Crystalline tremolite as a cause of pleural calcifications not associated with mesothelioma in an area in Trikala
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Pneumon 2005;18(2):214-222
In the 1980s, our investigation on “endemic calcifications” and increased incidence of mesothelioma in Metsovo revealed at least seven areas in Greece that showed a similar epidemiologic pattern of exposure and disease incidence. One of these areas was Megarchi in Trikala. In the twenty years that followed, despite the high incidence of calcifications in this area, there has been no case of mesothelioma. This paradox has stimulated the present study. Our findings showed that asbestos (tremolite) contained in the ground used in Megarchi has the form of crystals, which, in contrast to the thin/long fibers of asbestos found in Metsovo, has experimentally been shown to be unable to induce neoplasia. The study was expanded obtaining bronchoalveolar lavage fluid from all healthy inhabitants with calcifications. Amorphous, non-organic material inside and outside alveolar macrophages was found in all cases; the number of asbestos bodies ranged from low (8-30/100,000 cells) to null. Mineralogical studies of lavage fluid showed tremolite crystals. The present study shows that: i) there is a true high incidence of pleural calcifications, but no mesothelioma case has been reported in the area of Megarchi; ii) as in Metsovo, tremolite is implicated in the development of pleural calcifications; however, tremolite found in this area has completely different aerodynamic properties that have been shown to be associated with different biological effects. Hence, this type of tremolite has a fibrosing effect (pleural plaques), but lacks carcinogenicity (no mesothelioma case); iii) areas in Greece where “endemic calcifications” have previously been reported should be reassessed with a view to identify the causative agent and subsequently to rid the population of the threat of a “mesothelioma epidemic”, which may in fact never come up, provided that findings are similar to that in Megarchi. Pneumon 2005, 18(2):214-222.
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