Pleural mesothelioma clusters from outdoor environmental exposure have been highlighted also in Italy and, on the basis of epidemiological surveillance coordinated by the Italian National Mesothelioma Register, their frequency has been estimated at about 4.5%. Epidemiological studies and evaluations of some regional mesothelioma registers have made it possible to highlight that the dispersion of asbestos fibers in the outdoor environment was the only ascertained cause of mesothelioma in subjects from asbestos-cement factories, from the Balangero mine (Piedmont Region), from some serpentine rock quarries with tremolite outcrops in the Southern Apennines and in Alta Val di Susa (Piedmont Region); from chrysotile and serpentine caves in Valmalenco (Lombardy Region). Furthermore, cases of pleural mesothelioma were clearly caused by environmental pollution from fluoroedenite fibers in Biancavilla (Sicily Region). On the other hand, regional mesothelioma registers have also reported other circumstances of environmental asbestos exposure, like in the case of steel industry, shipbuilding, chemical plants, railway lines, and repair/demolition of railway carriages. However, these reports have not found confirmation on the basis of ad-hoc studies and it is likely that there is a lack of homogeneity in the assessment of individual cases. Apart from the scenarios which have been the subject of ad-hoc studies, the assessment of the causal role of environmental exposure to "in place" asbestos in the onset of pleural mesothelioma is problematic without an effort to more carefully examine the circumstances of possible exposure, harmonization of the attribution criteria used in the individual regional registers, analytical assessment of the impact of such exposure on the risk of onset of mesothelioma.
Keywords: Asbestos; Outdoor environmental exposure; Pleural malignant mesothelioma.