Asbestos
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“Asbestos” (a misuse of "quicklime" from ancient Greek: a-, "not" and -sbestos, "extinguishable") describes any of a group of minerals that can be fibrous, many of which are metamorphic rock. Asbestos occurs naturally in many forms. The resistance of asbestos to fire has long been exploited for many purposes. The name comes from its historical use in lamp wicks. Asbestos was also used in fabrics such as burial shrouds and tablecloths.
Manufacturers often mix asbestos fibers are with cement or weave it into fabric or mats. Asbestos is used in brake shoes and gaskets, and in the past was used on electric oven and hotplate wiring as electrical insulation at high temperatures. It was also used in buildings for its flame-retardant and insulating properties, tensile strength, flexibility, and resistance to chemicals.
The inhalation of some kinds of asbestos fibers, however, can cause a number of serious illnesses, including cancer. Many countries have banned the use of many forms of asbestos.
Kinds of asbestos
- White asbestos
- chrysotile, is obtained from serpentine rocks. Chrysotile is the type most often used industrially in the United States. There is evidence that this type of asbestos is harmful, although not perhaps as harmful as other forms (refer to UK Health & Safety Commission report Asbestos: Effects on health of exposure to asbestos, 1985).
- Brown asbestos
- amosite, is a trade name for the amphibole known as Grunerite, from Africa, named as an acronym from Asbestos Mines of South Africa.
- Blue asbestos
- riebeckite, also known under the variety name of crocidolite, is an amphibole from Africa and Australia. It is the fibrous form of the amphibole riebeckite. Blue asbestos is commonly thought of as the most dangerous type of asbestos.
In 1989, In the United States, the Environmental Protection Agency (EPA) passed the Asbestos Ban and Phase Out Rule which was subsequently overturned in the case of Corrosion Proof Fittings v. U.S. Environmental Protection Agency, 1991. This ruling leaves many consumer products that can still legally contain trace amounts of asbestos. For a clarification of products which legally contain asbestos visit the EPA's clarification statement: [1]
Uses
Asbestos linings were once used in automobile brake pads and shoes. Since the mid-1990s, a majority of brake linings, new or replacement, have been manufactured with Kevlar linings (the same material used in bulletproof vests).
Serpentine group
“Chrysotile” is the form of asbestos from the serpentine group that has been used commercially.
In the United States, chrysotile is the most commonly used type of asbestos. Chrysotile is often present in many materials, including:
- sheetrock taping
- mud and texture coats
- vinyl floor tiles, sheeting, adhesives and ceiling tiles
- plasters and stuccos
- roofing tars, felts, siding, and shingles
- transite panels, siding, countertops, and pipes
- acoustical ceilings
- fireproofing
- putty
- caulk
- gaskets
- brake pads and shoes
- clutch plates
- stage curtains
- fire blankets
Amphibole group
Amosite and crocidolite were used in many products until the early 1980s. The use of all types of asbestos in the amphibole group was banned in the mid-1980s. These products were mainly:
- Low density insulation board and ceiling tiles
- asbestos-cement sheets and pipes for construction, casing for water and electrical/telecommunication services
- thermal and chemical insulation
Asbestos Mining
Typical asbestos mining in the United States has consisted of open pit extraction followed by milling. Peak production of asbestos in the United States was over 299 million pounds/year in the late 1960s and early 1970s. Production decreased to 112 million pounds in 1987, 37 million pounds in 1989, 30 million pounds in 1993, 15.4 million pounds in 1997, and 13.2 million pounds in 1998 and 1999. (Heritage Research)
Open-pit mining, or “opencast mining”, refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow pit. Open-pit mines are used when deposits of commercially useful minerals or rock are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling.
Open-pit mines that produce building materials such as asbestos are commonly referred to as “quarries”. Open-pit mines are typically enlarged until the mineral resource is exhausted. When this occurs, the exhausted mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is usually required to keep the mine pit from becoming a lake.
Extraction
Open cut mines are dug on benches, which describe horizontal levels of the mine. These benches are usually on 3 meter or 6 meter levels, depending on the size of the machinery being used. Most walls of the pit are generally dug on an angle less than vertical, to prevent and minimize damage and danger from falling rocks. The walls are stepped. In some instances additional ground support is required and rock bolts, cable bolts and shotcrete are used. De-watering bores may be used to relieve water pressure by drilling horizontally into the wall, which is often enough to cause failures in the wall by itself.
A haul road is situated at the side of the pit, forming a ramp up which trucks can drive, carrying the asbestos and waste rock. Waste rock is piled up at the surface near the edge of the open cut. This is known as the waste dump. The waste dump is also tiered and stepped, to minimize erosion.
Steps in the mining process
- Prospecting to locate ore
- Exploration to find and then define the extent and value of ore where it is located ("ore body")
- Conduct resource estimate to mathematically estimate the extent and grade of the deposit
- Conduct mine planning to evaluate the economically recoverable portion of the deposit (and including reclamation planning)
- Conduct a feasibility study to evaluate the total project and make a decision as whether to develop or walk away from a proposed mine project. This includes a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation.
- Development to create access to an ore body
- Exploitation to extract ore on a large scale
- Land rehabilitation to make land where a mine had been suitable for future use
Environmental impact
Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of groundwater by chemicals from the mining process and products.
Modern mining companies in many countries are required to follow strict environmental and rehabilitation codes, ensuring the area mined is returned to close to its original state, or an even better environmental state than before mining took place. In some countries with pristine environments, this is impossible despite the best intentions. Past mining methods have had, and methods used in countries with lax environmental regulations can continue to have, devastating environmental and public health effects.
Mining can have adverse effect on surrounding surface and ground water if protection measures are not exercised. The result can be unnaturally high concentrations of some chemical elements over a significantly large area of surface or subsurface. In well-regulated mines hydrologists and geologists take careful measures to mitigate any type of water contamination that could be caused by mines. In modern American mining, operations must, under federal and state law, meet standards for protecting surface and ground waters from contamination, including acid mine drainage (AMD). The five principal technologies used to control water flow at mine sites are: diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems, and subsurface barriers. In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants.
Rehabilitation
After mining finishes, the mine area must undergo rehabilitation. Waste dumps are contoured to flatten them out, to further stabilize them. If the ore contains sulfides it is usually covered with a layer of clay to prevent access of rain and oxygen from the air, which can oxidize the sulfides to produce sulfuric acid. This is then generally covered with soil, and vegetation is planted to help consolidate the material. Eventually this layer will erode, but it is generally hoped that the rate of leaching or acid will be slowed by the cover such that the environment can handle the load of acid and associated heavy metals. There are no long term studies on the success of these covers due to the relatively short time in which large scale open pit mining has existed. It may take hundreds to thousands of years for some waste dumps to become "acid neutral" and stop leaching to the environment. The dumps are usually fenced off to prevent livestock denuding them of vegetation. The open pit is then surrounded with a fence to prevent access, and it generally eventually fills up with ground water. In arid areas it may not fill due to the deep groundwater levels.
To ensure completion of rehabilitation the Office of Surface Mining requires that mining companies post a bond to be held in escrow until productivity of reclaimed land has been convincingly demonstrated. Since 1978 the mining industry has reclaimed more than 2 million acres (8,000 km²) of land. This reclaimed land has renewed vegetation and wildlife in previous mining lands and can even be used for farming and ranching.
Mining Industry
While exploration and mining can sometimes be conducted by individual entrepreneurs or small business, most modern-day mines are large enterprises requiring large amounts of capital to establish. Consequently, the mining sector of the industry is dominated by large, often multinational, mostly publicly-listed companies.
However, what is referred to as the “mining industry” is actually two sectors, one specializing in exploration for new resources, the other specializing in mining those resources. The exploration sector is typically made up of individuals and small mineral resource companies dependant on public investment.
Miners
There are many different jobs, direct and indirect, in the mining industry, ranging from engineers and lab technicians to geologists and environmental specialists. Beyond employment directly linked to mine-site activity, the modern mining industry also employs many other professionals, including accountants, lawyers, sales representatives, public relations specialists, not to mention thousands of men and women involved who manufacture the machines and equipment necessary to mine minerals.
Employment in the mining industry offers highly competitive wages and benefits, especially in rural or remote areas. According to the Bureau of Labor Statistics (BLS), wages for coal miners are 30% higher than the wage earned by the average American. Employees possessing at least a bachelor's degree in mining or geological engineering can earn a median pay of over $80,000 annually.
The US Bureau of Labor Statistics estimates that 675,000 are employed in the natural resources and mining sector.
The mining industry has an experienced but aging workforce with a mean average age of 50 years and median of 46 years. Indeed, while the industry will require new employees to meet future demand, the largest dilemma currently facing mine operators is finding employees to fill vacancies left by a generation of miners, mine engineers, senior managers, technical experts and others who are set to retire between 2005 and 2015. However, the industry is struggling to meet that demand due to current low enrollment levels in mining education programs at American colleges and universities.
Mining is regulated under a comprehensive federal safety law (Federal Mine Safety and Health Act) that is administered by the Department of Labor's Mine Safety and Health Administration (MSHA). Currently under federal law, and enforced by MSHA each U.S. miner must have an approved worker training program in health and safety issues, including at least 40 hours of basic safety training for new underground miners with no experience; 24 hours for new miners at surface mines with no experience; plus eight hours of annual refresher training for all miners.
Mine Planning Software
Once the decision has been taken to proceed with a mine, companies need to create detailed designs that take into account the topography, infrastructure, and physical parameters of the ore-body. One of the most dramatic changes in the mining industry has been the role that sophisticated three-dimensional mine planning software packages have had. Manual design and planning methods can be painstakingly slow and there are many obstacles that are unique to a given mine. Computer technology makes relatively simple tasks - like rendering graphic images of drill holes - easier for surveyors, geologists, mine planners, mining engineers and other technical staff to manipulate and visualize data. In recent years the range of integrated mine planning tools have meant that massively complex models can be built to optimize the extraction and processing of mineral resources.
Milling
The milling of asbestos involves using milling machines to grind raw asbestos into a fine, fibrous material that manufacturers can then add to their products. Mill workers are often dangerously exposed to asbestos fibers and must were protective clothing and respitory equipment.
Safety
Safety has long been a controversial issue in the mining business especially with sub-surface mining. While mining today is substantially safer than it was in the previous decades, mining accidents are often very high profile such as the Quecreek Mine Rescue, which saved 9 trapped Pennsylvania coal miners in 2002.
Mining ventilation is also seen to be a safety concern for many miners and their families. Poor ventilation of mining causes exposure to harmful gases, heat and dust. These can cause harmful physiological effects or death. High temperatures and humidity may result in any of the heat illnesses including heat stroke which can be fatal. Dusts can cause lung problems. In open-pit asbestos mines, these include asbestosis and mesothelioma (see below).
Mining is regulated under the federal Mine Safety and Health Act by MSHA, which employs nearly one safety inspector for every four mines. Miners can report violations, request additional inspections and cannot lose their jobs for doing so.
Immediately reportable accidents and injuries:
- death of an individual at a mine
- injury to an individual at a mine which has a reasonable potential to cause death
- entrapment of an individual for more than thirty minutes
- unplanned inundation of a mine by a liquid or gas
- unplanned ignition or explosion of gas or dust
- unplanned mine fire not extinguished within 30 minutes of discovery
- unplanned ignition or explosion of a blasting agent or an explosive
- unstable conditions at an impoundment, refuse pile, or culm bank which requires emergency action in order to prevent failure, or which causes individuals to evacuate an area; or, failure of an impoundment, refuse pile, or culm bank;
- event at a mine that causes death or bodily injury to an individual not at the mine at the time the event occurs
Statistical analyses performed by the United States Department of Labor's Mine Safety and Health Administration (MSHA) show that between 1990 and 2004, the industry cut the rate of injuries (a measure comparing the rate of incidents to overall number of employees or hours worked) by more than half and fatalities by two-thirds following three prior decades of steady improvement.
Machinery
Mining machinery resembles that of other heavy industries. Heavy machinery is needed in mining to break and remove rocks of diverse hardness and toughness. Bulldozers, drills, explosives and trucks are important for digging into the land, especially in surface mining. Continuous mining equipment manufacturers include Joy Mining Machinery, Caterpillar Inc., Komatsu, Volvo, Hitachi, Dynapac, Terex, Dresser, TCM, Kawasaki Heavy Industries, Furukawa, Elphinstone, Poclain and Demag, Eimco Elecon India Limited. A piece of mining machinery can cost hundreds of thousands of dollars.
Asbestos-related Diseases
Asbestos as contaminant
There are traces of asbestos in the air we breathe and the water we drink, including water from natural sources. [2] Studies have shown that members of the general (nonoccupationally exposed) population have tens of thousands to hundreds of thousands of asbestos fibers in each gram of dry lung tissue, which translates into millions of fibers and tens of thousands of asbestos bodies in every person's lungs. [3]
The EPA has proposed a concentration limit of 7 million fibers per liter of drinking water for long fibers—lengths greater than or equal to 5 micrometers (µm). OSHA (Occupational Safety and Health Administration) has set limits of 100,000 fibers with lengths greater than or equal to 5 µm per cubic meter of workplace air for 8-hour shifts and 40-hour work weeks. [4]
Most breathable asbestos fibers are invisible to the unaided human eye because their size is about 3.0-20.0 µm in length and can be as thin as 0.01 µm. Human hair ranges in size from 17 to 181 µm.[5] Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by polymer molecules lining up parallel with each other and forming crystal lattices. When sufficient force is applied, they tend to break along their weakest directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring and one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers.
As asbestos fibers get smaller and lighter, they more easily become airborne and human respiratory exposures can result. Fibers will eventually settle but may be re-suspended by air currents or other movement.
Asbestos does not tend to remain localized at its initial release point and may eventually spread throughout all available accessible areas of buildings, even into areas that don't have their own asbestos-containing products. Any small impact or damage to a typical asbestos containing product can easily release billions to trillions of fibers of asbestos into the immediate environment.
Diseases
Diseases caused by asbestos include[6][7]:
- Asbestosis: a scarring of the lung tissue from an acid produced by the body's attempt to dissolve the fibers. The scarring may eventually become so severe that the lungs can no longer function. The latency period (the time it takes for the disease to develop) is often 10-20 years.
- Mesothelioma: A cancer of the mesothelial lining of the lungs and the chest cavity, the abdominal cavity or the pericardium, a sac surrounding the heart. It is believed that mesothelioma is caused by generation of reactive oxygen species (ROS) by asbestos fibers. There is also some evidence to suggest that simian virus 40 (SV40) works together with asbestos in the development of malignant mesothelioma [8]. Asbestos exposure is linked to at least 50% of patients developing malignant mesothelioma. [9] Malignant mesothelioma has a peak incidence 35-45 years after asbestos exposure. [10] Median survival for patients with malignant mesothelioma is 11 months.[11] Asbestos has a synergistic effect with tobacco smoking in the causation of pleural mesothelioma. [12]
- Cancer: Studies link cancer of the larynx to asbestos. Other studies suggest that asbestos exposure is linked to a slightly increased risk of stomach, pharyngeal, and colorectal cancer. [13]
The Environmental Working Group estimates that in the United States about 9,900 people die each year of asbestos-related diseases, such as mesothelioma, asbestosis, lung cancer, and gastrointestinal cancer. [14]
Litigation
Asbestos litigation is the longest, most expensive mass tort in U.S. history, involving more than 6,000 defendants and 600,000 claimants. [15] Current trends indicate that the rate at which people are diagnosed with the disease will likely increase through the next decade. Analysts have estimated that the total costs of asbestos litigation in the USA alone will eventually reach $200 billion. Due to the prevalence of asbestos, it is normally part of the scope of a Phase I Environmental Site Assessment to inspect for potential asbestos in a building which is being sold.
The volume of the asbestos liability has alarmed the manufacturers and insurance industry. The amounts and method of allocating compensation have been the source of many court cases, and government attempts at resolution of existing and future cases.
Asbestos Removal
Many buildings contain asbestos, contained within spray-applied flame retardant, thermal system insulation, and in a variety of other materials. Asbestos was sometimes "[ http://en.wikipedia.org/wiki/Flocking_%28texture%29 flocked]” above false ceilings, inside technical ducts, and in many other small spaces where firefighters would have difficulty gaining access. Structural components like asbestos panels were also used. In residences, asbestos was often a component of a type of flocked acoustic ceiling called "popcorn ceiling", until its production was banned in the U.S. in 1978. However, the ban allowed installers to use up remaining stocks, so houses built as late as 1986 could still have asbestos in their acoustic ceilings. The only way to be sure is to remove a sample and have it tested by a competent laboratory.
Depending on how and where asbestos was applied, it might not pose any risk to most users of the building. If the fibers cannot become dislodged, they cannot be inhaled, and thus the asbestos poses no risk.
However, some methods of applying asbestos, particularly flocking, allow asbestos fibers to gradually drop off into the air. Asbestos poses hazards to maintenance personnel who have to drill holes in walls for installation of cables or pipes.
Even if the workers are protected, such maintenance operation may release fibers into the air, which others may inhale. Interventions in areas where asbestos is present often have to follow stringent procedures. If workers must perform a removal when occupants are still present in the building, it is usually necessary to relocate some occupants temporarily. Typically, the part of the building where workers are removing asbestos has to be sealed off in order to prevent contamination of other areas.
If the building is closed to normal occupants, it may be necessary to seal it off from the outside as well, so that no accessible air is contaminated. Demolition workers may have seal a building that contains asbestos, then remove the asbestos before demolition. Asbestos removal may take longer and cost more than the actual demolition.
Works Cited
Wikipedia.org Asbestos Article
Wikipedia.org Open-Pit Mining Article
History of Science and Technology Asbestos Entry
Encyclopedia of Earth: Asbestos
NCBI Article, "Pathogenesis of pleural fibrosis"
External Links
- Coalinga Asbestos Mine
- An environmental survey in chrysotile asbestos milling processes in India
- U.S. EPA Asbestos Home Page
- Congressional Research Service (CRS) Reports regarding asbestos
- Health History Source: Article by the SafetyLine Institute - WorkSafe - Western Australian state government
- Asbestos and Occupational Health in the World
- British Government Health and Safety Executive (HSE)
- Parachrysotile (asbestos) at the webmineral.com Mineral Database
- Univ. of Minn.: Asbestos
- Asbestos Newspaper Articles Archive
- Asbestos in the World
- White Gold Pioneers: Asbestos Mining
- Encyclopedia of Earth: Asbestos health hazards
- About Your House — General Series — Asbestos
- Hazards.org
- Case Studies in Environmental Medicine: Asbestos Toxicity
- CBC Digital Archives - Asbestos: Magic mineral or deadly dust?
- An article on the health impact of asbestos from Liverpool's 'Nerve' magazine
- The Wittenoom Tragedy, Asbestos Diseases Society of Australia.
- Health and Safety - Asbestosis (TUC Resources, UK)
- UK asbestos news Thames Laboratories
- Old Video - Asbestos Siding and Roofing (1951)
- International Asbestos Victims Memorial
- About Asbestos (OSHA)
- Asbestos contamination near abandoned mine
- Mining Technology Mining, quarrying and tunnelling industry news, projects, suppliers and glossary.
- MBendi World Mining Overview, including detailed reports by commodity, operator and geographical area
- National Mining Association
- Northeastern Mine Research Abandoned mine research and history.
- Western Mining History Mining in the American West.
- Western Museum of Mining and Industry
- The Society for Mining, metallurgy and Exploration SME-AIME
- The Australasian Institute of Mining and Metallurgy The AusIMM
- Photographic Essays of New Jersey's Abandoned Mines
