Overview

Asbestos exposure becomes a health concern when relatively high concentrations of asbestos fibers are inhaled over a long time period. People who become ill from asbestos are almost always those who are exposed on a day-to-day basis in a job where they work directly with the material. As a person's exposure to fibers increases, either by breathing large amounts of fibers or by breathing fibers for a longer time, the risk of disease also increases. It can take anywhere from 10 to 40 years after exposure for an asbestos-related illness to develop. There is no known safe level of asbestos exposure. Great care should be exercised when asbestos exposure is likely.

The following government offices and regulatory agencies have deemed asbestos a known human carcinogen based on extensive review of the data and of the evidence regarding the carcinogenicity of asbestos.

  • The U.S. Department of Health and Human Services (DHHS).
  • The U.S. Environmental Protection Agency (EPA).
  • The International Agency for Research on Cancer (IARC).

    Potential Exposure

    Asbestos minerals are widespread in the environment. They may occur in large natural deposits or as contaminants in other minerals. For example, tremolite asbestos may occur in deposits of vermiculite and talc. Asbestos may also be found in soil formed from the erosion of asbestos-bearing rock.

    You are most likely to be exposed to asbestos by breathing in fibers that are suspended in air. These fibers can come from naturally occurring sources of asbestos, or from the wearing down or disturbance of asbestos-containing manufactured products including insulation, automotive brakes and clutches, ceiling and floor tiles, dry wall, roof shingles, and cement.

    Low levels of asbestos that present little, if any, risk to your health can be detected in almost any air sample. For example, 10 fibers are typically present in a cubic meter (fibers/m3) of outdoor air in rural areas. (A cubic meter is about the amount of air that you breathe in 1 hour.) Health professionals often report the number of fibers in a milliliter (mL) (equivalent to a cubic centimeter [cm3]) of air rather than in a cubic meter of air. Typical levels found in cities are about 10-fold higher than in rural areas. Levels may reach 10,000 fibers/m3 or higher near an asbestos factory or mine. Above average levels may also occur near a building containing asbestos products that is being torn down or renovated, or near a waste site where asbestos is not properly covered up or stored. The concentration of asbestos in indoor air depends on whether asbestos is present (for example, insulation, ceiling or floor tiles) and whether these asbestos-containing materials are in good condition, or are deteriorated and easily crumbled.

    People who work with asbestos or asbestos-containing products (for example, miners, insulation workers, asbestos abatement workers, and automobile brake mechanics) without proper protection are likely to be exposed to much higher levels of asbestos fibers in air. In addition, custodial and maintenance workers in buildings with asbestos-containing materials may be exposed to higher levels of asbestos. Since vermiculite and talc may contain asbestos, both workers and the general population may be exposed to asbestos when using these products.

    You can also be exposed to asbestos by ingesting asbestos fibers present in drinking w ater. Even though asbestos does not dissolve in water the small fibers can be suspended in water like dust particles. The fibers can enter water through erosion from natural deposits or piles of waste asbestos, from asbestos-containing cement pipes used to carry drinking water, or from filtration through asbestos-containing filters. Most drinking water supplies in the United States have concentrations of less than 1 million fibers per liter (MFL), even in areas with asbestos deposits or with asbestos-cement water supply pipes. However, in some locations, water samples may contain 10-300 million fibers per liter or even higher. The average person drinks about 2 liters of water per day.

    The health effects of swallowing small amounts of asbestos are unclear. Some groups of people exposed to asbestos fibers in their drinking water have higher-than-average death rates from cancer of the esophagus, stomach, and intestines; however, it is very difficult to tell whether this is caused by asbestos or by something else. Animals given very high doses of asbestos in food did not get more fatal cancers than usual, although a higher than normal rate of nonfatal tumors did occur in the intestines of rats in one study.

    Asbestos does not pass through the skin.


    Entering and Leaving Body

    If you breathe asbestos fibers into your lungs, some of the fibers will be deposited in the air passages and on the cells that make up your lungs. Most fibers are removed from your lungs by the natural process of coughing up mucus that is then swallowed and carried into the stomach. This process usually takes place within a few hours. Fibers deposited in the deepest parts of the lung are removed more slowly. In fact, some fibers may remain in place for many years and may never be eliminated from your body. Amphibole asbestos fibers are retained in the lung longer than chrysotile asbestos fibers. If you swallow asbestos fibers (either those present in water or those that are moved to your throat from your lungs), nearly all of the fibers pass through your digestive system and are excreted in the feces within a few days. A small number of fibers may penetrate the cells that line the stomach and intestines, and a few may penetrate and enter the blood. Asbestos fibers in the bloodstream may become trapped in other tissues or eliminated in urine. Asbestos fibers do not pass through the skin.


    Treatment

    A chest x-ray is the most common test used to determine if you have received sustained exposure to asbestos. A chest x-ray is recommended only for persons who have sustained relatively heavy exposure to asbestos. A chest x-ray is of no value for the detection of asbestos exposure in a person whose exposure to asbestos has been only brief (industrial or occupational) or transient (environmental). The x-ray cannot detect the asbestos fibers themselves, but it can detect the early signs of lung damage caused by asbestos. While substances other than asbestos can sometimes produce similar changes in the lungs, a chest x-ray is usually reliable for detecting asbestos-related effects produced by long-term exposures at relatively high concentrations of asbestos fibers.

    Other tests, such as gallium-67 lung scanning and high-resolution computer tomography, are also useful in detecting changes in the lungs; however, no currently available test can detect exposure-related effects from normal environmental exposures.

    The most reliable test to determine exposure to asbestos is a biopsy. In this test small pieces of lung tissue are removed surgically and examined for the presence of microscopic asbestos fibers. Another direct test involves determining the presence of asbestos fibers in material rinsed out of the lung through lavage. Both biopsy and lavage are invasive and uncomfortable. Asbestos fibers can also be detected in mucus (sputum), urine, or feces, but these tests are not reliable for determining how much asbestos may be in your lungs since nearly all people show low levels of asbestos fibers in body waste products. Higher-than-average levels in mucus, urine, or feces can indicate exposure to asbestos, but it is not yet possible to use the results of these tests to estimate how much asbestos you have been exposed to, or to predict whether you are likely to suffer any health effects.

    Individuals who have been exposed (or suspect they have been exposed) to asbestos fibers on the job or at home 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, although these tests do not indicate the actual amount of asbestos in the lungs. Your doctor may recommend a thorough physical examination, including a chest x-ray and lung function tests. 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 experienced in reading x-rays for asbestos-related diseases. Other tests may also be necessary. 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 (mucus) coughed up from the lungs.
  • Pain in the chest or abdomen.
  • Difficulty in swallowing or prolonged hoarseness.
  • Significant weight loss.

    • Prevention

    The most important way that families can lower their exposures to asbestos is to be aware of the sources of asbestos in their homes and avoid exposure to these sources.

    The most important source of asbestos in a home is damaged or deteriorating asbestos-containing insulation, ceiling tiles, or floor tiles. Should you suspect that your house contains asbestos, you may wish to use this website to locate a company that is trained to abate the asbestos.

    Prior to disturbance or when damaged, contact a professional to identify asbestos-containing materials in the home and take appropriate action to control release of asbestos fibers.

    If you live close to locations where asbestos and certain other ores are mined or processed, where a building that contains asbestos products is being torn down or renovated, or a waste site where asbestos is not properly covered, then the levels of asbestos in dust and wind-blown soil may be higher. Keep windows shut to avoid dust accumulation inside your home. Be sure to clean dust from your shoes or remove your shoes upon entry into the house. Pets can also bring asbestos into the home by carrying dust or dirt on their fur or feet if they spend time in places that have high levels of asbestos in the soil.

    Ingesting asbestos in house dust or soil by hand-to-mouth activities (like thumb sucking or mouthing toys) is a significant exposure pathway for children that can be reduced in many ways. Regular hand and face washing to remove asbestos-containing dusts and soil, especially before meals, can lower the possibility of asbestos fibers on the skin being accidentally ingested while eating.

    Families can lower exposures to potential household hazards, such as asbestos, by using a high efficiency particulate air (HEPA)-equipped vacuum cleaner during regularly cleaning the home. By doing this settled fibers on the floors and horizontal surfaces are picked up along with the normal dust and tracked in soil. Residents should not attempt to clean-up asbestos fiber contamination from releases from damaged asbestos in the home, but should seek professional assistance to determine the extent of hazard and to remove contamination.

    Planting grass and shrubs over bare soil areas in the yard can lower the contact that children and pets may have with soil, and reduce the tracking of soil into the home.

    You can also bring asbestos into your home in the dust on your hands or clothes if you work in mine or are involved with the processing of minerals that contain asbestos, in asbestos removal, or in buildings with damaged or deteriorating asbestos. (Federal law regulates work practices to limit the possibility of asbestos being brought home in this way. Your occupational health and safety officer at work can tell you whether materials you work with contain asbestos and what measures you must take to avoid exposures to yourself and your family as a result of you work.)