High natural radiation exposure in radon spa areas: a detailed field investigation in Niska Banja (Balkan region)

The measurement campaigns have been done in the rural community of Niska Banja, a spa town located in southern Serbia, to evaluate population exposure to natural radioactivity. After a screening survey in 200 houses, annual radon and thoron concentrations were measured in 34 houses, and in 2004 a detailed investigation was carried out at six houses with elevated indoor radon concentrations. The paper presents the results of these detailed measurements. The complementary techniques were applied to determine radon and thoron concentrations in indoor air, in soil gas, radon exhalation from soil, soil permeability, and indoor and outdoor gamma doses. Soil and water samples were collected and analysed in the laboratory. Indoor radon and thoron concentrations were found to be more than 1kBqm(-3) and 200Bqm(-3), respectively. Extremely high concentrations of soil-gas radon (>2000kBqm(-3)) and radon exhalation rates (1.5mBqm(-2)s(-1)) were observed. These results will be utilised to set up the methodology for a more systematic investigation.     

Comparative studies of health hazard from radon (Rn-222) in two selected lithologic formations in the Suwałki region (in Poland)

The aim of this work was to make a comparison of indoor radon concentrations in dwellings and in soil air in the area of two geological formations in the Suwa?ki region (Poland). The mean arithmetic airborne concentration was found to be the highest (301 Bq m (-3)) in the basements of buildings in the gravel and sand areas, whereas in the boulder clay areas it reached 587 Bq m (-3). Out of 54 measurements of radon concentrations performed at the ground floor, in eight cases concentrations were found to exceed 200 Bq m (-3) - permissible radon level in new-built houses in Poland and in three cases these values were even higher than 400 Bq m (-3). The highest radon levels were noted in houses with earthen basement floors and with direct entrance from the basement to rooms or kitchens. The mean arithmetic radon concentration in the soil air in the sandy and gravel formations was 39.7 kBq m (-3) and in clay formation it was 26.5 kBq m (-3). Higher radon levels were also found in the water obtained from household wells reaching 8367 Bq m (-3) as compared with tap water (2690 Bqm (-3)). The mean indoor concentration for the whole area under study was found to be 169.4 Bq m (-3), which is higher than the mean value for Poland (49.1 Bq m (-3)) by a factor of 3.5.     

Contribution of (222)Rn-bearing water to the occupational exposure in thermal baths

The present study investigates the short- and long-term effects of radon ((222)Rn) released from water on the progeny exposure in a thermal spa. For the purposes of this work, the Polichnitos spa was used as a case study. The bathroom was supplied with water containing 110-210 kBq m(-3) of (222)Rn. The (222)Rn concentration in air and the short-lived (222)Rn progenies in attached and unattached form were monitored into the bathroom and the surrounding premises. The equilibrium factor (F-factor) and the unattached fraction were estimated. The results of this study show that water flow during bath filling is by far the dominant mechanism by which (222)Rn is released in the air of the bathroom. The progeny exposure was correlated linearly with the (222)Rn concentration in the entering water. The annual effective dose received by a worker was found to be below the lower limit value of 3 mSv recommended by ICRP 65. The dose limit was exceeded only for water containing more than 300 kBq m(-3).     

Dispersion of 222Rn from two New Zealand geothermal power plants

The dispersion of ²²²Rn from emitted waste gases at Wairakei geothermal power station, New Zealand, is modelled. It is concluded that resulting concentrations in the nearby township of Taupo will never exceed the maximum permissible in any meteorological situation. The greatest possible accumulation is calculated to be less than one eighth of the normal background radon concentration. A more realistic set of assumptions predicts long-term mean concentrations about 4% of background levels. A new geothermal power station, Ohaaki, a factor of three times more distant, is calculated to produce ten times lower concentrations than Wairakei. Measurements using a few passive solid-state radon detectors show that the natural variation of radon concentrations greatly exceeds any calculated contribution from either geothermal station; hence, much of the radon is probably due to more local minor sources. Local sources have increased due to draw-off of ground water by the Wairakei station. Thus, there could be some indirect contribution to radon concentrations by its operation. The measured six-month integrated mean radon concentration at Taupo is a significant fraction of the maximum permissible concentration. It seems likely that natural sources alone may lead to levels in air which are above the maximum when temperature inversion exists. It is concluded that these two geothermal power plants are unlikely to produce concentrations of radon hazardous to the population or to plant workers.     

A survey of radon level in underground buildings in China

From 2003-2004, using solid state nuclear detectors, a survey of the air radon level in 234 underground buildings in 23 cities of China was carried out during spring as well as summer and winter. The annual radon concentrations in these underground buildings range from 14.9 to 2482 Bq m(-3), with an overall mean value of 247 Bqm(-3). When radon concentrations are averaged according to cities, Fuzhou and Baotou have the relatively higher radon levels, which are 714 and 705 Bqm(-3), respectively. Guangzhou and Shanghai have the relatively lower radon levels with 71.1 and 72.6 Bqm(-3). The annual effective dose by exposure to radon received by people working in these cities is concluded to be 1.6 mSv. The geological formation, coating level, decorating materials and ventilation situation all affect the radon concentration in underground buildings. The radon level in underground buildings has the lowest value in winter and the highest value in summer.     

Variations of airborne and waterborne Rn-222 in houses in Maine

Concentrations of airborne radon ranging from 0.05 to 135 pCi/L were found in houses in Maine. Tracketch cups were placed in five positions for 100 houses to determine integrated average radon concentrations over the period October 1980–May 1981. To investigate the association between elevated radon concentrations in well water and the indoor airborne radon concentrations, the radon in the water supplies of these houses was measured by liquid scintillation. Monitors of airborne radon, recording in intervals of 10 min for periods of 5–7 days, were used for dynamic studies in 18 houses, determining the component of airborne radon associated with major water uses, such as showers, laundry, and dishwashing, which liberate radon in bursts. House residents kept logs noting the time of major water uses. For some of the houses, ventilation rates ranging from 0.3 to 2 air changes per hour were determined by analysis of the dynamic data. The component of airborne radon associated with water sources was found to vary inversely with ventilation rate and directly with waterborne radon concentration, with 0.8 ± 0.2 pCi Rn/L air per nCi Rn/L water at a ventilation rate of 1.0 air change per hour. The data are pertinent to a study which has revealed significant correlations between county averages, from the National Cancer Institute, or age-adjusted cancer mortality rates in Maine and average values of radon concentrations in water for the counties.     

Experimental methods of determining the activity depth distribution of implanted 210Pb in glass

Glass is often used in radon surveys to estimate retrospective radon concentrations, as radon progenies are embedded in the upper surface layer. Experimental methods based on etching to determine the depth distribution of recoil-implanted 210Po in glass from radon decay in air is presented. By carefully controlling chemical concentrations and exposure time during which the glass is etched, stepwise removal of the surface material was possible. Two different etching agents, diluted HF/HNO3 and NaOH were utilised, with very similar results. Experimental recoil depths of 210Po agree with theoretical calculations from the literature. The maximum implantation depth obtained using this procedure was 100 +/- 20nm.     

Radon gas distribution in natural gas processing facilities and workplace air environment

Evaluation was made of the distribution of radon gas and radiation exposure rates in the four main natural gas treatment facilities in Syria. The results showed that radiation exposure rates at contact of all equipment were within the natural levels (0.09-0.1 microSvh(-1)) except for the reflex pumps where a dose rate value of 3 microSvh(-1) was recorded. Radon concentrations in Syrian natural gas varied between 15.4 Bq m(-3) and 1141 Bq m(-3); natural gas associated with oil production was found to contain higher concentrations than the non-associated natural gas. In addition, radon concentrations were higher in the central processing facilities than the wellheads; these high levels are due to pressurizing and concentrating processes that enhance radon gas and its decay products. Moreover, the lowest 222Rn concentration was in the natural gas fraction used for producing sulfur; a value of 80 Bq m(-3) was observed. On the other hand, maximum radon gas and its decay product concentrations in workplace air environments were found to be relatively high in the gas analysis laboratories; a value of 458 Bq m(-3) was observed. However, all reported levels in the workplaces in the four main stations were below the action level set by IAEA for chronic exposure situations involving radon, which is 1000 Bq m(-3).     

Seasonal variations of Rn concentrations in the air of a tunnel located in Nagano city

The seasonal variation of 222Rn concentrations in the air of tunnels constructed during World War II at Nagano City has been investigated. The determination of 222Rn concentrations in tunnel air was performed using a solid-state nuclear track detector technique. The monthly radon concentrations changed smoothly, decreasing towards winter and increasing towards summer, and it was found that the concentrations strongly correlate with the temperature difference between the inside and the outside of the tunnel. In the innermost areas of the tunnel, the maximum concentration was observed in July, its value being about 6500 Bq m (-3). The concentrations of radon in the tunnel air decrease exponentially towards the openings of the tunnel, which indicates that the radon concentration in the tunnel is basically governed by diffusion and mixing of radon gas with air. These observations lead to the conclusion that the seasonal variation of the radon concentration in the tunnel air is mainly caused by a convection current due to a stack effect induced by the temperature difference between the tunnel air and the outside air.     

Seasonal variations of 222Rn concentrations in the air of a tunnel located in Nagano city

The seasonal variation of 222Rn concentrations in the air of tunnels constructed during World War II at Nagano City has been investigated. The determination of 222Rn concentrations in tunnel air was performed using a solid-state nuclear track detector technique. The monthly radon concentrations changed smoothly, decreasing towards winter and increasing towards summer, and it was found that the concentrations strongly correlate with the temperature difference between the inside and the outside of the tunnel. In the innermost areas of the tunnel, the maximum concentration was observed in July, its value being about 6500 Bq m (-3). The concentrations of radon in the tunnel air decrease exponentially towards the openings of the tunnel, which indicates that the radon concentration in the tunnel is basically governed by diffusion and mixing of radon gas with air. These observations lead to the conclusion that the seasonal variation of the radon concentration in the tunnel air is mainly caused by a convection current due to a stack effect induced by the temperature difference between the tunnel air and the outside air.     

Radon levels in Cyprus

Radon levels in atmospheric and aquatic systems in Cyprus have recently been measured using the radon monitor Alpha Guard. Indoor and outdoor radon levels were obtained in situ, whereas analysis of radon concentrations in water was performed using tap and ground water samples collected from several areas of the island. The average value for outdoor and indoor radon concentration is 11+/-10 and 7+/-6 Bq m(-3), respectively, and for tap and ground water 0.4 Bq l(-1) and 1.4 Bq l(-1), respectively. From these data the annual dose equivalent of airborne radon to the Cypriot population is about 0.19 mSv y(-1), which is quite low compared to the total dose equivalent of natural and man-made ionising radiation in Cyprus. Radon levels in aquatic systems are relatively low due to an exhaustive utilisation of ground water resources and also to the increased input of desalinated sea water in the water distribution network and eventually into the ground water reservoirs.     

Radon concentrations in a spa in Serbia

The paper presents the results of indoor radon concentration survey in 201 homes and offices in Niska Banja (the Spa of Nis), a well-known health resort and a spa in the South-East of Serbia. Radon indoor concentrations were determined by active charcoal method, according to standard EPA procedure. The indoor radon concentrations were in the range of up to 200 Bq/m(3) (47%), from 200-600 Bq/m(3) (26%) and over 600 Bq/m(3) (27%). Three areas of extremely high average radon concentrations were found (1,340-4,340 Bq/m(3)), with a maximum above 13,000 Bq/m(3). The content of natural radionuclides ((226)Ra, (214)Pb, (214)Bi, (235)U, (228)Ac, (212)Pb, (212)Bi, (208)Tl, (40)K) and (137)Cs, as well as the content of total uranium, thorium and potassium in mud used in peloidotherapy in the Health Institute "Niska Banja" was determined, too. The activities of the radionuclides were determined on an HPGe detector, by standard gamma spectroscopy. The results indicated considerably high amounts of total uranium and thorium (0.021 g/kg mud and 0.003 g/kg mud, respectively), due to the karsts origin of the soil.     

Seasonal changes in radon concentrations in buildings in the region of northeastern Poland

In this study, seasonal observations of radon concentration changes inside buildings carried out in the northeastern region of Poland is presented. One-year measurements of radon concentrations were performed in chosen buildings. The integral method of Cr-39 trace detectors in diffusive chambers was used. Mean values of radon concentrations were determined in monthly, 2-, 3-, 6-month, and annual observations. The fraction of a mean annual concentration of the value obtained in a shorter observation was calculated. Monthly concentration values were from about 0.2 to 14.9 of the annual mean. All buildings revealed seasonal fluctuation of radon concentration. Negative correlation of indoor radon concentration in the buildings and the mean temperature outside was observed in most examined buildings. The lowest coefficient range, determining which part of the annual mean value would be obtained in the 6-month observation, was gained for exposure begun in April or October.     

Uranium-238 and thorium-232 series concentrations in soil, radon-222 indoor and drinking water concentrations and dose assessment in the city of Aldama, Chihuahua, Mexico

High-resolution gamma spectrometry was used to determine the concentration of 40K, 238U and 232Th series in soil samples taken from areas surrounding the city of Aldama, in Chihuahua. Results of indoor air short-time sampling, with diffusion barrier charcoal detectors, revealed relatively high indoor radon levels, ranging from 29 to 422 Bq/m3; the radon concentrations detected exceeded 148 Bq/m3 in 76% of the homes tested. Additionally, liquid scintillation counting showed concentrations of radon in drinking water ranging from 4.3 to 42 kBq/m3. The high activity of 238U in soil found in some places may be a result of the uranium milling process performed 20 years ago in the area. High radon concentrations indoor and in water may be explained by assuming the presence of uranium-bearing rocks underneath of the city, similar to a felsic dike located near Aldama. The estimated annual effective dose of gamma radiation from the soil and radon inhalation was 3.83 mSv.     

An overview of an indoor radon study carried out in dwellings in India and Bangladesh during the last decade using solid state nuclear track detectors

This paper reports on radon concentrations in dwellings from fifty different locations of India. The incorporated data were obtained using the passive solid state nuclear track detector technique. The estimated geometric mean value for India is 67.1 Bq m(-3). Chuadanga in Bangladesh had the lowest observed indoor radon concentration of 27.3 Bq m(-3) and Una in the northern part of India had the highest concentration of 281.5 Bq m(-3). This paper discusses the national geometrical mean value in terms of the national geometric mean values of other countries and also in terms of the geological influence. The estimated indoor radon levels are compared with the indoor radon levels as recommended by the International Commission on Radiation Protection (ICRP). It was observed that there are several locations in India where dwellings have higher indoor radon levels than the ICRP recommended value and requires some sort of intervention from regulating authorities. The mean value for indoor radon level given in the report of UNSCEAR 2000 for India needs to be revised.     

Radon concentration in hospital buildings erected during the last 40 years in Białystok, Poland

The aim of the study was to compare radon concentrations in neighbouring hospital buildings which were constructed in different years during the period 1963-2000 and are located in areas with similar radon potential. The value of arithmetic mean (AM) radon concentration in soil gas amounted to 14,464 Bq m(-3). In a hospital built 40 years ago, the AM radon concentration in the cellar was 38.4+/-36.7 Bq m(-3) and on higher levels it was 17.1+/-10.3 Bq m(-3). In a hospital built 16 years ago, these values equaled 45.5+/-47.2 Bq m(-3) and 20.4+/-12.5 Bq m(-3), respectively. In the newest hospital, built three years ago, radon concentration (AM) in a cellar was 32.3+/-27.4 Bq m(-3) and the respective value on higher levels amounted to 20.4+/-12.6 Bq m(-3). When comparing radon concentrations in the cellars, no statistically significant differences were found. Similarly, no statistically significant differences were observed between radon concentrations measured on higher levels in investigated hospital buildings.     

Indoor radon concentration in geothermal areas of central Italy

The indoor radon (²²²Rn) activity concentration was measured between January and June in the schools of two geothermal areas in Tuscany, central Italy. One of these areas (the Larderello area) is characterized by a large number of geothermal power plants, covering about 9% of the world’s geothermal power production. In contrast, the other area, Monte Pisano, has not any such facilities. About 250 measurements were made using track etch detectors. Only a slight difference in the concentrations between the two major sampling areas (98 Bq m⁻³ for Larderello area and 43 Bq m⁻³ for Monte Pisano area) was found, and this was related to different geological characteristics of the ground and not the presence of the geothermal plants. The measured radon concentrations were always well below the intervention levels in both areas, and health risks for students and personnel in the examined schools were excluded.     

Seasonal variations of aerosol residence time in the lower atmospheric boundary layer

During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived (222Rn) decay products 214Pb and 210Pb. The samples were taken by using a single-filter technique and gamma-spectrometry was applied to determine the activity concentrations. A seasonal fluctuation in the concentration of 214Pb and 210Pb in surface air was observed. The activity concentrations of both radionuclides were observed to be relatively higher during the winter/autumn season than in spring/summer season. The mean activity concentration of 214Pb and 210Pb within the whole year was found to be 1.4+/-0.27 Bq m(-3) and 1.2+/-0.15 mBq m(-3), respectively. Different 210Pb:214Pb activity ratios during the year varied between 1.78 x 10(-4) and 1.6 x 10(-3) with a mean value of 8.9 x 10(-4) +/- 7.6 x 10(-5). From the ratio between the activity concentrations of the radon decay products 214Pb and 210Pb a mean residence time (MRT) of aerosol particles in the atmosphere of about 10.5+/-0.91 d could be estimated. The seasonal variation pattern shows relatively higher values of MRT in spring/summer season than in winter/autumn season. The MRT data together with relative humidity (RH), air temperature (T) and wind speed (WS), were used for a comprehensive regression analysis of its seasonal variation in the atmospheric air.     

Variations in the concentration of radon in parts of the Ogof Ffynnon Ddu system, Penwyllt, South Wales and estimates of doses to recreational cavers.

A new winter and summer investigation of radon concentrations in parts of the Ogof Ffynnon Ddu system at Penwyllt, South Wales, has been carried out using 100 environmental National Radiological Protection Board track etch detectors. Fifty detectors were installed in the system in December 1998 and again in August 1999 for a period of a month. The data obtained confirm that the system has moderately high radon concentrations with a system mean of 2318 Bq m(-3) in winter and 2844 Bq m(-3) in summer. Traverse means have a summer high of 3094 Bq m(-3) for OFDI to Cwm Dwr and a winter low of 1946 Bq m(-3). The extremely high concentrations approaching 20,000 Bq m(-3), reported previously from the system (Hyland, 1995), have not been reproduced. The data show that the airflow directions at the entrances are not what might have been predicted. Air appears to be largely continuously emerging from the lowest entrance but, at the higher entrances, conversely to the predictions, in winter air enters and in summer appears to be coming out or is variable. Internally, there are sites that in winter have very low radon concentrations that can only be explained by the ingress of fresh air. These are not matched in the summer experiment, again indicating that ingress of fresh air to some parts of the system is very variable. The data illustrate the complexity of airflow within a multi-entrance system but behind these variations several mean concentrations can be obtained from which an approximation of the dose likely to be received can be calculated. Using the maximum mean concentration obtained, 3094 Bq m(-3), and using the latest dose conversion, a 10 h underground trip in the Ogof Ffynnon Ddu system yields a calculated dose of 0.12 mSv. Given that the recommended limit for a member of the public is 1 mSv, this dose would be reached after about 80 h of caving in the system.     

A simple and rapid method for analyzing radon in coastal and ground waters using a radon-in-air monitor

We have developed a simple and portable technique for measuring moderately high levels of 222Rn (t1/2=3.8d) in natural waters such as coastal water, groundwater, and river water. The water sample is carefully collected in a glass bottle, and the sample bottle is connected to a radon-in-air monitor in a closed air-loop mode. By purging air through the sample, radon is emanated from the water until a chemical equilibration is obtained between the two phases. The radon in the air loop is determined using the radon-in-air monitor. Then, the radon in water is calculated by a radon-partitioning factor between water and air for a measured water temperature. This technique is especially convenient for determination of 222Rn in natural waters on field sites, since it eliminates the preparation of He gas, cold traps, and alpha-scintillation cells and counter, which are required for traditional radon emanation methods.