# Mineral Fibres and Asbestos Bodies in Human Lung Tissue: A Case Study
## 3 Results and Discussion
### Mineral Fibres
All mineral fibres recovered from the lung tissue of the human subject fit the WHO counting criteria concerning both width and aspect ratio, but 15% of the fibres are shorter than the length value set by the WHO. Compared to the morphometric parameters of the asbestos fibres recovered from the rats' lung tissue, the fibres found in the human subject are longer and thinner [18]. After 109 weeks in the lungs of the rats, crocidolite fibres had an average length and width of 13.7 and 0.5, respectively [18]. Crocidolite fibres found in the human lung tissue, on the other hand, display an average length and width of 17.2 and 0.35, respectively. Crystalline chrysotile was not found in the human samples. Nevertheless, as mentioned above, a silica-rich fibre was found, and most likely it represents a relict obtained by dissolution of a chrysotile fibre. This fibre had a length of 99.1 and a width of 1.71. Instead, chrysotile was found in the rats' lung tissue after 128 weeks and it exhibited an average length and width of 14.3 and 0.45, respectively. Figure 4 illustrates the relationship between length (L) and width (W) of all coated and non-coated fibres examined in this study. Only fibres longer than 1 and thinner than 0.5 were coated by ABs. This peculiarity of ABs to develop only on longer fibres was reported previously for both in vivo and in vitro studies [17; 37]. In Figure 4, values related to non-coated fibres display a wide distribution and a positive correlation (R\({}^{2}\) = 0.67) between L and W. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{6}{c}{**Percentiles \({}^{*}\)**} \\ \hline
**Morphometry** & **Min** & **15 th** & **25 th** & **50 th** & **75 th** & **90 th** & **Max** & \(\sigma_{\mathbf{n-1}}\) \\ \hline
**L (um)** & 2.17 & 4.96 & 7.45 & 19.8 & 47.3 & 61.6 & 107 & 26.2 \\
**W (um)** & 0.06 & 0.13 & 0.18 & 0.28 & 0.44 & 0.66 & 2.82 & 0.47 \\
**L/W** & 13.5 & 24.5 & 29.5 & 55.2 & 141 & 243 & 601 & 107 \\ \hline \end{tabular}
\end{table} 
Table 1: Morphometry of the coated and non-coated fibres recovered from the studied lung tissue. \({}^{*}\) Percentile indicates the value below which a given percentage of values in a data set fall. L (length); W (width); Min (minimum); Max (maximum); \(\sigma_{\mathbf{n-1}}\) (standard deviation). Results of SEM-EDX semi-quantitative chemical analysis of non-coated fibres are reported in Table 2. Non-coated amosite and crocidolite show Fe/Si ratios of 1.53 and 2.18, respectively. The reference asbestos amphibes UICC amosite and UICC crocidolite, on the other hand, have Fe/Si ratios of 0.8 and 0.7, respectively [38]. Figure 5 displays a HRTEM image and the corresponding FFT electron diffraction patterns of a non-coated crocidolite fibre recovered from the lung tissue. The FFT patterns demonstrate that, after several decades of residence in the human lung, the crocidolite fibre preserves its bulk crystallinity (Figure 5a) but exhibits a thin amorphous layer on its surface (Figure 5b). The FFT pattern of the fibre edge (Figure 5b) reveals the characteristic diffuse pattern of amorphous material, whereas Figure 5a shows the typical diffraction pattern of crystalline materials. From Figure 5a, the \(d\)-spacings returns a value of 9.9 A along (100) and of 5.3 A along (001). These values are consistent with the \(d\)-spacing of the crocidolite sample reported by [PERSON] [39]. The spatial distribution of Si, Fe, Mg and Na, shown Figure 6, appears uniform along this fibre. The width of the amorphous layer of crocidolite fibres ranges from 3 to 7 nm (Figure 7).The comparison of the results of our HRTEM study with