How Asbestos Works

In most commercial forms, asbestos looks like attic insulation -- a ball of thick fuzz. The individual asbestos fibers that are released into the air are microscopic. The U.S. government defines asbestos as a naturally occurring group of fibrous minerals that are very strong, can be woven, and resist heat and most chemicals [source: EPA]. The current federal definition includes these classes of asbestos:

While both chrystotile and amphibole are known to cause respiratory diseases, the more durable, thinner strands of amphibole asbestos are considered more dangerous and more likely to cause mesothelioma (a form of cancer caused by asbestos) because they tend to stay in the lungs longer [source: Agency for Toxic Substances and Disease Registry]. However, the more flexible chrystotile asbestos is used in about 95 percent of all asbestos in commercial products and is still considered carcinogenic [source: Encyclopedia Britannica].

Asbestos has been used for thousands of years, dating as far back as the ancient Greeks. Its durability and ability to withstand heat and erosion made it attractive to builders, and it was even used in some clothing because of its fire-resistant qualities. Modern asbestos production began in 1868 through mining deposits [source: Encyclopedia Britannica].

Reports of long-term harmful effects of asbestos exposure began appearing in the 1970s, although dangers associated with asbestos were suspected decades earlier. In 1989, the U.S. government issued a ban on products containing asbestos. This regulation was overturned in 1991, but certain products were still banned, as were "new uses" of asbestos [source: EPA]. So where do we find asbestos? Read on to find out.

The fact is, we're all exposed to asbestos, although usually in such small quantities that it poses no threat. The typical air concentration of asbestos fibers is 0.00001 to 0.0001 fibers per milliliter. In comparison, U.S. workplaces are limited to exposing employees to 0.1 fiber/mL, and significant exposure is considered years of exposure to 0.125 to 30 fibers/mL [source: Agency for Toxic Substances and Disease Registry].

In nature, the fibrous asbestos is embedded in rocks, most commonly ultramafic rock (a type of igneous rock), which is found in much of California and near fault zones. Not all ultramafic rock contains asbestos, but all ultramafic rock has the potential to contain veins of asbestos [source: Agency for Toxic Substances and Disease Registry]. Mining areas in the eastern United States have also been discovered to contain naturally occurring asbestos. To obtain the asbestos for use -- and to make it airborne -- the rock must be crushed to release the fibers.

In commercial products, asbestos is still found in heat and acoustic insulation, fire proofing, and building materials like roofing and flooring. Additionally, asbestos can be found in older automotive parts like disc brake pads and drum brake linings, which used asbestos because of its friction properties [source: Asbestos Project Plan]. Banned new products include flooring felt, cement shingles (also known as asbestos siding), and corrugated, commercial and specialty paper. However, older material that used asbestos can still be found widely [source: EPA].

Asbestos testing should be conducted by licensed government agencies, and trained asbestos abatement professionals should be the only ones performing the removal. In some cases, it's safer to seal the asbestos in rather than remove it. For more information on getting asbestos out of your house, see Is it safer to remove asbestos from a building or leave it there? In cases of emergency asbestos exposure -- when Hurricane Katrina hit New Orleans or the fall of the World Trade Center, for example -- the best thing to do is get out of the area (keeping your mouth and nose covered with a wet cloth when possible) and contact your state and local agencies or the Environmental Protection Agency for more information on proper testing, removal or containment.

Now that you know what and where to look for asbestos, we'll talk about warning signs to watch out for if you've been exposed to asbestos.

So you've been exposed to asbestos; how likely are you to get sick? Diseases from asbestos exposure take a long time to appear. The typical range is 10 to 40 years after exposure, although it depends on the type of illness as well as other factors, such as whether the patient is a smoker (which increases the probability of the person developing respiratory ailments). The concentration, duration and frequency of asbestos exposure also has a hand in determining your chances of developing an illness. The long and thin fibers of amphibole asbestos are more likely to reach the lower airways and inflame the lungs and pleura, the membrane that lines the lungs [source: Agency for Toxic Substances and Disease Registry].

The three most common illnesses associated with asbestos exposure are lung cancer, asbestosis and mesothelioma. All three share the common symptom of difficulty breathing.

Lung cancer causes the most deaths due to asbestos exposure, although asbestos exposure is not the only culprit [source: EPA]. Common symptoms include coughing, chest pains, hoarseness and anemia.

Asbestosis is the result of asbestos scratching and scarring lung tissue. It usually shows up the earliest of all the respiratory ailments -- typically 10 to 20 years following exposure [source: Agency for Toxic Substances and Disease Registry]. A common symptom is a dry, cracking sound in the lungs while inhaling.

Mesothelioma is a rare cancer that affects the pleura. The majority of mesothelioma cases are due to asbestos exposure [source: Mesothelioma]. It may take years to develop, and may resemble pneumonia. Some common symptoms include chest pains and a persistent cough.

If you think you may have an asbestos-related respiratory illness, consult a pulmonary physician immediately.

For more information on asbestos, lung disease and related topics, see the links on the next page.