Up until about 30 years ago asbestos was material that was widely used in construction and in commercial and industrial applications. Products containing asbestos ended up in these structures in the form of products like floor tiles or roofing felt. Any asbestos-containing material like roofing felt was a hazard for the workers who installed it. Roofing felt was usually installed on the flat roofs found on commercial buildings and other buildings like schools and institutions. The felt was made up of sheets of asbestos material that was then covered with asphalt.
As long as the asbestos remained sealed beneath the asphalt, the roof felt was not dangerous for those who worked, lived, or played inside the buildings. But the workers who installed the felt were very likely exposed to the dangerous asbestos fibers. These fibers can break loose when the asbestos is manipulated in any way, and the felt often needed to be cut to fit the individual installation. Removing the felt also creates a hazard for those without proper protective equipment.
After many years, some of these roofers developed illnesses that are directly due to their exposure the asbestos. These diseases include lung cancer, asbestosis, and mesothelioma. If one of these older building requires renovation the workers as well as the inhabitants are at risk. A licensed asbestos removal team should remove the asbestos.