Assessment of exposure to total asbestos, chrysotile and amphiboles

Introduction
The ability to clarify the question of different potencies of chrysotile and amphiboles is limited by a lack of quantitative data. For this work an exposure assessment was conducted among 6,714 production workers employed in Slovenian asbestos cement factory in the period between 1947 and 1994. The factory made two products, one of chrysotile and the other of chrysotile and amphiboles, each in a separate facility with a separate workforce. The objective of this study was to develop a quantitative estimate (cumulative exposure) of the airborne concentrations of total asbestos, chrysotile and amphibole for the time period of the study.

Methods
Exposure measurements were available for most exposed jobs. For the jobs and time periods lacking measurement data, the airborne concentrations of total asbestos, chrysotile and amphibole were estimated using production process records and interviews with long-service employees, factory managers, engineers, physicians and environmental managers. Production Job Exposure Matrices comprising quantitative exposure intensity estimates for total asbestos, chrysotile and amphibole were constructed for all production jobs and all years. A subset of the study population held jobs without fixed locations and for these workers, quantitative exposure estimates were made on individual level.

Results
More than 1,000 air samples were available. For these, estimates of asbestos airborne concentrations were made for major tasks and operations for the technological periods associated with changes in asbestos exposure. Also the quantitative estimates of chrysotile, amphibole and total asbestos for each job and production area for each year were made.

Discussion
On average, the airborne concentrations of total asbestos were low and similar to those found by Swedish and British asbestos-cement operations respectively. It was possible to estimate the airborne concentrations of amphibole and chrysotile separately in such a way that these estimates can be used to estimate separate exposure-response curves in a further epidemiological study.