An investigation on radon and thoron response of alpha-track detectors used in the Winnipeg case-control study.

The alpha-track detector was well designed for long-term radon measurements in the 1992 Winnipeg case-control study. However, its diffusion characteristic for thoron in comparison to radon was yet unknown. An investigation on radon and thoron response of these detectors was undertaken. The results showed that the relative sensitivity between thoron and radon is 2 %,, i.e. the detector sensitivity to radon is about 50 times higher than the sensitivity to thoron. It can be concluded that there was no significant influence of thoron on the radon measurements with these detectors.