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 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.     

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.     

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 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.     

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.     

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.     

Estimate of annual average radon concentration in the normal living area from short-term tests

Most residential radon guidelines refer to annual average radon concentration in the normal living area. However, decisions on whether a house needs mitigation are usually based on short term radon tests. Depending on where detectors are placed and when tests are performed, results of those measurements can differ significantly from the annual average radon concentration in the normal living area. We provide a practical method based on survey results in 5486 Canadian houses to estimate annual average radon levels from results of screening tests. The average ratio of radon concentration in the basement to that of the upper floors in a house is determined, and the average relative seasonal variations of radon levels in the basement and of the upper floors are identified. Based on these relative quantities, estimate factors are derived for four different combinations of detector location and the living area and tabulated for different calendar periods of radon testing. The annual average radon level can be estimated by multiplying the result of a short-term screening test with the appropriate estimate factor given in this study.     

Indoor radon and lung cancer in France

BACKGROUND: Several case-control studies have indicated an increased risk of lung cancer linked to indoor radon exposure; others have not supported this hypothesis, partly because of a lack of statistical power. As part of a large European project, a hospital-based case-control study was carried out in 4 areas in France with relatively high radon levels. METHODS: Radon concentrations were measured in dwellings that had been occupied by the study subjects during the 5- to 30-year period before the interview. Measurements of radon concentrations were performed during a 6-month period using 2 Kodalpha LR 115 detectors (Dosirad, France), 1 in the living room and 1 in the bedroom. We examined lung cancer risk in relation to indoor radon exposure after adjustment for age, sex, region, cigarette smoking, and occupational exposure. RESULTS: We included in the analysis 486 cases and 984 controls with radon measures in at least 1 dwelling. When lung cancer risk was examined in relation to the time-weighted average radon concentration during the 5- to 30-year period, the estimated relative risks (with 95% confidence intervals) were: 0.85 (0.59-1.22), 1.19 (0.81-1.77), 1.04 (0.64-1.67), and 1.11 (0.59-2.09) for categories 50-100, 100-200, 200-400, and 400+ becquerels per cubic meter (Bq/m), respectively (reference <50 Bq/m). The estimated relative risk per 100 Bq/m was 1.04 (0.99-1.11) for all subjects and 1.07 (1.00-1.14) for subjects with complete measurements. CONCLUSIONS: Our results support the presence of a small excess lung cancer risk associated with indoor radon exposure after precise adjustment on smoking. They are in agreement with results from some other indoor radon case-control studies and with extrapolations from studies of underground miners.     

降氡方法在室内氡污染治理中的应用与分析

目的 探索降低住宅氡及其子体浓度水平的合适方法.方法 选取3个房间分别采取自然通风、空气净化器、密封屏蔽的措施后,使用EQF3120型氡及其子体测量仪测量室内氡及其子体浓度,α核径迹探测器测量室内氡浓度,并比较不同方法的降氡效果.结果 自然通风2～10 h后,房间内氡、结合态氡子体和未结合态氡子体浓度平均降低率分别为8...     

Relationship between indoor and outdoor levels of fine particle mass, particle number concentrations and black smoke under different ventilation conditions

Fine particle mass (PM(2.5)), black smoke (BS) and particle number concentration (NC) were measured simultaneously indoors and outdoors at an urban location in Erfurt, Germany. Measurements were conducted during 2-month periods in summer and winter. Different ventilation modes were applied during each measurement period: windows closed; windows opened widely for 15 min twice per day; windows and door across the room opened widely for 5 min twice per day and windows tilted open all day long. The lowest indoor/outdoor (I/O) ratios for all pollutants were found for closed windows, whereas the ratios for ventilated environments were higher. For closed windows, the I/O ratios for PM(2.5) are larger than the corresponding values for BS and NC (0.63 vs. 0.44 or 0.33, respectively) probably due to lower penetration factors for particles sizes <500 nm and higher deposition rates for ultrafine particles (<100 nm). The largest differences for the I/O ratios between closed and tilted windows were found for NC (0.33 vs. 0.78). The indoor and outdoor levels of PM(2.5) and BS were strongly correlated for all ventilation modes. The linear regression models showed that more than 75% of the daily indoor variation could be explained by the daily outdoor variation for those pollutants. However, the correlation between indoor and outdoor NC for ventilation twice a day was weak. It indicates that rapid changes of the air exchange rates during the day may affect the correlation and regression analysis of NC indoor and outdoor concentrations. This effect was not observed for PM(2.5) or BS. This study shows the importance of the indoor air aerosol measurements for health effects studies and the need for more research on I/O transport mechanisms for NC.     

Indoor radon in the region of Brussels

The indoor radon (222Rn) concentration has been measured by charcoal detectors in 278 buildings in the region of Brussels, Belgium. The correlation with the nature of the subsoil can be studied in detail thanks to the available geotechnical map. With a geometrical mean indoor radon concentration of 19 Bq m(-3), Brussels can be considered as generally unaffected by the radon problem. No value higher than 400 Bq m(-3) (the EU reference level for existing houses) was measured in an occupied room. However, two factors that may enhance the risk are identified: the absence of a basement or a ventilated crawl space, and the presence of loess, under the house. About one third of the houses without basements or ventilated crawl spaces built on loess show an indoor radon concentration above 200 Bq m(-3) (the EU reference level for new houses).     

A study of building structural features associated with high indoor air concentrations of organochlorine termiticides

Abstract: As part of a two-year study of post-treatment residential exposure to the termiticide, aldrin, the building structural features of ten houses with crawl-space-type floors were assessed by an independent inspector. Building attributes recorded on a checklist included the age of the dwelling, room characteristics, floor details and the nature of subfloor ventilation. At the end of each inspection, the inspector, who was blinded to data on airborne aldrin concentrations, provided a rating of expected indoor air contamination. Several of the building attributes, including the age of the house, the area of exterior subfloor vents, as well as the inspector's rating, were significantly correlated with airborne aldrin values. No single building variable, however, was highly correlated with every measure of aldrin concentration over a 12-month period. The observed data are consistent with poor subfloor ventilation and a ‘leaky’ floor being important contributors to indoor air pollution. It is recommended that pest control companies advise householders about any obvious floor and ventilation deficiencies before soil treatment work is undertaken. Pesticide exposure (by analogy with geological radon exposure) may be reduced by sealing gaps in floors and/or by improving subfloor ventilation.     

Variation in indoor air pollutant concentrations with time in a newly constructed private house

An indoor air quality research project was conducted in a new private house built in January 1997 to investigate time course changes in formaldehyde concentrations during an 11-month period from April 1997 to February 1998. Indoor and outdoor concentrations of volatile organic compounds (VOCs) and nitrogen dioxide were also measured in August 1997 and February 1998. Indoor formaldehyde concentrations were measured 14 times (48 hrs sampling for each measurement) for 28 days in the living room, a bedroom and the kitchen in April '97. The concentrations exceeded the Japanese Government's guideline value of 0.08 ppm in 34 of the 42 (81.0%). Day to day variation in the formaldehyde concentration was found to be substantial, the range being between 0.073 and 0.232 ppm for the bedroom, for example. In June and August '97, values for 20 of 21 measurements exceeded the guideline, the results suggesting that indoor formaldehyde concentrations remain high until 7 months after the completion of construction. There were positive correlations between the formaldehyde concentrations in the living room and the kitchen and personal exposure levels to formaldehyde, the result indicating a direct influence of the home environment. The formaldehyde concentration in the living room also exhibited a positive correlation with the room temperature. Natural ventilation by opening windows was found to be effective for decreasing the concentration of formaldehyde in the indoor air. Indoor VOC concentrations decreased rapidly after the completion of construction except for that of toluene, which was higher than the outdoor concentration even after 7 months. Indoor concentrations of all of the VOCs were, however, found to be almost the same as those outdoor at the 13 month time point. Indoor nitrogen dioxide concentrations measured in the bedroom in winter (February '98) exceeded the Environmental Air Quality Standard in Japan, this result being considered due to use of an oil fan heater. These data suggest that personal exposure levels to formaldehyde and nitrogen dioxide are high in newly constructed private homes in Japan. In order to avoid prolonged exposure to high concentrations of indoor air pollutants, it is considered very important to take measures such as of use building materials with low formaldehyde emissions and to discontinue the use of oil fan heaters.     

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。     

Human radiation action of radon and its daughter disintegration products

Radon-222 and its daughter disintegration products are present within all the buildings without except, which is an inevitable source of radiation both in the dwellings and in working places. There may be higher concentrations of radon in some regions. Seasonal radon level changes depending on ambient air temperature and atmospheric pressure have been found in the atmospheric ground layers. The results of the performed sanitary-and-epidemiological studies may state that there is a cause-and-effect relationship between the level of radon in the air of accommodations and the higher incidence of lung cancer. Radon-resistant structures of dwellings, removal of the soil sources of radon, as well as air filtration and efficient ventilation of premises are basic methods for decreasing the concentration of radon.     

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.     

沈阳典型住宅居室内外环境氡的水平变化

环境氡(~(222)Rn)子体可诱发肺癌已得到公认。Harley等提出了一种用于预测环境~(222)Rn所致肺癌的危险度模型,估计在不吸烟的患肺癌的居民中约有20～100%的肺癌来源于环境~(222)Rn及其子体的照射、另一估算认为不吸烟患肺癌的人中3—20%的肺癌来源于环境~(222)Rn及其子体的照射。Cohen估算美国由于节能而减少室内通风率将使因现有~(222)Rn水平所致肺癌(约为10000例/年)增加一倍。居室内外环境~(222)Rn的水平与变     

Radon and thoron in cave dwellings (Yan'an, China)

222Rn and 220Rn concentrations were measured in cave dwellings and brick houses in the region of Yan'an (China) during summer 1997. The underground dwellings are built into Quaternary loess, and all investigated houses are founded on it. The median values of indoor 222Rn and 220Rn concentrations are 42 (n = 18) and 77 Bq m(-3) (n = 15) for brick houses and 92 (n = 23) and 215 (n = 17) Bq m(-3) for cave dwellings. To classify the dwellings in respect to their "cave-character," the fraction of walls having a direct contact to the loses is calculated for each dwelling. While the 222Rn concentrations are increasing with higher fractions, the 220Rn concentrations are not correlated with this fraction. On the other hand, due to the short half-life of 220Rn the distance from the measuring point to the walls is negatively correlated with the 220Rn concentration, while there is no correlation with the 222Rn concentration. Therefore, concentric isolines of 220Rn concentrations showing a strong gradient were detected in cave dwellings. An influence of the ventilation rate is distinct for 222Rn but weak for 220Rn. The effective dose rates for 222Rn and 220Rn and their progenies are calculated for brick houses (2.7 mSv y(-1)), cave dwellings (7.1 mSv y(-1)), and for traditional cave dwellings with a bed foundation built with loess (16.7 mSv y(-1)). These calculations are based on summer measurements only. It is expected that the true effective dose rates will be significantly higher.     

A comparison of indoor air pollutants in Japan and Sweden: formaldehyde, nitrogen dioxide, and chlorinated volatile organic compounds

Indoor and outdoor concentrations of formaldehyde (HCHO), nitrogen dioxide (NO2), and selected chlorinated volatile organic compounds (chlorinated VOC) were measured in 37 urban dwellings in Nagoya, Japan, and 27 urban dwellings in Uppsala, Sweden, using the same sampling procedures and analytical methods. Indoor as well as outdoor air concentrations of HCHO, NO2, and chlorinated VOC were significantly higher in Nagoya than in Uppsala (P<0.01), with the exception of tetrachlorocarbon in outdoor air. In Nagoya, HCHO and NO2 concentrations were significantly higher in modern concrete houses than in wooden houses and higher in newer (less than 10 years) than in older dwellings (P<0.01), possibly due to less natural ventilation and more emission sources in modern buildings. Dwellings heated with unvented combustion sources had significantly higher indoor concentrations of NO2 than those with clean heating (P<0.05). Moreover, dwellings with moth repellents containing p-dichlorobenzene had significantly higher indoor concentrations of p-dichlorobenzene (P<0.01). In conclusion, there appear to be differences between Nagoya and Uppsala with respect to both indoor and outdoor pollution levels of the measured pollutants. More indoor pollution sources could be identified in Nagoya than in Uppsala, including construction and interior materials emitting VOC, use of unvented combustion space heaters, and moth repellents containing p-dichlorobenzene.