Studio preliminare sulla valutazione indiretta delle fibre inorganiche respirabili aerodisperse in Valle di Susa (Piemonte - Alpi Occidentali)

The presence of asbestos in serpentinite rocks of the Western Alps has been known for a century. Further investigations have revealed the presence of nine fibrous minerals, besides the asbestos tremolite, actinolite and chrysotile, some of them in high amount. All these fibres are carried away over a long distance both by the wind and by human activities. Mineral fibres are therefore a constant component of environmental background; the potential effects on human health of this kind of exposition, generally at low dose, are currently investigated. The assessment of the breathable fibrous minerals fraction (bfmf) can be done on animals called «animal sentinel system» (SSA) as an alternative to humans. Animal studies are free from some of the factors that blur the evidence (such as occupational risk factors and lifestyle) and yield information about environmental exposure only. This study concerns the assessment of bfmf in lungs of cattle from the Susa Valley, an area of the Piedmont Region (NW Italy) underlain by rocks bearing asbestos tremolite, actinolite and chrysotile. The data are compared with that of lungs of cattle from the Asti province, an area free of serpentinite, and therefore chosen as control case. Samples have been suitably prepared and then examined by optical microscopy (OM) to detect ferruginous bodies (Fb) and by Scanning Electron Microscopy (SEM) with annexed Energy Dispersive Spectrometer (EDS) to identify and quantify inorganic fibres. OM data show that Fb are present in both animal groups, but are more frequent in the one from Asti. The presence of inorganic fibres (mainly silicates) has been detected by SEM-EDS throughout the samples from the Susa Valley, as against only a few from Asti. The set of data, though small, makes it clear that the Susa Valley samples mainly contain fibres from natural sources (tremolite and actinolite). Similar quantities of tremolite asbestos were met in NE Corsica (DUMORTIER et alii, 2002), an area with extensive outcrop of serpentinite bearing asbestos tremolite and chrysotile. Our results show that bfmf assessment in lung tissues of SSA can give information about the local environmental background (itself dependent on topographic, geological, climatic and anthropic characteristics). This method also highlights the geology dependent difference of mineralogical burden in geologically different areas. The two techniques provide useful information, both for health and environmental investigations. Research aimed at identifying inorganic fibres in lungs by micro-Raman spectroscopy is currently under way.