Indoor radon measurements

Aside from the difficulty in correlating soil radon measurements with indoor radon measurements, various field studies have also shown that obtaining a representative soil gas measurement is difficult. Soil gas radon measurements were made with a permeameter in seven central Florida houses.42... 

George, A. C., and J. Eng, Indoor Radon Measurements in New Jersey, New York and Pennsylvania, Health Phys. 45 397 (1981). 

The objectives of this study are to determine the frequency distribution of radon levels in residential structures on a nationwide basis and to investigate factors which affect these levels. This study is needed to obtain a more accurate estimate of the average radon level in homes and to provide reliable data on the number of homes exceeding various radon levels. Such information will provide a better understanding of the magnitude of the public health problem associated with indoor radon levels. In addition this information will establish the base line level against which results of other surveys and indoor radon measurements can be compared. 

A relatively large number of indoor radon measurements have already been made, particularly during the last 6-12 months. However, most of these measurements are not useful in defining the national frequency distribution of indoor radon levels because there are a number of uncertainties and limitations associated with these measurements. These uncertainties include the different purposes for the measurements, the widely varying sample designs, and the many different sample collection and measurement procedures used. 

Fleischer, R.L. and Turner, L.G., Indoor radon measurements in the New York capital district, Health Phys, 46 5, pp. 999-1011,... 

Alter, H. W., and R. A. Oswald, Nationwide Distribution of Indoor Radon Measurements A Preliminary Data Base, JAPCA, 37, 227-231 (1987). 

Alter H, Oswald R. 1987. Nationwide distribution of indoor radon measurements a preliminary database. J Air Pollut Control Assoc 37 227-231. 

Indoor radon measurements obtained for homes in North Virginia, USA, revealed that existing high or low median indoor radon levels in each house persist through four seasons [59], however, attempts to compare between the soil radon outside and the soil... 

In an effort to evaluate the risk of an indoor radon problem occurring in a home built on a particular site, researchers have made many types of measurements. The measurements commonly made include9... 

In addition to the above measurements, indexes using soil concentrations in combination with permeability measurements have been suggested by some researchers.4142 As elaborated on later in this section, these methods have been successful in establishing relationships between some of the site measurements and indexes, and indoor radon concentrations for specific areas and regions. 

Attempted Correlations between Indoor Radon and Measurement Made at Sites... 

The Florida data reported by Geomet have been evaluated and the houses are listed in order of highest measured indoor radon levels. This analysis is shown in Table 31.3.4445... 

It is clear from Table 31.3 that soil radon measurements that varied over an order of magnitude produced significantly less than a factor of 2 difference in the indoor radon levels. Predictions of radon potential based on soil radon measurements would be highly suspect based on these data. 

The major drawback to using the Florida study to support the correlation between indoor and soil measurements was that the indoor measurements were obtained from 3-day closed-house charcoal measurements, and soil radon was obtained from 1-month alpha track measurements buried 1 ft beneath the soil surface. Comparisons of charcoal and alpha track data are generally not recommended since they are quite different measurement techniques, and represent radon levels over different time periods. However, the study was subjected to numerous quality control checks including deployment of alpha track detectors in 10% of the houses to obtain a check on indoor air measurements made by charcoal canisters. In spite of the measurement drawbacks, the study indicates that soil radon measurements taken alone are not a dependable predictor of potential indoor radon concentration. 

In U.S. EPA Office of Radiation Program s New House Evaluation Program (NEWHEP), two builders in the Denver area, two in Colorado Springs, and one in Southfield, Michigan, installed various radon-resistant features in houses during construction. A sampling of subsequent measurements of indoor radon, adjacent soil gas radon, and soil radium content is summarized in Table 31.6.36... 

The major difference between these data and the Florida survey data in Table 31.3 is that this portion of the NEWHEP data was collected from newly constructed houses where passive radon-resistant construction features were being tested. There are no data on control houses in the same area that did not have those built-in features, making it difficult to compare soil radon measurements with indoor radon concentrations. It appears, however, that passive-only building techniques do not consistently result in indoor radon levels below 4 pCi/L. 

Indoor Radon and Soil Radon Measurements in Colorado and Michigan... 

The State of New Jersey has been able to correlate airborne radiation measurements to clusters of buildings with elevated indoor radon 49 In this study, researchers compared airborne y-ray spectrometer data with indoor radon data to see if any trends emerged. For the conditions in New Jersey,... 

This house was also part of a study of remedial measures for the reduction of indoor radon concentrations (Turk fit al . 1986),... 

As part of the radon program at EML to develop or improve and field test radon monitors, a modified activated carbon device (Warner, 1986) was developed to obtain higher measurement sensitivity. As a result, we have surveyed 380 buildings in six states in the eastern United States. The purpose of the measurements reported in this paper was to test the feasibility of the new version of the passive activated carbon device and to obtain data on indoor radon levels in different geographical locations. 

The detector used to measure indoor radon was the latest version of the passive activated carbon device developed at EML (George, 1984 Warner, 1986), which consists of a thin-walled aluminum canister with a screen cover to expose 80 g of carbon to the test atmosphere. Although not as physically rugged as earlier models, properly packed this monitoring device was as successful in conducting the surveys through the mail. 

George, A. C., Passive Integrated Measurement of Indoor Radon Using Activated Carbon, Health Phvs. 46 867 (1984). 

However, since the data used in this study are subject to the limitations and uncertainties cited above, the results of this analysis represent only a very rough approximation of the national frequency distribution of indoor radon levels. EPA s national survey will seek to more accurately characterize this distribution through use of a larger sample size, a statistically based survey design, and consistent, quality assured sample collection and measurement procedures. 

The distribution of radon levels in houses located in these 20 areas will be measured either through EPA/State cooperative surveys or as a part of EPA s national survey. If correlations can be shown to exist between geological characteristics and indoor radon levels, then this information can be used to design surveys to more efficiently identify homes with high indoor radon levels. 

Numerous radon and radon decay measurements in houses are now being made by a large number of private and governmental organizations. In order to assure valid and consistent measurements, it is important that proven methods be used following standardized procedures. To address this need, EPA issued "Interim Indoor Radon and Radon Decay Product Measurement Protocols" and established a Radon/Radon Progeny Measurement Proficiency program. 

E., Interim Indoor Radon and Radon Decay Product Measurement Protocols, EPA 520/1-8604, U.S. Environmental Protection Agency, Washington, D.C. (April 1986). 

Using the procedure described above we have constructed a distribution estimate for the concentrations in detached houses. When the dwellings in multi-family houses are taken into account, we have had to base our estimates on measurements in only 142 dwellings in 15 towns. Thus, our present estimate of the mean indoor radon concentration in Finland, 90 Bq/m3, is still subject to revision. 

It is a sufficiently long time to obtain a "representative" measure of the indoor radon concentration in a dwelling. The small number of dwellings found to have a mean radon concentration greater than about 200 Bq/nr are sent a second detector for a further six month period thereby obtaining a measure of the annualised mean radon level in such houses. 

Frequency distributions of indoor radon concentrations measured in Nagasaki, Hiroshima, Misasa and Mihama are shown in Figure 3. The data for these have approximately log-normal distributions. 

Figure 3 is an example of simultaneous measurements of radon concentration in indoor air. The measurements shown in this figure were made under changing condition the indoor radon concentration increased after the room had been closed tightly. 

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