What Is Asbestos?
Asbestos is the name given to a number of naturally occurring
fibrous silicate minerals that have been mined for their useful
properties such as thermal insulation, chemical and thermal stability,
and high tensile strength. The three most common types of asbestos
are: a) chrysotile, b) amosite and c) crocidolite. Chrysotile,
also known as white asbestos and a member of the Serpentine mineral
group is the commonest. Asbestos can only be identified under
a microscope.
Asbestos differs from other minerals in its crystal development.
The crystal formation of asbestos is in the form of long thin
fibers. Asbestos is divided into two mineral groups --- Serpentine
and Amphibole. The division between the two types of asbestos
is based upon the crystalline structure. Serpentines have a sheet
or layered structure where amphiboles have a chain-like structure.
As the only member of the serpentine group, Chrysotile( A, B)
is the most common type of asbestos found in buildings. Chrysotile
makes up approximately 90%-95% of all asbestos contained in buildings
in the United States.
In the amphibole group, there are five types of asbestos. As
an acronym for the Asbestos Mines of South Africa, Amosite is
the second most prevalent type of asbestos found in building materials.
Amosite is also known as "brown asbestos." Next, there is Crocidolite
or "blue asbestos," which is an asbestos found in specialized
high temperature applications. The other three types (Anthophyllite,
Tremolite, and Actinolite) are rare and found mainly as contaminants
in other minerals. Asbestos deposits can be found throughout the
world and are still mined in Australia, Canada, South Africa,
and the former Soviet Union.
Why is asbestos a hazard?
Asbestos is made up of microscopic bundles of fibers that may
become airborne when distributed. These fibers get into the air
and may become inhaled into the lungs, where they may cause significant
health problems. Researchers still have not determined a "safe
level" of exposure but we know the greater and the longer the
exposure, the greater the risk of contracting an asbestos related
disease. Some of these health problems include:
- Asbestosis - a lung disease first found in naval shipyard
workers. As asbestos fibers are inhaled, they may become trapped
in the lung tissue. The body tries to dissolve the fibers by
producing an acid. This acid, due to the chemical resistance
of the fiber, does little to damage the fiber, but may scar
the surrounding tissue. Eventually, this scarring may become
so severe that the lungs cannot function. The latency period
(meaning the time it takes for the disease to become developed)
is often 25-40 years.
- Mesothelioma - a cancer of the pleura (the outer lining of
the lung nad chest cavity) and/ or the peritoneum (the lining
of the abdominal wall). This form of cancer is peculiar because
the only known cause is from asbestos exposure. The latency
period for mesothelioma is often 15-30 years.
- Lung Cancer - caused by asbestos. The effects of lung cancer are often greatly
increased by cigarette smoking ( by about 50%). Cancer of the gastrointestinal
tract can also be caused by asbestos. The latency period for cancer is often 15-30
years.
Despite the common misconception, asbestos does not cause head-aches, sore muscles or other
immediate symptoms. As mentioned above, the effects often go unnoticed for 15-40 years.
When is asbestos a hazard?
Asbestos is not always an immediate hazard. In fact, if asbestos can be maintained
in good condition, it is recommended that it be left alone and
periodic surveillance performed to monitor its condition. It is
only when asbestos containing materials (ACM) are disturbed or
the materials become damaged that it becomes a hazard. When the
materials become damaged, the fibers separate and may then become
airborne. In the asbestos industry, the term "friable"
is used to describe asbestos that can be reduced to dust by hand
pressure. 'Non-friable' means asbestos that is too hard to be
reduce to dust by hand. Non-friable materials, such as transite
siding and floor tiles are not regulated provided it does not
become friable. Machine grinding, sanding and dry-buffing are
ways of causing non-friable materials to become friable.
