POTENTIAL TOXICITY OF NONREGULATED ASBESTIFORM MINERALS: BALANGEROITE FROM THE WESTERN ALPS. PART 1: IDENTIFICATION AND CHARACTERIZATION

Abstract

In the Italian western Alps, asbestos mineralization (both chrysotile and tremolite amphibole) takes place from serpentinites, together with other less common asbestiform minerals not regulated by the current legislation. In the context of a study on the evaluation of the asbestos risk in this area, the possible role played by the associated asbestiform minerals in the overall toxicity of the airborne fraction has been examined. The first mineral investigated was balangeroite [(Mg,Fe²⁺,Fe³⁺,Mn²⁺)₄₂Si₁₆O₅₄(OH)₃₆], an iron-rich asbestiform contaminant of chrysotile from the Balangero mine (Piedmont), which crystallizes as rigid and brittle fibers. In order to prepare a sample in a form appropriate for chemical and cellular tests, the fibers were separated from the rock and comminuted without damage to their crystalline structure and surface state (as confirmed by X-ray diffraction [XRD] and ultraviolet–visible [UV-Vis] spectroscopy). The first properties examined were durability in simulated body fluids (Gamble’s solution) and toxicity to epithelial cells. When compared to UICC crocidolite (the amphibole blue asbestos, regarded as the most pathogenic form), balangeroite appears even more durable than crocidolite. Balangeroite and UICC crocidolite showed a similar in vitro cytotoxic effect on a human epithelial cell line, as evidenced by leakage of intracellular lactate dehydrogenase (LDH) activity, which, observed after a 24-h incubation, was dose dependent and maximal at 12 μg/cm² for each fiber type. Data show that chemical composition, form, durability, and cell toxicity indicate balangeroite as a potentially harmful fibrous mineral that needs to be examined by further chemical and cellular tests.

The research has been carried out with the financial support of Regione Piemonte, Assessorato all’ Ambiente, as part of a muldisciplinary project, entitled “Asbestos Hazard in the Western Alps.” Elena Gazzano, Chiara Groppo, and Francesco Turci are recipients of a doctoral fellowship and Maura Tomatis of a postdoctoral fellowship from Regione Piemonte in the framework of the project.

Notes

In the Balangero mine, as well as in the whole Lanzo Massif, two different generations of chrysotile veins can be distinguished. The first vein generation is deformed and consists of long-fiber chrysotile (up to several centimeters in length). They probably formed during an early stage of the metamorphic evolution, prior to the high-pressure early Alpine metamorhic event. The second vein generation consists of short-fiber chrysotile (a few millimeter in length), formed during a late Alpine metamorphic event (Compagnoni et al., 1980).

Kindly provided by the Lanzo Mineralogic Museum (Pierluigi Ambrino, Antonello Barresi and Mario Cajolo).