Joint Russian-American-Finnish project "Health and Exposure Surveillance of Siberian Asbestos Miners". Ten years follow-up

Introduction
The Russian-American-Finnish project "Health and Exposure Surveillance of Siberian Asbestos Miners" was realized in 1995-97 at world's largest chrysotile asbestos mining and milling complex “Uralasbest” (Asbest, Russia).

Methods
Research included evaluation of existing exposure levels, retrospective analysis of old measurements and work history interviews and X-ray examinations of 2003 workers. Forming a cohort of 1640 workers with defined exposure history was one of the results.

Results
About 10 % of workers at time of the examination in 1996 had small irregular opacities (ILO 0/1 or more) and 6 % had bilateral pleural plaques. Other asbestos-related abnormalities were rare. Parenchymal fibrosis was twice frequent in smokers than in nonsmokers, whereas bilateral plaques were detected similar. About 95 % of findings occurred in persons older than 40 years and those who had worked in old production plants. There was significant correlation between individual dust doses and X-ray findings. Follow-up study correlates the mortality rates of the cohort members with their X-ray findings in 1996 and updated exposure data for next 10 years. SMR’s calculated in comparison to the general population of the Sverdlovsk region from all cases among men was 0,49 (CI 0,41-0,59), from all malignancies – 0,74 (0,48-1,13) and cancers of respiratory system – 0,74 (0,37-1,47). Among women SMR from all cases was 0,72 (CI 0,50-1,02), from all malignancies – 0,70 (0,30-1,64) and cancers of respiratory system – 1,32 (0,07-25,99). Statically significant increased risk of death from cancer of respiratory system was defined among smokers and workers with founded at initial X-ray examination pleural and parenchymal abnormalities.

Discussion
Statistically insignificant results can be explained by relatively short period of surveillance and small amount of deaths in the examined group. Further surveillance of this group is going on. A larger epidemiological study for all workers employed at "Uralasbest" for the period of 1980-2010 started.