Tremolite asbestos

Over the past several decades six different silicate minerals have been mined as asbestos and processed for industrial and commercial applications. The most commonly encountered asbestos mineral today is chrysotile. The five other minerals are tremolite, actinolite, anthophyllite, grunerite, and rie-beckite. All five are members of the amphibole group of minerals, and each can occur as chunky, acicular, or equant crystals, as well as in fibrous form. When found as fine fibrous aggregates, in quantities appropriate for mining, they are usually distinguished as a special variety—for example, tremolite-asbestos. 

Tremolite-asbestos An amphibole-asbestos composed of the mineral tremolite. 

Talc fibers may be present in some talcs, especially if the talcs contain anthophyllite or tremolite asbestos and a metamorphosis or transition to talc has taken place. The transition is sometimes incomplete as in talcs from the Gouveneur district of upper New York State. If talc fibers are present, further testing as described below will be necessary. 

National Public Health Activities regarding Tremolite Asbestos Exposure Medical Testing, Libby, Montana, Summer 2000 - Over 6,000 Libby, Montana, residents screened for asbestos-related diseases associated with living or working near a vermiculite mine contaminated with a fibrous amphibole. National Assessment of Vermiculite Sites, Mortality Review of Cancer and Noncancer Cases Associated with Asbestos Exposure, and other projects. 

The profile also contains a health consultation on tremolite asbestos, a name that has been used in the popular press to refer to fibrous amphibole that occurs in vermiculite ore from Libby Montana (Appendix... 

Along these same lines, further work would be helpful in defining other fiber characteristics that are important determinants of carcinogenicity. It is suspected, for example, that amphiboles, such as crocidolite and tremolite asbestos, are more likely to cause mesothelioma than chrysotile, but it is not certain if this is attributable to differences in fiber length alone or to differences in chemical properties (e g., fiber morphometry, iron content, durability in biological fluids and tissues). Consequently, additional animal studies of the relative carcinogenic potency of airborne asbestos fibers of different types (e.g., chrysotile versus amphibole asbestos), carefully matched with regard to fiber size distribution, may be valuable. 

Andrion A, Bosia S, Paoletti L, et al. 1994. Malignant peritoneal mesothelioma in a 17-year-old boy with evidence of previous exposure to chrysotile and tremolite asbestos. Hum Pathol 25(6) 617-622. 

Baris YI, Bilir N, Artvinli M, et al. 1988b. An epidemiological study in an Anatolian village environmentally exposed to tremolite asbestos. Brit J Ind Med 45 838-840. 

HSDB. 1999b. Tremolite asbestos. Hazardous Substances Data Bank. National Library of Medicine, National Toxicology Information Program, Bethesda, MD. June 16, 1999. 

Metintas M, Gibbs AR, Harmanci E, et al. 1997. Malignant localized fibrous tumor of the pleura occurring in a person environmentally exposed to tremolite asbestos. Respiration 64 236-239. 

RTECS. 1999a. Tremolite asbestos. Registry of Toxic Effects of Chemical Substances. National Institute for Occupational Safety and Health. April 19, 1999. 

Schneider J, Rodelsperger K, Briickel B, et al. 1998. Environmental exposure to tremolite asbestos Pleural mesothelioma in two Turkish workers in Germany. Rev Environ Health 13(4) 213-220. 

Voisin C, Marin I, Brochard P, et al. 1994. Environmental airborne tremolite asbestos pollution and pleural plaques in Afghanistan. Chest 106 974-976. 

CHEMICAL-SPECIFIC HEALTH CONSULTATION TREMOLITE ASBESTOS AND OTHER RELATED TYPES OF ASBESTOS... 

Physical and Chemical Properties, Occurrence, and Detection Tremolite Asbestos... 

Regulatory agencies such as the U.S. Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) recognize six asbestos minerals chrysotile, a serpentine mineral and five amphibole minerals, actinolite asbestos, tremolite asbestos, anthophyllite asbestos, crocidolite asbestos, and amosite asbestos. Nonasbestiform amphibole minerals are not included in U.S. health regulations regarding asbestos because there is insufficient evidence that they will produce adverse health effects of the same type and severity produced by chronic exposure to asbestos. 

Samples of the fibrous amphibole in the Libby vermiculite ore, popularly referred to as tremolite asbestos, were recently analyzed by U.S. Geological Survey scientists. On the basis of variable chemical composition, several different mineral names were assigned to the samples winchite, richterite, tremolite, actinolite, ferro-edenite, and magnesio-arfvedsonite. All of these are classified as amphibole minerals. 

Nonasbestiform tremolite is the predominant form of tremolite in the earth s cmst, but there are many reports of tremolite asbestos occurring around the world in specific locations (including some locations in Maryland and California) and natural materials. Tremolite asbestos has only rarely been found in commercially mined deposits. It has never been a nationally important commercial source of asbestos in the United States. Two minerals of commercial importance that have been reported to contain tremolite asbestos or other amphibole asbestos are vermiculite and talc. 

Before 1990, the now closed mine in Libby, Montana, was a significant source of vermiculite in the United States. In 1998, vermiculite was mined in the United States predominantly in South Carolina and Virginia and was also imported from South Africa and China. A 1984 study reported that the percentage of tremolite asbestos fiber by weight varied from 3.5% to 6.4% in raw vermiculite ore from Libby, Montana. In contrast, several studies of vermiculite mined elsewhere (South Carolina, Virginia, and South Afiica) reported that levels of amphibole asbestos were either not detectable or only present at much lower levels than those found in the Libby vermiculite. 

The chest x-ray is the most common and important tool to detect lung and pleural disease caused by chronic exposure to tremolite asbestos or other types of asbestos. Results from pulmonary function tests and high resolution computerized tomography can also be used in the diagnosis. 

The Libby amphibole mineral, popularly known as tremolite asbestos, has been assigned a number of different names by scientists over the years (Meeker et al. 2001 Wylie and Verkouteren 2000) however, scientists agree that exposure to the mineral increased the risk of nonmalignant respiratory and pleural disorders, lung cancer, and mesothelioma in groups of people who worked in the now closed Libby mine and mill. These health problems are similar to those experienced by workers exposed to other types of asbestos before modem workplace air regulations were established. 

The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this chemical-specific health consultation to provide support for public health decisions regarding Libby, Montana, and other locations where tremolite asbestos and related asbestos can be found. This document ... 

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