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.     

Indoor natural radiation levels in Ireland

The principal results of a preliminary study made on indoor radiation levels in Ireland are presented. During the period 1983–1984 measurements were made in over 250 houses. Most measurements were made using passive devices: TLDs for penetrating radiation and CR-39 alpha track plastic detectors for radon measurements. The median value of the doses from penetrating radiation was 0.78 milligray/year with a maximum value of 1.47 m Gy/year detected. The radon concentrations showed a large degre of variability with a median value of 43 Bq/m³. About 10% of the houses had radon air concentrations in excess of 100 Bq/m³ with a maximum of 700 Bq/m³ being recorded. A tentative analysis of the data with regard to the geological situation is presented.     

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.     

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.     

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.     

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.     

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.     

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 radon concentrations caused by construction materials in 23 workplaces

The aim of this study was to compare the measured and the calculated concentrations of indoor radon caused by building materials at 23 workplaces. The measured concentrations of radon were clearly higher than the calculated radon concentrations from the building materials, which indicated that the main source of indoor radon was the soil under and around the buildings. The highest means of continuously (933 Bq m(-3)) and integrated (169 Bq m(-3)) measured and calculated (from 70 to 169 Bq m(-3)) concentrations of radon were found in hillside locations. On the other hand, the median (27 and 43 Bq m(-3)) and maximum (626 and 1002 Bq m(-3)) values of calculated indoor radon concentrations exhaled from construction materials were the highest at the ground level places. On average, only 7-19% of the radon seemed to originate from the construction materials.     

Effects of energy retrofits on Indoor Air Quality in multifamily buildings

We assessed 45 multifamily buildings (240 apartments) from Finland and 20 (96 apartments) from Lithuania, out of which 37 buildings in Finland and 15 buildings in Lithuania underwent energy retrofits. Building characteristics, retrofit activities, and energy consumption data were collected, and Indoor Air Quality (IAQ) parameters, including carbon monoxide (CO), nitrogen dioxide (NO₂), formaldehyde (CH₂O), selected volatile organic compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX), radon, and microbial content in settled dust were measured before and after the retrofits. After the retrofits, heating energy consumption decreased by an average of 24% and 49% in Finnish and Lithuanian buildings, respectively. After the retrofits of Finnish buildings, there was a significant increase in BTEX concentrations (estimated mean increase of 2.5 µg/m³), whereas significant reductions were seen in fungal (0.6‐log reduction in cells/m²/d) and bacterial (0.6‐log reduction in gram‐positive and 0.9‐log reduction in gram‐negative bacterial cells/m²/d) concentrations. In Lithuanian buildings, radon concentrations were significantly increased (estimated mean increase of 13.8 Bq/m³) after the retrofits. Mechanical ventilation was associated with significantly lower CH₂O concentrations in Finnish buildings. The results and recommendations presented in this paper can inform building retrofit studies and other programs and policies aimed to improve indoor environment and health.     

Correlations between radon concentration and indoor gamma dose rate, soil permeability and dwelling substructure and ventilation

Correlations between radon concentration and indoor gamma dose rate, soil permeability and dwelling substructure and ventilation were studied using data from 84 low rise residential houses collected in an area of enhanced indoor radon concentration. The radon concentrations varied from 30 to > 5000 Bq m(-3). Cross-tabulation, comparisons of means and multiplicative models were used to test the significance of the effects. In this study a quite high percentage of explained variation R2 (68%) was found. It was found that the most important factors were the substructure and the permeability of the soil. Due to the rather small sample size and moderate variation in the uranium content of the bedrock of the area, the effect of the indoor gamma dose rate was not so prominent. The effects of ventilation habits and sleeping with open windows were not detected in this study.     

Large-scale radon hazard evaluation in the Oslofjord region of Norway utilizing indoor radon concentrations, airborne gamma ray spectrometry and geological mapping

We test whether airborne gamma ray spectrometer measurements can be used to estimate levels of radon hazard in the Oslofjord region of Norway. We compile 43,000 line kilometres of gamma ray spectrometer data from 8 airborne surveys covering 10,000 km² and compare them with 6326 indoor radon measurements. We find a clear spatial correlation between areas with elevated concentrations of uranium daughters in the near surface of the ground and regions with high incidence of elevated radon concentrations in dwellings. This correlation permits cautious use of the airborne data in radon hazard evaluation where direct measurements of indoor radon concentrations are few or absent. In radon hazard evaluation there is a natural synergy between the mapping of radon in indoor air, bedrock and drift geology mapping and airborne gamma ray surveying. We produce radon hazard forecast maps for the Oslofjord region based on a spatial union of hazard indicators from all four of these data sources. Indication of elevated radon hazard in any one of the data sets leads to the classification of a region as having an elevated radon hazard potential. This approach is inclusive in nature and we find that the majority of actual radon hazards lie in the assumed elevated risk regions.     

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.     

Case Study of Radon Diagnostics and Mitigation in a New York State School

This is a case study of the radon diagnostics and mitigation performed by the U.S. Environmental Protection Agency's (EPA's) Office of Research and Development in a New York State school building. Research focused on active subslab depressurization (ASD) in the basement and, to a lesser degree, the potential for radon reduction in the basement and slab-on-grade sections using the heating, ventilating, and air-conditioning (HVAC) system. Based on radon diagnostic measurements in the basement, a five-point ASD system was installed, and recommendations were made to increase the outdoor air supply through the basement unit ventilator. Because of the high radon levels in the basement (1720 bequerels per cubic meter, Bq m^?3) and limited subslab pressure field extension, both mitigation approaches were needed to reduce radon to below the current EPA guideline of 148 Bq m^?3. The effects of excavating a suction pit under each of the five suction points were also investigated. Pit excavation, together with adjustment of the airflows at the suction points, decreased average radon levels in the basement by an additional 40 percent. In the slab-on-grade section, it was recommended that the school hire a HVAC contractor to evaluate the unit ventilators for increased outdoor air supply. This was recommended both to improve indoor air quality and because diagnostic measurements indicated that an ASD system would require an excessive number of suction points in the slab-on-grade classroom.     

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.     

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.     

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.     

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.     

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.     

广州市室内氡浓度调查报告

我公司于2008～2009年承担了全国室内氡调查项目中广州地区的调查工作。本次调查中,按全国室内氡浓度调查方案的要求,按行政区、人口分布、建筑物和种类等分布了采样点,共布了146个采样盒,回收了135个。结果表明,广州市室内氡平均浓度为32.70Bq/m3,最大值156Bq/m3,最小值4Bq/m3。这次全国10个城市室内氡浓度调查结果的均值为34.9Bq/m3。在广州室内氡调查结果比较低的主要原因是人们长期开窗通风的生活习惯。与工程验收检测的氡浓度相差甚远,主要的原因是检测时的状态不同。