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The misconception, that radon gas concentrations are a property of the house, could be affecting the results of case-control studies. Radon concentrations are a function of source term and ventilation rate. Ventilation rate is, in part, related to the lifestyle of the occupants. As I understand it, case-control studies use radon measurements, performed after diagnosis, to infer the radon exposure of the patient before lung cancer diagnosis. Is it really reasonable to assume that a sick ex-smoker has the same lifestyle as a healthy smoker? I would think that a healthy smoker would tend to have the doors and windows open more often than a sick ex-smoker. This would lead to overestimating radon exposures for cases and could produce a positive association between radon and lung cancer. This mechanism would affect most case-control radon studies. The Iowa study shows the average radon concentrations for the basements and first and second levels for both cases and controls. The controls actually had higher radon levels in the basements, while cases had higher radon levels in the living quarters. I would think that the basement concentrations are more indicative of the source term, while the upper level readings would be more a function of lifestyle. Kai PS: Before I get flamed too badly: I am not out to trash anybody’s research, but it is important to understand the limitations of all the data that’s out there. The correct theory will explain all data to within these limitations. |