Asbestos
Asbestos is a fibrous mineral silicate, occurring in numerous forms, of which amosite [Fe5Mg2(Si8O22)(OH)2] has been shown to cause mesothelioma, squamous cell carcinoma and adenocarcinoma of the lung after long exposure times. This substance has been listed by the Environmental Protection Agency (EPA). Lung cancer is most likely to occur in those individuals who are exposed to high air-borne doses of asbestos and who also smoke. The pathogenic potential of asbestos appears to be related to its aspect ratio (lengthto-diameter ratio), size (particles less than 2 micrometers in length are the most hazardous), and to its surface reactivity.
Asbestos exposure causes thickening of and calcified plaques on the lining of the chest cavity. When inhaled it forms "asbestos bodies" in the lungs, yellowish-brown particles created by reactions between the fibers and lung tissue. This disease was first described by W. E. Cooke in 1921 and given the name asbestosis. The latency period is generally longer than 20 years—the heavier the exposure, the more likely and the earlier is the onset of the disease. In 1935 an association between asbestos and cancer was noted by Kenneth M. Lynch. However, it was not until 1960 that Christopher Wagner demonstrated a particularly lethal association between cancer of the lining of the lungs and asbestos. By 1973 the National Institute of Occupational Safety and Health recommended adoption of an occupational standard of two asbestos fibers per cubic centimeter of air.
During this time, many cases of lung cancer began to surface, especially among asbestos workers who had been employed in shipbuilding during World War II. The company most impacted by lawsuits was the Manville Corporation which had been the supplier to the United States government. Manville Corporation eventually sought Title 11 Federal Bankruptcy protection as a result of these law suits.
More recently, the Reserve Mining Company, a taconite (iron ore) mining operation in Silver Bay, Minnesota, was involved in litigation over the dumping of tailings (wastes) from their operations into Lake Superior. These tailings contained amositic asbestos particles which appeared to migrate into the Duluth, Minnesota water supply. In an extended law suit, Reserve Mining Company was ordered to shut down their operations. One controversial question raised during the legal action was whether cancer could be caused by from drinking water containing asbestos fibers. In other cancer cases related to asbestos, the asbestos was inhaled rather than ingested. Federal courts held that there is reasonable cause to believe that asbestos in food and drink is dangerous—even in small quantities—and ordered Reserve Mining to stop dumping tailings in the lake.
A significant industry has developed for removing asbestos materials from private and public buildings as a result of the tight standards placed on asbestos concentrations by the Occupational Safety and Health Administration. At one time, many steel construction materials, especially horizontal beams, were sprayed with asbestos to enhance their resistance to fires. Wherever these materials are now exposed to ambient air in buildings, they have the potential to create a hazardous condition. The asbestos must either be covered or removed, and another insulating material substituted as great cost. Removal, however, causes its own problems, releasing high concentrations of fibers into the air. Many experts regard covering asbestos in place with a plastic covering to be the best option in most cases. What was once considered a life-saving material for its flame retardancy, now has become a hazardous substance which must be removed and sequestered in sites specially certified for holding asbestos building materials.
Resources
Books
Bartlett, R. V. The Reserve Mining Controversy: Science, Technology, and Environmental Quality. Bloomington: Indiana University Press, 1980.
Brodeur, P. Asbestos and Enzymes. New York: Ballantine Books, 1972.
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