A material’s refractory characteristics are indicative of its ability to retain its tensile strength at extremely high temperatures. These are the materials that are included in the manufacture of such items as crucibles, blast furnaces, kilns and commercial incinerators. The minimum requirement is generally recognized as the ability to remain rigid and strong at temperatures in excess of 2000 degrees Fahrenheit (1100 degrees C).
Asbestos was long recognized as such a material. It was used by the ancient Romans for “everlasting” lamp wicks; according to one legend, Charlemagne, emperor over much of modern-day France and northwestern Europe some 1200 years ago had a tablecloth made from asbestos fabric that he was known to clean by tossing it in the fireplace.
With the advent of the Industrial Age and the use of steam and internal combustion engines, asbestos was seen as increasingly useful; ultimately, asbestos fabric was used in almost every part of industry, and from 1920 onward was a common construction material as well.
The bottom line is that asbestos is found wherever heat and fire resistant surfaces are necessary – meaning that refractory workers are at an elevated risk for asbestos-related diseases such as asbestosis and mesothelioma.
The Nature of Asbestos
The reason for asbestos’ fire, heat and chemical resistant properties are not as mysterious as the ancients believed. Science has understood for some time that asbestos fibers are really a form of stone; as such, it shares many of the characteristics of the rocks among which it is typically found. Unlike most rock however, asbestos is quite flexible, enabling it to be woven into fabric and used as insulation, among other things.
Asbestos fibers are categorized as either serpentine or amphiboles.
Most of the asbestos used in construction materials in the U.S. was a king of serpentine known as chrysotile. It is also called “white asbestos” because of its white or light-gray color. Chrysotile fibers are softer and curl-shaped under a microscope, they look like tiny springs.
Some sources consider chrysotile a “safe” form of asbestos. This view has long been disproved by medical research, primarily the 1996 study conducted by the Department of Pathology at the Mount Sinai Hospital School of Medicine. Another study conducted in Louisiana in 1987 concluded that at best, chrysotile fibers work more slowly, but nonetheless poses a substantial risk of developing into asbestos cancer or other related diseases.
Amphibole asbestos fibers resemble microscopic needles under magnification. They are quite rigid, and strongly indicated in the development of malignant mesothelioma. Amphibole fibers are found primarily in amosite, or “brown asbestos,” and crocidolite, or “blue asbestos.” Amosite is especially resistant to acids and corrosive chemicals, and thus was found in many chemical plants. Crocidolite fibers are the strongest of all asbestos fibers; they are less heat resistant, but stand up to caustics quite effectively. This type of asbestos was commonly used in thermal insulation up until 1950 and was an ingredient in sprayed-on insulation until it was banned in most countries in the 1980s. It is considered the most deadly form of asbestos.
Asbestosis is the most common asbestos-related disease resulting from the extended inhalation of asbestos fibers. It is the result of the build-up of scar tissue caused by the irritation of lung tissue. This build-up reduces the lungs’ oxygen capacity.
Mesothelioma is a rare form of cancer that attacks the outer, or pleural lining of the lungs in its most common form, pleural mesothelioma. (Other, considerably rarer forms of mesothelioma can affect other organs, such as the stomach or the heart) Medical research indicates that amphibole fibers (which are often a contaminant of, and found with, chrysotile fibers) actually burrow through lung tissue, emerging into the outside pleural lining. During this process, it somehow alters the DNA of healthy cells, causing them to mutate into cancer cells.
This sheet-like tumor spreads across the surface of the lungs, restricting their ability to expand, essentially asphyxiating the victim.