Presentation on theme: "Serpentine Family of Minerals Mg 6 [Si 4 O 10 ] (OH) 8 Chrysotileorthorhombic Antigoritemonoclinic Lizarditemonoclinic."— Presentation transcript:
Serpentine Family of Minerals Mg 6 [Si 4 O 10 ] (OH) 8 Chrysotileorthorhombic Antigoritemonoclinic Lizarditemonoclinic
Layer Structures Layer Structure – but with a mismatch problem Tridymite layer 5.0 8.7 Å Brucite layer 5.4 9.3 Å
Asbestos Asbestos is a commercial term: Any fibrous mineral utilized in an industrial process with a 3:1 length to width. This is a legal and commercial definition, not a mineralogical one.
Uses of Asbestos Uses: Fireproofing Re-enforcing concrete, tiles Brake linings Pot holders and ironing board pads Roofing materials. Artificial fireplaces and materials Patching and spackling compounds Wall and ceiling panels Pipe and duct insulation Building insulation
Asbestos Minerals Amphiboles: tremoliteCa 2 Mg 5 Si 8 O 22 (OH) 2 anthophyllite [Mg 2 Mg 5 ]
Asbestos Minerals Amphiboles: tremoliteCa 2 Mg 5 Si 8 O 22 (OH) 2 anthophyllite [Mg 2 Mg 5 ] riebeckite = ‘crocidolite’ Na 2 [(Fe,Mg) 3 Fe 3+ 2 ] grunerite = ‘amosite’ [Fe 2 Fe 2+ 5 ] Asbestos Mines Of South-africa ITE
Asbestos Minerals Amphiboles: tremoliteCa 2 Mg 5 Si 8 O 22 (OH) 2 anthophyllite [Mg 2 Mg 5 ] “ riebeckite = ‘crocidolite’ Na 2 [(Fe,Mg) 3 Fe 3+ 2 ] “ grunerite = ‘amosite’ [Fe 2 Fe 2+ 5 ] “ Asbestos Mines Of South-africa ITE Serpentine: chrysotileMg 6 Si 4 O 10 (OH) 8
Health concerns Exposure from natural and technological sources Fibers > 5 micrometers long remain in the lower respiratory tract. Fibers < 3 micrometers can penetrate cell membranes In time, Mg is lost from chrysotile to form silica structures Fe is gained around amphiboles, Mg is lost. Fibers become coated with hemosiderin, ferritin. => O 2 - radicals
Asbestos Diseases I 1)Asbestosis: Fibrosis of the lung tissue associated with heavy and prolonged exposure to all types of asbestos. It leads to breathing problems and heart failure. Pleural plaques: localized fibrous scars lining the space surrounding the lungs.
Asbestos Diseases II 2) Mesothelioma: rare, malignant tumors of the pleural, pericardial, or peritoneal linings. It has a strong association with crocidolite asbestos. Heavy exposure to chrysotile does not increase the risk. It becomes significant 20 years after the 1st exposure and continues to climb in rate even after 45 years. It is usually fatal [50% of 280 such deaths per year in US & Canada are linked to asbestos]. The problem is international. Stucco in Greece uses it.
Asbestos Diseases III 3)Bronchoginic carcinoma: lung cancer Increased death rate appears after 10 to 14 years from 1st exposure. Incidence peaks after 35 years. Strongly correlated with smoking. Non-smokers probably are not at risk. Associated with all types of asbestos.
Asbestos: Scientific Developments and Implications for Public Policy Mossman et al. (1990) Science 247, Cause Annual rate (deaths per million) Smoking 1200 Home accidents (1-14 yr olds) 60 Motor vehicle accident, pedestrian 32 Drowning (5-14 yr olds) 27 High school football 10 Aircraft accidents 6 Whooping cough vaccination 6 Asbestos exposure in schools Comparative Risks with asbestos
Health Effects of Chrysotile I Chrysotile: If one breaths 1 fiber /cc for 8 hours a day, over the course of 40 years (at 5 liters of air per breath) there is no health effect over a lifetime. At 20 fibers per cc, the effects are not statistically significant.
Health Effects of Chrysotile II Chrysotile: At Asbestos, Canada, there were no problems identified with ingestion of 10 9 fibers per liter of drinking water.
Health Effects of Asbestos: legal considerations Chrysotile: At the San Jose Dam, in California, the dump has serpentinite. It was designated a toxic dump by the EPA. Tremolite: Likewise, termolite particles in play sand is considered hazardous.
Libby, Montana Zonolite Mountain near Libby, MT, contains deposits of vermiculite, a widely used mineral material for insulation and soil conditioners. Vermiculite Mine Expanded vermiculite
Tremolite in Vermiculite Scanning electron micrograph of asbestiform amphibole from a former vermiculite mining site near Libby, Montana. Source: U.S. Geological Survey and U.S. Environmental Protection Agency, Region 8, Denver, Colorado.
Libby, Montana The EPA reported that 23 cases of mesothelioma, a rare type of asbestos-related cancer, apparently have their origins in Libby. That’s a rate of one case for every 1,000 residents, 100 times the national average.
Libby, Montana 18% of those x-rayed in Libby had abnormalities in the lining of their lungs (pleural abnormalities). The risk of pleural abnormalities increased with increasing age and increasing length of residence in the Libby area. The rate of pleural abnormalities found in groups within the United States that have no known asbestos exposures ranges from 0.2% to 2.3%.
Libby, Montana Asbestos in the vermiculite ore has been blamed for hundreds of illnesses and at least 200 deaths. The EPA has been cleaning up the mine site and other contaminated areas in the town since 1999, and Libby was declared a Superfund site October, 2002.