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Asbestos
by Conal Ward
Physical Geology
Spring 2012
                  

  

                                                                                                                Asbestos 

                When somebody hears the word asbestos, they generally assume it is a nasty, dangerous mineral that should be avoided no matter what. However, of the six types of asbestos, the safest variety is the most favorable.  At a staggering 95% usage rate, the form chrysotile is the go-to candidate of asbestos (Wisconsin Department of Natural Resources). On the other hand, the less often used types should be avoided. Luckily, there are distinct features to tell the good kinds from the bad.

Photo courtesy of chrysotile.com

 

                Asbestos is a fibrous mineral that comes in many different flavors (Cahill).  There are two categories of asbestos that are used in industry today: amphibole and serpentine. Chrysotile, pictured above, is the only asbestos mineral in the serpentine group.  It is generally white and it is distinguishable by its curly fibers compared to that of the needle fibers found in the amphibole variety.  Chrysotile is more flexible than the other types as it can be woven into fabric. It is used in a wide variety of products such as: drywall, plaster, vinyl floors, adhesives, caulk, pipe insulation, and fireproofing to name a few (Wisconsin Department of Natural Resources). Despite its usefulness, the European Union has banned it as a potential health hazard (Ascc.gov.au).

The other five types of asbestos fall into the amphibole group.  Other than the needlelike trait that all amphibole types share, their color can help distinguish the actual variety.

Photo courtesy of arlengineering.com

Amosite has a brown color and is the second most likely type to be found in buildings.  It is found in fire retardants, insulation, and ceiling tiles.  

Photo courtesy of asbestosattorney.yolasite.com 

Crocidolite is blue and generally has soft, friable fibers. It is the most hazardous form of asbestos.  Amosite and crocidolite were formerly used in products until the early 1980s (Ascc.gov.au).

Photos courtesy of Didier Descouens 

Actinolite and Tremolite, pictured respectively, are often found together and make up a dark green color when iron is present.  

Photos courtesy of Didier Descouens 

The last type of asbestos is anthophyllite and its colors can range from gray to green, brown, and beige.  It is not always classified as asbestos; only when it has the distinct fibers.  The use of asbestos from the amphibole group was banned in much of the world in the mid-1980s.

How is asbestos exactly hazardous to one’s health? Simply working around it and inhaling it has been observed to cause four health disorders.  Pleural thickening occurs after heavy asbestos exposure.  The lining of the lung thickens and swells which can squeeze the lung itself. Asbestosis is formed by the stiffening of the lungs and has caused many miners their deaths.  Lung cancer has a higher chance in miners who also smoke, with the chance of developing cancer proportional to the amount they smoke. However, cancer caused by asbestos is rarely found in nonsmokers. Those working around chrysotile have the lowest recorded incidences of cancer.  Sometimes, about 30 years or later, a fatal tumor can develop which is called mesothelioma. Around 70-80% of mesothelioma cases are caused by exposure to asbestos.  A large 18% of all mortalities in crocidolite workers are caused by this disease (Weisstein).

From this data, there appears to be a formidable difference in damaging effects of asbestos depending on which category it is from.  In fact, "crocidolite-exposed workers have shown an appreciable lung burden of amphibole fibers.  In contrast, chrysotile has been found post-mortem in smaller amounts than expected in the lungs of asbestos workers" (Mossman, p. 296). "Data suggests that amphiboles are the major cause of mesothelioma in asbestos workers."  On the basis of medical studies, "amphiboles are more potent than chrysotile in the induction of fibrotic lung disease and associated lung cancer."  The reason for the difference in virulence is that "rod-like amphiboles appear to penetrate the peripheral lung more readily than chrysotile fibers, which are curly" (Mossman, p. 294-295).  Furthermore, according to the Stanton hypothesis, "fibers longer than 8 micrometers and less than 0.25 micrometers in diameter have the most marked carcinogenic potential."  This is a result of being a different shape, which implies that "chrysotile fibers, in comparison to amphibole fibers, are cleared more readily from human lungs."  As one can see, “Crocidolite asbestos is much more hazardous than chrysotile, anthophyllite, and amosite.  Mesothelioma deaths have been reported among the residents of these areas who are not employed in the mines or mills" (Ross, p. 314).  However, “mesothelioma is very rare where amosite is mined” (Ross, p. 315).

Of the six forms of asbestos, only four have been used to any significant degree in commerce.  These are amosite, crocidolite, anthophyllite, and chrysotile (Ross, p. 316). "Lung cancer can be caused by exposure to chrysotile, anthophyllite, amosite, and crocidolite asbestos; however, increased risk of this disease is probably found only in those who smoke cigarettes” (Ross, p. 317).  Asbestosis is also caused by heavy and prolonged exposure to all four forms of asbestos. Mesothelioma is caused principally by exposure to crocidolite asbestos. There is good evidence that anthophyllite and chrysotile asbestos do not cause any significant increase in mesothelioma mortality, even after heavy exposure for many years” (Ross, p. 317).

It can be assumed by this data that chrysotile is a virtually safe form of asbestos. The lungs don’t have a problem rapidly removing this form from the lungs due to its curly fibers and it should not be expected that miners suffer any measurable excess cancer (Ross, p. 318).  As stated previously, nearly 95% of asbestos used in the industry is the friendly chrysotile type—the runner up being amosite which does not cause nearly as many instances of mesothelioma compared to that of the crocidolite type.  When confronted with asbestos, to ensure safety, confirm that the fibers are wavy and white.  It is fairly easy to tell chrysotile apart from the amphibole group due to these unique features.

 References: 

Mossman, B. T. et al. "Asbestos: Scientific Development and Implications for Public Policy." Science 247, 294-301, 1990. 

Ross, M. "The Geologic Occurrences and Health Hazards of Amphibole and Serpentine Asbestos." In Reviews in Mineralogy, Volume 9A: Amphiboles and Other Hydrous Pyriboles--Mineralogy (Ed. D. R. Veblen). Washington, DC: Mineralogical Society of America, pp. 279-323, 1981. 

"Asbestos - History and Uses". Wisconsin Department of Natural Resources. August 31, 2007. 

"Asbestos". Weisstein, Eric. Weisstein's World of Chemistry. http://scienceworld.wolfram.com/chemistry/Asbestos.html 

“The Finer Fibers”. An autobiography on the tragedies of asbestos. Cahill, Phil. June 5, 2001. 

"Australian prohibition on use of chrysotile asbestos". Ascc.gov.au. 2009-11-09. Retrieved 2010-01-12. 

"Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) and establishing a European Chemicals Agency". Publications Office of the European Union. Retrieved 2010-07-05.