The term asbestos describes a group of highly stable, non-flammable minerals with a fibrous structure. Until the early 90s they were predominantly used in heat insulation material or fire barriers.  Asbestos is also contained in brake linings, clutches, electronic devices, machines and technical installations, heating systems, and, most importantly, in the construction material of numerous buildings. When entering the lungs asbestos fibres may bring on so-called asbestosis, i.e. the hardening and scarring of connective tissue and eventually cause cancer.
Meanwhile even asbestos surrogates such as man-made mineral fibres (MMMF) have been proven to have a potentially carcinogenic effect.