In this study, the cellular profile in samples obtained by two methods (induced sputum and BAL) in workers exposed to chrysotile asbestos was compared. The study demonstrated that samples recovered by induced sputum in workers exposed to asbestos show a similar cellular profile to samples recovered by BAL. Few similar comparative studies have been published for healthy subjects, patients with asthma, chronic bronchitis, and suspected pneumoconiosis [7, 10, 14, 15].
In multivariate analysis, ABs in IS samples was strongly related to the presence of asbestos bodies and lymphocytes count in BALF, although as other reports have shown, far less ABs were identified in IS compared to specimens recovered by BAL . Analysis of BALF in the same setting has suggested that long-lasting exposure to chrysotile asbestos triggers an inflammatory response of the tracheobronchial tree independently of smoking; its type was primarily lymphocytic when asbestos bodies are present otherwise the alveolitis was polymorphonuclear .
We also found that IS samples contained a higher percentage of neutrophils and a lower percentage of macrophages compared with the samples recovered by BAL whereas the percentage of lymphocytes exhibited higher relation. These results agree with previous studies and furthermore indicate that IS derived mainly from upper lung (neutrophil-rich secretions), whereas the BAL derived from the macrophages-rich distal alveolar space [7, 15, 17, 18]. The similarity in the pattern of cellular profile between IS and BALF samples indicating the involvement of the same inflammatory process as was also previously shown .
In our setting both asbestos exposure and fine dust exposure was encountered, confirmed by the existence of high levels of iron laden macrophages and dust cells in BALF and sputum samples. The interrelations of these factors may have hampered the real influence on specific cellular profiles. In these workers who were exposed for long periods, the presence of iron laden macrophages and dust cells is a marker of both mucociliary clearance and the main defensive phagocytic cell (alveolar macrophages) [20, 21].
It is worth mentioning that brake lining workers are one of the few groups formed ferruginous bodies mainly on chrysotile cores opposed to that most ferruginous bodies are formed on one of the amphibole types of asbestos as Dumortier et al. have shown .
Limitations of the study include its cross-sectional design which does not permit causal inference, and the size of the study population which is relatively small. It has to be mentioned however, that it is particularly difficult to apply even minimally invasive techniques, such as BAL, without the presence of any indication of disease. Detailed data on exposure were not available but the long employment history and the relatively high estimated exposure possibly provides a homogeneous sample. In our setting, any attempt was not made to study control subjects since the interest was on the comparison of surveillance methods in exposed employees.