Diagnostic limitations of lung fiber counts in asbestos-related diseases


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.
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).
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).
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.
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