Light micrograph section through human lung tissue showing asbestosis. This is a serious lung condition caused by long-term exposure to asbestos. While asbestos can be dangerous, it's not harmful if left alone. If the material containing asbestos is damaged, it can release a fine dust that contains asbestos fibres. If breathed in over a long period of time (maybe years), it can cause asbestosis, an irretrievable scarring of the lungs.