Introduction to Asbestos Lung Cancer Symptoms and Causes

What is asbestos?
Asbestos is the name given to a group of
minerals that occur naturally in the
environment as bundles of fibers that can be
separated into thin, durable threads. These
fibers are resistant to heat, fire, and
chemicals and do not conduct electricity. For
these reasons, asbestos has been used widely
in many industries.
Chemically, asbestos minerals are silicate
compounds, meaning they contain atoms of
silicon and oxygen in their molecular
structure.
Asbestos minerals are divided into two major
groups: Serpentine asbestos and amphibole
asbestos. Serpentine asbestos includes the
mineral chrysotile, which has long, curly fibers
that can be woven. Chrysotile asbestos is the
form that has been used most widely in
commercial applications. Amphibole asbestos
includes the minerals actinolite, tremolite,
anthophyllite, crocidolite, and amosite.
Amphibole asbestos has straight, needle-like
fibers that are more brittle than those of
serpentine asbestos and are more limited in
their ability to be fabricated (1, 2).
2.
How is asbestos used?
Asbestos has been mined and used
commercially in North America since the late
1800s. Its use increased greatly during World
War II ( 3, 4). Since then, asbestos has been
used in many industries. For example, the
building and construction industries have used
it for strengthening cement and plastics as
well as for insulation, roofing, fireproofing,
and sound absorption. The shipbuilding
industry has used asbestos to insulate boilers,
steam pipes, and hot water pipes. The
automotive industry uses asbestos in vehicle
brake shoes and clutch pads. Asbestos has
also been used in ceiling and floor tiles;
paints, coatings, and adhesives; and plastics.
In addition, asbestos has been found in
vermiculite-containing garden products and
some talc-containing crayons.
In the late 1970s, the U.S. Consumer Product
Safety Commission (CPSC) banned the use of
asbestos in wallboard patching compounds
and gas fireplaces because the asbestos
fibers in these products could be released into
the environment during use. In addition,
manufacturers of electric hairdryers
voluntarily stopped using asbestos in their
products in 1979. In 1989, the U.S.
Environmental Protection Agency (EPA)
banned all new uses of asbestos; however,
uses developed before 1989 are still allowed.
The EPA also established regulations that
require school systems to inspect buildings for
the presence of damaged asbestos and to
eliminate or reduce asbestos exposure to
occupants by removing the asbestos or
encasing it ( 2).
In June 2000, the CPSC concluded that the
risk of children's exposure to asbestos fibers
in crayons was extremely low ( 1). However,
U.S. manufacturers of these crayons agreed
to eliminate talc from their products.
In August 2000, the EPA conducted a series of
tests to evaluate the risk for consumers of
adverse health effects associated with
exposure to asbestos-contaminated
vermiculite. The EPA concluded that exposure
to asbestos from some vermiculite products
poses only a minimal health risk. The EPA
recommended that consumers reduce the low
risk associated with the occasional use of
vermiculite during gardening activities by
limiting the amount of dust produced during
vermiculite use. Specifically, the EPA
suggested that consumers use vermiculite
outdoors or in a well-ventilated area; keep
vermiculite damp while using it; avoid
bringing dust from vermiculite into the home
on clothing; and use premixed potting soil,
which is less likely to generate dust ( 2).
The regulations described above and other
actions, coupled with widespread public
concern about the health hazards of asbestos,
have resulted in a significant annual decline
in the U.S. use of asbestos. Domestic
consumption of asbestos amounted to about
803,000 metric tons in 1973, but it had
dropped to about 2,400 metric tons by 2005
( 3, 5).
3.
What are the health hazards of exposure to
asbestos?
People may be exposed to asbestos in their
workplace, their communities, or their homes.
If products containing asbestos are disturbed,
tiny asbestos fibers are released into the air.
When asbestos fibers are breathed in, they
may get trapped in the lungs and remain
there for a long time. Over time, these fibers
can accumulate and cause scarring and
inflammation, which can affect breathing and
lead to serious health problems ( 6).
Asbestos has been classified as a known
human carcinogen (a substance that causes
cancer) by the U.S. Department of Health and
Human Services, the EPA, and the
International Agency for Research on Cancer
( 2, 3, 7, 8). Studies have shown that
exposure to asbestos may increase the risk of
lung cancer and mesothelioma (a relatively
rare cancer of the thin membranes that line
the chest and abdomen). Although rare,
mesothelioma is the most common form of
cancer associated with asbestos exposure. In
addition to lung cancer and mesothelioma,
some studies have suggested an association
between asbestos exposure and
gastrointestinal and colorectal cancers, as
well as an elevated risk for cancers of the
throat, kidney, esophagus, and gallbladder
(3, 4). However, the evidence is inconclusive.
Asbestos exposure may also increase the risk
of asbestosis (an inflammatory condition
affecting the lungs that can cause shortness of
breath, coughing, and permanent lung
damage) and other nonmalignant lung and
pleural disorders, including pleural plaques
(changes in the membranes surrounding the
lung), pleural thickening, and benign pleural
effusions (abnormal collections of fluid
between the thin layers of tissue lining the
lungs and the wall of the chest cavity).
Although pleural plaques are not precursors
to lung cancer, evidence suggests that people
with pleural disease caused by exposure to
asbestos may be at increased risk for lung
cancer ( 2, 9).