Continuous Radon Monitoring Research Articles

Monitoring Radon Levels in Hospital Environments. Findings of a Preliminary Study in the University Hospital of Sassari, Italy

Background: The aim of this preliminary study was to measure radon concentrations in a hospital in order to verify to what extent these concentrations depend on various environmental variables taken into consideration, and consequently to determine the urgency to implement mitigation actions. Methods: The rooms where the concentration of the gas was potentially highest were monitored. Investigators adopted a Continuous Radon Monitor testing device. Qualitative and normally distributed quantitative variables were summarised with absolute (relative) frequencies and means (standard deviations, SD), respectively. As regards environmental variables, the difference in radon concentrations was determined using the rank-based nonparametric Kruskal–Wallis H test and the Mann–Whitney U test. Results: All measurements, excluding the radiotherapy bunkers that showed high values due to irradiation of radiotherapy instruments, showed low radon levels, although there is currently no known safe level of radon exposure. In addition, high variability in radon concentration was found linked to various environmental and behavioural characteristics. Conclusions: The results on the variability of radon levels in hospital buildings highlighted the key role of monitoring activities on indoor air quality and, consequently, on the occupants’ health.

Prediction of Indoor Radon Concentration through the Exhalation from Korean Yellow Residual Soil, Hwangtoh as a Building Material

The radon gas from nature mainly considers a cause of radon problems, and it is closely affect human life cycle. Korean yellow residual soil, Hwangtoh, widely used as a building material, is considered to be one of major sources of indoor radon. However, there have, as yet, been no studies about radon from Hwangtoh in mass market brands. Here, we investigated the indoor radon concentrations and exhalation rates in four Hwangtohs from different brand names and regional features. The Closed Chamber Method (CCM) conducted by a Continuous Radon Monitor (CRM) has been used for the rates of radon exhalation. Based on equations of previous references, the indoor radon concentrations were deducted. As a result, the radon surface exhalation rates resulted in the 1.4208 to 3.0293 Bq·m2·h-1 range. Significant differences were found among Hwangtohs according to production regions. Materials with higher radon concentration required a longer time to reach a quasi-steady state in a given environment, in other words, the number of half-life cycles increased from a set starting point. The experimentally identified Hwangtohs demonstrated its safety for construction purposes. There exists, so far, a possibility to exert influence radon emanation due to unidentified factors. Therefore, it is necessary to corroborate with more research by increasing the number of Hwangtohs, considering the other references reported high radon exhalation rates. In addition, it is highly recommended that the radon exhalation rates should be measured for all building materials for preventing human health before the material usage.

Estimation of Organs Doses for People (Male and Female) Exposed to Indoor Radon in Al-Najaf

In this paper, the radon concentrations in the houses of (10) locations were measured using real-time continuous radon monitor RAD-7 detector together with estimating the corresponding female and male organ doses using Monte Carlo (MC) simulation software at Al- Najaf city-Iraq. It is found that the radon concentrations varied from (8.75±1.1 Bq/m3) to (32.32±4.0 Bq/m3 with an average (20.57±2.90 Bq/m3). The resulted data for male reveal that the bladder received the highest dose at 9.78E-05 μGy/h in Missan, while the salivary gland was noticed to have the highest dose in each of Jmhorria, Adalh, Saad and Milad regions with dose rates of 4.65E-05, 3.59E-05, 5.72E-05 and 3.45E-05 μGy/h respectively. In Asskry Najaf regions the highest dose was seen to be with the Lung with 9.30E-05 μGy/h. In Asskiry Kufa and Mutnaby the highest organ doses were attributed to the bone surface at 9.73E-05 and 9.62E-05 μGy/h respectively. In Tmoz and Sirai regions, the highest organ doses were with Extrathor airways and thyroid at 6.64E-05 and 9.65E-05 μGy/h respectively. By contrast, the female findings reveal the doses for all organs and across all considered neighborhoods ranged from 1. E-04 μGy/h to 9E-05 μGy/h. Finally, it can be concluded that all results of radon concentrations in ten locations samples were within the range allowed according to ICRP. The organ doses seem to be very low which in turn reduce the concern realted to the effect of radiation.

Continuous radon monitoring during seven years of volcanic unrest at Campi Flegrei caldera (Italy)

This is a seven-year study (1/7/2011-31/12/2017) of radon monitoring at two sites of Campi Flegrei caldera (Neaples, Southern Italy) that in the last 70 years experienced repeated phases of volcanic unrest. The sites are equipped with devices for radon detection, based on the spectrometry analysis of the α-particles of radon daughters. A hybrid method, as combination of three known methods, is applied for the identification of residuals (anomalies) and trends of the time series of Radon. The results are compared with the following indicators of current caldera unrest: the tremor caused by the major fumarolic vent registered by a seismic station; the cumulative of background seismicity; the maximum vertical deformation acquired by GPS networks during the current phase of uplift; the temperature-pressure of the hydrothermal system estimated based on gas geo-indicators. The comparisons show strong correlation among independent signals and suggest that the extension of the area affected by current Campi Flegrei crisis is larger than the area of seismicity and of intense hydrothermal activity from which the radon stations are 1–4 km away. These results represent an absolute novelty in the study of a such calderic area and mark a significant step forward in the use and interpretation of the radon signal.

Response verification of integrated device used for radon measurements in air

In order to establish the national radon level according to the ICRP recommendations, radon levels should be estimated in different living environments (dwellings, workplaces, hospitals, etc.). A particular attention should be given to the correctness of the radon concentration measurement devices in order to maintain their traceability to primary standard laboratory. Radon monitor systems have thus been calibrated using a NIST standard source which is considered as an important step in standardizing radon measurement methods.In this paper, we describe the system used in our laboratory for the verification against radon response of different radon monitors such as Electret Ion Chamber (EIC) and AlphaGUARD continuous radon monitor (AG), and then we present comparison between these two measurements devices used in some locations at the Centre de Recherche Nucléaire d’Alger (CRNA). As results, EIC system produces results comparable to those produces by the AG system.

A study on the anomalous behaviour of Radon in different depths of soil at a tectonic fault and its comparison with time-series data at a distant continuous monitoring station

The present study reports the anomalous behaviour of Radon isotope pairs (222Rn, 220Rn) in different soil depths at Mat fault, Mizoram (India). The measurement was taken for six occasions between November 2017 and April 2018 under dry soil condition in majority of the occasions. The Radon isotope pair’s data were generated in situ online at depths of 5 cm, 50 cm and 1 m from ground surface in nine selected grid locations at Mat fault. At the same time, to identify geophysical phenomena Radon data were generated at Mizoram University (MZU) in a continuous monitoring station (CMS), located about 57 km from Mat fault. A ZnS/Ag scintillation-based continuous Radon monitor (Model: SMARTRnDuo, BARC, India) was deployed for monitoring Radon at Mat fault as well as in MZU. Correlation study shows that 222Rn data at 5 cm and 50 cm depths of Mat fault region vary in the same manner with 222Rn data at the CMS during all geophysical and non-geophysical process as identified by the CMS 222Rn data. However, 222Rn data at 1 m depth in the fault region does not show any definite correlation with CMS data. The variation of 220Rn data at 50 cm depth in Mat fault also match the CMS 220Rn data but deviated from it at 5 cm and 1 m depth. The influence of meteorological parameters on 222Rn and 220Rn data monitor at the CMS and Mat fault was also reported, and comparison was made with observation reported by other authors in the region.

Radon Exhalation from Five Wood Species

Radon radiation exposures in home have been posed as a potential cancer hazard. This research aims to present the basic data of the indoor radon concentration level by examining the radon exhalation rates of wood species. Radon exhalation rates from five commonly used wood species in Korean wood building construction were measured with Continuous Radon Monitor (CRM), Model 1028 (Sun Nuclear Co., USA) using the Closed Chamber Method (CCM). The mass exhalation rate was observed to vary from 0.00089 Bq·kg-1·h-1 to 0.00181 Bq·kg-1·h-1, whereas the surface exhalation rate was observed to be 0.00677 - 0.01517 Bq·m-2·h-1. The radon exhalation rate of Quercus accutissima Carruth (white oak) which has the highest density showed the highest figure among the five wood species, on the other hand, the rest of four species showed similar results which were similar to the radon exhalation rates of wood in the U.S.A. and Canada. The average of the concentration measured by the CCM represented well up to the second half-life period (7.7 days). Because result of these small quantities seems to indicate that radon exhalation from the tested wood species has almost negligible impact, the main culprit of the high indoor radon concentration is clearly derived from the background of surrounding wood house. Therefore, as a safety precaution, infrastructures made of wood materials should be designed with the consideration of influx of radon and built accordingly. Furthermore, it is highly desirable that wood will be needed to use for furniture and interior finishing material in indoor environment.

Tracing groundwater inputs to Bay of Bengal from Sankarabarani River Basin, Pondicherry, India, using continuous radon monitoring

Sankarabarani river basin gains importance due to agriculture, an industrial and recreational activity that delivers large groundwater fluxes to the Bay. Attempt has been made by continuous monitoring of radon isotopes to evaluate submarine groundwater discharge with reference to groundwater and surface and pore water samples with distance perpendicular to the coast. 222Rn in groundwater samples were higher (543.0 Bq m−3) signifying major radon sources due to coastal groundwater discharge. Radon mass balance model attempted by considering fluxes like tides, atmospheric emissions, and sediment diffusion suggests higher groundwater and surface water fluxes (7.2 and 20.15 m day−1) near to the coast and higher fluxes (19.7 and 9.7 m day−1) in pore water away from the coast, suggesting influence of hydraulic gradient and radium retention in sediments. The average fresh submarine groundwater discharge calculated accounts 0.88 m day−1, higher in comparison with world studies.

UNCERTAINTY OF THE RESULTS OF THE RADON CONTROL IN HOUSINGS. PART 2. EXPERIMENTAL ASSESSMENT OF THE TEMPORAL VARIATIONS OF RADON

The first part of the paper was devoted to a detailed investigation of the problems of radon control in buildings as well as to the description of the accurate principle of radon control on housings, which is based on the new parameter – temporal variation coefficient K V (t). This coefficient equalizes the main component of the uncertainty of the average annual level of radon depending on the protocol and duration of measurements. Additionally, a novel algorithm for the estimation of K V (t) is proposed, developed on the base of the results of continuous annual radon monitoring in representative experimental housings. This part of the paper is focused on the results of the annual continuous monitoring of volume activities of radon and its daughter products in ten experimental housings in 2006–2013. These housings were located in seven buildings mainly in the Moscow region. All the experimental buildings have the detailed description. The use of original algorithm of the processing of the results of annual monitoring allowed estimating particular and table values of K V (t) co-efficient, depending on the protocol and duration of the measurements. The values of the coefficient are lower up to a factor of two if the temperature is considered. However, the possibility of such consideration is significantly limited by the number of factors. Additionally, an importance of considering a geological factor is discussed. Evaluation of the representativeness of the data obtained and the method for verification and elaboration of the table values of K V (t) are provided as well. Based on the results obtained, there is a possibility for the development of the approaches in the field of sanitary-epidemiologic surveillance in the field of practical realization of the strategy of mass radon control and effective identification of buildings with increased radon levels.

UNCERTAINTY OF THE RESULTS OF THE RADON CONTROL IN HOUSINGS. PART 1. THE PROBLEM OF ASSESSMENT OF THE RADON CONCENTRATION AND MODERN CONTROL PRINCIPLES

Radon control in buildings is being performed for decades in different countries of the world, including Russia. However, there is a lack of unified standard for the assessment of the uncertainty of the results of the control, considering the protocol and duration of the measurements. It is obvious that the uncertainty of the control increases with the reduction of the duration of the measurements. The lack of data on confidence interval for the average annual radon concentration in housings does not allow correct and precise comparison with the regulatory level, both for the commissioned and operated buildings. Additionally, it complicates a development of the effective method, mass control strategy and identification of buildings with high radon concertations. A reliable method of control, considering time variations of radon and duration of exposure, was developed in Russia several years ago, but it is not well-known and not applied on practice. This paper is focused on a novel principle of radon control, based on simple criteria, widely used in metrology and complying to the modern standards. This principle introduces a new parameter – the radon time variation coefficient KV(t), which reflects main constituent of the uncertainty of the average annual radon concentration depending on the protocol and duration of the measurements. A novel algorithm for the estimation of KV(t) is proposed, developed on the base of the results of continuous annual radon monitoring in representative experimental housings. Additionally, the structure of the correcting coefficient is presented, considering an impact of the temperature on the radon behavior. The use of the corrective coefficient allows lowering the KV(t)value, but its application is limited.

Setup and procedure for routine measurements of radon exhalation rates of building materials

A practical procedure and the necessary setup for routine measurement of the exhalation rate of 222Rn from building materials are described. The setup comprises a continuous radon monitor, based on an ionization chamber, and a relatively large-volume accumulation chamber. The experimentalist can interact with the setup in real time via a PC. Therefore it is possible to determine the exhalation rates by determining the optimum accumulation time before the effects of back-diffusion and radon decay set in. This, in turn, reduces the time required to test a sample and makes the setup useful for routine measurements. The exhalation rate values (Bq m−2 h−1) for selected building materials made from gypsum, marble, ceramic, and granite were found to be 1.63, 2.29, 3.99 and 5.39 Bq m−2 h−1, respectively. The optimal test-times for the samples ranged from 9 to 19 h.

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.

Assessment of annual effective dose due to outdoor radon activity in the environment of Bengaluru

Soil is the major source of radon to enter the living environment. In the present study, an effort was made to see the contribution of radon activity to the dose received by the public of the study region. The radon activity in soil gas and radon exhalation rate from the surface soil were measured in the Bangalore University campus using a continuous radon monitoring device called RAD7. The value obtained in the present investigation is ranged from 1690 ± 362 to 7390 ± 324 Bq/m3, with the geometric mean (GM) of 4120 ± 307 Bq/m3, and 13.97 ± 7.55–24.82 ± 8.38 mBq/m2/s, with the GM of 18.13 ± 6.52 mBq/m2/s, respectively. The radon exhalation rate was also calculated using the values obtained from the radon activity in soil gas and is compared with the measured value. The annual effective dose (AED) was estimated from the measured radon concentration near to the soil surface and is found to be ranged from 0.02 to 0.07 mSv/y, with the GM of 0.04 mSv/y. The AED due to inhalation is well within the global average as reported in the UNSCEAR 2000, which indicates that there is no threat to the human due to the outdoor radon concentration in the study area.

SIGNAL DECOMPOSITION AND ANALYSIS FOR THE IDENTIFICATION OF PERIODIC AND ANOMALOUS PHENOMENA IN RADON TIME-SERIES.

This work concerns continuous monitoring of radon and thoron specific activity in soil gas within the framework of identifying possible anomalies. It is based on the analysis of a medium-term data record obtained from soil gas in an area of geophysical interest. The RaMonA spectrometric system is also used to measure the climatic parameters and a specific analysis of the alpha spectra is performed to better determine the alpha lines intensity. Since radon emission is also influenced by meteorological parameters, it is mandatory to differentiate the changes due to the deep phenomena. Different procedures are utilized to reach the above objective: statistical analysis using the Empirical Mode Decomposition technique, the Multiple Linear Regression method and the Remote Radon Estimation by using of the thoron trend to eliminate the locally produced radon fraction. The results of such methods are compared to recognize and to highlight radon anomalies.

ASSESSMENT OF RADIUM ACTIVITY CONCENTRATION AND RADON EXHALATION RATES IN IBERIAN PENINSULA BUILDING MATERIALS.

Radium (226Ra) is a natural radioactive element of the uranium decay series, which could also be present in building materials. Radon (222Rn) is continuously produced by the decay of 226Ra and its presence inside buildings can contribute to the increase of the population exposure to ionizing radiation. In this work, the amount of radium activity concentration and radon exhalation rates in several types of building materials that are commonly used in the Iberian Peninsula have been tested. The radium activity concentration was measured by gamma-ray spectrometry, whereas the radon exhalation rates were carried out using a continuous radon monitor (active measuring technique) and a solid state nuclear track detectors (passive measuring technique). The 226Ra mean values range from 5.0 to 123.4 Bq kg-1. As expected, the results show that the radon exhalation rate is higher in granites samples relatively to others building materials analysed. A positive correlation was found between radium activity concentration and radon exhalation rates in both techniques. The emanation fraction and alpha index were also calculated.

RADON CONCENTRATIONS IN UNDERGROUND DRINKING WATER IN PARTS OF CITIES, CHINA.

222Rn concentrations in underground drinking water samples in 12 cities from seven provinces (municipalities), China were determined by using a continuous radon monitor with air-water exchanger. A total of 73 underground water samples were collected. The observed radon levels were in a range of 1.0-63.8 Bq l-1, with a mean of 11.8 Bq l-1. The annual effective dose from inhalation of water-borne radon for average radon content in underground water was 72.6 μSv and for maximal observed radon concentration in underground water the corresponding dose was 393.8 μSv. The dose contribution of inhalation dose from water-borne radon should be paid attention in some granitic area.

Measurement of Radon Concentration in Selected Houses in Ibadan, Nigeria

Radon is a natural radioactive gas without colour or odour and tasteless. The World Health Organization (WHO) grouped radon as a human lung carcinogen. For this reason, there has been a lot of interest on the effects of radon exposure to people all over the world and Nigeria is no exception. The aim of this study is to investigate the radon concentration in selected houses in three local government areas of Ibadan. The indoor radon was measured in both mud and brick houses. Fifty houses were considered from the three Local government areas. A calibrated portable continuous radon monitor type (RAD7) manufactured by Durridge company was used for the measurement. A distance of 100 to 200 m was maintained between houses in all the locations. The living room was kept closed during the measurements. The mean radon concentration measured in Egbeda is 10.54 ±1.30 Bqm-3; Lagelu is 16.90 ± 6.31 Bqm-3 and Ona-Ara is 17.95 ± 1.72 Bqm-3. The mean value of the annual absorbed dose and annual effective dose for the locations in the three local government areas was 0.19 mSvy-1and 0.48 mSvy-1respectively. The radon concentration for location 10 in Ono-Ara local government exceeded the recommended limit. However, the overall average indoor radon concentration of the three local governments was found to be lower than the world average value of 40 Bqm-3. Hence, there is need for proper awareness about the danger of radon accumulation in dwelling places.

Multi-parametric approach to the analysis of soil radon gas for its validation as geoindicator in two sites of the Phlegrean Fields caldera (Italy)

Radon is considered one of the short- and immediate-term earthquake precursors by International Association of Seismology and Physics of the Earth’s Interior. For this reason, the accurate and reliable measurement of its specific activity in soil gas is mandatory. Since its presence is influenced by many environmental factors, in order to eliminate this influence on the radon activity measurement a multi-parametric and multi-site analysis is necessary. Following this approach, a continuous radon monitoring was carried out in two sites of the Phlegrean Fields caldera (Campania, Italy) using the RaMonA system, which also allows for the measurement of temperature, relative humidity and pressure. In particular, the dependence of measured radon specific activity on the meteorological conditions was studied using the multiple linear regression method. The analysis was implemented also by testing data averages on different timescales. In this paper, the results of a preliminary analysis performed on data collected throughout 2012 are presented; the outcomes obtained allow to emphasize site-specific behavior and to discriminate apparent radon “anomalies” of climatic origin from those tied to the phenomena occurring in the earth’s crust. The method employed showed its usefulness by removing the effects of meteorological conditions and thus to better identify the possible radon anomalies caused by seismo-volcanic activity. The peculiarities of the different sites and some correlations with earthquakes are discussed.

Radon dynamics in a dwelling with high radon levels in a karst area

Abstract Year-long continuous radon monitoring was carried out (using Sarad Radon Scout devices) in a dwelling with high radon levels in the karst region of Slovenia. Two living rooms were selected: one on the ground floor with normal housework activities; and the second, on the first floor, closed and unattended. Meteorological data were also recorded. The following seasonal geometric means of radon activity concentration (kBq m −3 ) have been found: 6.28×/: 3.05 for spring, 1.25×/: 3.78 for summer, 5.17×/: 2.03 kBq m −3 for autumn and 9.83×/: 1.48 for winter on the ground floor; and 1.43×/: 3.71 for spring, 0.168×/: 2.49 for summer, 1.08×/: 2.39 for autumn and 2.08×/: 2.14 for winter on the first floor. Results are supported by additional radon measurements in other rooms; and in water the results indicate a strong radon source associated with an underground karst shaft.

Exploring the relationship between soil degassing and seismic activity by continuous radon monitoring in the Longitudinal Valley of eastern Taiwan

Donghua (DH) continuous soil gas monitoring station is located on the suture zone in eastern Taiwan. The variations in radon concentration are synchronized to variations in carbon dioxide (CO2), which is considered as the companion gas for radon (Rn). Results reveal that semi-diurnal variation of soil-gas, probably generated by the solar tide effect, achieve values of ~500Bq/m3 for Rn and 0.4% for CO2. The variations exceeding the threshold by statistical analysis can be used to identify events associated with geodynamic processes such as earthquakes. A significant increase in soil-gas concentrations was recorded 2months before the Rueisuei earthquake (ML=6.4, October 31, 2013) and recurrent anomalies were observed 3weeks before the Fanglin earthquake (ML=5.9, May 21, 2014). Both earthquakes occurred in the Longitudinal Valley area of eastern Taiwan. This study suggests that longer periods of soil gas anomalies are positively correlated with impending earthquake of larger magnitude. From the high precision GPS data showed an appreciable decrease in extension rate was also observed approximately 4months before the Rueisuei earthquake. It is worthy to have a continuous monitoring on multiple parameters (soil radon, carbon dioxide, atmospheric pressure, humidity, temperature and precipitation) at DH station.