Recommended Action Level Research Articles

The chemistry of Norwegian groundwaters: I. The distribution of radon, major and minor elements in 1604 crystalline bedrock groundwaters

A quality-controlled hydrogeochemical dataset of 1604 groundwater samples from Norwegian crystalline bedrock aquifers has been obtained and subject to analyses of radon (scintillation counting), major and minor elements (ion chromatography and ICP-AES), pH and alkalinity. Cumulative probability curves may be constructed to assess the risk of given parameters violating drinking water norms. Parameters such as radon and fluoride show clear lithological correlation, occurring at high concentrations in granites and low concentrations in anorthosites. Other parameters exhibit a lower degree of correlation with aquifer geochemistry (e.g. pH, major ions) and are likely to be governed by more universal thermodynamic equilibria (the calcium carbonate system) and kinetic factors. On a national basis 13.9% of the bedrock groundwaters exceed the recommended action level for radon, while 16.1% exceed the drinking water norm for fluoride. Considering pH, sodium, radon and fluoride together, 29.9% of all wells violate drinking water maximum concentrations for one or more of these parameters.

A proposed method to minimize waste from institutional radiation safety surveillance programs through the application of expected value statistics.

Institutional radiation safety programs routinely use wipe test sampling and liquid scintillation counting analysis to indicate the presence of removable radioactive contamination. Significant volumes of liquid waste can be generated by such surveillance activities, and the subsequent disposal of these materials can sometimes be difficult and costly. In settings where large numbers of negative results are regularly obtained, the limited grouping of samples for analysis based on expected value statistical techniques is possible. To demonstrate the plausibility of the approach, single wipe samples exposed to varying amounts of contamination were analyzed concurrently with nine non-contaminated samples. Although the sample grouping inevitably leads to increased quenching with liquid scintillation counting systems, the effect did not impact the ability to detect removable contamination in amounts well below recommended action levels. Opportunities to further improve this cost effective semi-quantitative screening procedure are described, including improvements in sample collection procedures, enhancing sample-counting media contact through mixing and extending elution periods, increasing sample counting times, and adjusting institutional action levels.

Study of Caesium Contamination in Foodstuffs in Ghana After the Chernobyl Nuclear Accident

Fallout radioactivity has been studied in foodstuffs in the Environmental Monitoring Laboratory after the Chernobyl nuclear catastrophe. The study covers the analysis of reference samples of imported foods, mainly mean and milk, for 137Cs and 134Cs contamination using a low level gamma spectrometer. The purpose of this study is to determine whether it is necessary to control food imports in order to reduce the risk from intake of radionuclides by the Ghanaian public resulting from transboundary contamination. Measurement of caesium levels in various foods over a period of seven years has shown contamination to be within the recommended action levels for international trade in foods. The committed effective dose for intakes in any single years is far below the 1 mSv annual recommended by the ICRP in Publication 60.

Lung Cancer in Radon-Exposed Miners and Estimation of Risk From Indoor Exposure

Radioactive radon is an inert gas that can migrate from soils and rocks and accumulate in enclosed areas, such as homes and underground mines. Studies of miners show that exposure to radon decay products causes lung cancer. Consequently, it is of public health interest to estimate accurately the consequences of daily, low-level exposure in homes to this known carcinogen. Epidemiologic studies of residential radon exposure are burdened by an inability to estimate exposure accurately, low total exposure, and subsequent small excess risks. As a result, the studies have been inconclusive to date. Estimates of the hazard posed by residential radon have been based on analyses of data on miners, with recent estimates based on a pooling of four occupational cohort studies of miners, including 360 lung cancer deaths. To more fully describe the lung cancer risk in radon-exposed miners, we pooled original data from 11 studies of radon-exposed underground miners, conducted a comprehensive analysis, and developed models for estimating radon-associated lung cancer risk. We pooled original data from 11 cohort studies of radon-exposed underground miners, including 65,000 men and more than 2700 lung cancer deaths, and fit various relative risk (RR) regression models. The RR relationship for cumulative radon progeny exposure was consistently linear in the range of miner exposures, suggesting that exposures at lower levels, such as in homes, would carry some risk. The exposure-response trend for never-smokers was threefold the trend for smokers, indicating a greater RR for exposure in never-smokers. The RR from exposure diminished with time since the exposure occurred. For equal total exposure, exposures of long duration (and low rate) were more harmful than exposures of short duration (and high rate). In the miners, about 40% of all lung cancer deaths may be due to radon progeny exposure, 70% of lung cancer deaths in never-smokers, and 39% of lung cancer deaths in smokers. In the United States, 10% of all lung cancer deaths might be due to indoor radon exposure, 11% of lung cancer deaths in smokers, and 30% of lung cancer deaths in never-smokers. This risk model estimates that reducing radon in all homes exceeding the U. S. Environmental Protection Agency's recommended action level may reduce lung cancer deaths about 2%-4%. These estimates should be interpreted with caution, because concomitant exposures of miners to agents such as arsenic or diesel exhaust may modify the radon effect and, when considered together with other differences between homes and mines, might reduce the generalizability of findings in miners.

Uncertainties About Health Effects of Radon

The validity of the studies and the interpretation of these studies that are the basis of the Environmental Protection Agency (EPA)'s recommended action level of 4 pCi/liter of radon in residences are strongly questioned. The many assumptions that were made to arrive at this figure and the large amount of money necessary to attain this level in some residences are highlighted. The synergistic effect of smoking and radon exposure on human health is noted. One epidemiological study carried out by Bernard L. Cohn at the University of Pittsburgh has stored relevant data for about a third of the counties of the US, and multivariant analysis of the data led to the conclusion that at low doses of radon found in the average home, radon does not have an adverse effect on health. The author suggests that EPA should give priority to identifying rare circumstances, high permeability and radon content, where high levels of radon prevail and encourage remediation there rather than wholesale action where levels of radon are low.

Radon-222, 222Rn Progeny, and 220Rn Progeny Levels in 70 Houses

A year-long, multipollutant, indoor air quality study involving 70 occupied houses in four states was completed in 1987. All of the houses included in the study had a partial or complete basement with a concrete slab floor and block walls. On an approximately quarterly schedule, integrating monitors for short-lived Rn progeny, nitrogen dioxide, formaldehyde, and water vapor were exposed for 1 wk in each house on both the basement and main floors. At the beginning of the study, a pair of alpha-track detectors were placed on top of the refrigerator in the kitchen (or some other sampling location on the main floor) and at a location in the basement. One detector at each location was left in place for a year while the other detector was retrieved and replaced once every 3-mo period. In addition, short-term measurements of Rn and 222Rn progeny were made at all sampling locations once per quarter. In this study, comparisons were made between: (1) seasonal and annual averages, (2) summer and winter averages, (3) living-area and basement results, (4) 222Rn and 220Rn progeny, and (5) short- and long-term measurements. The Rn and Rn progeny concentrations in houses near Huntsville, AL were found to be well above recommended action levels (150 Bq m-3). For houses near Birmingham, AL, summer Rn concentrations were found to exceed winter concentrations, whereas for the other houses in the study, winter concentrations exceeded summer concentrations. Potential alpha energy concentrations (PAEC) from 220Rn progeny were found to be generally less than PAEC from 222Rn.

Radon contamination in dwellings

Radon contamination of dwellings has only recently been recognized as a significant problem in the United States. This paper describes the geographical distribution of radon gas, along with a discussion of its fundamental health effects. Various methods to measure radon and radon daughter concentration levels are presented. Recommended action levels for radon gas exposure in dwellings are summarized, and factors which influence measured radon concentrations are discussed.

Regional levels of indoor radon in Virginia and Maryland

The levels of Rn-222 in homes located in Fairfax County, Virginia, and Montgomery County, Maryland, are currently being measured during four consecutive three-month seasonal intervals using alpha-track detectors. Significant variations occur between parts of northern Virginia and southern Maryland because the area is part of three very different geologic provinces. Results from the winter period in these three provinces show that the indoor radon levels were about twice as high as anticipated. Approximately 45 percent of the homes had winter indoor radon levels above 4 pCi/l, the EPA’s recommended action level, and in the spring period, more than 30 percent of the homes still had indoor levels above 4 pCi/l. Indoor radon variations due to seasonal control were about as significant as geological control. Worst-case combinations developed over some rock units in the winter, producing areas in which about 70 percent of the homes exceeded 4 pCi/l.

The effect of home construction on indoor radon in Virginia and Maryland

Abstract The levels of indoor radon in approximately 500 homes located in two contiguous counties of northern Virginia and southern Maryland have been measured during four consecutive, three month seasonal intervals using alpha-track detectors. These two counties represent an area of about 700 square miles. Results from the winter period show that the indoor radon levels were about twice as high as anticipated. In some areas, more than 50% of the homes had winter indoor radon levels above 4 pCi/liter, the EPA's recommended action level. For the spring and fall periods, indoor radon levels showed a considerable drop with approximately 35% of the homes above 4 pCi/L. Summer values were even lower with approximately 25% of the homes above 4 pCi/L. Indoor radon can be related to the weather, but home construction demonstrably determines indoor radon levels.