Survey of indoor radon concentrations in Fukuoka and Kagoshima prefectures

It is now well established that radon and its daughter products account for nearly half of the average population exposure to ionizing radiations and that radon is the greatest single source of natural radiation to the population. Radon and its daughters are alpha-emitters, which are more biologically damaging than beta- and gamma-radiations. A nationwide survey of radon concentration was conducted by the National Institute of Radiological Sciences in order to estimate the contribution of radon and its daughters to the population dose in Japan. Authors surveyed indoor radon concentrations in Fukuoka and Kagoshima prefectures as part of this project. A passive type radon dosimeter, in which a sheet of polycarbonate film as the alpha-ray detector was mounted, was used to measure indoor radon concentrations. The resulting distribution of the average annual indoor radon concentrations in both prefectures can be characterized by an arithmetic mean of 24.4 Bq/m3 and a standard deviation of 13.1 Bq/m3, by a geometric mean of 22.2 Bq/m3, and by a median of 20.7 Bq/m3. The geometric means of the distributions for Fukuoka and Kagoshima were 25.4, and 18.4 Bq/m3, respectively. Radon concentrations were also generally high in winter and low in summer. Regarding the analysis of correlations between the concentrations and construction materials, radon concentrations were generally high in Japanese houses with earthen walls and in concrete structures. These results showed that seasons, the type of building materials, and regional differences were significant factors in the variation of indoor radon concentration.     

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.     

Final results of the Austrian Radon Project

The Austrian Radon Project started in 1992 and ended in 2001. The Austrian Radon Project had two aims: firstly, finding areas of enhanced indoor radon concentration for future radon mitigations, and, secondly, defining areas with elevated radon risk where radon safe construction is necessary for new houses. The project was based on systematic indoor measurements in randomly selected houses using different types of detectors. Successful intercomparison tests were made in a radon chamber, but simultaneous measurements by different detectors normally used in homes deviated sometimes up to a factor of two. We have to assume that this results from manipulations of the detectors by the inhabitants. The mean radon concentration in Austrian homes was found to be 99 Bq m(-3). A radon potential was derived from the results of the measurements and the information received from questionnaires. This radon potential was defined as an expected radon concentration in a standard situation and characterizes the radon risk from ground sources with all the influences of different living situations eliminated. A mean radon potential was computed for every municipality and the information is displayed as a map. The uncertainty and the reliability of the classification of municipalities according to the radon potential are discussed in more detail and compared with results from Switzerland.     

A nation-wide survey on indoor radon from 2007 to 2010 in Japan

In two previous nation-wide surveys in the late 1980s and early 1990s, Japanese indoor radon concentrations increased in homes built after the mid 1970s. In order to ascertain whether this trend continued, a nation-wide survey was conducted from 2007 to 2010. In total 3,900 houses were allocated to 47 prefectures by the Neyman allocation method and 3,461 radon measurements were performed (88.7% success). The fraction of reinforced concrete / concrete block buildings was 32.4%, similar to the value from national statistics. Arithmetic mean (standard deviation, SD) and geometric mean (geometric SD) of radon concentration after adjusting for seasonal fluctuation were 14.3 (14.7) and 10.8 (2.1) Bq/m(3). The corresponding population-weighted values were 13.7 (12.3) and 10.4 (2.0) Bq/m(3), respectively. It was estimated that only 0.1% of dwellings exceed 100 Bq/m(3), a new WHO reference level for indoor radon. Radon concentrations were highest in houses constructed in the mid 1980s and decreased thereafter. In conclusion, arithmetic mean indoor radon in the present survey was slightly lower than in previous surveys and significant reductions in indoor radon concentrations in both wooden and concrete houses can be attributed to alterations in Japanese housing styles in recent decades.     

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).     

Should radon be reduced in homes? A cost-effect analysis

BACKGROUND: Radon is a radioactive gas that may leak into buildings from the ground. Radon exposure is a risk factor for lung cancer. An intervention against radon exposure in homes may consist of locating homes with high radon exposure (above 200 Bq m(-3)) and improving these, and protecting future houses. The purpose of this paper is to calculate the costs and the effects of this intervention. METHODS: We performed a cost-effect analysis from the perspective of the society, followed by an uncertainty and sensitivity analysis. The distribution of radon levels in Norwegian homes is lognormal with mean = 74.5 Bq m(-3), and 7.6% above 200 Bq m(-3). RESULTS: The preventable attributable fraction of radon on lung cancer was 3.8% (95% uncertainty interval: 0.6%, 8.3%). In cumulative present values the intervention would cost $238 (145, 310) million and save 892 (133, 1981) lives; each life saved costs $0.27 (0.09, 0.9) million. The cost-effect ratio was sensitive to the radon risk, the radon exposure distribution, and the latency period of lung cancer. Together these three parameters explained 90% of the variation in the cost-effect ratio. CONCLUSIONS: The uncertainty in the estimated cost per life is large, mainly due to uncertainty in the risk of lung cancer from radon. Based on estimates from road construction, the Norwegian society has been willing to pay $1 million to save a life. This is above the upper uncertainty limit of the cost per life. The intervention against radon in homes, therefore, seems justifiable.     

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。     

Building-specific factors affecting indoor radon concentration variations in different regions in Bulgaria

The study was conducted to assess the spatiality of the building factors’ effect on air quality through evaluation of indoor radon concentration in areas with different geology and geographical position. For that matter, a survey of indoor radon concentration was carried out in 174 kindergartens of three Bulgarian cities. The time-integrated measurements were performed in 777 ground floor rooms using alpha tract detectors, exposed for 3 months in cold period of 2014. The results of indoor radon concentrations vary from 20 to 1117 Bq/m³. The differences in the mean radon concentrations measured in the different cities were related to geology. The effect of building-specific factors: elevator, basement, mechanical ventilation, type of windows, number of floors, building renovation, building materials, type of room, type of heating, construction period, and availability of foundation on radon concentration variations was examined applying univariate and multivariate analysis. Univariate analysis showed that the effects of building-specific factors on radon variation are different in different cities. The influence of building factors on radon concentration variations was more dominant in inland cities in comparison to the city situated on the sea coast. The multivariate analysis, which was applied to evaluate the impact of building factors simultaneously, confirmed this influence too.     

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.     

Validation of a geologically based radon risk map: are the indoor radon concentrations higher in high-risk areas?

Since geographically coded information is frequently used in studies of the relationships between environmental factors and illness at the population level and by authorities for promotion of mitigation, knowledge about the validity of proxy measures is essential. This study was an evaluation of a geologically based map describing the risk for high radon levels, which was used by the municipal authorities to determine the necessity of remedial actions. Annual mean radon gas concentrations for a random sample of one-family homes selected from high-risk areas (n = 252) were compared with those of a random sample of homes from normal and low-risk areas (n = 259). No difference in geometric mean radon concentration was found between the areas, 101 Bq m(-3) and 103 Bq m(-3), respectively. The proportion of homes in each area with radon gas concentrations above the current Swedish administrative limit value for mitigation (400 Bq m(-3)) was similar, approximately 10%. We conclude that the radon risk map was unsuitable for identifying areas of concern. The findings also indicate that geologically based and geographically coded information as a proxy for human exposures can be safely used for scientific and administrative purposes only following validation.     

Radon awareness and mitigation in Vermont: a public health survey

Radon exposure is associated with an increased incidence of lung cancer, and elevated levels may be found in as many as 1 out of 15 homes. The U.S. EPA recommends testing homes for radon and mitigating over the advisory level of 4 picocuries per liter (4 pCi L(-1), or 148 Bq m(-3)). A sample population from a list of Vermont residents who had tested their residence for radon through the Vermont Department of Health and who had elevated levels were mailed a survey to assess demographic characteristics, knowledge about radon, mitigation rates, types of mitigation, as well as barriers to mitigation. The response rate was 63%. Forty-three percent of respondents mitigated. Roughly half were not completely knowledgeable of radon based upon the ability to associate radon exposure with lung cancer risk. Reasons not to mitigate radon levels in homes were cost and lack of concern over elevated levels. A multivariate logistic regression analysis revealed factors associated with mitigating: an education level of college or higher (p = 0.02), concern that a high radon level would affect real estate value (p = 0.04), and home age less than 10 y (p = 0.05). In summary, less than half of Vermonters with elevated radon levels participating in the Department of Health program mitigated. We identify factors associated with radon mitigation that may lead to improved radon education and mitigation practice.     

地热田高氡建筑治理与效果评价

目的 探讨地热田高氡房屋氡的来源与治理.方法 α径迹探测器(ATD)分冬夏两个季节测量室内和土壤中的氡浓度.采用γ能谱法测量房屋主体建材放射性核素含量;采用6150 AD/6HX-γ剂量率仪测量房屋主体建材的外照射剂量率;对其中一栋房屋实施土壤减压技术的降氡改造.结果 夏冬季32个房间氡浓度均值分别为(106.4±63...     

寿光日光温室春秋季氡浓度变化趋势及辐射剂量估算

目的初步了解日光温室中氡浓度的本底值和变化趋势,估算温室作业人员氡及其子体造成的年均辐射剂量,探讨温、湿度对氡浓度的影响。方法 2009年5月和10月分别对选定的2座温室进行调查,使用Model1027连续测氡仪和干湿球温度计对温室环境中的氡浓度、温度和相对湿度进行8h连续监测。结果在测定范围内,5月温室氡浓度、温湿度最大值分别为355.0Bq/m3、30.5℃和93%,10月各指标的最大值分别为235.4Bq/m3、37.5℃和72%;根据实际情况粗略估算的温室作业人员年均辐射剂量为0.8686mSv。结论温度和相对湿度可能是影响温室中氡浓度的重要因素;温室作业人员由于职业因素所造成的氡及其子体的辐射剂量略高于当地平均室内暴露所造成的辐射剂量,氡子体对作业人员健康的影响应引起重视。     

Radon action level for high-rise buildings

Radon and its progeny are the major contributors to the natural radiation dose received by human beings. Many countries and radiological authorities have recommended radon action levels to limit the indoor radon concentrations and, hence, the annual doses to the general public. Since the sources of indoor radon and the methods for reducing its concentration are different for different types of buildings, social and economic factors have to be considered when setting the action level. But so far no action levels are specifically recommended for cities that have dwellings and offices all housed in high-rise buildings. In this study, an optimization approach was used to determine an action level for high-rise buildings based on data obtained through previous territory-wide radon surveys. A protection cost of HK$0.044 per unit fresh air change rate per unit volume and a detriment cost of HK$120,000 per person-Sv were used, which gave a minimum total cost at an action level of 200 Bq m(-3). The optimization analyses were repeated for different simulated radon distributions and living environment, which resulted in quite significantly different action levels. Finally, an action level of 200 Bq m(-3) was recommended for existing buildings and 150 Bq m(-3) for newly built buildings.     

Methodology of radon monitoring and dose estimates in Postojna Cave, Slovenia

Due to the specific work regime in the Postojna Cave, which depends primarily on the daily number of visitors, and on seasonal variations in air radon concentrations, an optimal methodology for radon and progeny measurement and dose calculation was sought. The program of measurement throughout the years was optimized, and now comprises 3-mo exposures of etched-track detectors, and twice a year, 8-10-d measurements using continuous monitors. Radon concentrations range from about 500 Bq m(-3) in winter to about 6,000 Bq m(-3) in summer, and equilibrium factors range from 0.42 to 0.69 in winter and from 0.33 to 0.86 in summer. Radiation doses from radon decay products for employees in the cave were calculated according to the ICRP 65 methodology. The basic input data are radon concentrations and equilibrium factors at two selected locations in the cave and the records of the time spent by a worker in the cave. Effective doses received by employees annually ranged from 0.02 to 8.4 mSv.     

Radon concentrations in some dwellings of Tunisia

Indoor air radon concentrations are still unknown in Tunisia. For the first time, they have been determined in several regions of the country using open alpha track dosimeters containing LR-115 film. Measurements were taken in 69 dwellings located around greater Tunis during 1 y, changing dosimeters every 2 mo. In 12 other locations, devices were placed during 2 winter months. The median of 1,217 measurements was 40 Bq m(-3) and 93.4% of them were less than 100 Bq m(-3). The highest concentration was 392 Bq m(-3). In Tunis, concentrations were higher during winter. Indoor air radon figures varied with geographic location: the highest values were found in Jendouba, Gafsa, Beja, and Tataouine government districts where phosphate and lead mines and deposits are present. This first study showed that indoor air radon concentrations are low in Tunisia, but further studies should be performed in localized areas, taking into consideration the geology, the climatic variations, and the building material.     

活性炭盒法测定矿井氡采样方法的初步研究

目的 本文研究了活性炭盒法测氡采样过程在炭盒吸附面增设滤膜、改变吸附面朝向等因素对测量结果的影响,为该方法应用于矿井高湿、高粉尘环境氡浓度检测提供技术支持。方法 按照实验方案布置活性炭盒,到吸附时间后盖上密封盖称重,放置5 h后用HD-2001型低本底γ能谱仪测试氡浓度。用RAD7氡浓度检测仪同步检测测试间氡浓度,以便于对测量结果进行比较。结果 活性炭盒吸附面朝上或朝下测得空气中氡浓度分别为（227.2 ±3.0） Bq/m³、（229.8 ±3.7） Bq/m³,两种放置方式测量结果相对偏差仅为1.1%。在活性炭盒吸附面增加定量滤纸或HI-Q型积尘滤膜后测得空气中氡浓度分别为（224.3 ±3.0） Bq/m³、（231.8 ±3.0） Bq/m³,与无滤膜时的测量结果相对偏差分别为-1.3%和2.0%。在相对湿度89.5%的环境下,活性炭盒法测得空气中氡浓度在221.5～238.1 Bq/m³之间,相同条件下RAD-7测氡仪测量结果为243 Bq/m³,两种检测方法测量结果相对偏差仅为-6.1%。结论 本次测试条件下,采样时在活性炭盒吸附面增加定量滤纸或HI-Q型积尘滤膜并将活性炭盒吸附面朝下放置,对测量结果无显著影响。该采样方法可避免由于采矿作业场所粉尘、矿渣等杂质落入活性炭盒影响检测结果。     

The effectiveness of mitigation for reducing radon risk in single-family Minnesota homes

ABSTRACT: Increased lung cancer incidence has been linked with long-term exposure to elevated residential radon. Experimental studies have shown that soil ventilation can be effective in reducing radon concentrations in single-family homes. Most radon mitigation systems in the U.S. are installed by private contractors. The long-term effectiveness of these systems is not well known, since few state radon programs regulate or independently confirm post-mitigation radon concentrations. The effectiveness of soil ventilation systems in Minnesota was measured for 140 randomly selected clients of six professional mitigators. Homeowners reported pre-mitigation radon screening concentrations that averaged 380 Bq m (10.3 pCi L). Long term post-mitigation radon measurements on the two lowest floors show that, even years after mitigation, 97% of these homes have concentrations below the 150 Bq m U.S. Environmental Protection Agency action level. The average post-mitigation radon in the houses was 30 Bq m, an average observed reduction of >90%. If that reduction was maintained over the lifetime of the 1.2 million Minnesotans who currently reside in single-family homes with living space radon above the EPA action level, approximately 50,000 lives could be extended for nearly two decades by preventing radon-related lung cancers.     

Residential radon and lung cancer risk in a high-exposure area of Gansu Province, China

In the general population, evaluation of lung cancer risk from radon in houses is hampered by low levels of exposure and by dosimetric uncertainties due to residential mobility. To address these limitations, the authors conducted a case-control study in a predominantly rural area of China with low mobility and high radon levels. Included were all lung cancer cases diagnosed between January 1994 and April 1998, aged 30-75 years, and residing in two prefectures. Randomly selected, population-based controls were matched on age, sex, and prefecture. Radon detectors were placed in all houses occupied for 2 or more years during the 5-30 years prior to enrollment. Measurements covered 77% of the possible exposure time. Mean radon concentrations were 230.4 Bq/m(3) for cases (n = 768) and 222.2 Bq/m(3) for controls (n = 1,659). Lung cancer risk increased with increasing radon level (p < 0.001). When a linear model was used, the excess odds ratios at 100 Bq/m(3) were 0.19 (95% confidence interval: 0.05, 0.47) for all subjects and 0.31 (95% confidence interval: 0.10, 0.81) for subjects for whom coverage of the exposure interval was 100%. Adjusting for exposure uncertainties increased estimates by 50%. Results support increased lung cancer risks with indoor radon exposures that may equal or exceed extrapolations based on miner data.