Mississippi Shipyard has had a varied building program and has been one of the state's largest industrial employers. Until the late 1970s, asbestos was employed in the production of approximately 300 items used in the shipbuilding industry. It was also a highly regarded building material that was used in floor coverings, ceiling tiles, and heating and ventilation system insulation. When asbestos is in good condition is unlikely to release fibers, but when the material is damaged or deteriorates, or when work is performed on it, fibers may be released into the air, where they may be breathed or swallowed. Because of their needle-like structure, these fibers are difficult to cough up, and they remain stuck in the lungs.