Chrysotile
{{short description|Most commonly encountered form of asbestos}}
{{About|the form of asbestos|the types of gemstone|Chrysolite (disambiguation){{!}}Chrysolite}}
{{Infobox mineral
|boxbgcolor=#c0d1a2| name = Chrysotile
| category = Phyllosilicates
Kaolinite-serpentine group
| boxwidth =
| image = Chrysotile 1.jpg
| imagesize =
| caption =
| formula = Mg{{sub|3}}(Si{{sub|2}}O{{sub|5}})(OH){{sub|4}}
(ideal)
| molweight = 277.11 g/mol (ideal)
| strunz = 9.ED.15
| system = Monoclinic: clinochrysotile (most common)
Orthorhombic: orthochrysotile and parachrysotile (both rare)
| class = Clinochrysotile: prismatic (2/m)
Orthochrysotile and parachrysotile: pyramidal (mm2)
| symmetry = Clinochrysotile: C2/m
Orthochrysotile and parachrysotile: Ccm21
| colour = White to greyish green
| habit = Acicular
| twinning =
| cleavage =
| fracture = Fibrous
| tenacity =
| mohs = 2.5–3
| lustre = Silky
| polish =
| refractive = nα = 1.569, nγ = 1.570
| opticalprop = Biaxial (+)
| birefringence = 0.001 (max)
| dispersion = Relatively weak
|extinction=parallel| pleochroism =
| fluorescence=
| absorption =
| streak = White
| gravity =
| density = 2.53 g/ml
| melt ={{cvt|600–850|C}} (decomposes)
| fusibility = dehydrates at {{convert|550|–|750|C}}
| diagnostic =White to grayish green thin, flexible curved fiber
| solubility = Insoluble in water
Fibres degrade in dilute acid
| diaphaneity = Translucent
| other =
| references = [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Chrysotile Mineralienatlas][http://www.mindat.org/min-975.html Chrysotile on Mindat.org][http://webmineral.com/data/Chrysotile.shtml#.Vp2ADZo4HRY Chrysotile data on Webmineral]
}}
Chrysotile {{pronunciation needed}} or white asbestos is the most commonly encountered form of asbestos,{{cite book | publisher = U.S. Department of Health and Human Services | year = 2005 | chapter-url = https://ntp.niehs.nih.gov/ntp/roc/content/profiles/asbestos.pdf | chapter = Asbestos | title = Report on Carcinogens, Eleventh Edition }} accounting for approximately 95% of the asbestos in the United StatesOccupational Safety and Health Administration, U.S. Department of Labor (2007). [http://edocket.access.gpo.gov/cfr_2007/julqtr/pdf/29cfr1910.1001.pdf 29 C.F.R. 1910.1001]. Appendix J. and a similar proportion in other countries.Institut national de recherche sur la sécurité (1997). "[http://www.inrs.fr/inrs-pub/inrs01.nsf/IntranetObject-accesParReference/FT%20145/$File/ft145.pdf Amiante] {{Webarchive|url=https://web.archive.org/web/20080625162132/http://www.inrs.fr/inrs-pub/inrs01.nsf/IntranetObject-accesParReference/FT%20145/$File/ft145.pdf |date=2008-06-25 }}." Fiches toxicologiques. n° 167. (in French) It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group. Its idealized chemical formula is Mg{{sub|3}}(Si{{sub|2}}O{{sub|5}})(OH){{sub|4}}. The material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled.
Polytypes
Three polytypes of chrysotile are known.{{cite journal |url=http://canmin.geoscienceworld.org/cgi/content/abstract/13/3/227 |journal=The Canadian Mineralogist |volume=13 |year=1975 |pages=227–243 |title=A reappraisal of the structures of the serpentine minerals |first1=F. J. |last1=Wicks |first2=E. J. W. |last2=Whittaker |issue=3}} These are very difficult to distinguish in hand specimens, and polarized light microscopy must normally be used. Some older publications refer to chrysotile as a group of minerals—the three polytypes listed below, and sometimes pecoraite as well—but the 2006 recommendations of the International Mineralogical Association prefer to treat it as a single mineral with a certain variation in its naturally occurring forms.{{cite journal |last1=Burke |first1=Ernst A. J. |title=A Mass Discreditation of GQN Minerals |journal=The Canadian Mineralogist |volume=44 |issue=6 |pages=1557–60 |year=2006 |doi=10.2113/gscanmin.44.6.1557 |bibcode=2006CaMin..44.1557B |url=http://pubsites.uws.edu.au/ima-cnmnc/GQNminerals.pdf |access-date=2010-11-30 |archive-url=https://web.archive.org/web/20120326091801/http://pubsites.uws.edu.au/ima-cnmnc/GQNminerals.pdf |archive-date=2012-03-26 |url-status=dead }}
| class="wikitable" |
| Name
! mindat.org reference ! Unit cell parameters ! Crystal structure reference |
|---|
| Clinochrysotile
| Złoty Stok*, Lower Silesia, Poland | | a = 5.3 Å; b = 9.19 Å; c = 14.63 Å; β = 93° |
| Orthochrysotile
| Kadapa* district, Andhra Pradesh, India | | a = 5.34 Å; b = 9.24 Å; c = 14.2 Å |
| Parachrysotile
| uncertain | | a = 5.3 Å; b = 9.24 Å; c = 14.71 Å |
| colspan=6 | Source: mindat.org. *Złoty Stok and Kadapa have formerly been known as Reichenstein and Cuddapah respectively, and these names may appear in some publications. |
Clinochrysotile is the most common of the three forms, found notably at Val-des-Sources, Quebec, Canada. Its two measurable refractive indices tend to be lower than those of the other two forms.In principle, all polytypes of chrysotile should have three independent refractive indices: in practice, two of the three are so close as to be indistinguishable by experimental measurement. The orthorhombic paratypes may be distinguished by the fact that, for orthochrysotile, the higher of the two observable refractive indices is measured parallel to the long axis of the fibres (as for clinochrysotile); whereas for parachrysotile the higher refractive index is measured perpendicular to the long axis of the fibres.{{cn|date=January 2024}}
Physical properties
File:Chrysotile SEM photo.jpg photo of chrysotile]]
Bulk chrysotile has a hardness similar to a human fingernail and is easily crumbled to fibrous strands composed of smaller bundles of fibrils. Naturally-occurring fibre bundles range in length from several millimetres to more than ten centimetres, although industrially-processed chrysotile usually has shorter fibre bundles. The diameter of the fibre bundles is 0.1–1 μm, and the individual fibrils are even finer, 0.02–0.03 μm, each fibre bundle containing tens or hundreds of fibrils.
Chrysotile fibres have considerable tensile strength, and may be spun into thread and woven into cloth. They are also resistant to heat and are excellent thermal, electrical and acoustic insulators.
Chemical properties
The idealized chemical formula of chrysotile is Mg{{sub|3}}(Si{{sub|2}}O{{sub|5}})(OH){{sub|4}}, although some of the magnesium ions may be replaced by iron or other cations. Substitution of the hydroxide ions for fluoride, oxide or chloride is also known, but rarer. A related, but much rarer, mineral is pecoraite, in which all the magnesium cations of chrysotile are substituted by nickel cations.{{cn|date=January 2024}}
Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland cement), but when the fibres are attacked by acids, the magnesium ions are selectively dissolved, leaving a silica skeleton. It is thermally stable up to around {{convert|550|C}}, at which temperature it starts to dehydrate. Dehydration is complete at about {{convert|750|C}}, with the final products being forsterite (magnesium silicate), silica and water.
The global mass balance reaction of the chrysotile dehydration can be written as follows:
:
The chrysotile (serpentine) dehydration reaction corresponds to the reverse of the forsterite (Mg-olivine) hydrolysis in the presence of dissolved silica (silicic acid).
Applications
Previously, in the 1990s it was used in asbestos-cement products (like pipes and sheets).{{Cite journal |last=Pigg |first=B. J. |date=August 1994 |title=The uses of chrysotile |url=https://pubmed.ncbi.nlm.nih.gov/7978966/ |journal=The Annals of Occupational Hygiene |volume=38 |issue=4 |pages=453–458, 408 |doi=10.1093/annhyg/38.4.453 |issn=0003-4878 |pmid=7978966}}
Magnesium sulfate (MgSO4) may be produced by treating chrysotile with sulfuric acid (H2SO4).{{Cite journal |last1=Bedelova |first1=Zh. D. |last2=Tabylganova |first2=A. N |last3=Homyakov |first3=A. P. |last4=Dagubaeva |first4=A. T. |date=2017 |title=DEVELOPING THE TECHNOLOGY OF WASTE SULFURIC ACID LEACHING OF CHRYSOTILE ASBESTOS PRODUCTION |url=https://mtmcongress.com/proceedngs/2017/Summer/4/13.DEVELOPING%20THE%20TECHNOLOGY%20OF%20WASTE%20SULFURIC%20ACID%20LEACHING%20OF%20CHRYSOTILE%20ASBESTOS%20PRODUCTION.pdf |journal=Machines. Technologies. Materials. |location=National center on complex processing of mineral raw materials of the Republic of Kazakhstan |volume=4 |pages=288–290 |issn=1313-0226 |eissn=1314-507X}}
Safety concerns
File:White asbestos (Chrysotile).jpg
Chrysotile has been included with other forms of asbestos in being classified as a human carcinogen by the International Agency for Research on Cancer (IARC)International Agency for Research on Cancer (1998). "Asbestos." However, the study states " In some of these case reports and in other studies, asbestos fibres have been identified in the lung. Amphibole fibres have usually predominated, but in a few cases mainly or only chrysotile fibres were found." [http://monographs.iarc.fr/ENG/Monographs/suppl7/suppl7.pdf IARC Monographs on Evaluating the Carcinogenic Risks to Humans. Supplement 7] {{webarchive|url=https://web.archive.org/web/20080306134819/http://monographs.iarc.fr/ENG/Monographs/suppl7/suppl7.pdf |date=2008-03-06 }}. and by the U.S. Department of Health and Human Services. These state that "Asbestos exposure is associated with parenchymal asbestosis, asbestos-related pleural abnormalities, peritoneal mesothelioma, and lung cancer, and it may be associated with cancer at some extra-thoracic sites".Agency for Toxic Substances and Disease Registry (ATDSR), U.S. Department of Health and Human Services (2007). "[http://www.atsdr.cdc.gov/csem/asbestos/cover2.html Asbestos Toxicity] {{webarchive |url=https://web.archive.org/web/20110606012916/http://www.atsdr.cdc.gov/csem/asbestos/cover2.html |date=June 6, 2011 }}." Case Studies in Environmental Medicine. In other scientific publications, epidemiologists have published peer-reviewed scientific papers establishing that chrysotile is the main cause of pleural mesothelioma.{{cite web |url=http://asrg.berkeley.edu/96SmithChrysotile.pdf |title=Archived copy |access-date=2011-10-03 |url-status=dead |archive-url=https://web.archive.org/web/20100609230055/http://asrg.berkeley.edu/96SmithChrysotile.pdf |archive-date=2010-06-09 }} See e.g., Smith, Allen "Chrysotile is the main cause of pleural mesothelioma", Amer.J.Indus.Med., Vol. 32, pp. 252 to 266 (1996)[http://www.sjweh.fi/show_abstract.php?abstract_id=226] Tossavainen A, "Asbestos, asbestosis, and cancer: the Helsinki criteria for diagnosis and attribution" Scand J Work Environ Health 1997;23(4):311–316 (stating that all types of malignant mesothelioma can be induced by asbestos, with the amphiboles showing greater carcinogenic potency than chrysotile){{cite journal | doi = 10.1289/ehp.1002446 | volume=118 | title=Chrysotile Asbestos and Mesothelioma | year=2010 | journal=Environmental Health Perspectives | page=a282 | last1 = Lemen | first1 = Richard A.| issue=7 | pmid=20601327 | pmc=2920924 }}
Chrysotile has been recommended for inclusion in the Rotterdam Convention on Prior Informed Consent,[http://www.pic.int/TheConvention/Chemicals/Recommendedforlisting/Chrysotileasbestos/tabid/1186/language/en-US/Default.aspx Rotterdam Convention: Chrysotile] an international treaty that restricts the global trade in hazardous materials. If listed, exports of chrysotile would only be permitted to countries that explicitly consent to imports. Canada, a major producer of the mineral, has been harshly criticized by the Canadian Medical Association{{cite journal |first1=Amir |last1=Attaran |first2=David R. |last2=Boyd |first3=Matthew B. |last3=Stanbrook |title=Asbestos mortality: a Canadian export |journal=CMAJ |volume=179 |issue=9 |pages=871–2 |date=October 2008 |pmid=18936444 |pmc=2565724 |doi=10.1503/cmaj.081500}}{{cite journal |last=Collier |first=Roger |date=December 2008 |title=Health advocates assail Canada's asbestos stance |volume=179 |issue=12 |pmid=19047602 |doi=10.1503/cmaj.081806 |pages=1257 |pmc=2585122 |journal=CMAJ}} for its opposition to including chrysotile in the convention.{{cite news|url=https://www.theglobeandmail.com/servlet/Page/document/v5/content/subscribe?user_URL=https://www.theglobeandmail.com%2Fservlet%2Fstory%2FLAC.20080910.ASBESTOS10%2FTPStory%2FNational&ord=87597914&brand=theglobeandmail&force_login=true|title=Canada still blocking action on asbestos|last=MITTELSTAEDT|first=MARTIN|date=September 10, 2008|access-date=2008-10-01|location=Toronto|work=The Globe and Mail}}
According to EU Regulation 1907/2006 (REACH) the marketing and use of chrysotile, and of products containing chrysotile, are prohibited.[http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2007:136:0003:0280:DE:PDF Amtsblatt der Europäischen Union, L 396 from 30-12-2006] (PDF 1,8 MB; S. 129)
As of March 2024, the U.S. Environmental Protection Agency finalized regulations banning imports of chrysotile asbestos (effective immediately) due to its link to lung cancer and mesothelioma. However, the new rules can allow up to a dozen years to phase out the use of chrysotile asbestos in some manufacturing facilities.[https://www.nytimes.com/2024/03/18/climate/biden-administration-bans-asbestos.html U.S. Bans the Last Type of Asbestos Still in Use] by Coral Davenport in the New York Times, Mar. 18, 2024. The long phase-out period was a result of a strong lobby by Olin Corporation, a major chemical manufacturer, as well as trade groups like the U.S. Chamber of Commerce and the American Chemistry Council. Chrysotile asbestos is now banned in more than 50 other countries.
Critics of safety regulations
=1990s: Canada-European dispute GATT dispute=
In May 1998, Canada requested consultations before the WTO and the European Commission concerning France's 1996 prohibition of the importation and sale of all forms of asbestos. Canada said that the French measures contravened provisions of the Agreements on Sanitary and Phytosanitary Measures and on Technical Barriers to Trade, and the GATT 1994. The EC claimed that safer substitute materials existed to take the place of asbestos. It stressed that the French measures were not discriminatory under the terms of international trade treaties, and were fully justified for public health reasons. The EC further claimed that in the July consultations, it had tried to convince Canada that the measures were justified, and that just as Canada broke off consultations, it (the EC) was in the process of submitting substantial scientific data in favour of the asbestos ban.[http://www.wto.org/english/news_e/news98_e/wdsboct.htm EC measures affecting asbestos products]. World Trade Organization News. 29 October 1998
=2000s: Canadian exports face mounting global criticism=
In the late 1990s and early 2000s, the Government of Canada continued to claim that chrysotile was much less dangerous than other types of asbestos.{{cite news |title=Canada diminished by asbestos hypocrisy |first=Tim |last=Harper |date=3 July 2011 |work=The Chronicle Herald |url=http://asbestosexposuresymptoms.us/2011/07/03/canada-diminished-by-asbestos-hypocrisy/ |access-date=28 September 2012 |archive-url=https://web.archive.org/web/20121120174559/http://asbestosexposuresymptoms.us/2011/07/03/canada-diminished-by-asbestos-hypocrisy/ |archive-date=20 November 2012 |url-status=dead }} Chrysotile continued to be used in new construction across Canada, in ways that are very similar to those for which chrysotile was exported.{{cite news |title=What Exactly Is Asbestos?
|first=Guy |last=Versailles |date=8 July 2015 |url=http://southbaymitigation.com/what-exactly-is-asbestos/|work=South Bay Mitigation}} Similarly, Natural Resources Canada once stated that chrysotile, one of the fibres that make up asbestos, was not as dangerous as once thought. According to a fact sheet from 2003, "current knowledge and modern technology can successfully control the potential for health and environmental harm posed by chrysotile".{{cite web |url=http://www.nrcan.gc.ca/mms/pdf/chry_e.pdf |title=Chrysolite Asbestos Fact Sheet |publisher=Natural Resources Canada |date=3 February 2009 |access-date=2010-01-12 |url-status=dead |archive-url=https://web.archive.org/web/20070927060339/http://www.nrcan.gc.ca/mms/pdf/chry_e.pdf |archive-date=27 September 2007 }} The Chrysotile Institute, an association partially funded by the Canadian government, also prominently asserted that the use of chrysotile did not pose an environmental problem and the inherent risks in its use were limited to the workplace.{{cite news |title=NDP MP Martin's one-man battle to ban asbestos mining in Canada gains traction |first=Bea |last=Vongdouangchanh |date=5 July 2011 |work=The Hill Times |url=http://www.hilltimes.com/news/2011/07/05/ndp-mp-martins-one-man-battle-to-ban-asbestos-mining-in-canada-gains-traction/27900}}
However, under increasing criticism by environmental groups, in May, 2012, the Canadian government stopped funding the Chrysotile Institute.{{Cite web |url=https://montrealgazette.com/health/asbestos+advocacy+group+shuts+doors/6537818/story.html |title=Asbestos Advocacy Group Shuts Its Doors, Montreal Gazette |access-date=2018-10-04 |archive-date=2012-07-10 |archive-url=https://web.archive.org/web/20120710050845/http://www.montrealgazette.com/health/asbestos+advocacy+group+shuts+doors/6537818/story.html |url-status=dead }}{{Cite web |url=http://www.cancer.ca/Canada-wide/About%20us/Media%20centre/CW-Media%20releases/CW-2011/Chrysotile%20Institute%20Funding.aspx?sc_lang=en |title=Canadian Cancer Society Disappointed with Proposed Federal Government Funding for Chrysotile Institute, 3 March 2012 |access-date=28 September 2012 |archive-date=28 June 2011 |archive-url=https://web.archive.org/web/20110628010332/http://www.cancer.ca/Canada-wide/About%20us/Media%20centre/CW-Media%20releases/CW-2011/Chrysotile%20Institute%20Funding.aspx?sc_lang=EN |url-status=dead }} As a result, the Chrysotile Institute has now closed.[http://www.themadskeptic.com/ R.I.P. Chrysotile Institute, The Mad Scientist Blog]>[https://vancouversun.com/health/asbestos+advocacy+group+shuts+doors/6537818/story.html Asbestos Advocacy Group Shuts Its Doors, Vancouver Sun, 29 April 2012]{{Dead link|date=July 2020 |bot=InternetArchiveBot |fix-attempted=yes }}{{Cite web |url=http://www.sierraclub.ca/en/trade-and-environment/publications/minister-flaherty-stop-funding-chrysotile-institute |title="Minister Flaherty: Stop Funding The Chrysotile Institute", 2 Feb. 2011 |access-date=2012-09-28 |archive-date=2019-04-04 |archive-url=https://web.archive.org/web/20190404044352/https://www.sierraclub.ca/en/trade-and-environment/publications/minister-flaherty-stop-funding-chrysotile-institute |url-status=dead }}
The Canadian government continues to draw both domestic and international criticism for its stance on chrysotile, most recently in international meetings about the Rotterdam Convention hearings regarding chrysotile. The CFMEU pointed out that most exports go to developing countries. Canada has pressured countries, including Chile, and other UN member states to avoid chrysotile bans.[http://www.cfmeu-construction-nsw.com.au/tacanadianasbestos.htm Stop Canada's Export Of Asbestos] CFMEU {{webarchive |url=https://web.archive.org/web/20100710154834/http://www.cfmeu-construction-nsw.com.au/tacanadianasbestos.htm |date=July 10, 2010 }}
In September 2012, governments in Quebec and Canada ended official support for Canada's last asbestos mine in Asbestos, Quebec,{{cite news |title=Canada axes support for asbestos mining |date=17 Oct 2012 |author=Daniel Lak |work=Al Jazeera |url=http://www.aljazeera.com/indepth/features/2012/10/201210167129546890.html}} now renamed as Val-des-Sources.
See also
- Erionite
- {{annotated link|Serpentinite#Serpentinite reactions|Serpentinite reactions}}
- Antigorite
References
{{Reflist}}
External links
- [http://www.chrysotile.com/ The Chrysotile Institute]
- {{ICSC|0014|00}}
- [http://ibe.sagepub.com/cgi/content/abstract/14/1/83 "Asbestos-containing Floor Tile and Mastic Abatement: Is there Enough Exposure to Cause Asbestos-related Disease?"]
- Deer William Alexander, Howie Robert Andrew, Zussman Jack, An introduction to the rock-forming minerals, {{ISBN|0-582-30094-0}}, OCLC 183009096 pp. 344–352, 1992
- Ledoux, RL (ed), Short course in mineralogical techniques of asbestos determination, Mineralogical Association of Canada, pp. 35–73, 185, 1979.
- http://www.microlabgallery.com/ChrysotileFile.aspx Photomicrographs of parachrysotile and clinochrysotile
- Nolan, RP, Langer AM, Ross M, Wicks FJ, Martin RF (eds), "The health effects of chrysotile asbestos", The Canadian Mineralogist, Special Publication 5, 2001.
{{Phyllosilicates}}
Category:IARC Group 1 carcinogens
Category:Minerals in space group 12