Chrysotile, a serpentine asbestos fibre, is the only type of asbestos produced and consumed in the world today. It is an established human carcinogen. We have begun fieldwork on a retrospective cohort study of employees of one of the world's largest chrysotile mine and mills, situated in Asbest, Russia. The primary aim of the study is to better characterize and quantify the risk of cancer mortality in terms of (i) the dose-response relationship of exposure with risk; (ii) the range of cancer sites affected, including female-specific cancers; and (iii) effects of duration of exposure and latency periods. This information will expand our understanding of the scale of the impending cancer burden due to chrysotile, including if chrysotile use ceased worldwide forthwith. Herein we describe the scientific rationale for conducting this study and the main features of its study design.

Our study shows that dust to fibre conversion is possible by unit but extrapolations are needed. The patterns for exposure by dust and fibre will be similar but estimated fibre levels will show less contrast due to the conversion factor being smaller at higher dust concentrations.

ObjectivesMining and processing of chrysotile, an established carcinogen, has been undertaken in Asbest, Russian Federation since the late 1800s. Dust concentrations were routinely recorded at the open-pit mine and its asbestos-enrichment factories. We examined the temporal trends in these dust concentrations from 1951 to 2001.MethodsAnalyses included 89290 monthly averaged gravimetric dust concentrations in six factories (1951–2001) and 1457 monthly averaged concentrations in the mine (1964–2001). Annual percent changes (APC) in geometric mean dust concentrations were estimated for each factory and the mine separately from linear mixed models of the logarithmic-transformed monthly averaged concentrations.ResultsDust concentrations declined significantly in the mine [APC: −1.6%; 95% confidence interval (CI): −3.0 to −0.2] and Factories 1–5 but not 6. Overall factory APCs ranged from −30.4% (95% CI: −51.9 to −8.9; Factory 1: 1951–1955) to −0.6% (95% CI: −1.5 to 0.2; Factory 6: 1969–2001). Factory trends varied across decades, with the steepest declines observed before 1960 [APCs: −21.5% (Factory 2) and −17.4% (Factory 3)], more moderate declines in the 1960s and 1970s [APCs from −10% in Factory 2 (1960s) to −0.3% (not statistically significant) in Factory 4 (1970s)], and little change thereafter. Mine dust concentrations increased in the 1960s (APC: +9.7%; 95% CI: 3.6 to 15.9), decreased in the 1990s (APC: −5.8%; 95% CI: −8.1 to −3.5) and were stable in between.ConclusionsIn this analysis of >90000 dust concentrations, factory dust concentrations declined between 1951 and 1979 and then stabilized. In the mine, dust levels increased in the 1960s, declined in the 1990s and were unchanged in the interim.

BackgroundThe Sverdlovsk region of the Russian Federation is characterised by its abundance of natural resources and industries. Located in this region, Asbest city is situated next to one of the largest open-pit chrysotile asbestos mines currently operational; many city residents are employed in activities related to mining and processing of chrysotile. We compared mortality rates from 1997 to 2010 in Asbest city to the remaining Sverdlovsk region, with additional analyses conducted for site-specific cancer mortality.MethodsPopulation and mortality data for Asbest city and Sverdlovsk region were used to estimate crude and age-specific rates by gender for the entire period and for each calendar year. Age-standardized mortality rates were also calculated for the adult population (20+) and Poisson regression was used to estimate standardized mortality ratios, overall and by gender.ResultsDuring the period of 1997 to 2010, there were similar mortality rates overall in Asbest and the Sverdlovsk region. However, there were higher rates of cancer mortality (18 % males; 21 % females) and digestive diseases (21 % males; 40 % females) in Asbest and lower rates of unknown/ill-defined in Asbest (60 % males; 47 % females). Circulatory disease mortality was slightly lower in Asbest. Cancer mortality was higher for men in Asbest from oesophageal, urinary tract and lung cancers compared to the Sverdlovsk region. In women, cancer mortality was higher for women in Asbest from stomach, colon, lung and breast cancers compared to the Sverdlovsk region.ConclusionsThis large population-based analysis indicates interesting differences but studies with individual exposure information are needed to understand the underlying factors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0125-0) contains supplementary material, which is available to authorized users.

A historical cohort study in workers occupationally exposed to chrysotile was set up in the town of Asbest, the Russian Federation, to study their cause-specific mortality, with a focus on cancer. Chrysotile has different chemical and physical properties compared with other asbestos fibres; therefore it is important to conduct studies specifically of chrysotile and in different geographical regions to improve the knowledge about its carcinogenicity. Setting was the town of Asbest, Sverdlovsk oblast, the Russian Federation. Participants were all current and former employees with at least one year of employment between 1/1/1975 and 31/12/2010 in the mine, enrichment factories, auto-transport and external rail transportation departments, the central laboratory, and the explosives unit of the company. Of the 35,837 cohort members, 12,729 (35.5%) had died (2,373 of them of cancer, including 10 of mesothelioma), 18,799 (52.5%) were known to be alive at the end of the observation period (2015), and 4,309 (12.0%) were censored before the end of 2015. Mean follow-up duration was 21.7 years in men and 25.9 years in women. The mean age at death was 59.4 years in men and 66.5 years in women. This is the largest occupational cohort of chrysotile workers to date, and the only one with a large proportion of exposed female workers.