Study Objectives and Design

Study Design

The study is a retrospective, or historical, cohort study. Members of the study cohort include individuals who were employed in the mine, processing mills, internal auto and rail transport departments, laboratory for production control, or explosives unit of JSC Uralasbest for at least one continuous year between 1975 and 2010, regardless of year of first employment (i.e. including workers who first started working before 1975).

A detailed written record of occupational history is available for each worker, from worker registration cards that document all changes in employment status. These cards provide information on the workers′ jobs (and tasks) (e.g. loader of conveyor belt, electrician, packer, truck driver), locations (factory name and section; e.g. enrichment, packaging, laboratory, mine), and dates of employment at JSC Uralasbest.

The work history information can be linked to extensive monthly measurements of airborne gravimetric (that is, by weight) dust concentrations taken in the mine and factories since the 1950s. There are more than 90 000 dust concentration measurements for the period 1950-2001. There are also almost 2000 parallel gravimetric dust and fibre concentrations measured at multiple time points (1995, 2007, 2013-2014) in the mine and two of the factories, used for estimating conversion factors by stage in the mining and by processing of chrysotile.

Follow-up of the cohort will be carried out by linkage with the region's Civil Registry (Vital Statistics) Office (in 2016-17) and Medical Information Analytical Center (in 2016), which also hold information on cause of death, and the Migration Bureau (in 2017-18). The study will combine work history and follow-up data to analyse overall and cancer-specific mortality associated with chrysotile.