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.     

Anomalously high radon concentrations in dwellings located on permeable glacial sediments.

Indoor radon concentrations were measured in different seasons in 104 dwellings located on a highly permeable ice-marginal moraine in Kinsarvik, Western Norway. The measurements revealed the highest indoor radon levels ever detected in Norway and extreme variations in seasonal and short-term indoor radon levels. Annual average indoor radon concentrations up to 56 000 Bq m(-3) and a mean value of 4340 Bq m(-3) for the whole residential area are reported. By using the ICRP conversion factors to effective dose, these indoor radon values correspond to a total annual effective dose of 930 mSv and 72 mSv, respectively. By using the conversion as recommended by UNSCEAR, the effective doses would be about 50% higher. The indoor radon concentrations are found to be strongly influenced by thermally induced flows of radon-bearing soil air directed towards the upper part of the ice-marginal deposit in winter and towards the area of lowest elevation in summer. The pattern of seasonal variations observed suggests that in areas where thermal convection may occur, annual average indoor radon levels should be derived from measurements performed both in summer and in winter.     

西藏居室内氡浓度调查及所致居民剂量估算

目的 在国内城市室内氡呈上升趋势的背景下,为了获取现阶段西藏地区室内氡浓度水平,开展本次西藏地区室内氡浓度调查工作。方法 采用KF606B型固体核径迹氡累积探测器,对西藏自治区居室氡浓度进行测量,测量周期6～12个月。结果 西藏地区138间居室内氡浓度范围为14～119 Bq·m^-3,均值为（47.8 ±23.0） Bq·m^-3。氡浓度大于100 Bq·m^-3房间有5个,占总调查房间数的4%。居室内氡所致西藏地区居民有效剂量范围为0.46～3.89 mSv·a^-1,均值为1.56 mSv·a^-1。文章还对不同调查地区、城镇/农村、不同建筑类型和不同建筑年代居室内氡浓度进行了比较分析。结论 本次居室内氡浓度调查结果比上世纪八九十年代西藏地区测量结果有显著增高。     

The equilibrium factor F

Consideration of the equilibrium factor F between the concentration of the radon daughters and the concentration of radon is a part of the evaluation of the measurements of radon daughter concentrations in dwellings when applying limits. Measurements of radon, radon daughters and air exchange rates have been carried out in 225 dwellings in Sweden. The F-factors have been compared with the theoretical model described by Wicke, taking into account the wall effect. The parameters of the model are discussed. The situation of the dwelling and the habits of the occupants can be expected to have the greatest importance for the F-factors although the ventilation rate is usually the most important modifying factor. For low air exchange rates (l less than 0.30 hr-1) the probability that the F-factors were between 0.28 and 0.74 was 95% calculated according to the t-distribution. The arithmetical mean was found to be 0.51. For air exchange rates close to the average rate (0.30 less than l less than 0.60 hr-1), the F-factors were between 0.21 and 0.66 with a mean of 0.43, and for high air exchange rates (l greater than 0.60 hr-1) the F-factors were between 0.21 and 0.47 with a mean value of 0.33.     

The usability of wood as a volume trap for the purpose of retrospective radon exposure assessment.

The possibility of using wood samples as a retrospective radon monitor was investigated. Retrospective radon monitors are based on the analysis of the enhanced 210Po content of the bulk of the sample as a result of radon exposure. Several wood samples in different sizes and shapes were tested for their radon penetrability and the speed at which radon can diffuse throughout the material. Also, the volume ratio of air to solid material and the natural occurring 210Po background were determined. It was seen that only in fairly exceptional cases wood can be used as an acceptable volume trap. This is mostly due to the high and variably occurring natural 210Po background in wood samples with respect to the expected increase in radon-related 210Po due to common radon concentrations in dwellings.     

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.     

氡防护标准和剂量评价中值得注意的几个问题

最近,居民氡流行病学调查取得了明显的进展,氡致肺癌超额相对危险为0.16%/100Bqm-3。在执行氡行动标准时,应注意对住宅和工作场所中,行动水平的含义是不同的。暴露量限值和导出空气浓度均是针对个人的,不能作为工作场所(源)控制的主要依据,工作场所中氡浓度控制主要应根据辐射防护最优化和约束值确定。     

Radon in Tunisian buildings

Radon is a natural radioactive gas produced by decay of uranium and radium present in soils. Diluted in air, in confined atmospheres, it may accumulate in high concentrations. Inhalation of radon and its progeny is thought to increase lung cancer risk. For the first time, air radon concentrations were determined in 1151 dwellings situated in all the inhabited regions of Tunisia, using open alpha-track dosimeters exposed during two months. The median of 1864 measurements was 36 Bq m(-3) (with a maximum of 512 Bq m(-3), most of them being less than 100 Bq m(-3). All results were under the International Instances recommended range.     

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.     

Exposure to indoor background radiation and urinary concentrations of 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage

We investigated whether exposure to indoor [gamma]-radiation and radon might be associated with enough free radical formation to increase urinary concentrations of 8-hydroxydeoxyguanosine (8-OHdG), a sensitive marker of DNA damage, due to a hydroxyl radical attack at the C8 of guanine. Indoor radon and [gamma]-radiation levels were measured in 32 dwellings for 6 months by solid-state nuclear track detectors and thermoluminescent dosimeters, respectively. Urine samples for 8-OHdG determinations were obtained from 63 healthy adult subjects living in the measured dwellings. An overall tendency toward increasing levels of 8-OHdG with increasing levels of radon and [gamma]-radiation was seen in the females, presumably due to their estimated longer occupancy in the dwellings measured. Different models were considered for females, with the steepest slopes obtained for [gamma]-radiation with a coefficient of 0.500 (log nmol/l of 8-OHdG for each unit increase of [gamma]-radiation on a log scale) (p<0.01), and increasing to 0.632 (p = 0.035), but with larger variance, when radon was included in the model. In conclusion, there seems to be an effect of indoor radioactivity on the urinary excretion of 8-OHdG for females, who are estimated to have a higher occupancy in the dwellings measured than for males, for whom occupational and other agents may also influence 8-OHdG excretion. ree radicals; [gamma]-radiation; radon.     

贵州省某磷矿区氡气及放射性水平的评价

目的 研究和评价贵州省某磷矿区磷矿氡气及放射性水平。方法 通过现场检测和实验室分析对磷矿区周围辐射水平、氡气、矿石和土壤核素分析、水的总放射性水平分析。结果 磷矿区的γ外照射为7~18(×10^-8 Gy/h),平均值为12×10^-8Gy/h;氡浓度水平为105~246Bq/m³;矿石²²⁶Ra放射性核素水平为156.7~372.3Bq/kg,平均值为222.6Bq/kg;矿井水总放射性水平最大为总α为0.175Bq/L、总β为0.374Bq/L,饮用水总放射性水平最大为总α为0.0327Bq/L、总β为0.174Bq/L。结论 磷矿放射性水平符合国家相关标准的要求;矿井水和饮用水的总放射性水平相关无显著性意义;井下氡气浓度未达到干预水平。     

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).     

Indoor exposure to radon from the ground and bronchial cancer in women

Summary A case-referent study on the possible association between radon emanating from the ground and bronchial cancer was carried out on 292 female lung cancer cases and 584 matched population referents. Both groups had lived for at least 30 years in the city of Stockholm, Sweden. The cases were diagnosed during 1972 to 1980 with oat-cell and other types of anaplastic pulmonary carcinomas. A sample of about 10% of the dwellings where cases and referents had lived was selected for measurements of radon and radon daughters. There was a relative risk of 2.2 (P = 0.01) for lung cancer associated with living in dwellings close to the ground in areas with an increased risk of radon emanation. Smoking habits did not appear to be a major confounding factor for this association, although a detailed evaluation was not possible. The measurements indicated increased radon daughter concentrations in ground level dwellings within radon risk areas where lung cancer cases had lived, suggesting that this exposure was of etiologic importance.     

Evaluation and equity audit of the domestic radon programme in England

The UK has a radon programme to limit the radon risk to health. This involves advice on protective measures in new buildings, technical guidance on their installation, encouragement of radon measurements and remediation in existing dwellings in high radon areas. We have audited the radon programme at the level of individual homes to identify factors that influence the likelihood of remediation. 49% of the householders responded to our survey and 30% of the respondents stated that they had done some remediation to reduce the indoor radon levels. We found that householders with higher incomes and higher socio-economic status are more likely than others to remediate. Householders are less likely to remediate if they have one of the following: living in a property with a high radon concentration, current smokers in the dwelling, being unemployed or an unskilled worker, long length of time living in that property or elderly (65+ years) living by themselves. Householders appeared to be more likely to remediate if they considered the information on radon and its risk to be very clear and useful. This emphasises the importance of communication with householders.     

Measurements of radon-daughter concentrations in and around dwellings in the northern part of The Netherlands; a search for the influences of building materials, construction and ventilation

The concentration of radon daughters has been determined in and around 80 dwellings located in the northern part of the Netherlands by using a one-filter method. Median values of 2.0 and 0.4 mWL were measured for the indoor and outdoor concentrations, respectively. The average outdoor concentration was about an order of magnitude higher for wind directions between SE and SW than for SW-NW. On the average, dwellings with double-pane windows and/or concrete floors were found to have significantly higher radon concentrations than those with single-pane windows and/or wooden floors. For the living room of a particular dwelling 18 measurements were carried out. The data for this dwelling indicate a linear relation between the concentration indoors and outdoors with a slope of 3.8 +/- 2.0. This unexpected behaviour is thought to be related to ventilation via the crawl space. Measurements of ventilation patterns and measurements of radon concentrations in the living room and the crawl space are consistent with this picture.     

Models for retrospective quantification of indoor radon exposure in case-control studies

In epidemiologic studies on lung cancer risk due to indoor radon the quantification of individual radon exposure over a long time period is one of the main issues. Therefore, radon measurements in one or more dwellings, which in total have been inhabited by the participants for a sufficient time-period, are necessary as well as consideration of changes of building characteristics and ventilation habits, which influence radon concentration. Given data on 1-y alpha-track measurements and personal information from 6,000 participants of case-control studies in West and East Germany, an improved method is developed to assess individual radon exposure histories. Times spent in different rooms of the dwelling, which are known from a personal questionnaire, are taken into account. The time spent outside the house (average fraction 45%) varies substantially among the participants. Therefore, assuming a substantially lower radon exposure outside the dwelling, the residence time constitutes an important aspect of total radon exposure. By means of an analysis of variance, important determinants of indoor radon are identified, namely constant conditions such as type of house (one family house or multiple dwelling), type of construction (half-timbered, massive construction, lightweight construction), year of construction, floor and type of basement, and changeable conditions such as heating system, window insulation, and airing habits. A correction of measurements in former dwellings by factors derived from the analysis is applied if current living conditions differ from those of the participants at the time when they were living in the particular dwellings. In rare cases the adjustment for changes leads to a correction of the measurements with a factor of about 1.4, but a reduction of 5% on average only. Exposure assessment can be improved by considering time at home and changes of building and ventilation conditions that affect radon concentration. The major concern that changes in ventilation habits and building conditions lead to substantial errors in exposure (and therefore risk) assessment cannot be confirmed in the data analyzed.     

Radon mitigation survey among New York State residents living in high radon homes.

Residential exposure to radon has been considered an important environmental risk factor for lung cancer. Since 1986, U.S. EPA has recommended that all dwellings below the third floor be tested for the presence of radon and be mitigated to reduce indoor radon in homes with levels exceeding 148 Bq m(-3). In order to evaluate the effectiveness of New York State Department of Health's efforts to increase public awareness about radon risk and to promote radon testing and mitigation in compliance with EPA's guideline, a statewide radon mitigation survey was conducted between September 1995 and January 1996 among New York State residents whose homes had radon levels equal to or greater than 148 Bq m(-3) on the first floor (or above) living areas. The survey found that about 60% of 1,113 participants had taken actions for radon mitigation. The percentage of respondents who took actions to reduce radon levels in their homes increased with increasing education level as well as household income level. The method of installing a powered system to provide more ventilation was a more effective mitigation method than opening widows/doors or sealing cracks/openings in the basement. Mitigation performed by contractors was more effective in reducing radon levels than mitigation performed by residents. The reasons for performing radon mitigation given by the majority of respondents were those strongly related to radon health risk. High home radon level was an important motivational factor to stimulate radon mitigation. On the other hand, the cost of radon mitigation was a major barrier in decision making for performing radon mitigation and for selecting mitigation measures. Thus, public educational campaigns that focus on increasing awareness and knowledge about radon health risks and development of less expensive radon mitigation methods may help in promoting radon mitigation.     

Radon concentration in two largest cities in semitropical Taiwan.

Grab sampling either using the active charcoal method in combination with an ionization chamber or using a working level monitor was performed for the measurement of radon concentration in Taiwan's two largest cities Taipei and Kaohsiung. Long-term monitoring of radon concentration in dwellings and business buildings was also carried out with cellulose nitrate films as the alpha detectors. The average indoor radon concentration in these two cities is 17 +/- 6 Bq m-3. The outdoor radon concentration is about one-half of that on average. As assessed according to the model of UNSCEAR 1988, the induced effective dose equivalent is 0.67 mSv y-1. Radon concentration in coal mines showed an average of 88.5 +/- 9.5 Bq m-3.     

Radon: characteristics in air and dose conversion factors

The dose conversion factor (DCF) which gives the relationship between effective dose and potential alpha energy concentration of inhaled short-lived radon decay products is calculated with a dosimetric approach. The calculations are based on a lung dose model with a structure that is related to the new recommended ICRP respiratory tract model. The characteristics of the radon decay products concerning the unattached fraction and the activity size distribution of the radon decay products are important input quantities for the calculation of DCF. Experimental data about these parameters obtained from measurements in homes, at working places, and in the free atmosphere at ground level in the last past years are summarized. Taking into account the measured aerosol characteristics the DCF fractions of the unattached (DCFu) and aerosol-attached (DCFae) radon decay products for different places were calculated. Variation of DCF for different places were caused dominantly by the variation of DCFu of the unattached radon clusters (0.3-32 mSv WLM(-1)). Nose inhalation drastically reduced (about a factor 4) the dose contribution by the unattached cluster. The dose fraction by the radon decay product aerosol (DCFae) varies between 4-10 mSv WLM(-1). Taking into account a relative sensitivity distribution between bronchial, bronchiolar and alveolar regions of the thoracic lung with 0.80:0.15:0.05 and nose breathing the DCF of most of the working places (inhalation rate: 1.2 m3 h(-1)) vary between 5.7-6.7 mSv WLM(-1) depending on the number concentration of the aerosol particles. The DCF-value of 4.2 mSv WLM(-1) for the general public in dwellings with higher aerosol concentration (>4 x 10(4) particles cm(-3)) has about the same value as recommended by ICRP 65 (1994b). Significantly higher are the DCF-values for "normal" aerosol conditions indoors (5 x 10(3)-4 x 10(4) particles cm(-3)) and in the open air (7.3 mSv WLM(-1) and 9.7 mSv WLM(-1)).     

Investigation of atmospheric, mechanical and other pressure effects influencing the levels of radon and radon progeny in buildings.

Real-time data measurement and analysis have identified a number of influences affecting the variability and accumulation of radon and its progeny in indoor air. Observed cycles in radon concentrations were shown to be related to the influence of air-conditioning and water-heated central heating systems. The cyclical pattern, related to operation of the air-condition system, showed radon levels almost four times lower during the period when the system was switched On than when it was Off. When the heating system was switched On the radon and radon progeny levels were 40% lower than when it was switched Off. Under both regimes, it was possible to establish the over-riding influence of meteorological factors by separating the recurring cyclical component from the relevant data set. The general or trend level of indoor radon was determined substantially by the prevailing atmospheric conditions.