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Asbestos Basics


What is Asbestos?

Asbestos is the generic term for a group of naturally occurring highly toxic fibrous silicate minerals with high tensile strength, flexibility, and resistance to thermal, chemical, and electrical conditions.

Chemically, asbestos minerals contain silicon and oxygen atoms in their molecular structure. Asbestos is also resistant to heat and corrosion.

Asbestos fibers are 5 micrometers or longer with a length-to-diameter ratio of at least 3 to 1.

Asbestos includes the mineral fibers chrysotile, amosite, crocidolite, tremolite, anthophyllite, actinolite and any asbestos-containing material (ACM) or presumed asbestos-containing material (PACM) that have been chemically treated or altered.

Asbestos may also be “friable” or “non-friable”:

  • Friable asbestos is material containing more than 1% asbestos by weight or area that is crumbly, dusty or powdery. It can be crumbled, pulverized or reduced to powder form using the hands. Most asbestos-containing material is friable. Examples include: sprayed coatings or insulation, lagging, loose asbestos, or asbestos in its raw state.
  • Non-friable asbestos is material containing more than 1% asbestos which is held within another material and cannot be crumbled, pulverized, or reduced to powder using the hands.

Two Categories of Asbestos

Chrysotile, the most common form of ACM.

According to the Environmental Protection Agency (EPA), there are two major categories of asbestos:

  • Serpentine: These fibers can be woven together and are flexible and long.
    • Chrysotile, or white asbestos, is the primary type of serpentine and is used in manufacturing processes. It is in more than 95% of asbestos-containing materials (ACM) and used in about 90% of all commercial processes.
    • Amosite, also called brown asbestos, is generally used in spray coatings, heat insulation, and cement products.
    • Crocidolite, or blue asbestos, is not used much, but found in spray coatings on structure steelwork for fire protection and heat or noise insulation.
  • Amphiobole: These fibers are brittle, rod- or needle-shaped, straight and relatively stiff. These characteristics make this group, composed of actinolite, anthophyllite, and tremolite relatively useless for commercial processes.

When handled, asbestos can separate into microscopic-size particles that remain in the air and are easily inhaled. Persons occupationally exposed to asbestos have developed several types of life-threatening diseases, including asbestosis, lung cancer and mesothelioma. Although the use of asbestos and asbestos products has dramatically decreased in recent years, they are still found in many residential and commercial settings and continue to pose a health risk to workers and others.

Historical Perspectives

Asbestos has been used since the late 1800s in commercial applications and the use increased greatly throughout World War II. Asbestos was used in military ships, vehicles and aircraft until the 1970s and many thousands of those who served in the military were exposed.

Before experts knew that the inhalation of asbestos fibers caused several deadly diseases- including asbestosis, a progressive and often fatal lung disease, and lung and other cancers- asbestos was used in a large number of building materials and other products because of its strength, flame resistance, and insulating properties. Asbestos was used in asbestos-cement pipe and sheeting, floor and roofing felts, dry wall, floor tiles, spray on ceiling coatings, and packing materials.

Always presume building materials may contain asbestos. The U.S. has not banned asbestos entirely in all its forms, so employers must take caution when buildings, especially those built before 1980, are renovated or torn down. A commercial building or residence may still contain asbestos. Remember, when the asbestos-containing materials themselves are disturbed, fibers may be released into the air. The fibers are so small that workers cannot see it with the naked eye. The fact you can inhale these fibers without knowing it makes asbestos an even more dangerous hazard.

Asbestos in Demolition and Renovation – WorkSafeBC
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Where Asbestos is Used

Because asbestos is strong and resistant to heat, it has been used in many different types of products. In the construction industry, asbestos is used in more than 3,000 building products.

Some materials are presumed to contain asbestos if installed before 1981. For example, vinyl asbestos floor tiles may be as much as 15% to 20% asbestos, which is released when old flooring is removed.

Examples of products that may contain asbestos-containing materials (ACM) or presumed asbestos-containing materials (PACM) include:

  • Asbestos-cement Pipe and Sheet Material
  • Fireproofing/Acoustical Texture Products
  • Friction Materials
  • Gaskets and Packings
  • Insulation
  • Laboratory hoods and table tops
  • Spackling, Patching & Taping Compounds
  • Textile and Cloth Products
  • Tiles, Wallboard, Siding and Roofing
  • Vermiculite

Check out this comprehensive list of asbestos-containing-products.

Asbestos is not a serious health problem unless the fibers are disturbed and released into the air. The fibers are so small that workers cannot see it with the naked eye. The fact you can inhale these fibers without knowing it makes asbestos an even more dangerous hazard. Significant exposure to asbestos can cause breathing problems, lung cancer, and cancer of the lung lining many years after exposure. Therefore, only specially trained asbestos workers may remove asbestos.

Did You Know?

Dangerous insulation.
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Here’s some interesting information and highlights why asbestos in the U.S. is considered the Silent Killer:

  • Approximately 90,000 people die from asbestos-related diseases globally each year.
  • Asbestos has been banned in more than 60 countries, but not in the U.S.
  • Roofing products account for 72% of consumption.
  • One in every three deaths from occupational cancer is caused by asbestos.
  • In 2018, the U.S. chemical industry quadrupled its importation of asbestos compared to the year before.
  • Asbestos kills 12,000 to 15,000 Americans each year
  • Asbestos containing vermiculate insulation product called Zonolite is believed to be in 35 million homes, schools, and office buildings.
  • Asbestos snow was used in the poppy scene in the Wizard of Oz.
Asbestos - WorkSafeBC
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Health Effects of Asbestos
Health Effects of Asbestos
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Scars in Lung Tissue
Scars in lung Tissue - CDC
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Scars in Lung Tissue
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Health Hazards of Asbestos

Exposure to asbestos increases your risk of developing lung disease as fibers become embedded and accumulate in lung tissue over time. There is no known safe level of exposure to asbestos, so contact with any amount of asbestos should be avoided. Disease symptoms may take several years to develop following exposure.


Asbestosis is a serious, progressive, long-term non-cancer disease of the lungs. It is caused by inhaling asbestos fibers that lodge in the alveoli and cause the tissues to scar. The scarring makes it hard for oxygen to get into the blood.

Symptoms of asbestosis include shortness of breath and a dry, crackling sound in the lungs while inhaling. There is no effective treatment for asbestosis.

Lung Cancer

Lung cancer causes the largest number of deaths in the U.S. related to asbestos exposure. People who work in the mining, milling, manufacturing of asbestos, and those who use asbestos and its products are more likely to develop lung cancer than the general population.

The most common symptoms of lung cancer are coughing and a change in breathing. Other symptoms include shortness of breath, persistent chest pains, hoarseness, and anemia.


Epidemiologic evidence has increasingly shown that all asbestos fiber types, including the most commonly used form of asbestos, chrysotile, causes mesothelioma in humans.

Mesothelioma is a rare form of cancer due to asbestos fibers lodging in the thin lining of the lungs causing tumors to grow in the lung, chest, abdomen, and heart. This disease may not show up until many years after asbestos exposure.

It is important to know the following things about exposure to asbestos:

  • Airborne levels of asbestos are never to exceed legal worker exposure limits.
  • There is no "safe" level of asbestos exposure for any type of asbestos fiber.
  • Asbestos exposures as short in duration as a few days have caused mesothelioma in humans.
  • Every occupational exposure to asbestos contributes to the risk of getting an asbestos related disease.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. All buildings and homes, especially those built before _____ may contain asbestos-containing materials.

2. Which term below describes material that contains more than 1% asbestos and is crumbly, dusty or powdery?

3. Which of the following is in over 95% of asbestos-containing materials and used in about 90% of all commercial processes?

4. Why has asbestos been used in many different types of products?

5. Which of the following is a disease of the lungs caused by inhaling asbestos fibers that lodge in the alveoli and cause the tissues to scar?

Have a great day!

Important! You will receive an "error" message unless all questions are answered.