Asbestos is a term for a variety of naturally occurring minerals (and products that contain those minerals) that have highly unusual properties:
Unlike most minerals, asbestos minerals are composed of thin fibers, much longer than they are wide, that resemble organic fibers such as hair or cotton.
The crystals of most minerals are brittle and cannot be bent more than a few degrees. Asbestos is highly flexible and may be somewhat elastic. It can even be woven into textiles.
Asbestos possesses unusual strength, which increases as the diameter of the fiber becomes smaller.
It is extremely resistant to physical stress. It will not burn. And it is more resistant to dissolution by acid than other forms of the same minerals.
Asbestos fibers are infinitesimally small and are usually measured in terms of microns. A micron is a millionth of a meter. The diameters of asbestos fibers are usually described in fractions of a micron.
Asbestos is mined all over the world. In 1978, according to Malcolm Ross, a research mineralogist with the U.S. Geological Survey, the leading asbestos-mining countries were Canada, the Soviet Union, and the Republic of South Africa.
The commercial names for asbestos include “white” or “chrysotile” asbestos, which accounts for about 95 percent of all asbestos used in the United States; “brown” or “amosite” asbestos, which accounts for about 2 percent; and “blue” or “crocidolite” asbestos, which also accounts for about 2 percent. The names signal the type of mineral from which the variety is formed.
The Earliest Use of Asbestos
People have used asbestos at least since the beginning of recorded history. The Egyptians, Greeks, and Romans used it in some textiles--candle wicks, for example, and embalming cloth. Early communities in Finland used it to strengthen earthenware pots and cooking utensils. Marco Polo reported its use in China.
Until the late 19th century, however, asbestos was not mined in large enough amounts for widespread use. That changed when extensive deposits of asbestos were discovered in Canada, and mines in Northern Italy that dated back to Roman times were reopened toward the end of the 1800’s.
In the first half of the 20th century, the asbestos industry grew rapidly. Asbestos was used as insulation for the newly invented steam engine and as reinforcement for roofing and floor tiles. It was pressed into board, mixed into cement, smeared as spackling, and used as fire-proofing. By the mid-1930’s, asbestos had become one of the most common construction materials in the United States. The application of asbestos as a sprayable material expanded rapidly during World War II, when it was used widely for insulation in ships and submarines.
From the late 1940’s until the early 1970’s, substantial amounts of asbestos were installed in school ceilings, floors, wallboards, pipes, and boiler rooms.
Dr. Irving J. Selikoff, director of the Environmental Sciences Laboratory at the Mount Sinai School of Medicine of the City University of New York, estimates that some 30 million tons of asbestos were put in place between 1900 and 1980 “in our ships, buildings, schools, chemical plants, refineries, powerhouses, factories, etc.” Approximately 70,000 tons of insulation were installed during the same period.
Today, asbestos is found in some 3,000 commercial products, including the brake and clutch linings in automobiles.
In fact, asbestos is so omnipresent, that it is even found in the air, both indoors and outdoors--although at concentrations thousands of times lower than those found in industrial settings.
Man-made mineral fibers with some qualities similar to asbestos, such as fibrous glass and mineral wool, are sometimes substituted for asbestos in commercial products.
Although exposure to these fibers is fairly recent, initial studies indi-cate that these fibers may also cause diseases of the respiratory tract, such as lung cancer, after long-term exposure in the workplace. However, the health hazards do not appear as great as those of asbestos.
The knowledge that asbestos is dangerous is not new. Greek and Roman writers reported lung sickness among slaves who wove asbestos material.
By the early 1900’s, medical researchers had identified asbestosis, a progressive scarring of the lungs, as a disease associated with asbestos-laden factories. (The name of the disease was coined in 1927.) By the mid-1930’s, it was well established that asbestos inhalation could frequently cause diseases that might be fatal. Further research clarified the relationship between asbestos and cancer during the 1940’s, 50’s, and 60’s.
Courts have since determined that the asbestos-manufacturing in-dustry knew of the dangers associated with airborne asbestos as early as the mid-1930’s but maintained an attitude of “indifferent silence,” as one judge wrote in a 1981 decision on the case Hardy v. Johns-Manville Sales Corporation.
However, asbestos is only dangerous in the form of airborne fibers, which can be swallowed or inhaled. It is not dangerous when encased in a hard product. It is not dangerous to the touch.
The danger comes when asbestos-containing materials deteriorate or are damaged or disrupted in any way. “Friable” asbestos refers to asbestos that can be easily powdered or crumbled by hand, thus becoming airborne.
Because of the health hazards associated with asbestos, the Environmental Protection Agency in 1973 banned the spraying of materials that contain more than 1 percent asbestos in buildings, and specifiedel5lthat “no visible emissions” were allowed from permitted spraying. The agency has since broadened the regulations to ban the use of molded and wet-applied insulation and decorative materials containing more than 1 percent asbestos.
Since 1971, the Occupational Safety and Health Administration has limited the level of asbestos exposure in the workplace. The agency has lowered that limit several times, and is now considering lowering it again.
Asbestos exposure levels are generally measured in terms of the number of asbestos fibers at least 5 microns long that are present in one cubic centimeter of air.
The current osha limit is 2 fibers per cubic centimeter--or 2 million fibers per cubic meter--averaged over eight hours. Humans inhale about one cubic meter of air per hour, depending on the degree of their physical activity. Thus, at osha’s current limit, a worker would still inhale roughly 16 million as-bestos fibers, 5 microns or more in length, each workday, and many more shorter fibers.
Current epa regulations also specify methods of removing friable asbestos from buildings during demolition or renovation; and require the identification of asbestos in schools.
In addition, the agency has set emissions standards for the handling of asbestos in asbestos industries and for the disposal of asbestos-containing waste.
The epa has not established standards for exposure levels in nonindustrial settings or mandated corrective actions that need to be taken when asbestos-containing materials are found in buildings.
The epa is working on proposals that would eliminate the use of virtually all asbestos products over a 10-year period using a “phase-down’’ approach. The rules would gradually reduce all domestic min-ing of asbestos and all importation of asbestos-containing products over the next 10 years.--lo
Information for this report was drawn primarily from : The Attorney General’s Asbestos Liability Report to the Congress, U.S. Department of Justice, Washington, D.C., September 1981; Committee on Nonoccupational Health Risks of Asbestiform Fibers, National Research Council, Asbestiform Fibers: Nonoccupational Health Risks, National Academy Press, Washington, D.C., 1984; Malcolm Ross, “A Survey of Asbestos-Related Disease in Trades and Mining Occupations in Factory and Mining Communities as a Means of Predicting Health Risks of Nonoccupational Exposure to Fibrous Minerals,” American Society for Testing and Materials, Philadelphia, 1984; and Anthony Natale and Hoag Levins, Asbestos Removal & Control: An Insider’s Guide to the Business, Sourcefinders, Vorhees, N.J., 1984.
A version of this article appeared in the September 26, 1984 edition of Education Week as Long History of Miraculous, But Dangerous, Uses