Why is 220RN (thoron) measurement important?

New scientific findings based on the latest epidemiological analyses for lung cancer risk due to radon have been demonstrated. The residential radon concentration is mainly measured by passive radon detectors. Although the passive radon detector is usually designed to detect radon efficiently and exclusively, several types of them can detect thoron together with radon. In this case, these detector readings may include both radon and thoron signals. If the readings are overestimated, the lung cancer risk will be given as a biased estimate when epidemiological studies are carried out. In our experience, there seem to be no correlation among radon, thoron and thoron progeny concentrations. Therefore, one parameter cannot be estimated by the other. This study presents the importance of thoron measurement throughout results we have obtained in field and in laboratory so far. (authors)