Size characteristics of asbestiform fibers in lung tissue of animals that grazed in areas rich in ophiolitic outcrops in Central Calabria (Southern Italy)

Abstract

In Calabria (Southern Italy) naturally occurring asbestos (NOA) mainly occurs in the ophiolitic sequences cropping in the Mount Reventino area. The most common type of asbestos detected was the amphibole tremolite; fibrous antigorite and minor chrysotile were also found. The development of asbestos-related diseases depends on, among other things, the morphological characteristics of fibers, length and width, affecting the durability of asbestos fibers in the lung. In this work fifteen lung samples of sheep, goats and wild boars, grazing around the Mount Reventino area were collected and asbestos fibers analysed. Observed fibers (357), of which 97 % were tremolite and 3 % antigorite fibers, were grouped according to species, grazing area and age of the animals. The aim of this work was to highlight any differences among the groupings and to compare our size results with data in literature related to exposed populations. Principal Component Analysis (PCA) highlighted a positive correlation between tremolite fiber length and width and revealed groupings in terms of animal age. The Kruskal-Wallis test showed statistically significant differences between fiber mean widths in young and old animals. 63 % observed asbestiform fibers were longer than 5 μm and 7 % of the fibers were longer than 20 μm (critical fiber length connected to the frustrated phagocytosis by the macrophage). Fibers conforming to the Stanton Hypothesis size (predictor of the carcinogenic potency of fibers) were 1 %. Our size parameters of fibers detected in the animal lungs were in fairly good agreement with literature data for human asbestos exposure to tremolite. These results confirmed that an animal-sentinel system could be used to monitor the natural background of the airborne breathable fibers exposure. In addition, the size correlation of animal-human breathed fibers could be useful to study their potential toxicity. Additional data are necessary for improving the agreement with human exposure data.

Keywords: Animal sentinel system; Asbestiform minerals; Naturally occurring asbestos; Ophiolite; Tremolite.