# Mineral Fibres and Asbestos Bodies in Human Lung Tissue: A Case Study
## 3 Results and Discussion
### Asbestos Bodies (ABs)
Figure 9: FEG-SEM images of asbestos bodies found in the lung of the human subject. (**a**) Typical sub-rounded AB segments at the tips of fibres. (**b**) The AB at the fibre tip showing typical multiple sequences of coatings. (**c,d**) ABs showing a habit in which the individual segments are fused (or partially-fused) together; (**e**) disc-shaped beaded segments; (**f**) disc-shaped segments partially-fused. The results of semi-quantitative EDX analyses of the ABs are reported in Table 3, together with the elemental composition of ABs developed on a crocidolite fibre found in the lung tissue of another human subject studied by [PERSON] et al. [40]. For comparison, the elemental composition of ABs from crocidolite fibres that were in contact with rat tissue for 80 weeks is also reported (Table 3). The ABs recovered from the human lung tissue are considerably richer in Fe and Si than those recovered from rats which, on the other hand, are richer in Ca and P. Unfortunately, no data regarding the Na, K and Al contents of the rat ABs are available. The ABs investigated here are on average poorer in Ca and Si but richer in P than those studied by [PERSON] et al. [40] (Table 3). The discrepancies between different data sets in Table 3 may be due to the different analytical approaches, detectors and correction factors used by each study. STEM investigations reveal that the ABs recovered from the lung tissue of the male subject are composed of aggregates of small, rounded particles (Figure 11a,b) with a mean diameter of 52.3 A (n = 54; \(\sigma_{\text{n-1}}\) = 4.2). As reported in the literature [41; 42], these particles are mainly composed of ferritin (an Fe-storage protein) or hemosiderin. The nature of hemosiderin is not yet completely understood, but it is believed to be a degradation product of ferritin. It consists of fragments of ferritin usually mixed with other amorphous, decomposed proteins, lipids and/or mucopolysaccharide-based materials [19; 42]. An FFT pattern extracted from HRTEM images of ABs revealed the coexistence of a homogeneous halo (due to the presence of amorphous phases) and one to several concentric rings, which arise from the presence of a polycrystalline material (Figure 11c-f). Previous studies [42; 43; 44; 45] have shown that Fe is stored inside the hollow cavity of ferritin as ferrihydrite. Ferrihydrite is a poorly crystalline nanomaterial, which can be responsible for the yellow-orange colour of ABs when observed with an optical microscope [46; 47]. Ferrihydrite with some degree of crystallinity displays a major diffraction line between 2.5 and 2.6 A [44] and two minor lines at 1.7 A and 2.0 A [47]. In our samples, polycrystalline ferrihydrite was identified because of the presence of the rings at 2.6 A and at 1.7-2.0 A in the FFT patterns of the ABs (Figure 11c-f). Ferrihydrite is a metastable precursor of iron oxides, such as hematite and goethite [45]. The FFT pattern in Figure 11d shows a diffraction ring at 4.2 A, which may be attributed to (110) of goethite [48]. In Figure 11f, the diffraction ring at 2.5 A may be attributed to polycrystalline goethite [48]. The coexistence of both ferrihydrite and goethite in the same ferruginous material might result from a catalytic effect of the amphibide surface, where Si-O-Fe connections with ferrihydrite are observed [49]. In fact, these connections are thought to be responsible for the delay in the ferrihydrite-goethite transformation, which extends the stability range of ferrihydrite [50]. It should be noted that great prudence must be taken in extrapolating FFT  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & \multicolumn{6}{c}{**Element Weight Percent**} \\ \hline
**Asbestos bodies** & **Subject** & \begin{tabular}{c} **Descriptive** \\ **Statistics** \\ \end{tabular}  & **Fe** & **Si** & **Mg** & **Ca** & **P** & **Na** & **K** & **Al** \\ \hline \multirow{3}{*}{\ \begin{tabular}{c} **Present** \\ **Study** \\ \end{tabular}