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 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.     

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 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.     

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.     

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     

Risk assessment for indoor exposure to radon daughters

Approaches to and results for the estimation of healths risks from indoor exposure to radon and its daughter products are discussed. Particular weight is given to the derivation of exposure-time-effect relationships using a modified proportional hazard model which has been adapted to account for relevant epidemiological data.The results of this analysis indicate that about (10±5) % of the lung cancer rate observed in the general public might be correlated to the enhanced exposure to radon daughters in dwellings(at 10 – 20 Bq/m³ (Rn-eq)) and in outdoor air. A chronic exposure to indoor Rn-levels at home of about 300 – 500 Bq/m³ (Rn-eq) might possibly double the normal lung cancer rates. The relative fractions of radiogenic lung cancer rates might be nearly the same for smokers and non-smokers, and for men and women.     

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.     

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.     

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.     

Effects of Climatic Parameters on Formaldehyde Concentrations in Indoor Air

The results of measurements of indoor air formaldehyde concentrations in occupational and private residences are presented for the period 1986 to 1993, based on requests of persons who complained about irritations. In many cases, climatic parameters such as the air exchange rate, temperature and relative humidity were also monitored. Calculated mean values for temperature and humidity were 22°C and 45% respectively. The average air exchange rate was 0.36 h^?1, which is well below a recommended guideline value of 0.8 h?' and it was evident that the ventilation is clearly insufficient in many rooms. The average formaldehyde concentration was 119 μg/m ^?3 (252 data), which is only slightly below the German guideline value of 125 μg/m ^?3. In 31% of the cases this guideline was exceeded. As expected, a clear relation between formaldehyde concentrations and the air exchange rate was found. The highest levels result at AE≤0.8 h^?1, but only a single value exceeds 125 μg/m ^?3 at AE≥0.8 h^?1. The association of law ventilation rates with high formaldehyde levels is also evident from a comparison with theoretical data after normalization to AE=0.8 h^?1, using the Hoetjer-equation. It was also observed that the calculated annual mean concentrations decreased from 1986 to 1993.     

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.     

Measurement of radioactivity levels of the Sirt gulf,Libya

The paper presents the results of measurements on air and soil samples collected for their natural and artificial radioactivity content. The radionuclides studied under this programme are ⁷Be and ¹³⁷Cs. Average activity concentrations in surface air of ⁷Be and ¹³⁷Cs were found to be 1920 and 2.1 μBq m^‐3, respectively. ¹³⁷Cs activity concentration in surface soil is found to be 450m Bq kg^‐1. Estimated effective doses to adult from inhaled ⁷Be and ¹³⁷Cs were found to be 1 and 0.13 nSvy^‐1, respectively.

The average outdoors absorbed dose rate in air, 1 m above the ground level was found to be (48 ± 4.0 nGy h^‐1), based on the analysis of thermoluminescence dosimeters data collected.     

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 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.     

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.     

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.     

Formaldehyde and acetaldehyde exposure mitigation in US residences: in‐home measurements of ventilation control and source control

Measurements were taken in new US residences to assess the extent to which ventilation and source control can mitigate formaldehyde exposure. Increasing ventilation consistently lowered indoor formaldehyde concentrations. However, at a reference air exchange rate of 0.35 h^?1, increasing ventilation was up to 60% less effective than would be predicted if the emission rate were constant. This is consistent with formaldehyde emission rates decreasing as air concentrations increase, as observed in chamber studies. In contrast, measurements suggest acetaldehyde emission was independent of ventilation rate. To evaluate the effectiveness of source control, formaldehyde concentrations were measured in Leadership in Energy and Environmental Design (LEED)‐certified/Indoor airPLUS homes constructed with materials certified to have low emission rates of volatile organic compounds (VOC). At a reference air exchange rate of 0.35 h^?1, and adjusting for home age, temperature and relative humidity, formaldehyde concentrations in homes built with low‐VOC materials were 42% lower on average than in reference new homes with conventional building materials. Without adjustment, concentrations were 27% lower in the low‐VOC homes. The mean and standard deviation of formaldehyde concentration was 33 μg/m³ and 22 μg/m³ for low‐VOC homes and 45 μg/m³ and 30 μg/m³ for conventional.     

Characterization of Radon Decay Products in a Domestic Environment

Field measurements of the concentration and activity size distribution of radon decay products were conducted in a one-story house located in the Princeton, NJ area. Radon concentration and particle number concentration were also measured. The concentration and activity-weighted size distribution of radon decay products were determined using a microcomputer-controlled, semi-continuous screen diffusion battery system with 6 parallel sampler/detector units. A condensation nuclei counter was used for the measurements of indoor panicle number concentration. Several measurements were made in the living room as well as more than one hundred measurements in the master bedroom of the Princeton house. Aerosols were generated from taking a shower, burning a candle, smoldering a cigarette, vacuuming, and cooking. Therefore, the influence of various indoor panicle sources on the behavior of radon decay products was investigated. With panicles generated from typical household activities, Potential Alpha Energy Concentration (PAEC) increases and the unattached fraction decreases. Larger panicles generated from cigarette smoke and cooking dramatically shifted most of the radon decay products into the attached mode (15-500 nm). With regard to the higher attachment rate, the size distributions of radon decay products remained stable for long periods of time after particle generation. On the other hand, aerosols produced from candle burning and vacuuming were much smaller, with an average attachment diameter of 15 nm. These panicles did decrease the unattached fraction, especially during the aerosol generation period. However, the size distributions of radon decay products returned to the background condition within ISO minutes after the end of particle generation. In these cases, the panicles had a higher deposition rate and a lower attachment rate. The dose of alpha radiation per unit radon concentration resulting from each of these aerosol conditions was calculated using the measured activity size distributions and the most recent James dosimetric model. These doses to basal cells at a breathing rate of 0.45 m³ hr¹ ranged from 3 to 14 μGy Bq^?1 hr while the dose to secretory cells at a breathing rate of 1.5 m³ hr¹ ranged from 13 to 77 μGy Bq^?1 hr for the various aerosol conditions.