What is Asbestos?
Two different groups of the mineral known as asbestos can be found in almost every continent and in hundreds of countries. Within those two groups, amphibole and serpentine, are six mineral fibers that occur naturally and have all been termed "asbestos." All have been used commercially. The United States government regulates only the six forms mentioned, even though the United States Bureau of Mines recognizes over 100 forms of asbestos-like minerals. The lobbies on behalf of the stone and asbestos industries have effectively been able to stop government regulation of all but the six mentioned. Too small to be seen by the naked eye, the fibers of asbestos are able to separate and suspend in the air, making them a serious environmental threat. The Occupational Safety and Health Administration (OSHA) only considers fibers five micrometers in length, or three times the length of the diameter, a threat. Asbestos fibers are approximately 100 times thinner than human hairs.
All six of the asbestos minerals recognized by the U.S. government are molecules with oxygen and silicon properties, silicates, and they are as follows: Chrysotile
: Also called white asbestos. Less toxic than other forms, it is the variety currently most used and has a whitish, curly appearance. Although mined worldwide, most of the supply in the United States is imported from the former USSR, Africa and Canada. Crocidolite
: Believed to be the most toxic of all asbestos forms, this mineral is made up of straight fibers. It is mined in Australia and southern Africa, and is also known as blue asbestos or riebeckite. Amosite
: Named after the mines in Amosa, its name is an acronym for "Asbestos Mines of South Africa." These fibers are straight, and their structure is brittle. Known as brown asbestos, or cummingtonite-grunerite, it has excellent heat resistant properties and is used as protective insulation. Anthophyllite
: This asbestos has excellent chemical and heat-resistant properties. Containing several different iron forms, it appears white and is brittle. It has been widely used in chemical plants. Tremolite
: Found naturally in asbestiform and other minerals, tremolite has a chalky, white appearance in its raw form. Commercial and industrial talc contains this form of asbestos as its main ingredient. Actinolite
: This form of asbestos is used in home improvement and by construction companies. Its typical shape is long, with a flat structure that also appears prismatic. It does not boast a strong resistance to chemicals. The more complex structures of the amphibole group, which includes crocidolite, amosite, anthophyllite, tremolite and actinolite, are not used as frequently as the more simply-structured chrysotile asbestos in consumer goods. Furthermore, these forms are far more dangerous than chrysotile asbestos, which is softer and more flexible, because they can more easily penetrate bodily tissues and cause cancer. The three major health effects of asbestos exposure include asbestosis, lung cancer and mesothelioma. Duration and intensity of exposure likely increases the risk of developing one of these serious conditions.
- Alleman, James E. and Brooke T. Mossman. (July 1997) “Asbestos Revisited.” Retrieved April 19, 2011 from Scientific American.