2. RELEVANCE TO PUBLIC HEALTH 2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO ASBESTOS IN THE UNITED STATES Asbestos is a generic term for a group of six naturally-occurring, fibrous silicate minerals

Asbestos is a generic term for a group of six naturally-occurring, fibrous silicate minerals that have been widely used in commercial products. These minerals are more commonly found in nonfibrous forms that are not asbestos. Asbestos minerals fall into two groups or classes, serpentine asbestos and amphibole asbestos. Chrysotile, a serpentine asbestos, possesses relatively long and flexible crystalline fibers that are capable of being woven. Amphibole asbestos has crystalline fibers that are substantially more brittle than serpentine asbestos. Amphibole asbestos includes amosite, crocidolite, and fibrous forms of tremolite, anthophyllite, and actinolite (see Chapter 4 and Appendix F for more information on chemical and physical properties of asbestos). Over 99% of asbestos used in the United States is chrysotile. As a result of its low cost and desirable properties such as heat and fire resistance, wear and friction characteristics, tensile strength, heat, electrical and sound insulation, adsorption capacity, and resistance to chemical and biological attack, asbestos has been used in a very large number of applications and types of products. In most of its applications, asbestos is bonded with other materials such as Portland cement, plastics, and resins. In other applications, asbestos is used as a loose fibrous mixture or woven as a textile. Use of asbestos in the United States has been declining for 2 decades largely due to health concerns. In 1997, asbestos consumption was 6% of what it was in 1980. The 1997 domestic consumption pattern was 48% for roofing products, 29% for friction products (automobile clutch, brake, and transmission components), and 17% for packing and gaskets (see Chapter 5 for more information on production, import, use, and disposal of asbestos).