Diagnostic limitations of lung fiber counts in asbestos-related diseases

Abstract

Background Lung dust fibre analyses have been used by some pathologists to estimate past asbestos exposure in the workplace and its related health risks. Asbestos, however, especially the predominately applied chrysotile asbestos type, undergoes translocation, clearance and degradation in the lungs. Objectives We quantified the asbestos fibre and ferruginous (asbestos) body (FB) content in human tissue with respect to the German asbestos ban in 1993 and the interim period of more than 20 years in order to evaluate the diagnostic evidence of these analyses for asbestos-related diseases (ARD). Methods Lung dust analyses have been used in empirical assessments of ARD since 1982. Tissue samples of about 2 cm3 were used and processed in standardized manner. FB was analysed by light microscopy and asbestos fibres by scanning transmission electron microscopy (STEM). Results Chrysotile and amphibole fibre concentrations in the lung tissue depend roughly on the cumulative asbestos exposure levels in the workplace. However, the concentration of lung asbestos fibre and FB depends on the year of examination and especially on the interim period. As the interim period increases, the asbestos fibre burden decreases. There is no relationship between FB and chrysotile asbestos fibre concentrations and only a weak correlation between FB and crocidolite fibre concentrations. There was no significant difference in chrysotile and amphibole fibre concentrations as well as in FB counts between the different ARD. Conclusions Due to the length of interim periods, a past exposure to chrysotile or amphibole asbestos can no longer be detected with FB or asbestos fibre measurement in lung tissue. This means that negative results of such measurements cannot disprove a qualified occupational case history of asbestos exposures and the related health risks due to the fibrogenic and carcinogenic potential of asbestos.