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Summary It has been suggested that temporal variations of radon (Rn) concentrations in various media may be used as a possible predictive indicator of seismic activity. However, observed Rn measurements are a function of a number of different physical processes including seismic activity. This paper describes a generalized approach to removing ‘noise components’ from the observed data to leave a residual component of radon concentration that reflects geodynamic processes at depth. The approach is demonstrated using data gathered in Israel at the time of the 1992 October 12 Giza earthquake in Egypt.

The Dead Sea contains an anomalously high concentration of soluble radium, which is considerably in excess of its radiogenic parent uranium. Mass balance calculations demonstrated that the radium is brought to the Dead Sea by springs and shallow underground seepages. The primary source from which this radium-excess is derived has not been identified previously. Using a combination of alpha-spectrometry, delayed neutron activation (DNA), and gamma-ray spectrometric analyses, it was found that the extensive oil shales within the Dead Sea watershed exhibit exceptional loss of radium. It is only the coastal hot springs and saline groundwater that have traversed the oil shales that exhibit radium-excess. Thus, it is demonstrated that a significant portion of the radium-excess of the Dead Sea brines is derived from the Upper Cretaceous oil shales.

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Alpha track radon detectors were placed in the homes of 35 lung cancer patients and 35 matched controls for a period of 8 to 10 mo. Twenty lung cancer patients had small cell lung carcinoma; 11 had adenocarcinoma, 2 had squamous cell carcinoma, and 2 had unclassified carcinoma among 15 nonsmokers. Mean overall living on ground level was significantly higher in the group with small cell lung carcinoma (50 y +/- 15) than among controls (33 y +/- 19); the adjusted odds ratio for lung cancer was 5.2 (90% confidence interval [90% CI] = 1.1-24.9) per decade of living on the ground floor for the group with small cell lung carcinoma. Radon exposure of more than 1.0 pci/l in the group with small cell lung carcinoma was associated with increased risk of lung cancer, although it did not reach statistical significance [odds ratio = 1.5 (90% CI = 0.4-5.4)], adjusting for differences in smoking habits. Our study supports the presence of a differentially increased risk for small cell lung carcinoma following long-term radon exposure.

In December 1995, ambient radon levels exceeding 10,000 Bq/m3 were measured in a basement shelter workroom of a multilevel East Talpiot, Jerusalem, public elementary school (six grades, 600 students). The measurements were taken after cancers (breast and multiple myeloma) were diagnosed in two workers who spent their workdays in basement rooms. The school was located on a hill that geologic maps show to be rich in phosphate deposits, which are a recognized source for radon gas and its daughter products. Levels exceeding 100,000 Bq/m3 were measured at the mouth of a pipe in the basement shelter workroom, the major point of radon entry. The school was closed and charcoal and electret ion chamber detectors were used to carry out repeated 5-day measurements in all rooms in the multilevel building over a period of several months. Radon concentrations were generally higher in rooms in the four levels of the building that were below ground level. There were some ground-level rooms in the building in which levels reached up to 1300 Bq/m3. In rooms above ground level, however, peak levels did not exceed 300 Bq/m3. Exposure control based on sealing and positive pressure ventilation was inadequate. These findings suggested that radon diffused from highly contaminated basement and ground-floor rooms to other areas of the building and that sealing off the source may have led to reaccumulation of radon beneath the building. Later, subslab venting of below-ground radon pockets to the outside air was followed by more sustained reductions in indoor radon levels to levels below 75 Bq/m3. Even so, radon accumulated in certain rooms when the building was closed. This sentinel episode called attention to the need for a national radon policy requiring threshold exposure levels for response and control. A uniform nationwide standard for school buildings below 75 Bq/m3 level was suggested after considering prudent avoidance, the controversies over risk assessment of prolonged low-level exposures in children, and the fact that exposures in most locations in the Talpiot school could be reduced below this level. Proposal of this stringent standard stimulated the search for a strategy of risk control and management based on control at the source. This strategy was more effective and probably more cost effective than one based on suppression of exposure based on sealing and ventilation. Because many Israeli areas and much of the West Bank area of the Palestinian National Authority sit on the same phosphate deposits, regional joint projects for surveillance and control may be indicated.

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