The Application of Techniques to Retrospectively Assess Radon Exposure Retrospectively (invited paper)

An account is given of the need to obtain estimates of indoor radon exposures in past decades as a necessary support for radon epidemiological studies. Retrospective radon exposure assessment procedures based on the measurement of the alpha recoil implanted long-lived radon decay product 210Po are critically described. Particular emphasis is placed on the CR-LR Difference Method in which surface implanted 210Po is measured using the alpha track detectors CR-39 and LR-115 mounted side by side on glass surfaces. The results are presented of a series of retrospective radon measurements made both in the Schneeberg-Schlema former uranium mining district and in an adjacent non-mining district of the east of Germany. In Schneeberg-Schlema, due to the complex effects of mining, indoor radon levels in the past are estimated in some cases to have been above fifty times contemporary levels. (author)