Tremolite and Libby Amphibole
Fibers of the tremolite-actinolite series are a widespread mineral that has little commercial value. Marked inflammatory and fibrotic responses are seen after tremolite deposition in the lungs of animals, in contrast to the lack of histopathology after Calidria chrysotile exposures (Bernstein et al., 2005b). Since 1978, the human health effects of vermiculite contaminated with this asbestiform mineral have been studied (Amandus et al., 1987; ASTDR, 2003). The U.S. EPA now calls the complex tremolite-containing mineral "Libby asbestiform amphibole." A recent epidemiological study was published of 406 vermiculite mineworkers in Libby, MT, who were employed before 1963 and followed until 1999 and had average exposure for 9 years of 18 f/ml-yr. Twelve deaths (4.2% of all deaths) were attributed to mesothelioma. The overall proportional mortality is similar to that of crocidolite miners in South Africa and in Australia (McDonald et al., 2004). Locally widespread use of tremolitecontaining whitewash is reported to be the cause of the "Metsovo mesothelioma epidemic" (Constantopoulos et al., 1987; Langer et al., 1987; Sakellariou et al., 1996) and is strongly associated with mesothelioma risk in New Caledonia (Luce et al., 1994, 2000) and Anatolia (Baris et al., 1988; Metintas et al., 1999).