Asbestos is the name of a group of minerals with long, thin fibers. It was once used widely as insulation. It also occurs in the environment. Asbestos fibers are so small you can't see them. Disturbing asbestos can cause fibers to float in the air. When this happens, they are easy to inhale. You breathe out most fibers, but some become lodged in the lungs. Over time, they can build up in the lungs, causing scarring and inflammation. This can eventually affect breathing and lead to disease, such as Asbestosis, or scarring of the lungs that makes it hard to breathe Mesothelioma , a rare cancer that affects the lining of the lungs or abdomen Lung cancer Lung diseases associated with asbestos usually develop over many years. Smoking cigarettes increases the risk.