136 Occupational Exposure to Asbestos

Abstract

Abstract Asbestos containing materials (ACMs) are still found in many buildings even though the use of asbestos in building materials has been prohibited in Norway since 1985. Employees that may be at risk of exposure to airborne fibers are workers within the construction industry. However, firefighters and workers investigating fires may also encounter asbestos fibers in their work. The aim of this study was to investigate the airborne fiber concentration during abatement of various ACMs. A comparison of counting results from scanning electron microscope (SEM) and phase-contrast microscope (PCM) were performed for these measurements. A separate part of the study focused on thermal transformation of fibers during fires. Parallel personal air samples were collected during asbestos abatement of different building materials and analyzed with SEM and PCM, respectively. Material samples from abatement sites and from fire scenes were investigated in SEM. The highest fiber concentrations were measured during interior wall removal (1.5-4.5 fibers/cm3 (f/cm3)). Thin fibers (<0.2 µm in width) constituted up to 50% of the total fiber concentration for some ACMs. Asbestos fibers observed in ACMs after fire may show a thermal transformation, however, in many cases the fibers are unchanged. For ACMs investigated in this study, there seem to be a good correlation between samples analyzed by SEM and PCM if the only dominant fiber type present is asbestos fibers. Thin fibers may constitute a large fraction of the total fiber concentration released and counting these fibers are therefore important for an adequate risk and exposure assessments.