The analysis of results of radon/thoron measurements performed with the use of nuclear track detectors

Radon has been identified as one of the most important hazards, causing lung cancer. The most important isotope of radon is ²²²Rn (3.83 d), while thoron ²²⁰Rn (55 s) is treated as the less important isotope due to its short half-life. The radon/thoron hazard for people is related to inhalation of their decay products, but usually, only measurements of radon gas are done in dwellings. For such a purpose nuclear track detectors are used in most of the cases. Since several years simultaneous measurements are done to estimate thoron contribution to indoor radon and thoron exposure with the use of track detectors, too. Typically, a set of two detectors are applied and thoron concentrations are calculated on the basis of discriminative calculations. Unfortunately, very often results of these surveys are not accurate due to underestimation of the lower limit of detection (LLD) for thoron in the presence of elevated radon concentrations. Therefore an analysis of thoron LLDs in relationship to radon concentrations is presented. (note)