|
Asbestos (Greek a-, "not"; sbestos, "extinguishable") is a group of fibrous metamorphic minerals. The name is derived for its historical use in lamp wicks. It was also used in fabrics such as Egyptian burial cloths and Charlemagne's tablecloth, which, according to legend, he threw in a fire to clean. The fibers are typically mixed with cement or woven into fabric or mats. It is used in buildings for its flame-retardant and insulating properties, its tensile strength, flexibility, and resistance to chemicals. Asbestos is now known to be carcinogenic and is banned in many countries.
Most asbestos fibers are invisible to the unaided human eye because their size is about 3.0-20.0 µm.
Confusingly, the Modern Greek word asbestos means quicklime.
Types of asbestos
- Chrysotile, or white asbestos, is obtained from Canadian serpentine rocks. It is less friable (and therefore less likely to be inhaled) than the other types and is the type most often used industrially. Chrysotile should not be confused with chrysolite, a synonym of olivine.
- Amosite, or brown asbestos, is an amphibole from Africa.
- Crocidolite, or blue asbestos, is an amphibole from Africa and Australia. It is the fibrous form of riebeckite. Blue asbestos is commonly thought of as the most dangerous type of asbestos (see above and below).
Notes: Serpentine rocks are those with curled fibres. Amphiboles have straight, needle-like fibres.
The amphiboles, in their fibrous form, are friable and therefore the most carcinogenic, although they also exist in safer non-fibrous forms.
Other asbestos minerals, such as tremolite, actinolite and anthophyllite are not used industrially but occur in traces.
 Structures containing asbestos are marked Asbestosis and cancer
Strong concerns about the health hazards associated with asbestos had been described many times over the years. As early as 1898 the Chief Inspector of Factories of the United Kingdom reported to the Parliament in his Annual Report about the "evil effects of asbestos dust". He reported the "sharp, glass like nature of the particles" when allowed to remain in the air in any quantity, "have been found to be injurious, as might have been expected" (Report of the Select Committee 1994). In 1906 a British Parliamentary Commission confirmed the first cases of asbestos deaths in factories in Britain and recommended better ventilation and other safety measures. In 1918 an American insurance company produced a study showing premature deaths in the asbestos industry in the United States and in 1926 the Massachusetts Industrial Accidents Board processed the first successful compensation claim by a sick asbestos worker.
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.
Asbestos is carcinogenic. In the United States alone, it is estimated that ten thousand people die each year of asbestos-related diseases, such as mesothelioma, asbestosis, lung cancer, and gastrointestinal cancer. Asbestos has a synergistic effect with tobacco smoking in the causation of lung cancer.
Litigation
In the United States, asbestos was one of the first hazardous air pollutants regulated under Section 112 of the Clean Air Act of 1970.
Lawsuits claiming asbestos caused diseases are a gigantic part of the total amount of lawsuits pending in the United States courts. Asbestos liability is by far the largest issue facing the global insurance industry today, with the industry protesting because many are suing because they have been exposed but have not as yet contracted a disease.
In mid-2004, a huge public outcry across Australia followed revelations at a New South Wales government-sanctioned inquiry into the company James Hardie's handling of its asbestos injury liabilities. See that article for details.
See also
Other asbestos-related diseases
- asbestos warts caused when the sharp fibres lodge in the skin and are overgrown causing benign callous-like growths.
- pleural plaques discrete fibrous or partially calcified thickened area which can be seen on X-rays of individuals exposed to asbestos. They do not become malignant nor normally cause any lung impairment.
- diffuse pleural thickening similar to above and can sometimes be associated with asbestosis. Usually no symptoms shown but if extensive can cause lung impairment.
External links
|
