Results of a preliminary survey on radon in Belgium

Results of a preliminary national survey on radon in houses in Belgium are presented. The indoor radon concentration was determined in 1983 in 79 houses with passive integrating detectors. In 77 of the examined cases the radon concentration is less than 250 Bq/m³. The highest reported value is 330 Bq/m³. The frequency distribution is found to be log-normal with a geometric mean of 41 Bq/m³ and a geometric standard deviation of 1.7. The influence of some human and environmental parameters is also studied. Because of the limited scale of the pilot study only a tendency can be derived.     

Studies of high indoor radon areas in Finland

Solid state nuclear track detectors were used in a regional survey of radon in indoor air. The study area comprises seven rural municipalities and two towns in an area of 80×50 km² with a population of about 65,000. Measurements were made in 754 houses in 31 subareas.The highest and lowest subarea means were 1,200 Bq/m³ and 95 Bq/m³, respectively. The estimated mean for the whole area was 370 Bq/m³. The concentrations 2,000 Bq/m³ and 800 Bq/m³ were exceeded in 32 and 90 houses, respectively.The present lung cancer incidence does not differ significantly from the national mean.     

A pilot study of natural radiation in Danish houses

A pilot study was carried out to establish techniques and procedures for the measurement of indoor radiation in Denmark. A passive cup dosemeter was designed containing CR39 track detectors and TLD's to measure radon and external radiation, respectively.A total of 82 dwellings were selected covering most regions of the country. The dwellings were monitored in two three-month periods, one in winter and the other in summer. The average dose rate in air from external radiation was 0.09 μGy h^?1. In the winter the average radon concentrations were 88 Bq m^?3 and 24 Bq m^?3 for single-family houses and flats, respectively; and in the summer the corresponding values were 52 Bq m^?3 and 19 Bq m^?3.     

Radon Risk Mapping using Indoor Monitoring Data - A Case Study of the Lahti Area,Finland

An empirical statistical model is described for the use of indoor radon monitoring data as an indicator of the areal radon risk from soil and bedrock. The percentages of future homes expected to have radon concentrations exceeding the design level of 200 Bq/m³ unless constructed to provide protection against the entry of radon were assessed. The radon prognosis was made for different subareas, soil types and foundation types. This kind of report is used by the health and building authorities. In this study, 2689 indoor radon measurements were made in one of Finland's most radon-prone areas, consisting of eleven municipalities with a total area of 4600 km² and a population of 186,000. Radon concentrations were seasonally adjusted. Data on the location, geology and construction of buildings were determined from maps and questionnaires. The measurements covered different kinds of geological units in the area. The radon risk is highest in the gravel-dominated subarea in an ice-marginal formation and lowest in the northern half of the area in buildings constructed on bedrock. In these two areas, the design level of 200 Bq/m³ would be exceeded in 99% and 39% of new houses with slab-on-grade.     

Surveys of natural radiation exposure in UK dwellings with passive and active measurement techniques

A representative sample of over 2,000 UK dwellings was monitored for a year using thermoluminescent and etchable plastic dosemeters to measure gamma-ray dose rates and radon concentrations. The survey was carried out by post. Each householder completed a questionnaire on the type of dwelling and its characteristics. These data will be used in the assessment of the factors affecting indoor exposure. The mean gamma-ray dose rates were 0.062 and 0.057 μGy h^?1 in air and the mean radon concentrations were 25 and 18 Bq m^?3 for living areas and bedrooms respectively. Other results of the preliminary data analysis are given.More detailed surveys were conducted in areas where the local geology indicated that elevated exposures to natural radiation might occur. Over 800 dwellings were visited and measurements made of several parameters. The mean gamma-ray dose rates varied from 0.05 to 0.10 μGy h^?1 in air. The mean radon concentrations varied from 14 Bq m^?3 to 520 Bq m^?3. Other findings related to equilibrium factors and regional differences are discussed.     

Survey

A survey of radon concentrations in Dutch dwellings reveals a median value 0f 24 Bq/m³, while no excessive high values were observed. Correlations between radon concentration and (combinations of) building parameters will be presented and discussed in terms of the various sourc     

Radon and Natural Ventilation in Newer Danish Single-Family Houses

Abstract To investigate the effect of ventilation on indoor radon (²²²Rn), simultaneous measurements of radon concentrations and air change rates were made in 117 Danish naturally ventilated slab-on-grade houses built during the period 1984–1989. Radon measurements (based on CR-39 alpha-track detectors) and air change rate measurements (based on the perfluorocarbon tracer technique; PFT) were in the ranges 12–620 Bq m^?3 and 0.16?0.96 h^?1, respectively. Estimates of radon entry rates on the basis of such time-averaged results are presented and the associated uncertainty is discussed. It was found that differences in radon concentrations from one house to another are primarily caused by differences in radon entry rates whereas differences in air change rates are much less important (accounting for only 80,0% of the house-to-house variation). In spite of the large house-to-house variability of radon entry rates it was demonstrated, however, that natural ventilation does have a significant effect on the indoor radon concentration. Most importantly, it was found that the group of houses with an air change rate above the required level of 0.5 h^?1 on average had an indoor radon concentration that was only 50% (0.5±0.1) of that of the group of houses with air change rates below 0.5 h^?1. The reducing effect of increased natural ventilation on the indoor radon concentration was found to be due mainly to dilution of indoor air. No effect could be seen regarding reduced radon entry rates.     

Indoor Climate and the Performance of Ventilation in Finnish Residences

The purpose of the study was to gather information about the actual ventilation and indoor air quality and to evaluate the differences between houses and apartments with different ventilation systems. A sample of 242 dwellings in the Helsinki metropolitan area was studied over periods of no weeks during the 1988-1989 heating season. The mean air-exchange rates had a high variation (average 0.52 l/h, range 0.07-1.55 l/h). The ASHRAE minimum value of 0.35 l/h was not achieved in 28% of the dwellings. The air-exchange rates were significantly her in the houses than in the apartments (averages 0.45/0.64 l/h, p < 0.001); in the natural ventilation systems they, were slightly her than in the mechanical systems. The average temperature in the bedrooms was approximately 22 °C (range 18–27 °C), slightly but significantly higher in the apartment than in the houses. The average dust depositions were higher in the balanced ventilation systems than in the other systems. The median radon concentration was 82 Bq/m³ (range 5-866 Bq/m³); the Finnish target value of 200 Bq/m³ was exceeded in 17% of the houses but in none of the apartment. The measurements indicate that the indoor air quality in Finnish dwellings is not always satisfactory with reference to human health and comfort.     

Re-Entrainment and Dispersion of Exhausts from Indoor Radon Reduction Systems: Analysis of Tracer Gas Data

Tracer gas studies were conducted around four model houses in a wind tunnel, and around one house in the field, to quantify re-entrainment and dispersion of exhaust gases released from residential indoor radon reduction systems. Re-entrainment tests in the field suggest that active soil depressurization systems exhausting at grade level can contribute indoor radon concentrations 3 to 9 times greater than systems exhausting at the eave. With a high exhaust concentration of 37,000 Bq/m³, the indoor contribution from eave exhaust re-entrainment may be only 20% to 70% of the national average ambient level in the U.S. (about 14 Bq/m³), while grade-level exhaust may contribute 1.8 times the ambient average. The grade-level contribution would drop to only 0.18 times ambient if the exhaust were 3,700 Bq/m³. Wind tunnel tests of exhaust dispersion outdoors suggest that grade-level exhaust can contribute mean concentrations beside houses averaging 7 times greater than exhaust at the eave, and 25 to 50 times greater than exhaust midway up the roof slope. With 37,000 Bq/m³ in the exhaust, the highest mean concentrations beside the house could be less than or equal to the ambient background level with eave and mid-roof exhausts, and 2 to 7 times greater than ambient with grade exhausts.     

Challenges in Comparing Radon Data Sets from the Same Swedish Houses: 1955–1990

We compare data sets from two different Swedish studies which included measuremem of the indoor radon concentration both in 1955 and in 1990 in 178 of the same houses. The purpose is to learn more about how the indoor radon concentration changes over a time scale of years in the same houses. Many sources of both systematic and random errors exist when comparing these types of data sets. Specific types of errors are due to uncertainties in the calibration of the epuipment, the influence of the weather, the time lengths of sampling, airing of some of the dwellings, and changes in ventilation rates. The data indicate a general increase of the radon concentration in the dwellings between 1955 and 1990, with a 1990/1955 ratio of the averages of 1.3. The average radon concentration in all alum shale houses, (where the building material is a source of radon) in 1990 versus 1955 is 204 ± 22 and 163 ± 23 Bq/m³ and in non-alum shale houses is 62 ± 8 and 42 ± 7 Bq/m³, respectively.     

Comparative risk assessment of residential radon exposures in two radon-prone areas, ?tei (Romania) and Torrelodones (Spain)

Radon and radon progeny are present indoors, in houses and others dwellings, representing the most important contribution to dose from natural sources of radiation. Most studies have demonstrated an increased risk of lung cancer at high concentration of radon for both smokers and nonsmokers. The work presents a comparative analysis of the radon exposure data in the two radon-prone areas, ?tei, Transylvania, (Romania), in the near of old Romanian uranium mines and in the granitic area of Torrelodones town, Sierra de Guadarrama (Spain). Measurements of indoor radon were performed in 280 dwellings (Romania) and 91 dwellings (Spain) by using nuclear track detectors, CR 39. The highest value measured in ?tei area was 2650 Bq m^− 3 and 366 Bq m^− 3 in the Spanish region. The results are computed with the BEIR VI report estimates using the age-duration model at an exposure rate below 2650 Bq m^− 3. We used the EC Radon Software to calculate the lifetime lung cancer death risks for individuals groups in function of attained age, radon exposures and tobacco consumption. A total of 233 lung cancer deaths were observed in the ?tei area for a period of 13 years (1994-2006), which is 116.82% higher than expected from the national statistics. In addition, the number of deaths estimated for the year 2005 is 28, which is worth more than 2.21 times the amount expected by authorities. In comparison, for Torrelodones was rated a number of 276 deaths caused by lung cancer for a period of 13 years, which is 2.09 times higher than the number expected by authorities. For the year 2005 in the Spanish region were reported 32 deaths caused by pulmonary cancer, the number of deaths exceeding seen again with a factor of 2.10 statistical expectations. This represents a significantly evidence that elevated risk can strongly be associated with cumulated radon exposure.     

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.     

Investigations in Special “High Radon Areas” In Germany

The main source of high radon concentration indoors is the exhalation of radon from the soil. In the western part of Germany, two interesting regions, “Eifel” and “Hunsrück”, are selected for these radon investigations. The first region is an area with silt and sandstone of low uranium content but with tectonic fractures caused by postvolcanic activity, whereas in the part of the “Hunsrück” under consideration, the uranium concentration in the ground formerly allowed the extraction of uranium ores. An electrostatic deposit of the first radon daughter (Polonium-218-ion) onto a surface barrier detector and the subsequent analysis of the measured alpha spectra enables the determination of the concentration of radon in dwellings, its diffusion through and its exhalation rate from the soil. A maximum indoor concentration of radon of 8 kBq★m^?3 in a bedroom and approximately 35 kBq★m^?3 in a cellar room were determined in a house built in 1976. The daily variation between the minimum and the maximum concentration indoors amounts to a factor of ten. In these regions the radon concentration outdoors varies between 20 and 150 Bq★m^?3. The exhalation rates of radon from the soil are found to range from 0.002 to 1 Bq★m^?2★S^?1 The effects of sealing the ground slab with polyurethane and removing the air under the ground slab by suction will be presented.     

Indoor 222Rn in Tennessee Valley Houses: Seasonal,Building, and Geological Factors

A two-season survey of indoor ²²²Rn concentrations was conducted in 226 occupied houses in Roane County, TN, during 1985 and 1986. A similar survey of 86 houses in Madison County, AL, was conducted in 1988 and 1989. Alpha track detectors were placed in each of the houses for three or more months during the winter heating season. Detectors were placed at the same sampling sites during the following cooling season. In this study, comparisons were made between winter and summer sampling times and between building types. For the data from Madison County, additional comparisons were made among regions of the county that differed in geological characteristics, especially the thickness of overburden above the Chattanooga Shale layer a geological stratum that has high concentrations of ²²⁶Ra and is widely found in the southeastern United States. The geometric means of summer and winter measurements in Roane County were 33 and 54 Bq m^?3, respectively. For Madison County, the summer and winter geometric means were 121 and 88 Bq m^?3, respectively. The winter ²²²Rn concentrations for houses in Roane Coutuy exceeded summer ²²²Rn concentrations, as is generally the case for houses in the US. For houses in Madison County, we found the opposite and atypical situation of higher ²²²Rn concentrations in the summertime. ²²²Rn concentrations differed significantly among groups of houses in distinguishable regions of Madison County. Substructure and other building factors had no observable effect on indoor ²²²Rn concentrations found in this study.     

Occupational exposure to natural radiation

Natural sources of radiation can make an important contribution to the exposures of people at work. Two areas of ine interest are work with minerals having elevated concentrations of activity and work in buildings where radon daughter concentrations are elevated.The Euratom Directive on ionising radiation requires that the handling of radioactive substances be reported to national authorities. National authorities may waive this requirement where the activity per unit mass is below 100 Bq g^?1, or for solid natural radioactive substances, 500 Bq g^?1. An investigation was undertaken in five factories to determine whether work with minerals having levels of natural activity below these might lead to significant doses. Models based on the data collected were used to relate the activity in the minerals to the effective dose equivalent arising from gamma radiation, inhalation ohow that the activity, and intake of long-lived activity. These assessments show that the activity concentration at which exposures to airborne dust could lead to doses equal to one-tenth of the dose limit for workers are 0.3 Bq G^?1 for thorium-232 and 1 Bq g^?1 for uranium-238. Above these values, radiological supervision may be necessary.In a separate study, measurements of radon daughter concentrations were made in seventy workplaces. Concentrations in some premises approached or exceeded the derived air concentration for occupational exposure. The highest concentrations were found in premises with low ventilation rates.     

Radon in indoor air of primary schools: a systematic survey to evaluate factors affecting radon concentration levels and their variability

In order to optimize the design of a national survey aimed to evaluate radon exposure of children in schools in Serbia, a pilot study was carried out in all the 334 primary schools of 13 municipalities of Southern Serbia. Based on data from passive measurements, rooms with annual radon concentration >300 Bq/m³ were found in 5% of schools. The mean annual radon concentration weighted with the number of pupils is 73 Bq/m³, 39% lower than the unweighted 119 Bq/m³ average concentration. The actual average concentration when children are in classrooms could be substantially lower. Variability between schools (CV = 65%), between floors (CV = 24%) and between rooms at the same floor (CV = 21%) was analyzed. The impact of school location, floor, and room usage on radon concentration was also assessed (with similar results) by univariate and multivariate analyses. On average, radon concentration in schools within towns is a factor of 0.60 lower than in villages and at higher floors is a factor of 0.68 lower than ground floor. Results can be useful for other countries with similar soil and building characteristics.     

Variation in residential radon levels in new Danish homes

Radon‐222 gas arises from the radioactive decay of radium‐226 and has a half‐life of 3.8 days. This gas percolates up through soil into buildings, and if it is not evacuated, there can be much higher exposure levels indoors than outdoors, which is where human exposure occurs. Radon exposure is classified as a human carcinogen, and new Danish homes must be constructed to ensure indoor radon levels below 100 Bq/m³. Our purpose was to assess how well 200 newly constructed single detached homes perform according to building regulations pertaining to radon and identify the association between indoor radon in these homes and municipality, home age, floor area, floor level, basement, and outer wall and roof construction. Median (5–95 percentile) indoor radon levels were 36.8 (9.0–118) Bq/m³, but indoor radon exceeded 100 Bq/m³ in 14 of these new homes. The investigated variables explained nine percent of the variation in indoor radon levels, and although associations were positive, none of these were statistically significant. In this study, radon levels were generally low, but we found that 14 (7%) of the 200 new homes had indoor radon levels over 100 Bq/m³. More work is needed to determine the determinants of indoor radon.     

Prediction of residential radon exposure of the whole Swiss population: comparison of model‐based predictions with measurement‐based predictions

Radon plays an important role for human exposure to natural sources of ionizing radiation. The aim of this article is to compare two approaches to estimate mean radon exposure in the Swiss population: model‐based predictions at individual level and measurement‐based predictions based on measurements aggregated at municipality level. A nationwide model was used to predict radon levels in each household and for each individual based on the corresponding tectonic unit, building age, building type, soil texture, degree of urbanization, and floor. Measurement‐based predictions were carried out within a health impact assessment on residential radon and lung cancer. Mean measured radon levels were corrected for the average floor distribution and weighted with population size of each municipality. Model‐based predictions yielded a mean radon exposure of the Swiss population of 84.1 Bq/m³. Measurement‐based predictions yielded an average exposure of 78 Bq/m³. This study demonstrates that the model‐ and the measurement‐based predictions provided similar results. The advantage of the measurement‐based approach is its simplicity, which is sufficient for assessing exposure distribution in a population. The model‐based approach allows predicting radon levels at specific sites, which is needed in an epidemiological study, and the results do not depend on how the measurement sites have been selected.     

Coping with radon problem in a private house

In one of the 50 houses in which, during a national radon survey of 1000 homes in Slovenia, indoor radon concentrations exceeded 1000 Bq m⁻³, radon was further investigated. Except in the attic, elevated radon concentrations were found everywhere in the home, ranging from 0.5 to 12 kBq m⁻³. Applying ICRP 65 methodology, an annual effective dose in the range from 9 to 35 mSv was estimated for an inhabitant for different exposure scenarios. The radon problem was successfully mitigated and radon concentration reduced below 200 Bq m⁻³.