A retrospective cohort study of employees of one of the world’s largest chrysotile asbestos mine and mills (JSC Uralasbest, Asbest, Russia) is presently being conducted. The primary aim of the study is to more precisely characterise and quantify the exposure-response relationship for total and site-specific cancer risks associated with chrysotile exposure.Methods
The study includes workers employed for at least one year during 1975–2010 in the mine, enrichment factories, transportation, laboratory, and the explosives unit. Ascertainment of cohort members through extraction of occupational histories from the enterprises’ archives started in 2012.Results
At present, the cohort comprises more than 35 000 workers. A detailed occupational history was collected for each cohort member. Temporal trends in exposure levels were analysed using a database containing 89 290 monthly-averaged gravimetric dust concentrations from stationary sampling points in the enrichment factories (1951–2001) and 1457 in the mine (1964–2001). Parallel gravimetric and fibre (PCOM) concentrations were used to estimate dust to fibre conversion factors. Currently a job-exposure matrix is being developed to translate individuals’ job histories into exposure histories for both dust and fibre concentrations. Sverdlovsk region mortality data of cohort members have been ascertained by linkage with medical death certificates recorded at the Sverdlovsk Regional Civil Acts Registration Office. In addition, a comparison of mortality rates in Asbest city and in Sverdlovsk region (1997–2010) was performed. Further efforts are ongoing to ascertain vital status and migration of cohort members from Sverdlovsk region. A parallel cross-sectional survey aimed at estimating tobacco smoking in current workers and veterans (more than 7000 participants) was conducted.Conclusion
The study will continue through 2019. Given the large size of the cohort, the large proportion of female workers and the detailed exposure data, information obtained in this study will expand knowledge of the cancer burden and prevention potential after chrysotile exposure.