The Compact Disc as a Retrospective Radon Detector: Performance of the Methododlogy

Recently, a method for long-term Rn measurements was proposed that combines the radon absorption ability of some polycarbonates, like Makrofol, with their track-etch properties. The method is independent of any particular Rn progeny behavior and the very first evaluation of this approach showed that its range of sensitivity covers practically the entire range of indoor Rn-concentrations. This method has been extensively studied in the period 2001 – 2007. In this report we comprehend the performance of the method as demonstrated in the laboratory studies. INTRODUCTION The indoor radon exposure is probably the second most important cause of lung cancer, after smoking [1]. Exposure for many years contributes to the risk, but up to now the duration of most of the integrated radon measurements is at maximum one year. In search of methods for representative long-term radon exposure estimates, considerable efforts were put in retrospective measurements. One of the approaches is based on the recoilimplanted Pb/Po on glass surfaces [2, 3]. This “glass-implanted” method has a strong dependence on the particular behavior of radon progeny to aerosols in the indoor air and therefore its accuracy is at best a factor of two [4, 5]. Other approaches employ volume traps of spongy materials [6] or eyeglass lenses made out of CR-39 [7]. Methods based on volume traps give evidence of low sensitivity, low predictability and are strongly dependent on a suitable choice of spongy materials. Therefore they are of limited effectiveness for large-scale use. The eyeglass lenses method is affected also by a particular Rn progeny behavior, and a non-uniform plate-out. Furthermore it was found that the CR-39 etching behavior could vary significantly from one supplier to another. Recently, a method for long-term Rn measurements was proposed that combines the radon absorption ability of some polycarbonates, like Makrofol, with their track-etch properties [8]. The method consists in the removal from the detectors, after exposure, of a surface layer with a thickness that is greater than the range of the most energetic alphaparticles coming from Rn and Rn progenies plate-out on the surface. After that, the detectors are etched electrochemically and the tracks are counted. Makrofol and equivalent plastics (e.g., Makrolon) are widely used as a basic constructive material for commercial CDs and DVDs. Therefore, home-stored CDs/DVDs may serve as retrospective long-term radon detectors. The method is independent of any particular Rn progeny behavior and the very first evaluation of this approach showed that its range of sensitivity covers practically the entire range of indoor Rn-concentrations [9].