Assessment and assignment of exposure to asbestos for an industrial cohort of chrysotile miners and processors

Introduction Historical dust concentrations are available for an occupational cohort study of workers active for 12 months or more between 1975 and 2010 in a chrysotile mine and processing factories in Asbest, Russian Federation. Their occupational histories were ascertained back to as early as the 1930s. A cohort specific job-exposure matrix (JEM) to estimate exposure to asbestos dust and fibre was elaborated. Methods Almost 1 00 000 recorded dust concentrations were used to develop an asbestos dust JEM and previously derived conversion factors were applied to estimate an asbestos fibre JEM. Where dust concentrations were not available, linear mixed models were used to impute missing data. Both JEMs were applied to the occupational histories of over 30 000 individual workers (over 35% female workers) based on job title and year worked. Results Assigned exposures varied over time with higher levels in the earlier years of activity. Approximately 97% of 2 00 000 person-years in the factories and 89% of 3 15 000 person-years in the mine had exposure assigned based on actual measurements. The median cumulative dust exposure for the exposed cohort was almost 50 mg/m3-years, with women slightly lower than men. The median cumulative fibre exposure for was 37 fibres/cm3-years for both men and women. Discussion and conclusion A key strength of this study is the availability of high-quality measurement data covering workers’ occupational histories. The dust and fibre JEMs enable estimation of annual profession-specific exposure levels that will form the basis of quantitative exposure estimates in the study and consequently quantitative exposure-response analyses.