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PubMed1997

Radon measurements in the Gran Sasso Underground Laboratory.

Systematic radon monitoring in the Gran Sasso Underground Laboratory was performed in order to determine the background radon contribution to the sophisticated experimental apparatus and to check health physics standards for the personnel. As expected, the radon concentrations were found to depend strongly on the ventilation in the three experimental halls. Considerable reductions in the radon concentrations were obtained in 1993, when fresh air was drawn into the laboratory through a pipe and exhaust air was routed into the highway tunnel.

Air Pollutants, Radioactive↗

PubMed1997

Predictions and maps of county mean indoor radon concentrations in the mid-Atlantic states.

Measured surface radium content, geologic province information, information on the fraction of homes with basements and with living-area basements, and measurements from the EPA/State Residential Radon Surveys, were used in a Bayesian mixed effects regression to predict the distributions of short-term winter and annual living-area average radon concentrations by county in the mid-Atlantic states. The information provided by those explanatory variables is roughly equivalent to collecting an extra 12 observations per county, effectively doubling the amount of information in a typical county. Predicted county geometric means are subject to standard errors of 15% to 30% for typical counties, with the uncertainty in a given county depending on the number of radon measurements in the county and the amount of information about the geologic province that contains the county. After controlling for soil radium concentration and the effect of measuring in a basement vs. the first floor, typical geologic provinces are found to be associated with elevation or depression of indoor radon concentrations by 30% on average, with some provinces having effects of considerably larger magnitude.

Air Pollutants, Radioactive↗

PubMed1998

Discussion about surface boundary conditions of radon concentration and surface exhalation rate calculations in indoor concrete slab.

In this paper, the rationality of boundary conditions that assume radon concentration at the surface of a concrete slab to be zero, or radon concentration at an infinite point in air to be zero, are discussed in the calculations of radon concentration and surface exhalation rate from a concrete slab. Expressions to calculate radon concentration and surface exhalation rate in indoor concrete slab are given for both boundary conditions.

Air Pollutants, Radioactive↗

PubMed1998

Mapping radon-prone areas by lognormal modeling of house radon data.

Results of radon measurements in houses are generally distributed approximately lognormally, whether large or small areas are considered. The properties of the lognormal distribution allow the proportion of houses above a threshold level to be estimated even when there are insufficient data to calculate the proportion directly. In this paper the properties of the data set of radon measurements made in UK houses with etched-track radon detectors are examined, with the purpose of using them to map radon-prone areas. Individual results are normalized depending on the average outdoor temperature during the measurement to estimate the annual average radon level. For certain types of maps, results may also be normalized to estimate the radon level in a standard house or mixture of house types on the same site. Methods to use the lognormal model to estimate the geometric mean radon concentration and geometric standard deviation for data grouped by area have been developed. These data are then used to map radon-prone areas of England and Wales.

Air Pollutants, Radioactive↗

PubMed1998

Estimate of the annual per capita surplus dose due to the elevated indoor exposure to 222Rn progeny caused by the use of slag and spoil of uranium rich coal for building purposes in Ajka Town, Hungary.

Ajka is a mining and industrial town in Hungary. Brown coal rich in uranium (300 to 900 Bq kg(-1)) has been mined by the town since 1865. Slag and spoil of the coal were frequently used in the town for building purposes before 1960. Screening measurements of 222Rn progeny in indoor air were performed in 86 Ajka buildings. Elevated 222Rn progeny levels were found in houses that used the above by-products as building materials or foundations. Annual per capita surplus effective doses due to the exposure to elevated 222Rn progeny levels were estimated from the results of the screening measurements. The possibility of estimating the mean of the annual averages of 222Rn or 222Rn progeny concentration for a group of houses from the results of screening measurements is discussed in detail. The estimated annual surplus dose is 0.64 mSv for the population of the whole town and 1.86 mSv for the 7,000 occupants of family houses built before 1960.

Air Pollutants, Radioactive↗

PubMed1998

Tritium concentrations inside the homes of occupationally exposed workers: dosimetric implications.

The average tritiated water concentration in the indoor air of the occupationally exposed worker's residence (55 Bq m(-3), range 53-59 Bq m(-3)) was higher than the indoor air of control residences (0.7 Bq m(-3), range 0.4-0.8 Bq m(-3)). The worker had an average concentration of tritium-in-urine of 30 kBq L(-1) from chronic intakes of occupational levels of tritiated water. Higher residential concentrations of tritiated water vapor were due to tritium transferred by the worker. Urine samples from an adult co-occupant were collected and had tritiated water concentrations between 89 and 345 Bq L(-1). These concentrations were higher than for individuals (range, 6-32 Bq L(-1)) living in other residences having similar outdoor and indoor concentrations of tritiated water in air. The range of measured tritiated water in urine was in agreement with the prediction of biokinetic models for tritium intakes as recommended by the International Commission on Radiological Protection Publication 56. The tritiated water vapor in the indoor air of the exposed worker's residence contributed about 96% of the daily tritium intakes. The annual average tritium dose to the family member (7 microSv) was well below the International Commission on Radiological Protection Publication 60 recommended annual dose limit (1 mSv) for members of the public. We conclude that, for a few members of the public living near a heavy-water research reactor facility, daily intakes of tritium will relate to tritiated water dispersed by the exposed worker, as well as to tritium transported by the atmosphere from the reactor site.

Air Pollutants, Radioactive↗

PubMed1998

Radon properties in offices.

The radon concentration (RC), total potential alpha energy concentration of radon decay products (PAEC), equilibrium factor (F), and the fraction of unattached radon decay products (fp) were measured for 94 offices in Hong Kong. The mean values for RC, PAEC, F, and fp were 51 Bq m(-3), 1.19x10(-7) J m(-3) (5.7 mWL), 0.43, and 0.13, respectively. The first three are much higher than the corresponding values for dwellings. The radon properties vary significantly for different sites. The time for measurements, cumulative time since the air conditioning system was turned on, and whether smoking is allowed in the office have been identified from the available data as possible factors affecting the radon characteristics in offices. The mean contribution of the lung exposure to the annual effective dose equivalent due to radon in offices has been calculated to be 0.35 mSv y(-1). Considering other sources of natural radiation, a rough estimate of the total annual equivalent dose of about 2.7 mSv for a person living in Hong Kong is obtained. Two simple methods are proposed to mitigate the radon hazard in offices: (1) the provision of smoke-free environments and (2) switching on the air conditioners earlier. The first method reduces the equivalent dose by about 0.13 mSv y(-1) while the second reduces by about 0.1 mSv y(-1), which can be regarded as significant.

Air Conditioning↗

PubMed1998

Correlation between indoor radon concentration and dose rate in air from terrestrial gamma radiation in Japan.

A correlation between the indoor radon concentration and dose rate in air from terrestrial gamma radiation is studied using the results of nationwide indoor radon and external exposure surveys, although the surveys were not conducted at the same time nor at the same location. The radon concentration shows a log-normal-like distribution, whereas the terrestrial gamma radiation dose rate in air shows a normal-like distribution. A log-linear scatterplot for each pair of the indoor radon concentration and gamma-ray dose rate in air in each city reveals a clear relationship. The average, maximum, and minimum as well as regression line of radon concentration were found to increase with the gamma-ray dose rate in air. The group in higher quantile of radon concentration shows larger dependence on the gamma-ray dose rate. The rate of increase of radon concentration with the gamma-ray dose rate in air depends on the house structure. The wooden house has a larger rate of increase than the concrete house, and the regression lines cross at high air dose rate. Based on the finding in the present study a certain criterion level of air dose rate could be established and used for an effective survey to find out which houses might require a remedial action in conjunction with other screening tools. The criterion level of air dose rate might be more effective if the level is set for each house structure since the rate of increase of radon concentration depends on house structure.

Air Pollutants, Radioactive↗

PubMed1998

Indoor exposure to 222Rn: a public health perspective.

The objective of this study was to assess the lung cancer risk resulting from indoor radon exposure in the province of Quebec, Canada, and to evaluate the efficacy of mitigation measures to reduce this exposure. Concentrations of radon were determined in a representative sample of houses, and the corresponding lung cancer risk estimates were generated using the BEIR IV model, taking into account smoking, residential mobility, and regional variations in radon concentrations. Mean (geometric) radon concentrations in basements (n = 418) and on first floors (n = 319) were, respectively, 34.4 (95% CI-30.6 to 38.8) and 16.5 Bq m(-3) (14.2 to 19.3). A total of 109 deaths from lung cancer are predicted to occur as a result of this exposure in a cohort of 60,000 people. Detecting all residences with high radon concentrations (equal to or above 200 Bq m(-3)) and implementing mitigation measures in each of them would reduce by 4 the number of lung cancer deaths attributable to indoor radon exposure. A reduction of 0.05% in the prevalence of smoking would prevent as many deaths from lung cancer as would radon mitigation. From a public health perspective, in order to reduce mortality from lung cancer, most efforts should be focused on smoking, not on the relatively minor and hardly preventable population risk arising from household radon exposure.

Air Pollutants, Radioactive↗

PubMed1998

Behavior of 222Rn and its progeny in high-rise buildings.

Unlike detached or semi-detached houses, the main source of indoor radon in high-rise buildings is the building material. Radon released from the building material will be removed by ventilation, either forced or natural, so that its concentration, its progeny's concentration, and the equilibrium between the two will be different for different types of buildings and environmental factors. A number of surveys were carried out in buildings throughout the territory to look at the seasonal variation of indoor 222Rn levels; the dependence of indoor 222Rn concentration on the living environment; the indoor gamma dose rate and its relation to indoor 222Rn concentration; and the dependence of 222Rn progeny concentration and equilibrium factor on the environment in high-rise buildings.

Air Pollutants, Radioactive↗

PubMed1998

Spatial variation of residential radon concentrations: the Iowa Radon Lung Cancer Study.

Homeowners and researchers frequently estimate the radon concentrations in various areas of the home from a single radon measurement often performed in the home's basement. This study describes the spatial variation of radon concentrations both between floors and between rooms on the same floor. The geometric mean basement and first floor radon concentrations for one-story homes were 13.8% and 9.0% higher, respectively, as compared to their counterparts in two-story homes. The median first floor/basement ratio of radon concentrations for one-story homes was 0.60. The median ratios between first floor/basement and second floor/basement for two-story homes were 0.51 and 0.62, respectively. The mean coefficient of variation for detectors placed on the same floor was 9.5%, which was only 2.6% higher than the mean coefficient of variation found for collocated (duplicate) quality control detectors. The wide individual variations noted in radon concentrations serve as a reminder of the importance of performing multiple radon measurements in various parts of the home when estimating home radon concentrations.

Adult↗

PubMed1998

Radon reduction systems in the construction of new houses in Gainesville, Florida.

High radon level exposures increase human risk of lung cancer. The objective of this paper is to present the results of the effectiveness of applying the Enkavent mat method and the suction pit method; as tested by a University of Florida research team; to reduce radon entry in new houses built in the city of Gainesville and the surrounding Alachua County area in Florida. Both of these passive techniques include placement of a barrier under the concrete floor slab right on top of the soil at the new building sites. Passive and active techniques applied in the construction of new houses reduced radon levels to below the minimum requirements of 148 Bq m(-3) (4 pCi L(-1)). The mitigation systems investigated in this research were adopted by the Florida Legislature to become part of the new building construction code in Florida.

Air Pollutants, Radioactive↗

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↗

PubMed2000

Eyeglass lenses for personal radon dosimetry.

Eyeglass lenses are commonly composed of allyl-diglycol carbonate (CR-39), an alpha-particle detecting plastic, thus making such lenses personal radon dosimeters. Samples of such lenses have been etched to reveal that radon and radon progeny alpha tracks can be seen in abundance, and sensitivities have been calibrated in radon chambers as a primary calibration and with a uranium-based source of alpha particles as a convenient secondary standard. Natural, environmental (fossil) track densities ranged from 3,000 to 25,000 cm(-2) for eyeglasses that had been worn for various times from 1 to nearly 5 y. Average radon concentrations to which the wearers were exposed are inferred to be in the range 20 to 130 Bq m(-3) (0.5 to 3.5 pCi L(-1)). Procedures for consistent, meaningful readout are described.

Air Pollutants, Radioactive↗

PubMed2001

Thermodiffusion in concrete slab as a driving force of indoor radon entry.

The core of the hypotheses considered is that there is an additional strong driving force-the thermodiffusion of radon and soil air in concrete and soils, which can cause an intensive indoor radon entry. A vertical thermogradient in the slab causes thermodiffusion air flux through concrete into the house. The proof of this concept is based on consideration of concrete slab as a micro-porous system having a pore-size distribution that mostly pertains to Knudsen's region and a transition zone of pore sizes. The Knudsen's theory for a transition zone is developed, which is consistent with the known experimental data of thermodiffusion. Calculated thermodiffusion air flux across a concrete slab under thermogradient 80 K m(-1) approximately ranges 1 x 10(-7)-1 x 10(-6) kg x m(-2) x s(-1). The calculated typical radon-bearing advective air velocity in soil due to thermogradient in the slab is about 1 x 10(-6) m x s(-1).

Air Pollutants, Radioactive↗

PubMed2002

Airborne 222Rn concentration in an Egyptian village.

The indoor radon concentration in a typical Egyptian village in Delta was measured in 50 houses during summer 1999 and winter 2000. This survey was done using three different types of charcoal canisters: 4" open-faced, 2.75" open-faced, and 2.75" diffusion barrier. The average winter to summer ratio was 2.1 and 1.2 for open rooms and closed rooms, respectively, in clay buildings, while it was 0.8 and 1.0, respectively, in concrete buildings. The seasonal variations of radon concentration as well as the effect of building materials were discussed.

Air Pollutants, Radioactive↗

PubMed2003

Measurements with a Ge detector and Monte Carlo computations of dose rate yields due to cosmic muons.

The present work shows how portable Ge detectors can be useful for measurements of the dose rate due to ionizing cosmic radiation. The methodology proposed converts the cosmic radiation induced background in a Ge crystal (energy range above 3 MeV) to the absorbed dose rate due to muons, which are responsible for 75% of the cosmic radiation dose rate at sea level. The key point is to observe in the high energy range (above 20 MeV) the broad muon peak resulting from the most probable energy loss of muons in the Ge detector. An energy shift of the muon peak was observed, as expected, for increasing dimensions of three Ge crystals (10%, 20%, and 70% efficiency). Taking into account the dimensions of the three detectors the location of the three muon peaks was reproduced by Monte Carlo computations using the GEANT code. The absorbed dose rate due to muons has been measured in 50 indoor and outdoor locations at Thessaloniki, the second largest town of Greece, with a portable Ge detector and converted to the absorbed dose rate due to muons in an ICRU sphere representing the human body by using a factor derived from Monte Carlo computations. The outdoor and indoor mean muon dose rate was 25 nGy h(-1) and 17.8 nGy h(-1), respectively. The shielding factor for the 40 indoor measurements ranges from 0.5 to 0.9 with a most probable value between 0.7-0.8.

Air Pollutants, Radioactive↗

PubMed2003

Nationwide survey of radon levels in Korea.

A nationwide radon survey was conducted to provide data on the annual average indoor radon concentration in Korean homes. This survey also provided data on the variation of radon concentration with season, house type, and building age. The arithmetic mean (AM) of annual radon concentration in Korean homes was 53.4 +/- 57.5 Bq m(-3). The indoor radon concentration showed a lognormal distribution with a geometric mean (GM) and its standard deviation (GSD) of 43.3 +/- 1.8 Bq m(-3). The radon concentrations in the traditional Korean-style houses were about two times higher than those in apartments and row houses. The average annual outdoor radon concentration was 23.3 Bq m(-3). The average annual effective dose to the general public from radon was 1.63 mSv y(-1).

Air Pollutants, Radioactive↗