Amphiboles: Environmental and Health Concerns

In this chapter, we turn our attention to an issue that is often not based on rational science, but about fear—the issue of asbestos. As the geological community is well aware, all asbestos are minerals, and thus naturally formed; yet in the public arena, many people believe asbestos is something manufactured by humans and that one fiber is enough to kill you if inhaled. It is the intent of this chapter to provide background information for members of differing communities, be they mineralogists, geologists, medical researchers, regulatory workers, or legal professionals to better understand amphibole-related health and environmental issues. This chapter contains an introduction and overview of the health effects associated with the inhalation of amphibole minerals. Also, the chapter will discuss some of the current issues and research trends surrounding asbestos exposure, especially in the natural environment. In this chapter, we will define terminology used by the different fields of study. It is important for those working in any field dealing with asbestos to understand that terms vary significantly among the different fields. Often, attempts by one group to simplify the nomenclature have resulted in more confusion in the scientific literature as well as for the public. For instance, recently the term “naturally occurring asbestos” has become widely used by regulatory groups in the USA to distinguish it from occupational exposure to asbestos. The issue becomes even more complicated in that the majority of the minerals of concern in the natural environment are amphiboles, and the distinction between fibers and fragments of amphiboles remains a central issue. Clearly we are exposed to amphiboles and different types of asbestos on a daily basis. Many of these exposures are natural (i.e., nonoccupational or nonanthropogenic) while others result from widespread use of asbestos-containing products over the past 70-80 years. However, because approximately 95% of asbestos used in commercial products was chrysotile (which is a sheet silicate), the majority of occupational exposure was to chrysotile, not amphibole asbestos. In the natural environment amphibole exposure is much greater than chrysotile; this is due mainly to the fact that amphiboles are much more widespread than chrysotile. So we are again left to distinguish between amphibole and amphibole asbestos. Regardless, most of us who reach the age of 60 and 70 have not thousands but millions of particles of amphibole in our lungs due to these natural exposures. Thus, it seems to defy common sense that one fiber of asbestos will lead to death. The phrase “naturally occurring asbestos” was mentioned above. Exposure relating to it is now at the forefront of health concerns of asbestos exposure, at least in the USA. Because of the general fear of the word “asbestos,” the mere thought of exposure can cause panic in the general public, often driven by the popular media. Again, one of the goals in this chapter is to alleviate some of that fear. However, the media, especially in reports of Libby, Montana, USA, have continued to instill fear into the public by overstating the issues. In the USA, fear of asbestos exposure was heightened based on issues surrounding Libby that made it to the national media in 1999. These concerns were also heightened by the possible widespread asbestos exposure in the September 11, 2001, collapse of the World Trade Center. These two events combined to cause heightened concern to asbestos exposure in the natural setting of El Dorado County, California. While there was an increase in asbestos-related diseases from the miners at Libby, those who worked in the processing outside of Libby, and health concerns for the local citizens, there are no confirmed deaths for nonoccupationally exposed citizens living in El Dorado County. Even so, a statistical model shows possible correlations of mesothelioma with proximity to ultramafic rocks in El Dorado County. Turning our attention to Italy, there have been increased deaths from mesothelioma on a country-wide basis and even more concern on the island of Sicily in the village of Biancavilla on the side of the Mt Etna where exposure came from the first known occurrence of asbestiform amphiboles in volcanic rock.