Nationwide survey of radon levels in Korea

A nationwide radon survey was conducted to provide data on the annual average indoor radon concentration in Korean homes. This survey also provided data on the variation of radon concentration with season, house type, and building age. The arithmetic mean (AM) of annual radon concentration in Korean homes was 53.4 +/- 57.5 Bq m(-3). The indoor radon concentration showed a lognormal distribution with a geometric mean (GM) and its standard deviation (GSD) of 43.3 +/- 1.8 Bq m(-3). The radon concentrations in the traditional Korean-style houses were about two times higher than those in apartments and row houses. The average annual outdoor radon concentration was 23.3 Bq m(-3). The average annual effective dose to the general public from radon was 1.63 mSv y(-1).     

An evaluation of radiation and dust hazards at a mineral sand processing plant

This three-part article discusses the results of a 2-y study on radiation and dust hazards in a mineral sand processing plant involving: (1) evaluation of external gamma radiation levels and determination of isotopic composition of the different sand products; (2) evaluation of radiation carried in long-lived radioactive dust (LLRD) particles; (3) evaluation of Rn gas concentrations within the working environs of the plant. Gamma radiation levels had a mean value of approximately 40 nSv h-1, and monazite sand returned the highest activity concentrations of 0.16% and 3.4% for 238U and 232Th, respectively. Low volume gross respirable dust sampling revealed an average long-lived airborne alpha activity concentration of 0.07 +/- 0.02 Bq m-3 and an average dust mass concentration of 3.3 +/- 2 mg m-3. Gamma spectroscopy applied to high-volume air samples showed average airborne 232Th and 238U activities of 0.012 +/- 0.004 Bq m-3 and 0.005 +/- 0.002 Bq m-3, respectively, giving an airborne 232Th: 238U ratio of 2.4:1. Air sampling using a high volume, five-stage cascade impactor indicated an average activity median aerodynamic diameter (AMAD) of 3.2 microns with an associated average geometric standard deviation (GSD) of 2.8. Average radiation dose arising from the inhalation of LLRD was estimated to be 7 mSv per annum. CR-39 (polycarbonate plastic) nuclear track detectors indicated that Rn gas concentrations in the environs of the processing plant dry mill and main product warehouse ranged from 30 Bq m-3 to 220 Bq m-3, with an average value of 100 Bq m-3, which presents a possible inhaled dose from Rn daughters of 1.5 mSv y-1 (assuming an equilibrium ratio of 0.5).     

Seasonal variation in indoor radon concentrations in dwellings in six districts of the Punjab province, Pakistan

An indoor radon measurement survey has been carried out in six districts of the Punjab province. These included Gujranwala, Gujrat, Hafizabad, Sialkot, Narowal and Mandibahauddin districts. In each district, 40 representative houses were chosen and indoor radon levels were measured in these dwellings in autumn, winter, spring and summer seasons using CR-39 based NRPB radon dosimeters. After exposure to radon, the CR-39 detectors were etched in 25% NaOH at 80 degrees C and track densities were related to radon concentration levels. From the observed data, average radon concentration levels and a seasonal correction factor were calculated. The average 222Rn concentration level was found to vary from 40 +/- 15 to 160 +/- 32 Bq m(-3) and 38 +/- 17 to 141 +/- 26 Bq m(-3) in the bedrooms and living rooms of the houses surveyed, respectively. The annual mean effective dose received by the occupants has been calculated using ICRP (1993 Ann. ICRP 23) and UNSCEAR (2000 Sources and Effects of Ionizing Radiation (New York: United Nations)); it varied from 1.2 to 1.7 mSv and from 1.8 to 2.4 mSv, respectively.     

Population dose due to natural radiation in Hong Kong

In densely populated cities such as Hong Kong where people live and work in high-rise buildings that are all built with concrete, the indoor gamma dose rate and indoor radon concentration are not wide ranging. Indoor gamma dose rates (including cosmic rays) follow a normal distribution with an arithmetic mean of 0.22 +/- 0.04 microGy h(-1), whereas indoor radon concentrations follow a log-normal distribution with geometric means of 48 +/- 2 Bq m(-3) and 90 +/- 2 Bq m(-3) for the two main categories of buildings: residential and non-residential. Since different occupations result in different occupancy in different categories of buildings, the annual total dose [indoor and outdoor radon effective dose + indoor and outdoor gamma absorbed dose (including cosmic ray)] to the population in Hong Kong was estimated based on the number of people for each occupation; the occupancy of each occupation; indoor radon concentration distribution and indoor gamma dose rate distribution for each category of buildings; outdoor radon concentration and gamma dose rate; and indoor and outdoor cosmic ray dose rates. The result shows that the annual doses for every occupation follow a log-normal distribution. This is expected since the total dose is dominated by radon effective dose, which has a log-normal distribution. The annual dose to the population of Hong Kong is characterized by a log-normal distribution with a geometric mean of 2.4 mSv and a geometric standard deviation of 1.3 mSv.     

Radon in Irish schools: the results of a national survey.

This paper presents the results of a survey of radon concentrations in Irish primary and post-primary schools. The objective of this survey was to assess the distribution of radon in Irish schools and to identify those requiring remedial work to reduce radon exposure to children and staff. All primary and post-primary schools were invited to participate in the survey. Indoor radon concentrations were measured during the academic year using integrating passive alpha track-etch detectors with a measurement period from three to nine months. The survey was carried out on a phased basis from 1998 to 2004 and is one of the most comprehensive of its kind undertaken in Europe. Measurements were completed in 38 531 ground floor classrooms and offices in 3826 schools, representing over 95% of the approximate 4000 primary and post-primary schools in Ireland. Of these, 984 schools had radon concentrations greater than 200 Bq m(-3) in 3028 rooms and 329 schools had radon concentrations in excess of 400 Bq m(-3) in 800 rooms. The average radon concentration in schools was 93 Bq m(-3). This results in an annual average effective dose to an Irish child from exposure to radon of 0.3 mSv per year, assuming that the long-term radon concentration is equal to the radon concentration present during the working hours and that the annual average occupancy is 1000 h per year. A programme of remediation of schools with radon concentrations above 200 Bq m(-3) has been put in place.     

Radon concentrations in elementary schools in Kuwait

Measurements of indoor radon concentrations were performed in 25 classrooms in the capital city of Kuwait from September 2003 to March 2004 using track etch detectors. The investigation was focused on area, ventilation, windows, air conditioners, fans, and floor number. All the schools have nearly the same design. Mean indoor radon concentration was higher for case subjects (classrooms) than for control subjects (locations in inert gas, p < 0.001). The mean alpha dose equivalent rate for case subjects, 0.97 +/- 0.25 mSv y, was higher than the radiation dose equivalent rate value of control subjects, 0.43 +/- 0.11 mSv y. The average radon concentrations were found to be 16 +/- 4 Bq m for the first floor and 19 +/- 4.8 Bq m for the second floor after subtraction of the control. These values lead to average effective dose equivalent rates of 0.40 +/- 0.10 and 0.48 +/- 0.12 mSv y, respectively. The equilibrium factor between radon and its progeny was found to be 0.6 +/- 0.2.     

Residential radon exposure and lung cancer in Swedish women.

A case-control study was undertaken to investigate the role of residential radon exposure for lung cancer. The study included 210 women with lung cancer diagnosed from 1983-1986 in the county of Stockholm and 191 hospital and 209 population controls. Interviews provided information on lifetime residences and smoking. Radon concentrations measured in 1,573 residences of the study subjects showed a lognormal distribution with arithmetic and geometric means of 127.7 and 96.0 Bq m-3, respectively. Lung cancer risks tended to increase with estimated radon exposure, reaching a relative risk of 1.7 (95% confidence interval: 1.0-2.9) in women having an average radon level exceeding 150 Bq m-3 (4 pCi L-1). Stronger associations were suggested in younger persons and risk estimates appeared to be within the same range as those projected for miners. However, further studies are needed to clarify the level of risk associated with exposure to residential radon.     

Temperature calibration of Pico-Rad detectors for radon measurement

A simple mathematical equation linking the activity of adsorbed radon in the vials to the time and temperature of its exposure is discussed. The calibration coefficient--Ks, defined as activity measured in cpm after saturation time, corresponding to radon air concentration of 1 Bq m-3, was determined for four temperatures: 284, 291, 294 and 298 K. A linear relationship of ln Ks values versus T-1 was found. The relatively high difference in Ks values: 2.12 and 1.24 cpm/Bq m-3 for the temperatures of 284 and 298 K, respectively, was observed. It indicates that temperature fluctuations during Pico-Rad vial exposure may lead to erroneous results if the constant average temperature of exposure is introduced into a commonly used computer programme for calculating Rn concentration.     

Radon 222Rn in residential buildings of Swieradów Zdrój and Czerniawa Zdrój

Swieradrów Zdrój and Czerniawa Zdrój are located in Region Izera Block. A total of 789 radon passive dosimeters were distributed in 183 dwellings in these town Swieradów Zdrój and Czerniawa Zdrój to measure the indoor radon concentration in 1999. Three-five measurements were performed in each dwelling, one in the basement, and the others in the main bedroom, in the kitchen, in the bathroom, since these rooms are the most frequently occupied. In addition, the occupants of each dwelling were requested to answer a questionnaire in which a number of questions about the building, ventilation habits and other related aspects were formulated. A charcoal detectors (Pico-Rad system) were used in experiment. It is a passive short-term screening method of radon gas concentration measurements. The indoor radon level was found to range from 14.8 Bq/m3 to 5,723.9 Bq/m3. The arithmetic mean overall indoor concentration was 420.4 Bq/m3 and the geometric mean was 159.7 Bq/m3. The average concentration of indoor radon, which reflects the real risk for inhabitants, is 193.5 Bq/m3. The results hand a log-normal distribution. In Poland, an action level of 400 Bq/m3 was recommended for existing buildings and 200 Bq/m3 for newly built (after 1.01.1998) buildings. In about 23% rooms the level of Rn-222 were above the top limit of 400 Bq/m3. The highest average concentrations were present in a basement (mean 919.9 Bq/m3). A decrease of average activity were observed at the upper levels: at the ground floor (225.2 Bq/m3), at the first floor and at the higher floors (137.6 Bq/m3). The above results indicate that radon emission from the ground provides the main contribution to the radon concentration measured in dwellings indoors in Swieradów Zdrój and Czerniawa Zdrój. The effective dose to the population of the Swieradów Zdrój and Czerniawa Zdrój from indoor radon and its progeny can be derived from this data if we use an equilibrium factor of 0.4 between radon and its progeny and assuming an indoor occupation index of 0.8. Taking into account that a conversion coefficient of 1.1 mSv per mJ h m-3 is recommended in ICRP 65 for members of public, the measured average annual dose is then about 3.3 mSv per year.     

The effectiveness of radon remediation in Irish schools

An advisory reference level of 200 Bq m(-3) and a statutory reference level of 400 Bq m(-3) apply to radon exposure in Irish schools. Following the results of a national survey of radon in Irish schools, several hundred classrooms were identified in which the reference levels were exceeded and a remediation program was put in place. This paper provides an initial analysis of the effectiveness of that remediation program. All remediation techniques proved successful in reducing radon concentrations. Active systems such as radon sumps and fan assisted under-floor ventilation were generally applied in rooms with radon concentrations above 400 Bq m(-3). These proved most effective with average radon reduction factors of 9 to 34 being achieved for radon sumps and 13 to 57 for fan assisted under-floor ventilation. Both of these techniques achieved maximum radon reduction factors in excess of 100. The highest average reduction factors were associated with the highest initial radon concentrations. Passive remediation systems such as wall and window vents were used to increase background ventilation in rooms with radon concentrations below 400 Bq m(-3) and achieved average radon reductions of approximately 55%. Following the installation of active remediation systems, the radon concentration in adjacent rooms, i.e., rooms in which the radon concentration was already below 200 Bq m(-3) and therefore did not require remediation, was further reduced by an average of 25%. The long-term effectiveness of a number of radon sump systems with at least three years operation showed no evidence of fan failures. This study showed an apparent increase in sump effectiveness with time as indicated by an increase in radon reduction factors during this period.     

The Castleisland Radon Survey-follow--up to the discovery of a house with extremely high radon concentrations in County Kerry (SW Ireland).

In July 2003, a house with a seasonally adjusted annual average radon concentration of 49 000 Bq m(-3) was identified near Castleisland in County Kerry (SW Ireland). The possibility that other houses with similar extreme radon concentrations could be present in the surrounding area triggered the setting up of a localised radon survey, the so-called 'Castleisland Radon Survey' (CRS). To this end, approximately 2500 householders living in four 10 x 10 km2 grid squares from the Irish grid closest to the town of Castleisland were invited to participate. Four hundred and eighteen householders responded to the invitation (17% response rate) and 383 home results were used for further analysis. In the 400 km2 encompassing the four studied grid squares, 14% of the homes were found to have a seasonally adjusted annual average radon concentration above the national reference level of 200 Bq m(-3) while 2% above 800 Bq m(-3). An average radon concentration of 147 Bq m(-3) was calculated. This can be compared with the average radon concentration of 98 Bq m(-3) calculated for the same four grid squares on the basis of 80 measurements carried out during the Irish National Radon Survey (NRS) which was conducted between 1992 and 1997. The fourth highest radon concentration (6184 Bq m(-3)) and three of the ten highest ever measured in Ireland were all identified during the CRS. This shows that localised and targeted radon surveys are an invaluable tool for the identification of homes at highest risk from high radon concentrations. Two of the four grid squares investigated during the CRS are currently designated as high radon areas (defined as areas where 10% or more of all houses are predicted to exceed 200 Bq m(-3)) as predicted by the NRS. A thorough statistical analysis of the CRS and NRS data was carried out and indicated that both datasets could be merged and used to refine the original NRS predictions. The results indicate that two of the four studied grid squares could potentially be redesignated. The practical feasibility and overall benefit of updating the Irish radon map in light of this analysis is described.     

Study of radon concentrations in oil refinery premises and city dwellings.

Radon and its progeny concentrations were measured in several dwellings at an oil refinery premises and these concentrations were compared with those found in dwellings in Mathura and Agra cities. Radon progeny concentrations were measured using LR-115 type II nuclear track etch detectors. The radon concentrations were estimated by using a value of 0.42 for the equilibrium factor. The geometric means (GM) of radon concentrations in the refinery dwellings, Mathura city and Agra city dwellings were 97, 91 and 75 Bq m(-3) with geometric standard deviations of 1.7, 1.8 and 1.8 respectively. The average lifetime risk of lung cancer for an adjusted annual average chronic radon exposure of 69 Bq m(-3) (7.8 mWL; WL = working level) with an occupancy factor of 0.7 comes out to be 5.4 x 10(-3).     

黄山市环境辐射水平及居民受照剂量调查分析

目的研究黄山市环境辐射水平及居民受照剂量,为辐射防护和经济建设提供背景资料。方法采用FD-71型闪烁辐射仪,测量室内外、道路γ辐射剂量率;采用低本底闪烁测氡仪,测量氡浓度;采用γ能谱分析方法,测量建材中放射性核素226Ra、232Th、40K的含量。结果室内、室外、道路γ辐射剂量率均值分别为12.2×10-8Gy.h-1、8.5×10-8Gy.h-1、8.6×10-8Gy.h-1。地球γ辐射水平室内比室外高,平均比值为1.44,道路与室外的γ辐射水平差异无统计学意义。室内和室外宇宙射线辐射剂量率分别为2.7×10-8Gy.h-1和3.0×10-8Gy.h-1。室内、室外氡浓度均值分别为27.3 Bq.m-3和13.2 Bq.m-3。建筑材料除碳化砖及个别类型中的样品外,其他建材内、外照射指数均低于国家标准。结论黄山市环境辐射外照射所致居民人均年有效剂量当量为0.92mSv,其辐射水平属正常本底水平;室内、外氡浓度致居民受到的人均年有效剂量当量为1.88 mSv。在世界值范围内,传统建材放射性核素含量与世界建材典型值比较接近,其他建材有部分则高于世界建材典型值,应引起相关部门的注意。     

Assessment of natural radioactivity and radon exhalation rate in Sannur cave, eastern desert of Egypt.

Activity concentrations of 238U, 232Th and 40K in rocks and soil samples collected from Sannur cave, Beni Suef governorate, eastern desert of Egypt, were determined using the high-resolution gamma spectrometry technique. The results show that the concentrations of the naturally occurring radionuclides are the following: 238U ranged from 8.51 +/- 1.23 to 20.66 +/- 2.12 Bq kg(-1), 232Th ranged from 7.69 +/- 1.02 to 22.73 +/- 1.60 Bq kg(-1) and 40K ranged from 185.74 +/- 0.42 to 2084.70 +/- 23.30 Bq kg(-1). The radium equivalent activity (Raeq), the absorbed dose rate (D), and the external hazard index (Hex) were also calculated and compared to the international recommended values. The radon concentration and radon exhalation rate from the rock and soil samples were measured using the Can technique. The average value of annual effective dose for cave workers is 1.98 mSv y(-1), while for visitors it is 2.4 microSv per visit. The radon exhalation rate varies from 0.21 +/- 0.03 to 1.28 +/- 0.02 Bq m(-2) h(-1). A positive correlation has been observed between uranium content and radon exhalation rate.     

Radon daughter levels in some public and private buildings in India.

Radon daughter concentrations have been measured in some public and private buildings of Aligarh city. Approximately 320 CR-39 detectors were mounted in 30 sample sites. It was found that the Rn daughter concentrations vary from 3.5 mWL to 8.1 mWL with a geometric mean of 5.6 +/- 1.3 mWL. The average annual effective dose equivalent due to Rn daughters is found to be 1.46 mSv using an equilibrium factor of 0.45 and an occupancy factor of 0.8. About 33% of buildings were estimated to have a Rn concentration below 40 Bq m-3 and 79% below 60 Bq m-3. The measured levels do not require any intervention as recommended by the U.S. Environmental Protection Agency.     

Airborne radon and its progeny levels in the coal mines of Godavarikhani, Andhra Pradesh, India.

In India, out of about 0.7 million miners, nearly 0.5 million persons are directly engaged in coal operations. Radon and its progeny levels have been quantified in the coal-mining environment of Godavarikhani, Andhra Pradesh, India using solid-state nuclear track detectors. Seasonal and mine depth variations in radon levels have been recorded resulting in the identification of locations with a high radon level as areas with no mining activity, active mining operational zones and return air ventilation paths. All these radon levels were below the permissible levels. The average concentrations of radon and its progeny levels were found to be 144 +/- 61 Bq m(-3) and 20 +/- 11 mWL (working level) respectively in the two-incline mine, and these values for the five-incline mine are recorded as 315 +/- 71 Bq m(-3) and 30 +/- 9 mWL respectively.     

The measurement of radon working levels at a mineral separation pilot plant in Cox''s Bazar,Bangladesh

Beach Sand Exploitation Centre at Cox's Bazar, Bangladesh, produces commercial grade concentrations of magnetite, ilmenite, zircon, etc., from the high-grade accumulations available along the beach and foredune of Cox's Bazar. Solid state nuclear track detectors (CR-39 foils) were used to determine indoor radon concentration of radioactive mineral sands and the technologically enhanced radiation level inside the pilot plant of the Centre. It is found that the concentrations at processed mineral stock areas are high, and the maximum concentration was found to be 2,103 +/- 331 Bq m(-3) (0.23 +/- 0.03 WL). The indoor concentration of radon and its decay products in the raw sand stock area and at other locations was in the range of 116 +/- 27 Bq m(-3) (0.03 +/- 0.003 WL) to 2,042 +/- 233 Bq m(-3) (0.22 +/- 0.03 WL).     

Indoor radon in Kuwait

Indoor radon measurements were carried out in 300 dwellings in Kuwait using duplicate sets of charcoal detectors. Measurements were made at three different locations in the dwellings: living rooms, bedrooms, and basements. The results show that the radon concentration in the dwellings of Kuwait was found to vary in the range of 4.0-241.8 Bq m(-3) with a mean value of 32.8 Bq m(-3), and most values are confined within the range of 10-50 Bq m(-3) for all locations with few cases above the value of 100 Bq m(-3). Overall results show that the indoor radon concentration levels in Kuwait are relatively low, which is attributed to the use of air conditioning in summer and possible natural ventilation in winter. The radon concentration in basements was found to be relatively higher when compared to other rooms of the dwellings.     

Residential radon and lung cancer among never-smokers in Sweden.

In this study, we attempted to reduce existing uncertainty about the relative risk of lung cancer from residential radon exposure among never-smokers. Comprehensive measurements of domestic radon were performed for 258 never-smoking lung cancer cases and 487 never-smoking controls from five Swedish case-control studies. With additional never-smokers from a previous case-control study of lung cancer and residential radon exposure in Sweden, a total of 436 never-smoking lung cancer cases diagnosed in Sweden between 1980 and 1995 and 1,649 never-smoking controls were included. The relative risks (with 95% confidence intervals in parentheses) of lung cancer in relation to categories of time-weighted average domestic radon concentration during three decades, delimited by cutpoints at 50, 80, and 140 Bq m(-3), were 1.08 (0.8--1.5), 1.18 (0.9--1.6), and 1.44 (1.0--2.1), respectively, with average radon concentrations below 50 Bq m(-3) used as reference category and with adjustment for other risk factors. The data suggested that among never-smokers residential radon exposure may be more harmful for those exposed to environmental tobacco smoke. Overall, an excess relative risk of 10% per 100 Bq m(-3) average radon concentration was estimated, which is similar to the summary effect estimate for all subjects in the main residential radon studies to date.     

崇明县空气中氡浓度水平调查与评价

目的 了解崇明县室内外氡浓度水平并估算其所致公众的受照剂量。方法 根据2010年全国人口普查崇明县乡镇人口比例、房屋建筑类型、建筑年代和主体建筑材料等对测量样本进行分类选择。使用美国Durridge公司制造RAD7型电子氡气检测仪对室内外氡进行测量,数据采用SPSS 17.0软件进行统计分析。结果 本次调查的室内²²²Rn浓度范围为5.75~195.29 Bq/m³,平均浓度为(25.76±2.07) Bq/m³。约有73.89%的房屋内氡浓度低于40 Bq/m³。室外²²²Rn浓度的范围为5.70~19.32 Bq/m³,平均浓度为(9.92±1.43) Bq/m³。结论 本次调查的崇明县室内氡浓度均未超过国家推荐的控制限值。崇明县居民吸入氡所致人年均有效剂量为0.74 mSv。