Six types of asbestos have been identified and are divided into two groups:
- Serpentine – This variety of asbestos has a layered structure and curly fibers. Chrysotile asbestos is the only type in this category and was the kind of asbestos most often used in buildings in the United States.
- Amphibole –
This kind of asbestos is characterized by a long chain-like structure
of fibers that are sharp and straight and easy to inhale. This category
is comprised of the remaining five types of asbestos: amosite, crocidolite, anthophyllite, tremolite, and actinolite.
Amosite and crocidolite were widely used in products until the 1980s
and amosite is recognized as the second most likely type to be found in
buildings.
These
types of asbestos are often categorized by their color, although
tremolite, anthophyllite, and actinolite remain unclassified.
- White – chrysotile
- Brown – amosite
- Blue – crocidolite
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| Chrysotile asbestos |
Amosite Asbestos
The
commercial production of amosite, or “brown” asbestos, ended within the
last decade and this type of asbestos is no longer mined. It was at one
time, however, the second-most commonly used form of asbestos and, as a
result, many individuals were exposed to it during its peak use.
Amosite was employed as insulation in factories and buildings, as well
as both an acoustical and anti-condensation material. Its use has been
banned in most countries for approximately the last 30 years.
Crocidolite Asbestos
Crocidolite
asbestos accounted for about four percent of all asbestos once used in
the United States. This “blue” asbestos is harder and more brittle than
other types of the mineral and can break easily, releasing dangerous
needle-like fibers that are easily inhaled. Crocidolite, without a
doubt, is the most lethal form of asbestos. It was often used in making
yarns and rope lagging, and as a reinforcement material for plastics.
Crocidolite was generally mined in Western Australia, Bolivia, and South Africa. The percentage of miners who developed asbestos cancer due
to crocidolite exposure stands at a staggering 18 percent. The town of
Wittenoom, Australia (population 20,000), where blue asbestos was mined
for many years, had more than 1,000 people die of mesothelioma with
officials estimating that another 1,000 will eventually perish from
asbestos-related diseases. The town is now a ghost town, with only eight
residents remaining, and has literally been erased from the map.
Chrysotile Asbestos
The
most common type of asbestos and the only kind that is still mined,
chrysotile was the most widely used in the world’s developed countries.
Estimates show that about 90-95 percent of all asbestos that remains in
buildings in the U.S. and Canada is of this variety. Obviously, because
it was the most widely used, it accounts for the most health problems,
though the companies that mine it continue to attest to its safety.
Chrysotile
is most often used in fireproofing and in insulation products and was
widely used aboard U.S. Navy ships during World War II and the Korean
War. It can also be woven into cloth and was once used in theater
curtains and – ironically – to make protective clothing for those who
worked with high temperature equipment or liquids. It was also an
ingredient in cement and was helpful in the manufacture of friction
products because of its heat-resistant properties. These included brake
shoes, clutches, and disk pads. Its most recent uses were in the nuclear
energy industry.
Today,
the Canadian Chrysotile Institute maintains that the asbestos they mine
is much safer these days and claims that they only market dense and
non-friable products in which the chrysotile fiber is “encapsulated in a
matrix of either cement or resin.” Previously, the chrysotile that was
sold in the marketplace crumbled easily and was quite toxic.
Nonetheless,
most experts maintain that ALL asbestos can cause cancer, even
chrysotile, and even when exposure is minimal. This has been
demonstrated by the fact that those who live near chrysotile mines have a
much higher incidence of mesothelioma than the general public.
Anthophyllite Asbestos
Anthophyllite
asbestos, also known as “brown” asbestos is composed predominantly of
iron and magnesium. The fibers are known to be long and flexible. Of the
amphibole asbestos sub-classification, brown asbestos can be found in
many talc mines and has been associated different respiratory disorders,
though is not conclusively associated with mesothelioma as other
varieties of asbestos are.
Tremolite Asbestos
As
an amphibole variety of asbestos fiber, tremolite asbestos is indeed
associated with the development of mesothelioma and other
asbestos-related cancer. Like other varieties of asbestos, tremolite
asbestos is composed predominantly of magnesium and can range from
off-white to a dark green in color. Tremolite asbestos is particularly
common in vermiculite and vermiculite deposits.
Actinolite Asbestos
Actinolite
asbestos is a variety of the sub-classification of amphibole asbestos
and, as such, its makeup and consistency is similar to other forms of
this subset. Made predominantly of magnesium, actinolite asbestos is
extremely rare and ranges in color from white to dark brown. Actinolite
was not known to be used in asbestos products because of its rarity, but
is known to be found in metamorphic rock.
