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Purpose: To date, only a few studies have examined long-term health risks of exposures in the uranium processing industry and reported contradictory results, necessitating further research in this area. This is the first description of a cohort of ∼65,000 uranium processing workers (20.6% women) of the Siberian Group of Chemical Enterprises (SGCE) in Seversk, Russia, first employed during 1950-2010., Methods: SGCE is one of the largest and oldest uranium processing complexes in the world. SGCE workers at the Radiochemical, Plutonium, Sublimate and Enrichment plants were exposed to a combination of internal and external radiation, while workers at the Support Facility were primarily exposed to non-radiation factors., Results: Mean cumulative gamma-ray dose based on individual external dosimetry was 28.3 millisievert. About 4,000 workers have individual biophysical survey data that could be used for estimation of organ doses from uranium. SGCE workers were followed up for mortality and cancer incidence during 1950-2013 (vital status known for 80.8% of workers). The SGCE computerized database contains information on the results of regular medical examinations, and on smoking, alcohol and other individual characteristics., Conclusions: The SGCE cohort is uniquely suited to examine long-term health risks of exposures to gamma-radiation and long-lived radionuclides in uranium processing workers.

The characteristic of medical and dosimetric register database of Siberian Group of Chemical Enterprises personnel is represented. This characteristic includes the description of the database structure, main sources of information, quantitative composition of the cohort under study, methods of evaluation of the external and internal irradiation doses, modern data on cancer incidence and reasons of death. The database is the basis for estimating the risk of the cancer and non-cancer effects after a long-term radiation exposure and dependence of "dose-response" at different levels: from population and group to cell and molecular. Now the database of register contains the information about more than 66,500 employees at the Siberian Group of Chemical Enterprises, about 22,000 of whom were exposed to external irradiation and more than 7500 employees--to internal irradiation. The register is the information resource of a large biological material bank. Using this bank, the research of chronic radiation exposure genetic effects and markers of individual radio sensitivity is performed.

The paper analyzes the effects of spontaneous level of yH2AX and 53BP1 foci on a frequency of radiation-induced centromere-negative and centromere-positive micronuclei in peripheral blood lymphocytes of 54 healthy individuals after exposure to 2 Gy of ionizing radiation in vitro. An inverse correlation was found between the level of spontaneous yH2AX foci and the frequency of centromere-negative micronuclei after irradiation. The corresponding correlations between the spontaneous level of protein 53BP1 foci and the frequency of centromere-negative micronuclei were not statistically significant. In addition, cells of the individuals with a high frequency of radiation-induced micronuclei were also characterized by a low proliferative activity. It was suggested that DNA double strand break repair works less efficiently in cells of the individuals with low levels of spontaneous yH2AX foci, and a greater number of DNA double strand breaks after exposure to ionizing radiation remains unrepaired, thus leading to a cell cycle block and an increase of the frequency of centromere-negative micronuclei.