Asbestos Exposure

by National Cancer Institute

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.

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