NONREGULATORY ASBESTOS GROUP MINERALS

Recent studies indicate the potential toxicity of nonregulatory asbestos group minerals such as richterite, winchite, fluoro-edenite, balangeroite, carlosturanite, gageite, arfvedsonite, and magnesio-arfvedsonite which are potentially harmful. Some of these nonregulatory asbestos cites such as Libby Montana (richterite, winchite) and Balangore of western Alps, Italy (balangeroite) are of great concern for mesothelioma. Controversy surrounds the toxic potential of these minerals and several other mineral fiber types including chrysotile. Adverse health impact, epidemiological and pathological studies, in-vivo and in-vitro cellular and biodurability tests, dissolution, fiber length, and flexibility of these minerals were discussed and compared with regulatory asbestiform minerals in order to determine the linkage between these nonregulatory asbestos minerals and their carcinogenic potentials. Some of the known potent fibrous minerals have high iron contents such as regulatory amphibole fibers to generate reactive oxygen species (ROS). There is a controversy related with potential pathogenesis of chrysotile. Some of the fibrous minerals such as regulatory minerals of chrysotile and erionite, and nonregulatory fibrous minerals may not have iron cation in their structure. However, chrysotile may not have iron in the structure per se but intergrows with balangeroite and carlosturanite, and thus may have iron in their structure. Ballirano et al. (American Mineralogist, 2009, 94:1262-1270) found less than 9 micrometers super paramagnetic particles with trivalent iron attached to erionite. Therefore, extensive study of chemistry and crystal structures of fibrous minerals are crucial before using these minerals in vivo and/or in vitro experiments.