# Mineral Fibres and Asbestos Bodies in Human Lung Tissue: A Case Study
## 3 Results and Discussion
### Asbestos Bodies (ABs)  
In the present work, the term asbestos body (AB) refers to the overall coating material present on the surface of an asbestos fibres. AB segments refer to the individual knobs of the coating material. Fibres coated with ABs were found in all studied tissue samples. FEG-SEM and STEM images document that ABs occur with a wide variety of morphologies (Figures 8 and 9). As mentioned above, the ABs were found surrounding fibres with L \(>\) 20 \(\upmu\)m, but only the fibres with L \(>\) 30 \(\upmu\)m were completely coated by the ABs. The shape of ABs includes: dumbbell-shaped; beaded; fusiform; elliptical; spherical; cylindrical; and pearl-, lancet- and carrot-like shapes. The beaded structure was the most common appearance of ABs (Figure 8a,c and Figure 9a,e). ABs with beaded structures are variably segmented into spherical or rectangular segments spaced evenly along the fibre. The size of individual AB segments varies in length from 0.2 to 5.0 \(\upmu\)m, and width from 0.6 to 4.0 \(\upmu\)m. The space between the segments is in some cases covered by a secondary coating (Figure 8a,b). Segments are sub-cylindrical (Figure 8b) or disc-shaped (Figure 9e). Some beaded structures are fused (or partially fused) together (Figure 8d,e and Figure 9c,d,f). The AB segments that occur at the tips of fibres are in many cases sub-rounded, and typically display multiple sequences of coatings (Figure 9a,b). The width of these AB segments at the tip of the fibre range from 1.5 to 9.5 \(\upmu\)m. We also measured both the length of the fibres and the volume of ABs and observed that the largest ABs develop on the longer fibres (Figure 10). The volume of ABs was measured on the fibres that were fully visible in the field of view (11 fibres and associated 11 ABs). Depending on the AB form, we used either ellipsoidal, cylindrical or parallelepipedal models to determine the AB volume. By comparison with our results, the ABs developed in the lungs of rats exhibited various shapes, from cylindrical to elliptical and are often different from those observed here. Globular clusters were present on one or both ends of the coated fibres in the rat tissues. The size of all ABs (including AB  
Figure 7: Selected examples (HRTEM images) of four highly crystalline, non-coated crocidolite fibres with a very thin amorphous layer on their surface. Red arrows and red lines highlight the amorphous layer. \(c=c\)-axis of crocidolite. The crocidolite fibre shown in the right top box is the same as shown in Figure 5. The images were acquired after a check of the stability of fibre under an electron beam. The black arrow indicates the direction of the crystallographic c-axis. segments) recovered from rat tissue varies in length from 4 to 25 \(\upmu\)m, and width from 4 to 8 \(\upmu\)m. On the other hand, ABs (including AB segments) recovered from the human tissue samples from this study have lengths between 0.2 to 80 \(\upmu\)m and widths between 0.6 to 9.5 \(\upmu\)m.  
Figure 8: (**a**) FEG-SEM image showing an example of the beaded shape of asbestos bodies (ABs). (**b**) Close-up of red square shown in image (**a**). Image showing the beaded shape with the red arrow indicating the space between individual AB segments covered by a secondary coating. AB segments show sub-cylindrical shape. (**c**) FEG-SEM image showing the typical beaded shape of ABs. AB and associated fibre cores are curved. ABs show sub-cylindrical segments spaced evenly along the fibre. The AB segment at the fibre tip is sub-rounded. (**d**) STEM image of a partially coated fibre with elliptical-shaped ABs; (**e**) STEM image showing a typical example of the apical AB segments at the tips of fibres. Segments are partially fused. (**f**) TEM image of a partially coated fibre. The AB appears as a smooth, corrugated coating of the fibre. Figure 10: Scatter plot showing the volume of the ABs vs. the length of coated fibres. Dashed line represents an exponential fitting function (R\({}^{2}\) = 0.70) to the data points.