor radon concentration might experience an inverse seasonal behaviour – i.e., radon levels much higher in summer than in winter – under specific circumstances.In the framework of a study on long-term variations of annual radon concentration carried out in some tens of dwellings in Rome and surrounding small towns, two dwellings with very high – up to extreme – reverse seasonal variations were accidently discovered. These dwellings were located in a volcanic area, and they are both south-oriented and located on the lower part of a hill.In one of them, radon concentration was monitored by a continuous radon monitor for two years to find out when the greatest rises in radon levels occur. The indoor radon concentration resulted to experience extremely rapid, i.e. very few hours, increases up to 20 000 Bq m−3 during the spring period (i.e., April, May, and June especially). After about ten years from the first observation, the indoor radon concentration of the same house was monitored again for about five years: radon concentration peaks previously observed were found to be unchanged in terms of absolute values, duration, rising time and occurrence period.These reverse seasonal variations may lead to significant underestimation of the actual annual average radon concentration in case of measurements lasting less than one year if performed during the cold season and especially when seasonal correction factors are used. Moreover, these results suggest adopting specific measurement protocol and remediation strategies in houses having some peculiar characteristics, mainly regarding orientation, position, and attachment to the ground.

Radon Exposure in the Underground Tourist Route-Historic Silver Mine in Tarnowskie Góry, Poland.

An assessment of the exposure of workers and tourists to radon in the underground tourist route of the Historic Silver Mine in Tarnowskie Góry was carried out. The study was conducted over a one-year period to capture seasonal variations in radon concentrations. CR-39 track detectors were used to measure radon concentrations, which were exposed in the mine during the following periods: 9 February 2021-19 May 2021, 19 May 2021-26 August 2021, 26 August 2021-25 November 2021 and 25 November 2021-3 March 2022. The annual average radon concentration along the tourist route was 1021 Bq m-3. The highest measured concentration was 2280 Bq m-3 and the lowest concentration was 80 Bq m-3. Based on the measured concentrations, effective doses were calculated, assuming that employees spend 1350 h a year in underground areas and that the time of visiting the mine by tourists is ca. 1 h. The average annual effective dose a worker would receive is approximately 2.5 mSv, and a tourist below 2 μSv. The dose limit expressed as the annual effective dose is 1 mSv for members of the general public and 20 mSv for occupational exposure.

RADON-PRONE AREAS IN SLOVAKIA PREDICTED BY RESCALED RADON POTENTIAL MAPS.

Several scientific studies have shown that high content of radon in the soil environment can be a precursor of increased indoor radon levels. Inhabited areas where elevated indoor radon concentration appears for natural (geogenic) reasons are commonly referred to as radon-prone areas. In this study, radon-prone areas in the Slovak Republic were predicted on the basis of radon potential maps after its specific rescaling. In total, 99 municipalities have been identified in Slovakia where the annual average indoor radon concentration is expected to exceed the reference level of 300Bqm-3; five of those are even expected to exceed 1000Bqm-3. In these municipalities it is then required to conduct a survey of indoor radon measurements. Compared with a nationwide survey, the proposed approach of searching for houses with potentially high radon exposure is more efficient.

DETAILED INDOOR RADON SURVEY IN DWELLINGS OF PROVISIONAL RADON-PRONE AREAS IN KOREA.

The objective of this study is to determine indoor radon concentrations for 11 counties in Korea, develop a detailed radon distribution map and compare the results by some factors influencing indoor radon levels. The radon survey was conducted for 7y in provisional radon-prone areas selected based on the previous national surveys. The total number of samples was >2.5% of the entire dwellings by each county. The annual average indoor radon concentration for the survey areas had a geometric mean of 94Bqm-3 with 6.6% of all sampled dwellings showing values exceeding 300Bqm-3. Some areas with relatively high indoor radon concentration were identified through a spatial distribution map. Seasonal variations were observed with commonly the highest concentration in winter, and house characteristics influencing indoor radon levels. This study can serve as a basis for developing national radon action plans and guide for additional regional radon surveys.

Development of a corrective model of short-term radon concentrations to estimate annual effective doses in the primary schools of the Doukkala-Abda region, Morocco

In order to assess the radiological impact of radon on >250,000 students, the total annual effective dose was estimated inside 204 Moroccan primary schools sampled in the Doukkala-Abda region. The measurement of indoor radon concentrations was conducted using the LR115 detector for each month, each season and throughout the year. The evolution of indoor radon concentrations showed a decrease in annual average radon concentrations of 20–26% and 10–14%, respectively, compared to the monthly and seasonal annual average radon concentrations. For this purpose, a corrective model of short-term radon concentrations was developed to calculate the seasonal correction factors in order to estimate the annual indoor radon concentrations. For the qualitative evaluation of these factors, a percentage of deviation between the measured and estimated annual radon concentrations was calculated. Almost half of the estimated annual concentrations were 10% less than the measured concentration and the majority of these estimated values were within 40%. The estimated total annual effective doses received by students, except those in the Sidi Bennour city, were higher than the world average (1.15 mSv/y). Nevertheless, all these doses remained below the permissible limit recommended by the International Commission on Radiological Protection (3–10 mSv/y).

Upgrade of a Highly Sensitive Monitor for Atmospheric Radon Measurement

Atmospheric radon is an ideal tracer that is widely used in atmospheric science. To meet the need fora continuous online measurement of atmospheric radon concentration, an upgraded radon monitor based on an electrostatic collection method was developed following Iida’s measurement system. Two major improvements have been realized. First, an 18 mm × 18 mm Si-PIN detector and a multi-channel analysis system were used to distinguish different alpha particles. Second, the P2O5 desiccant was replaced by a new membrane drying system, and the influence of humidity was corrected by a humidity correction coefficient. Calibration and comparison experiments were carried out in detail, and a one-year continuous measurement was also performed. Results showed that the measurement sensitivity was evaluated to be 24.3 cph/(Bq·m−3), and the lower level detection limit was 0.2 Bq·m−3 for a 1-h cycle at the absolute humidity of 0.34 g·m−3. The annual average radon concentration of Beijing was 11.1 ± 4.0 Bq·m−3, which changed from 2.8 Bq·m−3 to 30.3 Bq·m−3 between 15 October 2018 and 1 October 2019. The upgraded monitor’s high data acquisition rate and good performance indicate that it is suitable for long-term observation on atmospheric radon.

Simultaneous measurements of radon, thoron and their progeny for inhalation dose assessment in indoors of Srinagar, J&K, India

A variety of toxins are known to affect indoor air quality, thereby affecting the health of the inhabitants of that region. One such natural contaminant is radon, which is a dense, colourless, odourless and inert gas. As per BEIR-VI report (Chauhan and Chauhan in J Environ Radioact, 2015. https://doi.org/10.1016/j.jenvrad.2015.03.009), Radon alone contributes to more than 50% of the total natural background radiation and is the second leading element causing lung cancer after smoking. Therefore, its quantification is vital to assess any risk to human health. In order to assess health risks, a recently developed LR-115 detector based technique was employed for time-integrated passive measurements of radon, thoron and their progeny concentrations. The annual average radon concentration was found to be 35.6 Bq m−3 and thus lies well below the global average of 40 Bq m−3. However, thoron concentration exceeded the global average value of 10 Bq m−3.

Human Health Risk Assessment for Exposure to Radioactive Radon with Due Regard for Its Nanodispersed Decay Products

A technique was designed to assess the human health risk associated with exposure to radioactive radon. As a focus, a dose–effect relationship model was developed on the basis of international and first-hand experience. The model suggests a multiplicative dependence on the probability of spontaneous lung cancer and takes account of the fact that radiation effects on the lungs are exerted by the radon decay daughter products entering the lungs in a nanodispersed form. The effects of radon are already present in the statistics of spontaneous lung cancer, and the risk of death from spontaneous and radiation-induced lung cancer depends strongly on the smoking status. A test calculation of the radon-associated risk was performed for a region of the Russian Federation and showed that radon may substantially contribute to mortality from lung cancer in areas with relatively high radon concentrations in the ambient air. Exposure to radon at an annual average radon concentration comparable with the standard level for new buildings under construction (200 Bq/m3) increases the risk of death from lung cancer by 20%. The method is suitable for assessing the health risk associated with exposure to radon for miners and the general population.

Radon concentration assessment in bank cellars in three Nigerian cities

Cellar workplaces are considered as confined environment with challenging indoor air quality having higher than normal pollutants particularly that of soil gas origin. Radon, a major soil gas, infiltrates and accumulates within indoor spaces and becomes harmful in the absence of ventilation. Radon level in bank basements (cellars) in Ilorin, Lagos and Akure have been sampled and analysed in this study. In Nigeria, most workers in basements are unaware of radon, and there is limited documented research on its health hazards. The survey parameters of radon concentrations were floor types, geographical locations and the influence of atmospheric conditions. Corentium monitor, a continuous, digital radon monitor, temperature meters and Prologue wireless weather station were used for the experiments. Annual average indoor radon concentration for the survey period was 23 Bq/m 3 . The calculated mean annual effective doses in basements and different floors were below the recommended ICTR level of 3 mSv/y. Keywords: Indoor air quality, Pollutants, Radon, Ventilation

A CASE STUDY ON THE USE OF SEASONAL CORRECTION FACTORS FOR INDOOR RADON MEASUREMENTS.

Radon concentration measurements were performed in the city Eskişehir, Turkey in order to quantify seasonal variation. Using the assumption that indoor radon concentrations exhibit annual cyclic behavior, Pinel's methodology was employed to obtain seasonal correction factors (SCFs). A total of 142 dwellings had radon concentration data for each season that enabled to obtain annual average radon concentrations. Estimated SCFs were applied to each of the 142 dwellings to assess the validity of the factors. The results demonstrate that even in a very small region significant variation in radon concentrations of different dwellings can be observed, and that a good care should be taken in applying SCFs to a short-term radon measurement to obtain average annual radon concentration.

A study of indoor radon, thoron and their exhalation rates in the environment of Fazilka district, Punjab, India

Over the last few decades, the study of radioactive radon gas has gained huge momentum due to its possible role in health related hazards. In the present work, pin-hole twin chamber single entrance dosimeters have been used for track measurements of radon and thoron. The annual average radon concentration varies from 50.3 to 204 Bq/m3 at all locations. Almost all the values are below the safe range provided by ICRP. Radon concentration is found to be higher in winter as compared to other seasons. Variation of radon with quality of dwellings is also discussed. The values of annual effective dose due to radon and thoron are also well within the range provided by ICRP and WHO. Radon and thoron exhalation rates are measured using SMART RnDuo monitor. The radon mass exhalation rates ranged from 11 to 71 mBq/kg/h while the thoron surface values ranged from 36 to 2048 Bq/m2/h. All the values are on the lower side. A weak correlation is found between radon and thoron concentrations and their exhalation rates. When compared with the values of other parts of northern India, the values of present investigation are on higher side.

Indoor radon regulation using tabulated values of temporal radon variation

Mass measurements of indoor radon concentrations have been conducted for about 30 years. In most of the countries, a national reference/action/limit level is adopted, limiting the annual average indoor radon (AAIR) concentration. However, until now, there is no single and generally accepted international protocol for determining the AAIR with a known confidence interval, based on measurements of different durations. Obviously, as the duration of measurements increases, the uncertainty of the AAIR estimation decreases. The lack of the information about the confidence interval of the determined AAIR level does not allow correct comparison with the radon reference level. This greatly complicates development of an effective indoor radon measurement protocol and strategy.The paper proposes a general principle of indoor radon regulation, based on the simple criteria widely used in metrology, and introduces a new parameter – coefficient of temporal radon variation KV(t) that depends on the measurement duration and determines the uncertainty of the AAIR. An algorithm for determining KV(t) based on the results of annual continuous radon monitoring in experimental rooms is proposed. Included are indoor radon activity concentrations and equilibrium equivalent concentration (EEC) of radon progeny. The monitoring was conducted in 10 selected experimental rooms located in 7 buildings, mainly in the Moscow region (Russia), from 2006 to 2013. The experimental and tabulated values of KV(t) and also the values of the coefficient of temporal EEC variation depending on the mode and duration of the measurements were obtained. The recommendations to improve the efficiency and reliability of indoor radon regulation are given. The importance of taking into account the geological factors is discussed. The representativity of the results of the study is estimated and the approach for their verification is proposed.

Identifying radon priority areas and dwellings with radon exceedances in Bulgaria using stored CD/DVDs

The implementation of the 2013/59/EURATOM directive in the part related to radon exposure imposes challenges for radon measurement methodology and radon survey design. Among them is the need to have estimates (preferably direct) of the annual average radon concentrations, which can be directly compared to the recommended reference levels. On this basis, the surveys should make possible the identification of dwellings with indoor radon above the reference levels and “radon priority areas” where significant proportion of the dwellings falls in this category. The performance of the CD/DVD method for radon measurements as a tool to address these issues is presented. A recent large scale field study based on the CD/DVD method that was carried out in the suburb area of Sofia, Bulgaria is described. Part of the studied area was affected in the past by the uranium mining and milling industry. In total 462 disks (CDs and DVDs) taken from 335 private dwellings from 10 districts in the region were analyzed. The results revealed the large heterogeneity in radon distribution in the area, with the percentage of dwellings with a 222Rn level above 300 Bq m−3 ranking from about 7% to 74%. The district of Yana, for which this percent was 74, was identified as the area of highest radon priority in the region. The paper also discusses how prompt identification of dwellings with radon above the reference level by CD/DVDs can be incorporated within an integrated approach to the radon problem. Within this approach the radon hazard is identified shortly after the stakeholder's decision to test, which allows fast solution of the problem without waiting the long (and usually demotivating) one-year period needed for direct results by the commonly used prospective methods.

Hazard indices and annual effective dose due to terrestrial radioactivity in Northern Kerala, India

Kerala is listed among the six highest background radiation areas of the world. The west coast of Kerala is very well studied. However, no data is available regarding the high ranges. This study reports measurement of terrestrial concentration of radionuclides in Wayanad district (altitude range 700–2100 m above mean sea level), a known tourist place of Kerala, India having a sizeable tribal population. Activities of 40K, 226Ra and 232Th in soil samples measured using gamma ray spectrometry were found to be 265 ± 334, 21 ± 15 and 39 ± 38 Bq kg−1 respectively. Similar studies were done for rock samples. The average indoor and outdoor hazard indices were found to be 0.24 and 0.20 for soil and 0.5 and 0.4 for rocks, respectively. The indoor radon and thoron concentrations were measured using solid state nuclear track detector. The annual average radon concentration was found to be 31 Bq m−3 and the annual average thoron concentration was 96 Bq m−3. Out of the samples, one house showed elevated thoron concentration with an annual average value of 621 Bq m−3.

Significant annual and sub-annual cycles in indoor radon concentrations: seasonal variation and correction

Abstract The majority of radon measurements in the built environment are made over sub-year periods and are then generally seasonally corrected (i.e. scaled by an appropriate seasonal correction factor (SCF)) to estimate the annual average radon concentration. SCFs are statistically derived and assume an underlying annual cycle, reflecting the widely observed seasonal variation in indoor radon concentrations. In the UK, Public Health England has pioneered the calculation and use of a national SCF set using an annual sinusoidal model for variations in radon concentration and averaging across the entire country. To test the validity of that model, a 4 year record of weekly radon data from four houses in Brixworth (Northamptonshire, UK) was analysed in conjunction with corresponding weather data for the period from a nearby weather station. The radon data showed a statistically significant annual cycle comprising both annual sinusoidal and second harmonic (i.e. 6 month period) terms. Two sets of SCFs were calculated: first, using a conventional annual sinusoidal model that explained 21.2% of the variance in the radon data; and, secondly, a second harmonic term was included in the model that explained 24.6% of the variance. This represents an improvement of 3.4 percentage points (15.9%) and, thus, will result in better SCFs.

Distribution of indoor radon concentrations between selected Hungarian thermal baths

Abstract Owing to the high potential of radon to increase the risk of lung cancer, health organizations are enforced to update their regulations and recommendations regarding indoor radon levels each year. In this study, the indoor radon concentrations of three randomly selected thermal baths in Hungary using CR-39 and an AlphaGUARD radon monitor were measured with regard to the new updated standards of the European Basic Safety Standard (EU BSS, Council Directive 2013/59/Euratom, 2014). The annual average of indoor radon concentrations in Parad Medical Bath, Igal Health Spa and Eger Turkish Bath were measured as 159 ± 19, 176 ± 27 and 301 ± 30 Bq/m3, respectively. Indoor radon concentration in all measurement locations were determined to be below the reference level, with the exception of the main pool, small pool and sparkling bath areas in the Eger Turkish Bath that were measured as 403 ± 42, 315 ± 32 and 354 ± 36 Bq/m3, respectively. In light of the results, the estimated annual average radon concentration in the thermal baths was below the EU BSS reference level of 300 Bq/m3. Personal dosimetry is required to estimate the annual effective dose from inhaled radon by the workers at the Eger Turkish Bath. This procedure is required in order to justify the application of the mitigation process of decreasing working hours, improving the ventilation rate or increasing the number of classified employees in response to the official radiation surveillance programme.

Indoor radon concentration and gamma dose rate in dwellings of the Province of Naples, South Italy, and estimation of the effective dose to the inhabitants

The indoor radon concentration was measured in 471 dwellings in the Province of Naples. Radon concentration measurements were carried out using LR-115 passive alpha track detectors (SSNTDs) that were exposed for two consecutive semesters. The annual average radon concentration in the dwellings was found to vary from 21 to 722 Bq m -3 with an average value of 107 ± 75 Bq m -3 . In about 93% of the dwellings the radon concentrations were found to be below 200 Bq m -3 , which is the recommended level by Italian law for new buildings. Simultaneously with the radon concentration measurements, indoor gamma dose rates were measured in 388 dwellings. Indoor gamma dose rates were measured using Thermoluminescent Dosimeters (TLDs) exposed in each dwelling for six months. The arithmetic mean value was found to be 327 ± 102 nGy h -1 , after the subtraction of the cosmic ray contribution. A weak correlation between the indoor radon concentration and gamma dose rate was found. The correlation between indoor radon measurements and gamma dose rates and the same building characteristics was also studied.