Asbestos has desirable properties that led to its widespread use in the 20th century. It makes an excellent insulator and is resistant to fire so it was used in thousands of different products for decades. For instance, the construction industry used rollboard, a flexible material that contained asbestos, in the walls and ceilings of buildings. It was especially used in places where insulation was required to protect those areas from fire or extreme heat like around wood stoves and furnaces. Rollboard made of asbestos usually contained about 80% asbestos. Asbestos becomes dangerous when its tiny fibers are inhaled or ingested in some manner. These fibers can cause certain serious diseases to develop like lung cancer, asbestosis, and mesothelioma. Mesothelioma is quite rare and aggressive and has a high rate of mortality. Each one of these diseases can lie dormant in the body and not begin to show symptoms for at least 20 years. The use of asbestos was restricted with the Asbestos Ban and Phaseout Rule in 1989, but not all products containing the mineral were banned.  Rollboard, however, is one of the six specific items mentioned in the ban, along with several types of asbestos-containing insulation paper, flooring felt, and new applications for asbestos.  Despite these regulations, asbestos-containing rollboard may still be present in structures built before the 1980s. Reference: