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PubMed1996

Bayesian prediction of mean indoor radon concentrations for Minnesota counties.

Past efforts to identify areas with higher than average indoor radon concentrations by examining the statistical relationship between local mean concentrations and physical parameters such as the soil radium concentration have been hampered by the variation in local means caused by the small number of homes monitored in most areas. In this paper, indoor radon data from a survey in Minnesota are analyzed to minimize the effect of finite sample size within counties, to determine the true county-to-county variation of indoor radon concentrations in the state, and to find the extent to which this variation is explained by the variation in surficial radium concentration among counties. The analysis uses hierarchical modeling, in which some parameters of interest (such as county geometric mean radon concentrations) are assumed to be drawn from a single population, for which the distributional parameters are estimated from the data. Extensions of this technique, known as random effects regression and mixed effects regression, are used to determine the relationship between predictive variables and indoor radon concentrations; the results are used to refine the predictions of each county's radon levels, resulting in a great decrease in uncertainty. The true county-to-county variation of geometric mean radon levels is found to be substantially less than the county-to-county variation of the observed geometric means, much of which is due to the small sample size in each county. The variation in the logarithm of surficial radium content is shown to explain approximately 80% of the variation of the logarithm of geometric mean radon concentration among counties. The influences of housing and measurement factors, such as whether the monitored home has a basement and whether the measurement was made in a basement, are also discussed. The statistical method can be used to predict mean radon concentrations, or applied to other geographically distributed environmental parameters.

Air Pollution, Indoor↗
PubMed1999

Radon emanation of building material--impact of back diffusion and difference between one-dimensional and three-dimensional tests.

Small-scale chamber experiments were conducted to investigate the radon emanation rates of commonly used building materials such as bare concrete, granite, red brick, and sand brick. It has been found that back diffusion caused by the accumulation of radon in the indoor environment has significant influence on the radon emanation rate. The radon emanation rate can be expressed as the summation of an initial emanation rate and the product of a specific back diffusion coefficient and the indoor radon level. In some occasions the radon emanation rate can be significantly lower than its initial value. A database was developed summarizing results from 26 samples. The influence of relative humidity on the radon emanation characteristics has also been discussed. Separate tests were done by coating the four sides of the building material with silicone gel to simulate a one-dimensional radon diffusion geometry. The results show that a factor has to be included when the three-dimensional test results are used to describe one-dimensional geometry, such as radon emanation from building wall surfaces.

Construction Materials↗
PubMed2000

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.

Air Pollutants, Radioactive↗
PubMed2003

Radon concentration measurements and personnel exposure levels in Bavarian water supply facilities.

As part of a study covering the whole of Bavaria, the southern most of Germany's 16 states, water supply facilities were examined to determine the radon (222Rn) concentrations in ground water and indoor air and the radon exposure to the staff working in these buildings. Bavaria can be divided into ten geological regions of different geogenic radon potential. From each region, a number of water supply facilities proportional to the size of the region were selected for measurements. Over 500 of a total number of 2,600 water supply facilities were asked to take a 1-L groundwater sample and expose several track-etch detectors in order to obtain the mean room concentration of the main staff work places. In addition, for a period of 2 mo, the personnel had to wear a track-etch detector during the time they spent in the supply facilities. The resulting measurements were then used to estimate their individual effective dose of radon and its progenies. In the East Bavarian crystalline region, the region of the highest geogenic radon potential within Bavaria, indoor radon gas concentrations of up to 400 kBq m(-3) were observed. About 10% of the process controllers in this region are subjected to an annual effective dose of more than 20 mSv. In the other Bavarian regions, only 2% of staff exposure levels exceed this limit. The correlation between the radon concentration measurements of the indoor air, the ground water, and individual personnel exposure levels was determined. The average ratio of the radon indoor air to the processed groundwater concentration is 0.14. But due to the different types of ventilation in the various supply facilities, there can be great variations in this figure. Therefore, there is no clear relationship between the groundwater and the indoor air concentration of a supply facility. This study also reveals no clear relationship between radon indoor air concentrations and the personnel exposure levels of a supply facility.

Air Pollutants, Radioactive↗
PubMed2003

Moisture dependence of radon transport in concrete: measurements and modeling.

The moisture dependence of the radon-release rate of concrete was measured under well controlled conditions. It was found that the radon-release rate almost linearly increases up to moisture contents of 50 to 60%. At 70 to 80% a maximum was found and for higher moisture contents the radon-release rate decreases very steeply. It is demonstrated that this dependence can be successfully modeled on basis of the multi-phase radon-transport equation in which values for various input parameters (porosity, diffusion coefficient, emanation factor, etc.) were obtained from independent measurements. Furthermore, a concrete structure development model was used to predict at any moment in time the values of input parameters that depend on the evolution of the concrete microstructure. Information on the concrete manufacturing recipe and curing conditions (temperature, relative humidity) was used as input for the concrete structure model. The combined radon transport and concrete structure model supplied sufficient information to assess the influence of relative humidity on the radon source and barrier aspects of concrete. More specifically, the model has been applied to estimate the relative contributions to the radon exhalation rate of a 20-cm-thick concrete slab of radon produced in the concrete slab itself and due to diffusive transport through the slab of radon from soil gas.

Construction Materials↗
PubMed2003

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.

Air Pollutants, Radioactive↗
PubMed2004

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.

Aged↗
PubMed2005

A simple radon chamber for educational use.

Radon chambers are typically able to maintain a constant, known concentration of radon by pumping a constant activity concentration of radon gas into the chamber. A radon chamber has been designed by placing a radon source inside the chamber volume and allowing radon to build up inside the chamber. Because the radon concentration is not constant, calculations have been made to determine the integrated equivalent constant radon concentration in MBqhm for up to 4 d. The chamber, made by placing a radium dial inside an incubator, has interior dimensions of 87.6 cm x 55.9 cm x 51.4 cm for a total volume of 0.25 m. The chamber can produce an integrated equivalent constant radon activity concentration level of 0.013 MBq h m over the initial 24 h, 0.043 MBq h m over the initial 48 h, 0.078 MBq h m over the initial 72 h, and 0.118 MBq h m over the initial 96 h. The chamber can also demonstrate, for educational purposes, the kinetics of the build-up of a radioactive gas in an enclosed environment as well as the kinetics of washout and leakage.

Atmosphere Exposure Chambers↗
PubMed1999

Characterization of uncertainty and variability in residential radon cancer risks.

Radon, a naturally occurring gas found at some level in most homes, is an established risk factor for human lung cancer. The U.S. National Research Council has recently completed a comprehensive evaluation of the health risks of residential exposure to radon and developed models for projecting radon lung cancer risks to the general population. This analysis suggests that radon may play a role in the etiology of 10-15% of all lung cancer cases in the United States, although these estimates are subject to considerable uncertainty. In this article, we present a detailed analysis of uncertainty and variability in estimates of lung cancer risk due to residential exposure to radon. We use a general framework for the analysis of uncertainty and variability that we developed previously. Specifically, we focus on estimates of the age-specific excess relative risk (ERR) and lifetime relative risk (LRR), both of which vary substantially among individuals. We also consider estimates of the population attributable risk (PAR), which reflects the proportion of the lung cancer burden attributable to radon. Variability in the ERR and LRR is largely determined by variability in residential exposure levels and in the dosimetric K-factor used to extrapolate from occupational to environmental settings. Uncertainty in the ERR and LRR is due to uncertainty in the model parameters, notably those reflecting the carcinogenic potency of radon and the modifying effect of attained age. Uncertainty in the PAR is determined by uncertainty about the values of the parameters in the risk models used to estimate the PAR. Uncertainty in radon levels in homes and the dosimetric K-factor contribute comparatively little to uncertainty in the PAR. These results suggest that reduction in uncertainty about the PAR for radon induced lung cancer can only be achieved if more reliable risk projection models can be developed.

Air Pollutants, Radioactive↗
PubMed1985

Potential health effects of indoor radon exposure.

Radon-222 is a ubiquitous noble gas arising from decay of radium-226 normally present in the earth's crust. Alpha radiation from inhaled short-lived daughters of radon readily irradiates human bronchial epithelium, and there is now good evidence of excess risk of lung cancer in underground miners exposed to higher concentrations. In homes, radon levels are highly variable, showing approximately log-normal distributions and often a small fraction of homes with high concentrations of radon and radon daughters. Factors affecting indoor concentrations include type of bedrock under dwellings, house foundation characteristics, radon dissolved in artesian water, and ventilation and degree of air movement in living spaces. Despite much recent work, exposures to radon daughters by the general public are not well defined. From application of risk assessments in miners to home conditions, it appears that about 25% or more of lung cancers among nonsmokers over the age of 60, and about 5% in smokers, may be attributable to exposure to radon daughters at home. It may be necessary to take remedial action to reduce this hazard in those dwellings with elevated levels of radon, and new construction should take account of this problem.

Adult↗
PubMed2000

[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.

Air Pollution, Indoor↗
PubMed1983

Experiences and concerns on lung cancer and radon daughter exposure in mines and dwellings in Sweden.

A high mortality from lung cancer among miners was reported from Central Europe already in the 19th century. In the 60s and 70s several reports have indicated an increased lung cancer mortality among uranium miners and other metal-miners, e.g. in the US, UK, France and Sweden, but also among fluorspar miners in Canada. The cause is supposed to be the decay products of radon as emanating from the rocks, i.e. the alpha-radiation from short-lived radon daughters. Radon and radon daughter exposure in dwellings have more recently attracted interest as a potential hazard to the general population, especially since radon daughter concentrations seem to have increased due to more effective insulation for energy saving. In many Swedish houses the radon daughter exposures amount to levels similar to that of mines. Some epidemiological evaluations of the relationship between lung cancer and exposure to radon daughters, i.e. residency in stone houses versus wooden houses (with and without consideration of the contribution of radon from the ground underneath the houses), seem to indicate a risk also to the general population and, moreover, the risk of smoking seems to be several times greater in stone houses than in wooden houses, the latter usually having less radon daughters on the average.

Adult↗
PubMed1995

The relationship of radon to gastrointestinal malignancies.

Radon has known and well-studied carcinogenic effects on pulmonary epithelium. The gastrointestinal tract has potential for radon exposure by swallowed air and/or pulmonary secretions or contaminated drinking water. However, the relationship between radon and gastrointestinal malignancies is poorly documented. Therefore, the purpose of this study was to investigate a potential relationship between radon levels and gastrointestinal malignancies within the Commonwealth of Pennsylvania. In a retrospective analysis, the radon levels as reported by the Department of Environmental Resources for each county in Pennsylvania were compared to the incidence and mortality of gastrointestinal cancer in Pennsylvania by county as reported by the Pennsylvania Tumor Registry from 1985 to 1989. The incidence and mortality of stomach, esophagus, colon, pancreas, and rectal cancer was reported for male, female, and total county population and compared to radon levels for that county. Using the NCSS computer package with P value set at 0.05, a positive correlation was found between radon levels and the incidence of stomach cancer in females, and the mortality of stomach cancer for male, female, and total population. This study suggests a relationship between radon levels and gastric cancer mortality. Further investigation into the role of radon carcinogenesis may be warranted.

Environmental Exposure↗
PubMed1995

Cigarette use and the estimation of lung cancer attributable to radon in the United States.

Residential exposure to radioactive radon and its decay products has been estimated to account for 10-12% of all lung cancer deaths in the U.S. It has been difficult to evaluate fully the impact of cigarette smoking, the most important cause of lung cancer, on this estimate, because factors for patterns of tobacco use have not been included in the risk models, since risk models are derived from studies of underground miners exposed to radon and detailed data on smoking are limited. Lung cancer risk estimates for exposure to radon progeny in smoker and non-smoker populations are obtained by applying the same risk model to each population group, thereby assuming the joint effects of smoking and exposure to radon progeny are multiplicative. However, in miners, joint relative risks (RR) for the two exposures are most consistent with an intermediate relationship between multiplicative and additive, so that the present approach likely results in an overestimate of risk in smokers and an underestimate of risk in nonsmokers. Lubin et al. (National Institutes of Health Publication No. 94-3644, 1994) present an ad hoc approach for adjusting risk models to incorporate smoking status. The approach is based on the relative magnitude of the effects of radon progeny in smokers and nonsmokers and therefore may not be applicable to non-miner populations if the proportion of smokers and the RR for smoking differ. We show that the modification can be derived explicitly by assuming an arithmetic mixture model for the joint RR for smoking and exposure to radon progeny. In this way, smoking parameters in the population of interest (the proportion of smokers and the RR of smoking) can be used directly to adjust radon progeny risk models and obtain risk estimates that are specific for smokers and nonsmokers. With an intermediate RR relationship for smoking and radon progeny, the attributable percentage of lung cancer deaths from residential radon may be twofold greater in non-smokers than in smokers.

Air Pollution, Indoor↗
PubMed2001

Experiences in radon-safe building in Finland.

A study was made of radon-safe buildings in 300 Finnish low-rise residential buildings using data obtained from a questionnaire study. The study also aims at finding the main defects in design and implementation and how the guidance given on radon-safe buildings in slab-on-grade houses has been followed. According to the guidelines, the prevention of the flow of radon-bearing air from the soil into the house is recommended to be carried out through installation of aluminised bitumen felt and use of elastic sealants. Second, as a precaution perforated piping should be installed in the subsoil of the floor slab. The median indoor radon concentration in the houses was 155 Bq/m3. This is 32% lower than the median of the estimated reference values. The action level of 200 Bq/m3 was still exceeded in 40% of the houses. In most houses with slab-on-grade the prevention was based only on the installation of a sub-slab depressurisation system. Sealing was performed in a low number of houses. In 80% of houses with a sub-slab piping connected to an operating fan, radon concentration was below the action level of 200 Bq/m3. In houses with piping but no fan, the corresponding fraction was only 45%. Sub-slab piping without a fan had no remarkable effect on radon concentration. In houses with crawl-space and edge-thickened slabs, radon concentrations were low. The choice of foundation system thus significantly affects the indoor radon concentration. The importance of complete and careful sealing work should be stressed in advice and guides concerning radon prevention.

Journal Article↗
PubMed2001

Radon and its daughter products behaviour in the air of an underground tourist route in the former arsenic and gold mine in Złoty Stok (Sudety Mountains, SW Poland).

This paper describes the occurrence of radon and its daughter products in the accessible workings, partially open to the public, in the former arsenic and gold mine in Zloty Stok. The geology of the area and the characteristics of the workings provide the background for explanation of the genesis of radon and its daughter products and of the spatial and temporal variations in their concentrations. The results demonstrate that well-ventilated areas along the tourist route have the lowest values of all the measured parameters and that temporal variations of these parameters are irregular. The highest concentration values for radon (up to 18.50kBq/m3) and its daughter products (up to 14.49kBq/m3) have been recorded in the workings with obstructed natural ventilation. These are the areas where seasonal oscillations in the concentrations of these isotopes have been registered, with the maxima in summer and the minima in winter. These sections of the workings are inaccessible to the casual visitor. Radon is supplied to the workings from the side walls and its concentration is influenced, most of all, by ventilation and the degree of rock fissuring. The reason is the uniform and not very high content of 226Ra in the rocks where the galleries were excavated. Only locally, in the workings of the Gertruda adit lying outside the tourist route, do open fault zones have significant influence on enhanced concentrations of radon and its daughter products. These fault zones constitute effective routes of radon migration to the workings. In spite of this, it must be stated that neither guides nor tourists are exposed to excessive concentrations of radon or its daughter products in the tourist route area. However, the extension of the route to other workings will require the introduction of forced ventilation in order to lower theconcentration of radon and its daughter products. reserved.

Arsenic↗
PubMed2002

Modelling lung tumour risk in radon-exposed uranium miners using generalizations of the two-mutation model of Moolgavkar, Venzon and Knudson.

PURPOSES: To model radon-induced lung cancer in uranium miners using a quasi-biological model of carcinogenesis. MATERIALS AND METHODS: Fitting of generalizations of the stochastic two-mutation carcinogenesis model of Moolgavkar, Venzon and Knudson to a case-control dataset nested within the cohort and to the full cohort of lung cancer mortality in the Colorado Plateau uranium miners, taking account of exposure to cigarette smoke and to radon daughters. RESULTS: Models with three mutations gave adequate descriptions of the time and age patterns of radon-daughter-induced excess lung tumour mortality. The overall fit of the two-mutation model to the case-control data was somewhat worse than that of the three-mutation model. For both the optimal two- and three-mutation models radon daughters and cigarette smoke were assumed to act on the first mutation rate. In the optimal two-mutation model, radon daughters also modified the intermediate cell death or differentiation rate. In the optimal three-mutation model, radon daughters modified the second mutation rate. In all models, the action of radon daughters and cigarette smoke was markedly non-linear, particularly in their action on the mutation rates. The optimal two- and three-mutation models fitted to the cohort data were of slightly different form to those fitted to the case-control data. The model fits to the cohort data are preferred to those to the case-control data on grounds of plausibility. CONCLUSIONS: Quasi-biological carcinogenesis models with three mutations give adequate descriptions of the time and age patterns of radon-daughter-induced excess lung tumour mortality. The overall fit of the two-mutation model is somewhat worse than that of the three-mutation model.

Humans↗
PubMed1989

Radon: is it a problem?

Radon gas is a major source of radiation exposure to the general public. Radon-222 is a product of uranium-238, present in varying concentrations in all soils. Radon enters buildings from soil, water, natural gas, and building materials. Its short-lived breakdown products, termed "radon daughters," include alpha-emitting solids that can deposit in the lungs. Firm evidence links lung cancer risk in miners with high exposure to radon daughters. The amount of risk associated with the much lower but chronic doses received in buildings is difficult to establish. By some extrapolations, radon daughters may be responsible for a significant number of lung cancer deaths. The existence or extent of synergism with smoking is unresolved. Local conditions can cause high levels of radon in some buildings, and measures that reduce indoor radon are of potential value.

Bismuth↗