Asbestos fibers are harmful to humans if inhaled. When a person breathes in the small fibers, they remain in the lungs and cause scar tissue to form on the walls of the alveoli (the tiny air sacs where oxygen and carbon dioxide are exchanged). The amount of oxygen that is available to the body is reduced through asbestos exposure and worsened through repeated encounters with asbestos. There are several asbestos-related diseases that can result from inhaling asbestos fibers, of which Asbestosis is one of the most common.
Domestically used asbestos fibers are classified into seven quality categories or grades. Grades 1, 2, and 3 include the longer, maximum-strength fibers and generally are used in the production of textiles, electrical insulation, and pharmaceutical and beverage filters. Grades 4, 5, and 6 are medium-length fibers used in the production of asbestos-cement pipes and sheets, clutch facings, brake linings, asbestos paper, packaging, gaskets, and pipe coverings. Grade 7 includes short fibers generally used as reinforcers in plastics, floor tiles, coatings and compounds, some papers, and roofing felts (OSHA 1986).
The potential for asbestos fibers to lead to mesothelioma, or any other asbestos-related disease depends on the dose delivered to the target organs in which they are found, the dimensions of the fiber, and the durability of the fiber in the lung tissue.
Between the years of 1995-2005, medical studies conducted in the US found an unexplained increase in crocidolite fibers in the lungs from 819 subjects with lung cancer, malignant mesothelioma, and asbestosis.