1. What is asbestos?
“Asbestos”
is the name given to a group of minerals that occur naturally as
bundles of fibers which can be separated into thin threads. These
fibers are not affected by heat or chemicals and do not conduct
electricity. For these reasons, asbestos has been widely used in many
industries. Four types of asbestos have been used commercially:
* Chrysotile, or white asbestos;
* Crocidolite, or blue asbestos;
* Amosite, which usually has brown fibers; and
* Anthophyllite, which usually has gray fibers.
Chrysotile
asbestos, with its curly fibers, is in the serpentine family of
minerals. The other types of asbestos, which all have rod-like fibers,
are known as amphiboles.
Asbestos
fiber masses tend to break easily into a dust composed of tiny
particles that can float in the air and stick to clothes. The fibers
may be easily inhaled or swallowed and can cause serious health
problems.
2. How is asbestos used?
Asbestos
was mined and used commercially in North America beginning in the
late 1800s. Its use increased greatly during World War II. Since then,
it has been used in many industries. For example, the building and
construction industry has used it for strengthening cement and
plastics as well as for insulation, fireproofing, and sound absorption.
The shipbuilding industry has used asbestos to insulate boilers,
steampipes, and hot water pipes. The automotive industry uses asbestos
in vehicle brakeshoes and clutch pads. More than 5,000 products
contain or have contained asbestos. Some of them are listed below:
*
Asbestos cement sheet and pipe products used for water supply and
sewage piping, roofing and siding, casings for electrical wires, fire
protection material, electrical switchboards and components, and
residential and industrial building materials;
* Friction products, such as clutch facings, brake linings for automobiles, gaskets, and industrial friction materials;
*
Products containing asbestos paper, such as table pads and
heat-protective mats, heat and electrical wire insulation, industrial
filters for beverages, and underlying material for sheet flooring;
*
Asbestos textile products, such as packing components, roofing
materials, and heat- and fire-resistant fabrics (including blankets and
curtains); and
*
Other products, including ceiling and floor tile; gaskets and
packings; paints, coatings, and adhesives; caulking and patching tape;
artificial ashes and embers for use in gas-fired fireplaces; plastics;
vermiculite-containing consumer 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. Additionally, asbestos was
voluntarily withdrawn by manufacturers of electric hair dryers. In
1989, the U.S. Environmental Protection Agency (EPA) banned all new
uses of asbestos; uses established prior to 1989 are still allowed. The
EPA has established regulations that require school systems to
inspect for damaged asbestos and to eliminate or reduce the exposure
to occupants by removing the asbestos or encasing it. In June 2000,
the CPSC concluded that the risk of children’s exposure to asbestos
fibers in crayons was extremely low. However, the U.S. manufacturers
of these crayons agreed to reformulate their products within a year.
In August 2000, the EPA recommended that consumers reduce possible
asbestos exposure from vermiculite-containing garden products by
limiting the amount of dust produced during use. 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 use into the home on clothing; and use premixed potting
soil, which is less likely to generate dust.
The
regulations described above and other actions, coupled with
widespread public concern about the hazards of asbestos, have resulted
in a significant annual decline in U.S. use of asbestos: Domestic
consumption of asbestos amounted to about 719,000 metric tons in 1973,
but it had dropped to about 9,000 metric tons by 2002. Asbestos is
currently used most frequently in gaskets and in roofing and friction
products.
3. What are the health hazards of exposure to asbestos?
Exposure to asbestos may increase the risk of several serious diseases:
* Asbestosis; a chronic lung ailment that can produce shortness of breath, coughing, and permanent lung damage;
* Lung cancer;
* Mesothelioma; a relatively rare cancer of the thin membranes that line the chest and abdomen; and
* Other cancers, such as those of the larynx, oropharynx, gastrointestinal tract, and kidney.
4. Who is at risk?
Nearly
everyone is exposed to asbestos at some time during their life.
However, most people do not become ill from their exposure. People who
become ill from asbestos are usually those who are exposed to it on a
regular basis, most often in a job where they work directly with the
material or through substantial environmental contact.
Since
the early 1940s, millions of American workers have been exposed to
asbestos. Health hazards from asbestos fibers have been recognized in
workers exposed in shipbuilding trades, asbestos mining and milling,
manufacturing of asbestos textiles and other asbestos products,
insulation work in the construction and building trades, brake repair,
and a variety of other trades. Demolition workers, drywall removers,
and firefighters also may be exposed to asbestos fibers. As a result
of Government regulations and improved work practices, today’s workers
(those without previous exposure) are likely to face smaller risks
than did those exposed in the past.
Although
it is known that the risk to workers increases with heavier exposure
and longer exposure time, investigators have found asbestos-related
diseases in individuals with only brief exposures. Generally, those
who develop asbestos-related diseases show no signs of illness for a
long time after their first exposure. It can take from 10 to 40 years
for symptoms of an asbestos-related condition to appear.
There
is some evidence that family members of workers heavily exposed to
asbestos face an increased risk of developing mesothelioma. This risk
is thought to result from exposure to asbestos fibers brought into the
home on the shoes, clothing, skin, and hair of workers. This type of
exposure is called paraoccupational exposure. To decrease these
exposures, people exposed to asbestos at work are required to shower
and change their clothing before leaving the workplace.
5. How great is the risk?
Not
all workers exposed to asbestos will develop diseases related to
their exposure. The risk of developing asbestos-related diseases varies
with the type of industry in which the exposure occurred and with the
extent of the exposure. Asbestos that is bonded into finished
products such as walls and tiles poses no risk to health as long as it
is not damaged or disturbed (for example, by sawing or drilling) in
such a way as to release fibers into the air. When asbestos fibers are
set free and inhaled, however, exposed individuals are at risk of
developing an asbestos-related disease.
In
addition, different types of asbestos fibers may be associated with
different health risks. For example, results of several studies
suggest that amphibole forms of asbestos may be more harmful than
chrysotile, particularly for mesothelioma. Even so, no fiber type can
be considered harmless, and people working with asbestos should always
take proper safety precautions to limit exposure.
6. How does smoking affect risk?
Many
studies have shown that the combination of smoking and asbestos
exposure is particularly hazardous. Smokers who are also exposed to
asbestos have a greatly increased risk of lung cancer. However, smoking
combined with asbestos exposure does not appear to increase the risk
of mesothelioma.
There
is evidence that quitting smoking will reduce the risk of lung cancer
among asbestos-exposed workers. People who were exposed to asbestos
on the job at any time during their life or who suspect they may have
been exposed should not smoke. If they smoke, they should stop.
7. Who needs to be examined?
Individuals
who have been exposed (or suspect they have been exposed) to asbestos
fibers on the job or at home via a family contact should inform their
physician of their exposure history and any symptoms. Asbestos fibers
can be measured in urine, feces, mucus, or material rinsed out of the
lungs. A thorough physical examination, including a chest x-ray and
lung function tests, may be recommended. It is important to note that
chest x-rays cannot detect asbestos fibers in the lungs, but they can
help identify any lung changes resulting from asbestos exposure.
Interpretation of the chest x-ray may require the help of a specialist
who is experienced in reading x-rays for asbestos-related diseases.
Other tests also may be necessary.
As
noted earlier, the symptoms of asbestos-related diseases may not
become apparent for many decades after exposure. If any of the
following symptoms develop, a physical examination should be scheduled
without delay:
* Shortness of breath;
* A cough or a change in cough pattern;
* Blood in the sputum (fluid) coughed up from the lungs;
* Pain in the chest or abdomen;
* Difficulty in swallowing or prolonged hoarseness; and/or
* Significant weight loss.
