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Asbestos and Disease: Established Links

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Medical researchers have strongly associated inhalation of asbestos fibers in the air with debilitating lung diseases and cancer. Following are brief descriptions of some of those diseases.

Asbestosis

Asbestosis refers to a permanent scarring of the lung tissue caused by asbestos fibers trapped in the lungs. It is not a cancer. The most common clinical manifestation of asbestos exposure is minor scarring on the lining of the lungs, according to Dr. Mark Cullen, assistant professor of medicine and epidemiology at the Yale University School of Medicine and director of the Yale-New Haven Occupational Medicine Program. He says that minor scarring does not have serious consequences.

However, once scarring has occurred, it is irreversible. Beyond a certain stage, the disease seems able to progress without additional exposure. After 10 to 30 years, the scars become thick and stiff. The lungs retract and become small and hard, making it difficult for oxygen to pass from within them into the bloodstream. At this point, the scars can cause serious disability. This is what most people commonly think of as asbestosis.

An afflicted person is unable to breathe adequately and eventually suffocates. However, asbestos victims can die before this stage from heart failure and pulmonary complications, such as pneumonia.

If asbestosis is detected early enough, and exposure to asbestos ends, doctors can sometimes halt the progress of the disease. They can also lower the risk of death (for example, by convincing a patient to stop smoking). But in its advanced stages, asbestosis is incurable and almost always fatal.

In general, large amounts of asbestos exposure are needed to develop substantial lung scarring. Doctors say such exposure is highly unlikely in school settings for students and most teachers. It may be likely for school maintenance personnel who actually work with asbestos6laden materials.

Mesothelioma

Mesothelioma is an extremely rare cancer of the lining of the chest or abdominal cavity. Doctors describe it as gradually encasing the lung and compressing it, until the cancer fills up the entire air space. The disease is always fatal; there is no cure.

Even brief or low levels of exposure to airborne asbestos fibers may cause mesothelioma. However, the disease usually does not appear until 30 to 40 years after exposure. By the time its symptoms are diagnosed, death usually occurs within one to two years.

Asbestos is virtually the only known cause of mesothelioma. (In central Turkey, a few cases of the disease have been associated with a volcanic mineral fiber called eronite.) The cancer accounts for about 10 percent of the deaths among asbestos workers, according to the Occupational Safety and Health Administration.

The incidence of mesothelioma has risen rapidly in the last 20 to 25 years, according to Dr. Irving J. Selikoff, director of the Environmental-Sciences Laboratory at the Mount Sinai School of Medicine of the City University of New York. Because of the long lag between the time of ex-posure and the appearance of mesothelioma, many doctors say that many more cases will appear in the years ahead.

Lung Cancer

Lung cancer begins as a mass or lump somewhere in the miles of tubes that make up the lungs and eventually spreads.

After exposure to asbestos, lung cancer may take up to 20 or 25 years to develop. The disease accounts for some 20 percent of all deaths among asbestos workers.

The chances of developing lung cancer depend upon a person's level of asbestos exposure, age, and background risk for lung cancer (such as whether the person smokes).

Other cancers that have been associated with asbestos exposure include cancers of the digestive system and of the upper-respiratory tract. In addition, asbestos may cause changes in the body's immunological system. The consequences of these changes are not known.--lo

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