Seasonal variation of indoor radon concentration in dwellings of Alexandria city, Egypt

Inhalation of radon ((222)Rn) and daughter products are a major source of natural radiation exposure. Keeping this in view, seasonal indoor radon measurement studies have been carried out in 68 dwellings belonging to 17 residential areas in Alexandria city, Egypt. LR-115 Type 2 films were exposed for four seasons of 3 months each covering a period of 1 y for the measurement of indoor radon levels. Assuming an indoor occupancy factor of 0.8 and a factor of 0.4 for the equilibrium factor of radon indoors, it was found that the estimated annual average indoor radon concentration in the houses surveyed ranged from 45 ± 8 to 90 ± 13 Bq m(-3) with an overall average value of 65 ± 10 Bq m(-3). The observed annual average values are greater than the world average of 40 Bq m(-3). Seasonal variation of indoor radon shows that maximum radon concentrations were observed in the winter season, whereas minimum levels were observed in the summer season. The season/annual ratios for different type of dwellings varied from 1.54 to 2.50. The mean annual estimated effective dose received by the residents of the studied area was estimated to be 1.10 mSv. The annual estimated effective dose is less than the recommended action level (3-10 mSv y(-1)).     

Seasonal variation of indoor radon-222 levels in dwellings in Ramallah province and East Jerusalem suburbs, Palestine

This study presents the seasonal variations of indoor radon levels in dwellings located in the Ramallah province and East Jerusalem suburbs, Palestine. The measurements were performed during the summer and winter of the year 2006/2007 using CR-39 solid-state-nuclear-track detectors. The total number of investigated buildings is 75 in summer and 81 in winter. A total number of 142 dosemeters are installed in dwellings for each season for a period of almost 100 d. The radon concentration levels in summer varied from 43 to 192 Bq m(-3) for buildings in the Ramallah province and from 30 to 655 Bq m(-3) for East Jerusalem suburbs. In winter, the radon concentration levels are found to vary from 38 to 375 Bq m(-3) in the Ramallah buildings and from 35 to 984 Bq m(-3) in East Jerusalem suburbs. The obtained results for radon concentration levels in most places are found to be within the accepted international levels.     

Radon prevention in new construction in Finland: a nationwide sample survey in 2009

The building code for radon prevention and the associated practical guidelines were revised in Finland in 2003-2004. Thereafter, preventive measures have become more common and effective and indoor radon concentrations have been markedly reduced. In this study, the indoor radon concentration was measured in 1500 new low-rise residential houses. The houses were randomly selected and represented 7 % of the houses that received building permission in 2006. The average radon concentration of all the houses measured, which were completed in 2006-2008, was 95 Bq m(-3), the median being 58 Bq m(-3). The average was 33 % lower than in houses completed in 2000-2005. The decrease was 47 % in provinces with the highest indoor radon concentration and 26 % elsewhere in the country. In houses with a slab-on-ground foundation that had both passive radon piping and sealing measures carried out using a strip of bitumen felt in the joint between the foundation wall and floor slab, the radon concentration was on average reduced by 57 % compared with houses with no preventive measures. Preventive measures were taken nationwide in 54 % of detached houses and in provinces with the highest radon concentration in 92 % of houses.     

Indoor radon concentrations in the town of Niksic, Montenegro

Indoor radon was systematically surveyed in the town of Niksic-the second largest town in Montenegro-which has some of its settlements built above red bauxite deposits. The radon concentrations were measured in 55 homes in 2002/03, in the summer and winter period, using CR-39 etched track detectors. The average annual radon concentrations were found to be lognormally distributed (geometric mean = 66.2 Bq m(-3), geometric standard deviation = 3.0) within the range from 10 to 966 Bq m(-3), with arithmetic mean of 122.7 Bq m(-3) and median of 61.7 Bq m(-3). Although the annual mean radon concentrations above the action level of 400 Bq m(-3) are found only in four dwellings, the indoor radon levels in the town of Niksic are relatively high when compared with the average in the South European countries, as well as with indoor radon levels in other regions in Montenegro.     

Indoor 222Rn concentration measurements in some buildings of Hebron province during the winter season of the year 2000

In this study, we report on the indoor radon concentration levels in a number of locations scattered in the Hebron province, Palestine. The measurements were performed during the winter season of the year 1999/2000 using the CR-39 detectors. The radon concentration levels were found to vary from 23 to 580 Bq m(-3). The arithmetic average of the obtained radon concentration levels was found to be 91 Bq m(-3). It was found that most of the radon concentration levels in houses and school rooms are below the low reference levels limits. Most of the high-radon concentration levels were found in unpainted storage rooms.     

National radon survey in Korea

To estimate annual average concentrations in Korean dwellings and the effective dose to the general public, nationwide surveys on radon were conducted in 1989, 1999-2000 and 2002-2005. The total number of dwellings was about 5600. A survey of thoron and its decay products was also conducted in 2002-2005. In 2008-2009, a new radon survey in 1100 public buildings was conducted. The annual arithmetic (AM) and geometric (GM) means of indoor radon concentration in total were 62.1 ± 66.4 and 49.0 ± 1.9 Bq m(-3), respectively. The annual AM and GM means of indoor thoron concentrations were 40.4 ± 56.0 and 10.7 ± 2.9 Bq m(-3), respectively. The radon and thoron concentrations in detached houses were much higher than those in apartments. The locations of the high radon or thoron houses seem to be correlated with the concentrations of their parent nuclides in surface soil. The mean individual doses of radon and thoron were calculated to be 1.65 and 0.17 mSv y(-1), respectively.     

Radon and thoron parallel measurements in Hungary

Hungarian detectors modified and developed at the National Institute of Radiological Sciences (NIRS), Japan were placed at different sites, including homes and underground workplaces in Hungary, in order to gain information on the average radon (222Rn) and thoron (220Rn) concentration levels. Measurements were carried out in dwellings in a village and a manganese mine in Hungary. The radon and thoron concentrations in the dwellings of the village in the summer period were found to be 154 (17-1083) and 98 (1-714) Bq m(-3), respectively. Considering the results of other radon measurements during the winter (814 Bq m(-3)) and summer (182 Bq m(-3)) periods, the thoron concentrations were also expected to be higher in winter. In the manganese mine, radon and thoron were measured at 20 points for 6 months, changing the detectors each month. The averages were 924 (308-1639) and 221 (61-510) Bq m(-3) for radon and thoron, respectively. These results showed significant variance with the date and place of the measurement.     

Population dose in the vicinity of closed Hungarian uranium mine

In order to determine the exposure to natural sources of radiation for people in the vicinity of remediated Hungarian uranium mine regional surveys were carried out. The surveys evaluated indoor radon concentrations and outdoor and indoor external gamma dose rates. Radon concentration has been measured with nuclear etched track detectors for 4 months in 129 houses in Kovágószolos and in 23 houses in Cserkút. In some houses measurements have been carried out for a year and the measurement results of the 4 months were corrected according to these. The corrected radon concentrations altered between 15 and 2314 Bq m(-3). An average of 257 Bq m(-3) in Kovágószolos and 125 Bq m(-3) in Cserkút was measured. The average was 434 Bq m(-3) for the 48 houses within 100 m of the passage of the former mine that is under the village of Kovágószolos. The higher values of Kovágószolos are likely to be the result of the influence of mining. The terrestrial gamma-ray dose rate was measured outdoors and indoors at these houses. Values of 139 (62-233) nGy h(-1) and 133 (93-275) nGy h(-1) were measured in Kovágószolos and Cserkút, respectively. The average annual effective doses for the two villages studied were 3 and 5 mSv y(-1), but the maximum value was 40 mSv y(-1).     

A study of indoor radon levels in rural dwellings of Ezine (Canakkale, Turkey) using solid-state nuclear track detectors

Indoor radon activity level and radon effective dose (ED) rate have been carried out in the rural dwellings of Ezine (Canakkale) during the summer season using Radosys-2000, a complete set suitable to radon concentration measurements with CR-39 plastic alpha track detectors. The range of radon concentration varied between 9 and 300 Bq m(-3), with an average of 67.9 (39.9 SD) Bq m(-3). Assuming an indoor occupancy factor of 0.8 and 0.4 for the equilibrium factor of radon indoors, it has been found that the 222Rn ED rate in the dwellings studied ranges from 0.4 to 5.2 mSv y(-1), with an average value of 1.7 (1.0) mSv y(-1). There is a possibility that low radon concentrations exist indoors during the summer season in the study area because of relatively high ventilation rates in the dwellings. A winter survey will be needed for future estimation of the annual ED.     

Indoor radon survey in dwellings of nine cities in the Eastern and the Western provinces of Saudi Arabia

The results of a first phase of an indoor radon survey in a total of 1610 dwellings distributed in nine cities of the Eastern and the Western provinces of Saudi Arabia are presented. The objective of this radon survey was to obtain representative indoor radon data for seven cities in the Eastern province. Khafji, Hafr Al-Batin, Abqaiq, Qatif, Al-Ahsa, Dammam and Khobar and to compare this with two cities in the Western province, Madina and Taif. So far, detailed radon data is not available for Saudi Arabia: therefore, this radon survey provides a base line for Saudi Arabia in the Radon World Atlas. On average, 200 indoor radon dosemeters were distributed in each city and placed for a period of one year starting from May 2001 to May 2002. The total number of collected dosemeters was 847. A total of 724 houses and 98 schools were covered in this survey. The results of the survey in the cities showed that the overall minimum, maximum and average radon concentrations were 1, 137 and 22 Bq m(-3), respectively. Geometric mean and geometric standard deviations of the radon distribution were found to be 18 and 1.92, respectively. In one of the dwellings in Qatif city, radon concentration, measured by a passive system and then confirmed by an active system, was found to be 535 +/- 23 and 523 +/- 22 Bq m(-3), respectively. The result of a radon survey in 98 schools showed that the minimum, maximum and average radon concentrations were 1, 70 and 19 Bq m(-3), respectively. The average radon concentration for each city was also determined. The lowest average radon concentration (8 Bq m(-3)) was found in Al-Ahsa while the highest average concentration (40 Bq m(-3)) was found in Khafji.     

Indoor radon concentration in the rural dwellings of Chhattisgarh state (India)

Inhalation of radon and its daughter products is the major contributor to the total exposure of the population to natural radiation. An indoor radon survey has been carried out in the state of Chhattisgarh (80.26 degrees N to 84.41 degrees N and 17.8 degrees E to 24.1 degrees E), India under the national coordinated radon project of the Department of Atomic Energy. In the frame of this project indoor radon concentration has been measured in 105 dwellings situated in different villages of Chhattisgarh state. Houses were selected for measurements to cover the most common type of houses generally existing in the rural areas. Measurements have been done on quarterly integrating cycle for one full year in each dwelling using radon cup dosemeter employing LR-115, type-II (pelliculable), solid-state nuclear track detectors. The gamma radiation level was also checked in each dwelling using a gamma survey meter. It was found that the annual average indoor radon concentration in these dwellings varies from 9.91 to 87.84 Bq m(-3) with overall mean value of 26.48 Bq m(-3). Gamma level in these rural dwellings varies from 14.84 to 26.56 microR h(-1) with mean value of 18.68 microR h(-1). We observed that the radon concentration is relatively higher in the houses where the floor is bare but relatively lower in those houses where the floor is tiled or cemented.     

Long-term measurements of thoron, its airborne progeny and radon in 205 dwellings in Ireland

Long-term (circa 3 months) simultaneous measurements of indoor concentrations of thoron gas, airborne thoron progeny and radon were made using passive alpha track detectors in 205 dwellings in Ireland during the period 2007-09. Thoron progeny concentrations were measured using passive deposition monitors designed at the National Institute of Radiological Sciences (NIRS), Japan, whereas thoron gas concentrations were measured using Raduet detectors (Radosys, Budapest). Radon concentrations were measured in these dwellings by means of NRPB/SSI type alpha track radon detectors as normally used by the Radiological Protection Institute of Ireland (RPII). The concentration of thoron gas ranged from <1 to 174 Bq m(-3) with an arithmetic mean (AM) of 22 Bq m(-3). The concentration of radon gas ranged from 4 to 767 Bq m(-3) with an AM of 75 Bq m(-3). For radon, the estimated annual doses were 0.1 (min), 19.2 (max) and 1.9 (AM) mSv y(-1). The concentration of thoron progeny ranged from <0.1 to 3.8 Bq m(-3) [equilibrium equivalent thoron concentration (EETC)] with an AM of 0.47 Bq m(-3) (EETC). The corresponding estimated annual doses were 2.9 (max) and 0.35 (mean) mSv y(-1). In 14 or 7% of the dwellings, the estimated doses from thoron progeny exceeded those from radon.     

Radiological characterisation of Artvin and Ardahan provinces of Turkey

Indoor radon concentration measurements were carried out and corresponding annual effective doses due to exposure to indoor radon were determined in Artvin and Ardahan provinces located in the eastern part of Turkey. The measurements were performed for four seasons in order to determine the seasonal fluctuations mostly observed in indoor environments. Indoor radon concentration values were observed to range from 21 to 321 Bq m?3 for the Artvin province and from 53 to 736 Bq m?3 for the Ardahan province. It was observed that minimum indoor radon concentration values were obtained in summer, while the highest ones were observed in winter. Indoor radon concentration values of the current study were compared with those of other provinces in Turkey. As elevated indoor radon concentrations are mostly correlated with high 23?U activity concentrations in soil, a total of 57 and 33 soil samples were collected from the Artvin and Ardahan provinces, respectively, to determine 23?U activity concentration as well as the concentration of 232Th and ??K--naturally occurring radionuclides. It was also observed that soil samples collected from the study areas contained 13?Cs as an artificial radionuclide.     

Concentrations of radon and its daughter products in and around Bangalore city

Indoor radon and its progeny levels were measured during 2005-06 in Bangalore rural district and in Bangalore City by using Solid State Nuclear Track Detector (SSNTD)-based twin cup dosemeters, and the activity of radium present in soils and rocks was measured by using HPGe detector. Fifty dwellings of different types were chosen for the measurement. The dosimeters containing the detector (LR-115 Type II Film) used in each house were fixed 2 m above the floor. After an exposure time of 90 days, films were etched to reveal tracks. From the track density, the concentrations of radon were evaluated. The value of radon concentration in the indoor air near granite quarries varies from 55 to 300 Bq.m(-3) with a median of 155 Bq.m(-3) and its progeny varies from 0.24 to 19.6 mWL with a median of 8.4 mWL. In Bangalore City, the concentration of radon varies from 18.4 to 110 Bq.m(-3) with a median of 45 Bq.m(-3) and its progeny varies from 1.62 to 11.24 mWL with a median of 4.15 mWL. Higher concentrations of radon and its progeny were observed in granite quarries compared with Bangalore City. The main reason for the higher indoor radon and its progeny concentration is due to the mining activity and the types of the bedrock. The concentration of radon mainly depends on the activity of radium present in soils and rocks and the types of building materials used. The activity of radium varies in granitic regions of Bangalore rural district from 42.0 to 163.6 Bq.kg(-1) with a median of 112.8 Bq.kg(-1). The concentrations of indoor radon and its daughter products and equivalent effective dose are discussed.     

Variation in indoor thoron levels in Mexico City dwellings

This paper presents the results obtained for thoron concentration in 50 single-family dwellings in normal occupancy conditions (open house conditions), measured by a passive electret system (type E-PERM, SSTB configuration) in a 2001-2002 monitoring survey in the Metropolitan Zone of Mexico City. The results show the general log-normal distribution of integrated indoor thoron concentration with annual arithmetic and geometric means of 82 and 55 Bq m(-3), respectively, with ranges from 8 to 234 Bq m(-3) higher than world average of 3 Bq m(-3). The seasonal variation shows the minimum mean values in the summer season that were 35% lower than in autumn.     

Indoor radon survey in dwellings of the Kars province, Turkey

Makrofol Solid State Nuclear Track Detectors were used to study the 222Radon concentration in dwellings of the Kars province in Turkey. Radon measurements were done for 3 months in 87 houses, selected as uniformly distributed in the area as possible. All values were seasonally corrected. In order to define the seasonal correction factors, the readings were taken in 12 homes for a 12-month period. A 1:100.000 scale geologic map of the region, prepared and published by the Institute of Mineral Research and Exploration (Ankara, Turkey), was used to present the radon results. Digitising, processing and integrating of the data were performed by using ArcView GIS. The results of the radon measurements in the study area range from 20 to 600 Bq/m3, with 114 Bq/m3 as average value. The results showed that the number of lung cancer deaths attributable to indoor radon exposure was estimated to be approximately 5.     

Anomalous indoor radon concentration in a dwelling in Qatif City, Saudi Arabia

An indoor radon survey was carried out recently in nine cities of Saudi Arabia using nuclear track detectors (NTD)-based passive radon detectors. The survey included Qatif City in the Eastern Province of Saudi Arabia, where 225 detectors were collected back successfully. It was found that the average indoor radon concentration in the dwellings was 22 +/- 15 Bq m(-3). However, one of the dwellings showed an anomalous radon concentration of 535 +/- 23 Bq m(-3). This finding led to a detailed investigation of this dwelling using active and passive techniques. In the active technique, an AlphaGUARD 2000 PRQ radon gas analyser was used. In the passive technique, CR-39 based passive radon detectors were used in all the rooms of the dwelling. Radon exhalation from the wall and the floor was also measured using the can technique. The active measurement confirms the passive one. Before placing the passive radon detectors in all the rooms of the two-storey building, the inhabitant was advised to ventilate his house regularly. The radon concentration in the different rooms was found to vary from 124 to 302 Bq m(-3). Radon exhalation from the floor and the wall of the room with the anomalous radon concentration was found to vary from 0.5 to 0.8 Bq m(-2) h(-1). These low radon exhalation rates suggest that the anomalous radon concentration is most probably due to underground radon diffusion into the dwelling through cracks and joints in the concrete floor.     

Indoor radon measurements in the granodiorite area of Bergama (Pergamon)-Kozak, Turkey

Indoor radon levels in 20 dwellings of rural areas at the Kozak-Bergama (Pergamon) granodiorite area in Turkey were measured by the alpha track etch integrated method. These dwellings were monitored for eight successive months. Results show that the radon levels varied widely in the area ranging from 11±1 to 727±11 Bq m(-3) and the geometric mean was found to be 63 Bq m(-3) with a geometric standard deviation of 2 Bq m(-3). A log-normal distribution of the radon concentration was obtained for the studied area. Estimated annual effective doses due to the indoor radon ranged from 0.27 to 18.34 mSv y(-1) with a mean value of 1.95 mSv y(-1), which is lower than the effective dose values 3-10 mSv given as the range of action levels recommended by International Commission on Radiation Protection. All dosimetric calculations were performed based on the guidance of the UNSCEAR 2000 report.     

An update on thoron exposure in Canada with simultaneous ²²²Rn and ²²⁰Rn measurements in Fredericton and Halifax

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While extensive radon surveys have been conducted, indoor thoron data are very limited. To better assess thoron exposure in Canada, radon/thoron discriminating detectors were deployed in 45 homes in Fredericton and 65 homes in Halifax for a period of 3 months. In this study, radon concentrations ranged from 16 to 1374 Bq m(-3) with a geometric mean (GM) of 82 Bq m(-3) and a geometric standard deviation (GSD) of 2.56 in Fredericton, and from 4 to 2341 Bq m(-3) with a GM of 107 Bq m(-3) and a GSD of 3.67 in Halifax. It is estimated that 18 % of Fredericton homes and 32 % of Halifax homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m(-3). This conclusion is significantly higher than the previous estimates made 30 y ago with short-term radon measurements. Thoron concentrations were below the detection limit in 62 % of homes in both cities. Among the homes with detectable thoron concentrations, the values varied from 12 to 1977 Bq m(-3) in Fredericton and from 6 to 206 Bq m(-3) in Halifax. The GM and GSD were 86 Bq m(-3) and 3.19 for Fredericton, and 35 Bq m(-3) and 2.35 for Halifax, respectively. On the basis of these results, together with previous measurements in Ottawa, Winnipeg and the Mont-Laurier region of Quebec, it is estimated that thoron contributes ～8 % of the radiation dose due to indoor radon exposure in Canada.     

Simultaneous measurements of indoor radon, radon-thoron progeny and high-resolution gamma spectrometry in Greek dwellings

Simultaneous indoor radon, radon-thoron progeny and high-resolution in situ gamma spectrometry measurements, with portable high-purity Ge detector were performed in 26 dwellings of Thessaloniki, the second largest town of Greece, during March 2003-January 2005. The radon gas was measured with an AlphaGUARD ionisation chamber (in each of the 26 dwellings) every 10 min, for a time period between 7 and 10 d. Most of the values of radon gas concentration are between 20 and 30 Bq m(-3), with an arithmetic mean of 34 Bq m(-3). The maximum measured value of radon gas concentration is 516 Bq m(-3). The comparison between the radon gas measurements, performed with AlphaGUARD and short-term electret ionisation chamber, shows very good agreement, taking into account the relative short time period of the measurement and the relative low radon gas concentration. Radon and thoron progeny were measured with a SILENA (model 4s) instrument. From the radon and radon progeny measurements, the equilibrium factor F could be deduced. Most of the measurements of the equilibrium factor are within the range 0.4-0.5. The mean value of the equilibrium factor F is 0.49 +/- 0.10, i.e. close to the typical value of 0.4 adopted by UNSCEAR. The mean equilibrium equivalent thoron concentration measured in the 26 dwellings is EEC(thoron) = 1.38 +/- 0.79 Bq m(-3). The mean equilibrium equivalent thoron to radon ratio concentration, measured in the 26 dwellings, is 0.1 +/- 0.06. The mean total absorbed dose rate in air, owing to gamma radiation, is 58 +/- 12 nGy h(-1). The contribution of the different radionuclides to the total indoor gamma dose rate in air is 38% due to 40K, 36% due to thorium series and 26% due to uranium series. The annual effective dose, due to the different source terms (radon, thoron and external gamma radiation), is 1.05, 0.39 and 0.28 mSv, respectively.