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Asbestosis Biogarphy

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Amphiboles including amosite (brown asbestos) and crocidolite (blue asbestos) were formerly used in many products until the early 1980s.[citation needed] Tremolite asbestos constituted a contaminant of many if not all naturally occurring chrysotile deposits. The use of all types of asbestos in the amphibole group was banned in much of the Western world by the mid-1980s, and in Japan by 1995.[citation needed] Some products that included amphibole types of asbestos included the following:
Low density insulating board (often referred to as AIB or asbestos insulating board) and ceiling tiles;
Asbestos-cement pipe (made until the early 1990s by at least one manufacturer);
Asbestos-cement sheets and pipes for construction, casing for water and electrical/telecommunication services;
Thermal and chemical insulation (e.g., fire rated doors, limpet spray, lagging and gaskets).
Cigarette manufacturer Lorillard (Kent's filtered cigarette) used crocidolite asbestos in its "Micronite" filter from 1952 to 1956.[35]
While mostly chrysotile asbestos fibers were once used in automobile brake pads, shoes, and clutch discs, contaminants of amphiboles were present. Since approximately the mid-1990s, brake pads, new or replacement, have been manufactured instead with linings made of ceramic, carbon, metallic and aramid fiber (Twaron or Kevlar—the same material used in bulletproof vests).
Artificial Christmas snow, known as flocking, was previously made with asbestos.[36]
Health problems[edit]
Left-sided mesothelioma (seen on the right of the picture): chest CT
All types of asbestos fibers are known to cause serious health hazards in humans.[37][38][39] While it is agreed that amosite and crocidolite are the most hazardous asbestos fiber types, chrysotile asbestos has produced tumors in animals and is a recognized cause of asbestosis and malignant mesothelioma in humans.[40]
Mesotheliomas have been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.[41] According to the NCI, "A history of asbestos exposure at work is reported in about 70 percent to 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos."[42] The most common diseases associated with chronic exposure to asbestos include: asbestosis and pleural abnormalities (mesothelioma, lung cancer).[43] Asbestosis has been reported primarily in asbestos workers, and appears to require long-term exposure, high concentration for the development of the clinical disease. There is also a long latency period (incubation period of an infectious disease, before symptoms appear) of about 12 to 20 years.[44]
Studies have shown an increased risk of lung cancer among smokers who are exposed to asbestos compared to nonsmokers.[45]
Asbestos exposure becomes a health concern when high concentrations of asbestos fibers are inhaled over a long time period.[46] People who become ill from inhaling asbestos are often those who are exposed on a day-to-day basis in a job where they worked directly with the material. As a person's exposure to fibers increases, because of being exposed to higher concentrations of fibers and/or by being exposed for a longer time, then that person's risk of disease also increases. Disease is very unlikely to result from a single, high-level exposure, or from a short period of exposure to lower levels.[46]
Possible mechanisms of carcinogenicity[edit]
Stanton and Layard hypothesized in 1977–78 that toxicity of fibrous materials is not initiated by chemical effects;[47] that is, any trigger-effects of asbestos must presumably be physical, such as (A) mechanical damage or (B) unwanted signal channels (a plausible property for slender transparent fibres) which might disrupt normal cell activity—especially mitosis.
(A) Mechanical Damage. There is experimental evidence that very slim fibers (<60 nm, <0.06 μm in breadth) do tangle destructively with chromosomes (being of comparable size).[48][49] This is likely to cause the sort of mitosis disruption expected in cancer.
(B) Unwanted Signal channels. This has recently been explored theoretically, but not yet experimentally. The theory argues that this effect would only be feasible for asbestos fibers >100 nm in breadth (>150 nm in the case of chrysotile), which suggests that we should be on the look-out for a possible mixture of different mechanisms for the different fiber-diameter-ranges.[50][51]
One popular idea of the causal chain is (1) Asbestos fiber → → (3) inflammation → (4) other pathology. While that may be true, it does not explain "(2), the actual trigger":
"What is the physical property of asbestos which initiates any such inflammation?" (After all, inflammation is usually seen as caused by chemical-based processes: immunological &/or bacterial). So inflammation (&/or oxidation etc.) may well be part of the causal chain, but not the crucial first step.[50]
Other asbestos-related diseases[edit]
Main article: Asbestos-related diseases
It is important to consult a doctor, particularly if the following symptoms develop: shortness of breath, wheezing, or hoarseness, persistent cough that worsens over time, blood in fluid coughed up, pain or tightening in chest, difficulty swallowing, swelling of neck or face, decreased appetite, weight loss, fatigue or anemia.[52]
Asbestosis: Progressive fibrosis of the lungs of varying severity, progressing to bilateral fibrosis, honeycombing of the lungs on radiological view with symptoms including rales and wheezing. Individuals who have been exposed to asbestos via home, environment, work should notify their doctors about exposure history.
Asbestos warts: caused when the sharp fibers lodge in the skin and are overgrown causing benign callus-like growths.
Pleural plaques: discrete fibrous or partially calcified thickened area which can be seen on X-rays of individuals exposed to asbestos. Although pleural plaques are themselves asymptomatic, in some patients this develops into pleural thickening.
Diffuse pleural thickening: similar to above and can sometimes be associated with asbestosis. Usually no symptoms shown but if exposure is extensive, it can cause lung impairment.
Pneumothorax: Some reports have also linked the condition of pneumothorax to asbestos related diseases.
Chemistry[edit]
Asbestos fibers (SEM micrograph)
Individual asbestos fibers are invisible to the unaided human eye because their size is about 3–20 µm wide and can be as slim as 0.01 µm. Human hair ranges in size from 17 to 181 µm in breadth.[53] Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by the polymeric molecules lining up parallel with each other and forming oriented crystal lattices. These crystals thus have three cleavage planes, and in this case, there are two cleavage planes which are much weaker than the third. 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.
When fibers or asbestos structures from asbestos containing materials(ACM) become airborne, the process is called primary release. Primary release mechanisms include abrasion, impaction, fallout, air erosion, vibration, and fire damage. Secondary release occurs when settled asbestos fibers and structures are resuspended as a result of human activities. In unoccupied buildings or during unoccupied periods, fiber release typically occurs by fallout or is induced by vibration or air erosion.[54]
Friability of a product containing asbestos means that it is so soft and weak in structure that it can be broken with simple finger crushing pressure. Friable materials are of the most initial concern because of their ease of damage. The forces or conditions of usage that come into intimate contact with most non-friable materials containing asbestos are substantially higher than finger pressure.
Identification and assessment[edit]
A fiber cannot be identified or ruled out as asbestos, either using the naked eye or by simply looking at a fiber under a regular microscope. The most common methods of identifying asbestos fibers are by using polarized light microscopy (PLM) or transmission electron microscopy (TEM). PLM is less expensive, but TEM is more precise and can be used at lower concentrations of asbestos.
If asbestos abatement is performed, completion of the abatement is verified using visual confirmation and may also involve air sampling. Air samples are typically analyzed using phase contrast microscopy (PCM). PCM involves counting fibers on a filter using a microscope. Airborne occupational exposure limits for asbestos are based on using the PCM method.
The American Conference of Governmental Industrial Hygienists has a recommended Threshold Limit Value (TLV) for asbestos of 0.1 fibers/mL over an 8 hour shift. OSHA in the United States and occupational health and safety regulatory jurisdictions in Canada use 0.1 fibers/mL over an 8 hour shift as their exposure limits.[55]
Common building materials containing asbestos[edit]
Most products manufactured today do not contain asbestos. In the industrialized world, asbestos was phased out of building products mostly in the 1970s with most of the remainder phased out by the 1980s. Asbestos containing building materials in residences includes a variety of products, such as: stiple used in textured walls and ceilings; drywall joint filler compound; asbestos contaminated vermiculite, vinyl floor tile; vinyl sheet flooring; window putty; mastic; cement board; furnace tape; and stucco. Asbestos was used a lot in roofing materials, mainly corrugated asbestos cement roof sheets and asbestos shingles. Other sources of asbestos containing materials include fireproofing and acoustic materials.[56]
Exposure[edit]
Asbestos exposure becomes an issue if asbestos containing materials become airborne, such as due to deterioration or damage. Building occupants may be exposed to asbestos, but those most at risk are persons who purposely disturb materials, such as maintenance/construction workers. Housekeeping/custodial employees may be at increased risk as they may potentially clean up damaged or deteriorated asbestos containing materials without knowing that the material contains asbestos. Asbestos abatement/remediation workers and emergency personnel such as firefighters may also become exposed.[57] Asbestos-related diseases have been diagnosed in asbestos workers' family members, and in residents who live close to asbestos mines or processing plants.[58]
Environmental asbestos[edit]
Asbestos can be found naturally in the air outdoors and in some drinkable water, including water from natural sources.[59] Studies have shown that members of the general (non-occupationally exposed) population have 10,000-999,999 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.[60]
Asbestos from natural geologic deposits is known as "naturally occurring asbestos" (NOA). Health risks associated with exposure to NOA are not yet fully understood, and current US federal regulations do not address exposure from NOA. Many populated areas are in proximity to shallow, natural deposits which occur in 50 of 58 California counties and in 19 other U.S. states. In one study, data was collected from 3,000 mesothelioma patients in California and 890 men with prostate cancer, a malignancy not known to be related to asbestos. The study found a correlation between the incidence of mesotheliomas and the distance a patient lived from known deposits of rock likely to include asbestos; the correlation was not present when the incidence of prostate cancer was compared with the same distances. According to the study, risk of mesothelioma declined by 6% for every 10 km that an individual had lived away from a likely asbestos source.[61]
Portions of El Dorado County, California are known to contain natural amphibole asbestos formations at the surface.[61][62] The USGS studied amphiboles in rock and soil in the area in response to an EPA sampling study and subsequent criticism of the EPA study. The EPA study was refuted by its own peer reviewers and never completed or published. The study found that many amphibole particles in the area meet the counting rule criteria used by the EPA for chemical and morphological limits, but do not meet morphological requirements for commercial-grade-asbestos. The executive summary pointed out that even particles that do not meet requirements for commercial-grade-asbestos may be a health threat and suggested a collaborative research effort to assess health risks associated with "Naturally Occurring Asbestos."
However, the main criticism pointed at EPA was that their testing was conducted in small isolated areas of El Dorado where there were no amphibole asbestos deposits, thus the language regarding amphibole, nonfibrous "particles". Actual surface amphibole deposits in residential areas were ignored for testing purposes. Because of this, no final findings were published by ATSDR.[63]
Great deals of Fairfax County, Virginia were also found to be underlain with tremolite. The county monitored air quality at construction sites, controlled soil taken from affected areas, and required freshly developed sites to lay 6 inches (150 mm) of clean, stable material over the ground.[61]
Globally, collected samples from Antarctic ice indicate chrysotile asbestos has been a ubiquitous contaminant of the environment for at least 10,000 years. Snow samples in Japan have shown ambient background levels are one to two orders of magnitude higher in urban than in rural areas. Higher concentrations of airborne asbestos fibers are reported in urban areas where there is more ACM (asbestos containing materials) and mechanisms of release (vehicles braking and weathering of asbestos cement materials); concentrations in the range of 1–20 ng/m^3 have been reported. Fibers longer than 5μm are rarely found in rural areas. Ambient concentrations using TEM analysis have been based on mass measurements.[54]

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