What is asbestos?
Asbestos is a natural mineral product known to be resistant to heat and corrosion. Its fibers, which are strong and flexible, are easily woven together and were used extensively in the past in the building and manufacturing industries. Some of its more common uses were in pipe and duct insulation, fire-retardant materials, brake and clutch linings, cement, and some vinyl floor tiles. There are three major types of asbestos used in building and industry. Chrysotile or white asbestos is used
as insulation, fireproofing and soundproofing. Amosite or brown asbestos is used in high friction applications like brake shoes & clutches. Crocilodite or blue asbestos is not as common as the other two, but the most toxic form.
Asbestos is composed of fibrous mineral silicates of different chemical compositions. When inhaled, asbestos fibers settle deep in the lungs, causing scars. Asbestos inhalation also can cause the two layers of membrane covering the lungs (the pleura) to thicken; these thickenings are called pleural plaques. These plaques do not become cancerous. The fine asbestos fibres are easily inhaled, and can cause a number of respiratory complaints, including a potentially serious lung fibrosis called asbestosis. Exposure to asbestos has also been determined to cause a very serious form of cancer, mesothelioma, that occurs in the chest and abdominal cavities. This aggressive disease is not properly referred to as a lung cancer, as the malignant cells are derived from the mesothelium, a tissue found on the inner walls of the chest and abdominal cavities and on the outer surface of the lungs rather than in the lung itself.
Inhaling asbestos fibers can occasionally cause fluid to accumulate in the space between the two pleural layers of the lungs (pleural space); this is called a noncancerous (benign) asbestos effusion. Asbestos also causes cancer in the pleura, called mesothelioma, or in the membranes of the abdomen, called peritoneal mesothelioma. Mesotheliomas most commonly appear after exposure to crocidolite, one of four types of asbestos. Amosite, another type, also causes mesotheliomas. Chrysotile probably causes fewer cases of mesotheliomas than other types, but chrysotile is often contaminated with tremolite, which does. Mesotheliomas usually develop 30 to 40 years after exposure and can occur after low exposure. Asbestos can also cause lung cancer. Lung cancer from asbestos is related in part to the level of exposure to asbestos fibers; however, among people with asbestosis, lung cancer occurs most commonly in those who also smoke cigarettes, particularly those who smoke more than a pack a day.