Asbestiform Minerals and Human Health
Asbestos is a commercial-industrial term with a long history, and is not a mineralogical definition. ‘‘Asbestos’’ in the latter half of the 20th century became widely used in regulatory language to refer to well developed, long, thin particles (fibers or fibrils) and fiber bundles of specific mineral compositions, which have fulfilled particular industrial applications. In the U.S., asbestos is most commonly defined as the asbestiform variety of 6 naturally occurring hydrated silicate minerals; these include chrysotile, the asbestiform member of the serpentine group, and five minerals of the amphibole group: (1) crocidolite, the asbestiform variety of riebeckite), (2) amosite, the asbestiform variety of cummingtonite-grunerite, (3) anthophyllite asbestos, (4) actinolite asbestos, and (5) tremolite asbestos.According to the US EPA and the Agency for Toxic Substances and Disease Registry potential health effects of exposure to asbestos can include asbestosis, mesothelioma, and lung cancers. In the past, most medical research and regulatory focus has been on the health effects of asbestos used industrially or commercially. However, there have been increasing concerns recently regarding the potential health effects of naturally-occurring asbestos (NOA), which occurs as an accessory mineral in some rocks (for example, tremolite in metamorphosed carbonate rocks, chrysotile in serpentinite rocks), or as an impurity in some other industrial minerals (for example, amphibole asbestos intergrown with vermiculite mined at Libby, Montana).
Current USGS research activities in collaboration with health scientists examine a number of still unresolved scientific questions regarding asbestos, such as:
Meeker, G.P., Bern, A.M., Brownfield, I.K, Lowers, H.A., Sutley, S.J., Hoefen, T.M., and Vance, J.S., 2003, The Composition and Morphology of Amphiboles from the Rainy Creek Complex, Near Libby, Montana: American Mineralogist, v. 88, 1955-1969.
Plumlee, G.S., and Ziegler, T.L., 2003, The medical geochemistry of dusts, soil, and other earth materials, in, Lollar, B.S.L. (ed.), Treatise on Geochemistry, Volume 9, Environmental Geochemistry, pp. 263-310.
Van Gosen, B.S., Lowers, H.A., Bush, A.L., Meeker, G.P., Plumlee, G.S., Brownfield, I.K., and Sutley, S.J., 2002, Reconnaissance study of the geology of U.S. vermiculite deposits—Are asbestos minerals common constituents?: U.S. Geological Survey Bulletin 2192, 8 p.; available on the world-wide web at http://pubs.usgs.gov/bul/b2192/.
Van Gosen, B.S., Lowers, H.A., Sutley, S.J., and Gent, C.A., 2004, Using geologic setting of talc deposits as an indicator of amphibole asbestos content: Environmental Geology, v. 45, p. 920-939.
Other Internet Sources