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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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