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Asbestos

Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its sound absorption, average tensile strength, its resistance to fire, heat, electrical and chemical damage, and affordability. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement (resulting in asbestos cement) or woven into fabric or mats.
Asbestos mining began more than 4,000 years ago, but did not start large-scale until the end of the 19th century. For a long time, the world's largest asbestos mine was the Jeffrey mine in the town of Asbestos, Quebec.
Pliny the Younger wrote in 61-114 AD that slaves who worked with the mineral asbestos became ill.29 In 1899 Dr. Montague Murray first recognized the negative health effects of asbestos.30 The first documented death related to asbestos was in 1906.31 In the early 1900s researchers began to notice a large number of early deaths and lung problems in asbestos mining towns. The first diagnosis of asbestosis was made in the UK in 1924.31 The Merewether Report, published in 1930,31 was the first epidemiological study of the asbestos industry to show cases without any complicating pneumonia or other co-morbidity such as tuberculosis.32
By the 1930s, the UK regulated ventilation and made asbestosis an excusable work-related disease, followed by the U.S about ten years later.7 The term mesothelioma was first used in medical literature in 1931; its association with asbestos was first noted sometime in the 1940s.
Approximately 100,000 people in the United States have died, or are terminally ill, from asbestos exposure related to ship building. In the Hampton Roads area, a shipbuilding center, mesothelioma occurrence is seven times the national rate.33 Thousands of tons of asbestos were used in World War II ships to insulate piping, boilers, steam engines, and steam turbines. There were approximately 4.3 million shipyard workers in the United States during WWII; for every thousand workers about fourteen died of mesothelioma and an unknown number died from asbestosis.34
The United States government and asbestos industry have been criticized for not acting quickly enough to inform the public of dangers, and to reduce public exposure. In the late 1970s court documents proved that asbestos industry officials knew of asbestos dangers since the 1930s and had concealed them from the public.34
In Australia, asbestos was widely used in construction and other industries between 1946 and 1980. From the 1970s there was increasing concern about the dangers of asbestos, and its use was phased out. Mining ceased in 1983. The use of asbestos was phased out in 1989 and banned entirely in December 2003. The dangers of asbestos are now well known in Australia and there is help and support for sufferers from asbestosis or mesothelioma.
All types of asbestos fibers are known to cause serious health hazards in humans.404142 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.43
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.44 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."45 The most common diseases associated with chronic exposure to asbestos include: asbestosis and pleural abnormalities (mesothelioma, lung cancer).46 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.47
Studies have shown an increased risk of lung cancer among smokers who are exposed to asbestos compared to nonsmokers.48
Asbestos exposure becomes a health concern when high concentrations of asbestos fibers are inhaled over a long time period.49 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.
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