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What is asbestos?Chrysotile-asbestos_thumb.jpg

Asbestos is a mineral fiber which comes from a group of naturally occurring minerals with silicate composition and crystalline structure. Three of the most common types of asbestos are chrysotile, amosite, and crocidolite. Asbestos has been mined and widely used throughout history to add strength, heat insulation, and fire resistance to thousands of products. It is also a hazardous air pollutant and known airborne carcinogen when fibers are released into the air and inhaled into the lungs.

...but I thought asbestos had been banned?

False. Products containing asbestos are still manufactured and sold in the United States today, and there are hundreds of thousands of buildings still standing that have asbestos-containing materials within them. It is impossible to visually tell if a material contains asbestos; building materials must be tested in a laboratory as the fibers are microscopic. The only building materials that do not require laboratory testing to verify if asbestos is present are glass, metal, and wood.

Where can I find asbestos?

Examples of products that might contain asbestos are:
  • Sprayed-on fire proofing and insulation
  • Insulation for pipes and boilers (Thermal system insulation) 
  • Wall and ceiling insulation
  • Ceiling tiles
  • Floor tiles
  • Old fume hoods and lab benches
  • Putties, caulks, and cements (i.e., window glaze)
  • Roofing shingles
  • Siding shingles on old residential buildings (i.e., transite siding) 
  • Wall and ceiling texture in older buildings and homes
  • Joint compound in older buildings and homes
  • Brake linings and clutch pads
When is asbestos dangerous?

The most common way for asbestos to enter the body is through inhalation. In fact, asbestos containing material is not generally considered to be harmful unless there has been a fiber release (through deterioration, damage, or disturbance), where microscopic fibers can be inhaled. Most of the fibers will become trapped in the mucous membranes of the nose and throat, but some may pass deep into the lungs, or, if swallowed, into the digestive tract. Once they are trapped in the body, the fibers can cause severe health problems.

Asbestos is most hazardous when it is friable. The term "friable" means that the asbestos is easily crumbled by hand, which releases fibers into the air. For example, sprayed-on asbestos-containing insulation is highly friable whereas asbestos-containing vinyl floor tile is not.

Asbestos-containing acoustical ceiling tiles, vinyl floor tiles, roof shingles, fire doors, and transite siding will not release asbestos fibers unless they are disturbed or damaged in some way. If an asbestos-containing ceiling tile is drilled into or broken, for example, it may release fibers into the air. If it is left alone and not disturbed, it will not.

Damage and deterioration will increase the friability of asbestos-containing materials. Water damage, continual vibration, aging, and physical impact such as drilling, grinding, buffing, cutting, sawing, or striking can break the materials down, making fiber release more likely.

Health Effects

As a result of the microscopic nature of the asbestos fibers, the body can not break them down or remove them once they are trapped in lung or body tissues. They remain in place where they can cause disease.

There are three primary diseases associated with asbestos exposure:
  • Asbestosis
  • Lung Cancer
  • Mesothelioma

Asbestosis is a serious, chronic, non-cancerous respiratory disease. Inhaled asbestos fibers aggravate lung tissues, which result in scarring. Symptoms of asbestosis include shortness of breath and a dry crackling sound in the lungs when inhaling. In its advanced stages, the disease may cause cardiac failure.

There is no effective treatment for asbestosis at this time. As a result, the disease is usually severely disabling and/or fatal. The risk of asbestosis is minimal for those who do not work with asbestos. Those who renovate or demolish buildings that contain asbestos may be at significant risk, depending on the nature of the exposure and the precautions taken.

Lung Cancer

Lung cancer causes the most deaths as a result of asbestos exposure. The incidence of lung cancer in people who are directly involved in the mining, milling, manufacturing, and use of asbestos and its products is much higher than in the general population. Common symptoms of lung cancer include coughing, shortness of breath, persistent chest pains, hoarseness, and anemia.

People who have been exposed to asbestos as well as other carcinogens, such as cigarette smoke, have a significantly greater risk of developing lung cancer than people who have only been exposed to asbestos. One study found that asbestos workers who smoke are about 90-times more likely to develop lung cancer than people who neither smoke nor have been exposed to asbestos.


Mesothelioma is a rare form of cancer that most often occurs in the thin membrane lining of the lungs, chest, abdomen, and (rarely) heart. About 200 cases are diagnosed each year in the United States. Virtually all cases of mesothelioma are linked with asbestos exposure.

Those who work in asbestos mines, mills, factories, and shipyards that use asbestos, as well as individuals who manufacture and install asbestos insulation, have an increased risk of mesothelioma. People who live near asbestos mining areas, factories, or near shipyards where use of asbestos has produced large quantities of airborne asbestos fibers also are at an increased risk.

Determining Factors

Three things seem to determine your likelihood of developing one of these asbestos related diseases:

  1. The amount and duration of exposure. The more often you are exposed to asbestos and the more fibers that enter your body, the more likely you are to develop asbestos related health problems. While there is no "safe level" of asbestos exposure, people who are exposed more frequently over a long period of time are more at risk.
  2. Whether or not you smoke. If you smoke and have been exposed to asbestos, you are far more likely to develop lung cancer than someone who does not smoke and who has not been exposed to asbestos. If you work with asbestos or have been exposed to it, the first thing you should do to reduce your chances of developing cancer is to stop smoking.
  3. Age. Cases of mesothelioma have occurred in the children of asbestos exposed workers as a result of dust/fibers brought home on clothing. The younger individuals are when they inhale asbestos, the more likely they are to develop mesothelioma over the course of their life. This is why enormous efforts are made to prevent school-aged children from being exposed.

Because each exposure to asbestos fibers increase the chances of contracting one of these diseases, it is very important to reduce and minimize your exposure.   

For more information on these and other health effects of asbestos exposure see the Agency for Toxic Substances and Disease Registry, the National Institute for Occupational Safety and Health and the National Cancer Institute.