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PubMed2006

Indoor and outdoor in situ high-resolution gamma radiation measurements in urban areas of Cyprus.

In situ, high-resolution, gamma-ray spectrometry of a total number of 70 outdoor and 20 indoor representative measurements were performed in preselected, common locations of the main urban areas of Cyprus. Specific activities and gamma absorbed dose rates in air due to the naturally occurring radionuclides of (232)Th and (238)U series, and (40)K are determined and discussed. Effective dose rate to the Cyprus population due to terrestrial gamma radiation is derived directly from this work. The results obtained outdoors match very well with those derived previously by high-resolution gamma spectrometry of soil samples, which were collected from the main island bedrock surface. This implies that the construction and building materials in urban areas do not affect the external gamma dose rate; thus they are mostly of local origin. Finally, the indoor/outdoor gamma dose ratio was found to be 1.4 +/- 0.5.

Air Pollutants, Radioactive↗
PubMed1991

Determining the 222Rn exhalation rate of building materials using liquid scintillation counting.

A new method for determining the free 222Rn exhalation rate from building materials is described. The sample is enclosed in a container from which the exhaled Rn is continuously purged by nitrogen gas. After 2-3 h, when the Rn level in the container has reached a steady-state concentration, the outflowing Rn is trapped on silica gel at about -190 degrees C. About 16 h after sampling, the silica gel is analyzed by liquid scintillation counting to determine the area exhalation rate. The method described has a good repeatability and reproducibility with coefficients of variation of 7.8% and 8.3%, respectively, at 5 Bq m-2 h-1. The low limit of detection of 11 mBq 222Rn offers the opportunity to quantify the exhalation rate of almost all kinds of building materials. It was found that the air humidity strongly influences the exhalation rates of building material and, therefore, should be controlled. Two typical building materials were investigated. For gypsum, an increase in the exhalation rate with increasing water vapor pressure was found, whereas for concrete, a linear decrease with increasing water vapor pressure was observed. The 222Rn area exhalation rates of 20 Dutch building materials, including some experimental ones, were determined at 50% RH, 20 degrees C, showing a range of less than 0.02-15.8 Bq m-2 h-1. The lowest values were found for natural gypsum board, the highest for phosphogypsum blocks. Building materials containing fly ash gave area exhalation rates comparable to those of similar materials without fly ash.

Air Pollutants, Radioactive↗
PubMed1991

Radon daughter levels in some public and private buildings in India.

Radon daughter concentrations have been measured in some public and private buildings of Aligarh city. Approximately 320 CR-39 detectors were mounted in 30 sample sites. It was found that the Rn daughter concentrations vary from 3.5 mWL to 8.1 mWL with a geometric mean of 5.6 +/- 1.3 mWL. The average annual effective dose equivalent due to Rn daughters is found to be 1.46 mSv using an equilibrium factor of 0.45 and an occupancy factor of 0.8. About 33% of buildings were estimated to have a Rn concentration below 40 Bq m-3 and 79% below 60 Bq m-3. The measured levels do not require any intervention as recommended by the U.S. Environmental Protection Agency.

Air Pollutants, Radioactive↗
PubMed1991

Short- vs. long-term indoor radon measurements.

The major advantage of short-term vs. long-term indoor Rn measurements is that the information is available rapidly. A study of the results obtained for Rn measurements developed in Spain, employing grab samples and 3-mo alpha-track measurements, is discussed.

Air Pollutants, Radioactive↗
PubMed1991

Validation of a personal radon monitor for use in residential 22Rn exposure studies.

A personal radon monitor (PRM) has been developed and validated for use in studies of residential 222Rn exposure. A pilot study was performed in six New Jersey homes with elevated Rn concentrations. Occupants wore PRMs, and identical monitors were placed in many rooms of the home. Extensive assessment of PRM performance has been done. A simple model for personal Rn exposure has been tested and measured occupant exposures have been compared with stationary Rn measurements. The PRM works well, with precision limited by the counting error in the exposure range examined (2-100 kBq m-3 h). The PRM sensitivity is 2.2 kBq m-3 h, and its efficiency is 2.6 tracks (kBq m-3 h)-1 per 81 mm2 film.

Air Pollutants, Radioactive↗
PubMed1991

Personal and home 222Rn and gamma-ray exposure measured in 52 dwellings.

A personal 222Rn and gamma-ray detector has been developed. The detector precision is limited only by the Poisson counting error and has a lower limit of detection in this study of 4.5 kBq m-3 h (4 pCi L-1 day). The detector was used in a study of 52 homes in Illinois to measure the personal exposure vs. the simultaneous exposure on all levels of the home. The ratio of personal exposure to basement 222Rn concentration averaged 0.22, with a high degree of scatter (R2 = 31%). The ratio of personal exposure to first floor 222Rn concentration was 0.71, with good correlation (R2 = 85%). In the absence of personal monitoring data, the best estimate of personal exposure appears to be from measurements in the first-floor living space of the home.

Air Pollutants, Radioactive↗
PubMed1991

A nationwide survey of 222Rn and gamma radiation levels in Australian homes.

A nationwide survey of Australian homes was conducted to determine the average annual dose equivalents to the Australian population from exposure to Rn and gamma radiation. The exposure to Rn was measured using solid-state track detectors (SSTD), while the gamma radiation dose was concurrently determined using thermoluminescent dosimetry. Dosimeters were placed in approximately 3,400 randomly distributed homes (representing about 1 in 1,400 occupied dwellings) for 12 mo. The average Rn concentration in Australian homes measured over a year is 11 Bq m-3. Using appropriate conversion factors, the annual average effective dose equivalents to the Australian population were determined to be 0.5 mSv and 0.9 mSv for Rn and gamma radiation exposure, respectively.

Air Pollutants, Radioactive↗
PubMed1991

Prediction of 222Rn from topography in Pennsylvania.

The relationships of Rn levels in basements and first floors of homes to topographic location in a northeastern ridge and valley section of Pennsylvania were investigated. Topographic variables relating to elevation and slope were quantified and related to house Rn levels using both conventional and classification and regression tree (CART) analyses. The original interest was in using topographic correlates to estimate missing values in epidemiologic studies. In this area, Rn levels are usefully predicted by relative and absolute elevations and nearness to hills and ridges. Three- to fourfold differences in geometric mean Rn levels can be obtained for categories representing significant portions of the population of houses. The relationship of first-floor to basement Rn levels was found to be curvilinear and modestly affected by topography.

Air Pollutants, Radioactive↗
PubMed1991

Determination of time-varying 222Rn concentrations using flow-through scintillation flasks.

This paper describes a method to obtain time-varying 222Rn concentrations from the series of gross alpha measurements recorded with a flow-through scintillation detector. The continuous input of 222Rn into the detector is treated as a series of independent pulses. The response of the detector to a single pulse containing 222Rn can be measured in the laboratory and is used to determine a normalized detector response function (NDRF). The NDRF contains information on the combined effects of detector design, operating parameters, and the presence of 222Rn progeny. The estimation of individual plate-out or counting efficiencies is not needed, as they are appropriately included in the NDRF. The equation describing the response function can be inverted to yield the actual 222Rn concentration in terms of detector output. The technique was applied to actual indoor monitoring data and the results presented.

Air Pollutants, Radioactive↗
PubMed1991

Indoor 222Rn levels in New York State, North Carolina, and South Carolina.

Results are presented from approximately 9000 Rn measurements made in New York state, North Carolina, and South Carolina. The estimated statewide geometric mean concentrations were 28.1 Bq m-3 and 55.8 Bq m-3 for basements in New York state, 27.5 Bq m-3 for living rooms and 108.9 Bq m-3 for basements in North Carolina, and 25.0 Bq m-3 for living rooms in South Carolina.

Air Pollutants, Radioactive↗
PubMed1992

Indoor 222Rn concentrations in a probability sample of 43,000 houses across 30 states.

The U.S. Environmental Protection Agency has assisted 30 of the 48 conterminous states in completing statistically designed surveys of indoor 222Rn over the past 4 y. In all states, the lowest livable level of 43,054 randomly selected houses was tested using charcoal canisters exposed for 48 h. The sampled population included owner-occupied ground-level houses having listed telephone numbers. Summary statistics along with the percentage of houses exceeding various concentration levels are given by state and over all states for houses with basements, for houses without basements, and for all houses. As expected, 222Rn concentration varies widely from one state to another and, in every state, basement houses exhibit higher concentrations than nonbasement houses. The lognormal distribution is shown to be a good approximation to the distribution of screening measurements over the 30-state area. There is, however, some evidence that the lognormal distribution underestimates, by a narrow margin, the upper tail of the observed distribution of basement measurements.

Air Pollutants, Radioactive↗
PubMed1992

Estimating radon potential from an aerial radiometric survey.

A radon screening survey of 719 residences in Nova Scotia was performed using liquid scintillation charcoal canisters. The readings have been correlated with an aerial radiometric survey map of the 1.76-MeV gamma emission of 214Bi, which is plotted in terms of uranium parts per million equivalent. A good correlation exists, suggesting that this particular map could be used to indicate the potential for radon problems in particular geographic areas.

Air Pollutants, Radioactive↗
PubMed1992

Activity size distribution of radon progeny in indoor air: comparison of model to data.

The activity size distributions of radon progeny in indoor air are considered. A general theoretical model is presented and then applied to this experiment where experimental data was obtained in a very large and nearly airtight laboratory for two cases: low particle concentration (Case 1) and high particle concentration (Case 2). The balance equations of aerosol particles, radon, and radon progeny in indoor air are solved numerically. The effects of particle coagulation are noticeable for u = 0.005 ms-1, (u. equals friction velocity) but negligible for u = 0.015 ms-1 as long as we adopt a certain theoretical model of wall deposition. Numerical results agreed rather well with this experimental data. Furthermore, an example calculation was done in the case of a usual living space with a high air-exchange rate.

Air Pollutants, Radioactive↗
PubMed1993

Factors affecting indoor radon concentrations in the United Kingdom.

Data collected in a nationwide study on natural radiation exposure in UK dwellings (Wrixon et al. 1988) were re-analyzed to investigate the effects of rock type and various building and lifestyle characteristics, taken into account simultaneously, on indoor radon concentrations. A multiplicative model which takes into consideration the outdoor radon concentration is used. Indoor radon concentrations were found to be influenced by type of rock underlying the dwelling, double glazing, house type, floor level of rooms in which measurements were taken, window opening habits in the main bedroom, building materials used in the construction of the walls, floor type, and draught proofing. However, these eight factors together account for only 22% of the variation between dwellings. Estimates of the size of the effect associated with each factor are given.

Air Pollutants, Radioactive↗
PubMed1993

Characterization of 222Rn entry into a basement structure surrounded by low-permeability soil.

An experimental facility has been developed to monitor the entry rate and concentration of 222Rn in a basement-type structure surrounded by soil having a permeability on the order of 10(-11) m2. A data acquisition system recorded environmental conditions outside and inside the structures, plus basement air exchange rate information, every 15 min. Indoor 222Rn concentrations ranged from 400 to 1,400 Bq m-3. The observed 222Rn entry rate is highly variable and has two primary components; a constant input rate caused by diffusion of 222Rn through the concrete walls and floor, and a variable rate that depends upon indoor-soil pressure differentials of only a few pascals. Pressure differentials are dependent upon wind speed and wind direction. Stack effect was not significant. During a 2-wk period, with relatively calm winds, diffusion through the concrete walls and floor plus the floor-wall joint accounted for more than 80% of the total 222Rn entry.

Air Pollutants, Radioactive↗
PubMed1993

A review of ecologic studies of lung cancer and indoor radon.

Although radon exposure is an established cause of lung cancer among underground miners, the lung cancer risk to the general population from indoor radon remains controversial. This controversy stems in part from the contradictory results of published studies of indoor radon and lung cancer, including 15 ecologic studies, seven of which found a positive association, six no association, and two a negative association. To address the misunderstanding of the indoor radon risk that has resulted from these ecologic studies, the authors discuss the general methodologic problems and limitations of ecologic studies, and the particular limitations of these 15 studies. The authors conclude that the shortcomings of the ecologic studies render them uninformative on the lung cancer risk associated with indoor radon.

Air Pollutants, Radioactive↗
PubMed1993

Benefits to a life insurance company from providing radon tests for clients.

If a life insurance company provided free radon tests to clients, clients' life expectancies would be extended and profits would thereby be increased. This effect is quantified and it is found that the direct monetary benefits to the company could be substantial. Several subsidiary advantages are also discussed.

Air Pollutants, Radioactive↗