Asbestos is a fibrous mineral silicate (a compound containing a negatively charged form of silicon) that occurs in numerous forms.
A form called amosite [Fe5Mg2(Si8O22)(OH)2] has been shown to cause mesothelioma, squamous cell carcinoma, and adenocarcinoma of the lung after inhalation over a long period of time. 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 airborne doses of asbestos and who also smoke. The potential of asbestos to cause disease appears to be related to the length-to-diameter ratio of particles. Particles less than 2 micrometers in length are the most hazardous.
Asbestos exposure causes thickening of and calcified hardened areas (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. Asbestosis does not develop immediately after inhalation of asbestos. Rather, there is usually a time lag. This is referred to as latency. 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.
Other examples of communities affected by asbestos include Baryulgil, New South Wales, and Libby, Montana. The latter was the site of a $60 million settlement in 2008 that involved homeowners and business people who had used products containing an ore called vermiculite that was mined at Libby. The vermiculite was contaminated with asbestos.
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.
In May 2008, researchers reported that nanotubes—microscopic, artificial, needle-like tubes, usually composed of carbon and used in many new materials because of their strength and conductivity—can have affects on lung tissue similar to those of asbestos. The research indicated that the nanotubes are not dangerous if sealed inside plastics or other materials; like asbestos fibers, they must be inhaled before they can do harm. Nanotubes are therefore mostly a threat to those handling them in manufacturing, not to the general public. Being forewarned of likely health hazards from nanotubes, manufacturers can take steps to protect workers. Nanoparticles (particles smaller than 100 nanometers across) have also been found to be a cancer hazard, causing DNA damage similar to that caused by ionizing radiation.
See also Asbestosis .
Craighead, John E. Asbestos and its Diseases. New York: Oxford University Press, USA, 2008.
Newman, Michael C. Fundamentals of Ecotoxicology, Third Edition. Boca Raton: CRC Press, 2014.
Webster, Peter. White Dust Black Death: The Tragedy of Asbestos Mining at Baryulgil. New York: Trafford Publishing, 2006.
Malcolm T. Hepworth