Asbestos is a general term applied to a wide variety of naturally occurring fibrous minerals. Because asbestos is strong, incombustible and corrosion-resistant, it was widely used in buildings constructed prior to 1975. Unfortunately the unique physical characteristics of asbestos that make it a good building material are the same characteristics that make it harmful. Although many substances are listed as suspected carcinogens, asbestos is one of the few substances that is a proven carcinogen. For these reasons, federal, state and local governments now regulate the use and removal of asbestos containing material.