Archives of Environmental Health, April, 2003 by Pietro Comba, Antonio Gianfagna, Luigi Paoletti
FLUORO-EDENITE is a new mineral species detected in Biancavilla, a city in eastern Sicily, Italy, characterized by a high incidence of pleural mesothelioma. In this study, we sought to provide new information about this fibrous amphibole and to discuss epidemiologic and environmental evidence supporting the etiologic role of fluoro-edenite in the occurrence of mesothelioma.
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In a national survey of mortality from pleura mesothelioma in Italy from 1988 to 1992, a cluster of cases (N = 4) was detected in Biancavilla (standardized mortality ratio [SMR] = 417 [95% confidence interval {CI} = 142,954]). (1) From 1993 to 1997, an additional 8 cases were observed (SMR = 721 [95% CI = 359, 1,300]). (2)These findings prompted an ad hoc epidemiological investigation. Paoletti et al. (3) reported that 17 cases were identified and reviewed, their pathological diagnoses were confirmed, and history of exposures to asbestos was evaluated. Information on both occupational exposures and exposures to asbestos in the work place (in-site exposure) was available for 16 subjects There was no evidence of exposure for 9 subjects; 2 had probable exposure (a construction worker and a foundry worker). Exposure could neither be ascertained nor ruled out for the remaining 5 subjects, who worked in bricklaying, printing, or the clothing and paper industries.
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Given that the occupational histories did not point to a common activity or source of exposure that could significantly increase the subjects' risk for developing mesothelioma, a general environmental source was considered. An environmental survey suggested that the general environmental source might be asbestos from the stone quarries located in Monte Calvario, southeast of the town. The materials extracted from the quarries--used widely in the local building industry--contained large quantities of fibrous amphiboles.
The Monte Calvario amphiboles were initially referred to by Paoletti et al. (3) as sodium (Na)--and fluorine (F)-rich tremolites and actinolites. The fibers were detected in the materials extracted from the quarries and in the plaster or mortar of the buildings in Biancavilla. The same fibers were detected in a lung tissue sample taken at autopsy from an 86-yr-old woman who resided in Biancavilla prior to succumbing to pleural mesothelioma. Other mineral fibers were not found in the sample, and it was impossible to reveal the presence of ferruginous bodies. Inasmuch as the quantity of the specimen was very limited, it was impossible to conduct histological investigations, the purpose of which was the elucidation of pathological changes related to an exposure to asbestos. No lung tissue samples were available from the other identified cases.
A subsequent crystal-chemistry investigation of the Monte Calvario amphiboles (4) identified the mineral as fluoro-edenite--a new end-member of the edenite [right arrow] fluoro-edenite series. The finding was confirmed by the Commission on New Minerals and Mineral Names on January 30, 2001. (5)
Environmental and Geological Investigations
The fluoro-edenite from Biancavilla (ideal formula: Na[Ca.sub.2][Mg.sub.5][Si.sub.7]Al[O.sub.22][F.sub.2]) is transparent, intense yellow with habit from prismatic to acicular. It is also fibrous and asbestiform, occurring in autoclasts of grey-red altered benmoreitic lavas where it is generally associated with potassium-feldspar and plagioclase, quartz, clino-and orthopyroxenes, fluoro-apatite, ilmenite, and hematite. In Table 1 are shown relevant mineralogical data for fluoro-edenite.
In the Monte Calvario area, the fluoro-edenite mineralization process yielded mainly prismatic, evenly sized acicular crystals (Fig. 1). Similar fibers have recently been found in neighboring areas of the quarry (Fig. 2), but in a different volcanic formation. The fibers are similar in size and morphology to some amphibolic asbestos fibers (tremolite, actinolite, antophyllite); sometimes they occur as elastic and tensile (filamentous) fibers (Fig. 2) (size: < 0.5 [micro]m in width to > 10 [micro]m in length).
[FIGURES 1-2 OMITTED]
The fluoro-edenite at Monte Calvario is found in cavities and cracks of benmoreitic lava that has been meta-somatized by hot, F-rich fluids. The asbestiform fluoro-edenite is found in refall pyroclastic products and scoriae that have been greatly altered; these are mainly found in the northwest of Monte Calvario. The finding of amphibolic fibers near Monte Calvario points to a very complex volcanic process with several evolutionary stages. It also suggests that the process may have also occurred in other areas that have not yet been identified, perhaps because the products are not at the surface or perhaps they have not yet been quarried.
Discussion and Conclusions
The physical processes that determined the genesis of this new amphibole are not yet understood. Among the various hypotheses posited, the most plausible points to an upsurge of very hot fluids directly from the magma chamber. These fluids altered and metasomatized the previously emplaced volcanic products (lavas, pyroclasts). Fluoro-edenite appears to have formed during this metasomatic process because there was an abundance of fluorine in the contaminating fluid. Concurrently, the rising fluid also conditioned other nionlavic formations peripheral to Mount Calvario and gave rise to asbestiform fluoro-edenite. The different morphology of the fibers may be ascribed to different rates of cooling of the materials affected: larger fluoro-edenite crystals in the central part of the dome represent a slower cooling rate, whereas asbestiform fibers in the more peripheral areas represent a faster cooling rate.
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