Ermittlung der Unsicherheiten in der Strahlenexpositionsabschätzung in der Wismut-Kohorte - Teil 2 - Vorhaben 3618S12223

Abstract

The Wismut cohort consists of a sample of 58 974 male employees from around 400 000 former employees of the Wismut company. The employees were exposed to various occupational exposures ranging from exposure to ionizing radiation through radon and its progeny, uranium dust and external gamma radiation to silica dust, arsenic and diesel exhaust. It constitutes one of the largest cohorts of uranium miners who were occupationally exposed to radon. When the cohort was established, individual exposure estimates for radon progeny were reconstructed through a Job Exposure Matrix (JEM) which provides information on the annual exposure for a hewer with 2000 working hours. In the early years of exposure in the Wismut cohort (1946 – 1954/55), there were no systematic exposure assessment, and exposure values received in this period therefore had to be reconstructed retrospectively by experts. Due to a lack of exposure information, it was however impossible to reconstruct the exposure values for each object and year independently. Starting in 1954/55, there was exposure monitoring for underground mining objects in the Wismut cohort based on measurements of radon gas concentration (1955/56 - 1965 in Saxony and 1955/56 - 1974 in Thuringia) and radon progeny concentration (1966 - 1990 in Saxony and 1975 - 1990 in Thuringia). In this exposure assessment period, measurements were taken in each year and object to estimate a mean annual radon gas concentration and radon progeny concentration, respectively. Radon gas or radon progeny estimates were multiplied by a working time factor, an activity weighting factor, and either an equilibrium factor (for radon gas concentration measurements) or a ventilation correction factor (for radon progeny concentration measurements). Part 2 of the research project “Determination of uncertainties of radiation exposure assessment in the Wismut cohort” included the following tasks: (1) Quantification of uncertainty, (2) Definition of measurement models and development of an approach to correct for measurement error, (3) Design and implementation of a simulation study to compare the proposed approach with simulation extrapolation and regression calibration, and (4) Application to the data of the Wismut cohort without accounting for effect modifying variables and excluding workers who were employed in Wismut processing companies at any point during their working career.