Asbestos-Related Disorders (cont.)
What are the types of asbestos fibers?
There are two major groups of fibers, the amphiboles and
chrysotile fibers. Chrysotile (white asbestos), also
called "Serpentine" fibers, are long and curled. The
amphiboles, long straight fibers (including actinolite,
amosite, anthrophyllite, crocidolite, and tremolite) are
much more likely to cause cancer of the lining of the lung
(mesothelioma) and scarring of the lining of the lung
(pleural fibrosis). Either group of fibers can cause
disease of the lung, such as asbestosis.
The risk of developing asbestos-related lung cancer
varies between fiber types. Studies of groups of patients
exposed chrysotile fibers show only a moderate increase in
risk. On the other hand, exposure to amphibole fibers or
to both types of fibers increases the risk of lung cancer
by two fold. Although the Occupational Safety and Health
Administration (OSHA) has a standard for workplace exposure
to asbestos (0.2 fibers/milliliter of air), there is debate
over what constitutes a safe level of exposure. While some
believe asbestos-related disease is a "threshold
phenomenon," which requires a certain level of exposure for
disease to occur, others believe there is no safe level of
asbestos.
In most buildings, asbestos does not become airborne.
However, surfaces that are damaged or disturbed can cause
asbestos to become inhalable. High concentrations can
occur after cutting, sanding, or remodeling asbestos-
containing materials.
Reducing asbestos exposure involves either the removal or
sealing of asbestos-containing materials. Inexperienced
attempts to remove asbestos can release dangerous levels of
the fibers.
what does fiber size have to do with asbestos-related lung disease?
Depending on their shape and size, asbestos fibers deposit in different areas of the lung. Fibers less than 3 mm easily move into the lung tissue and the lining surrounding the lung (pleura). Long fibers, greater than 5 mm (1/5 inch), cannot be completely broken down by scavenger cells (macrophages) and remain in the lung tissue. These asbestos fibers can cause inflammation. Substances damaging to the lungs are then released by the cells of inflammation that are responding to the foreign asbestos material. The persistence of these long fibers in the lung tissue and the resulting inflammation seem to initiate the process of cancer formation.
As inflammation and damage to tissue around the asbestos fibers continues, the resulting scarring can extend from the small airways to the larger airways and the tiny air sacs (alveoli) at the end of the airways. Some of these fibers can move to the surface of the lung where they form plaques (white-gray regions of scarred tissue) in the tissue lining of the lung (pleura). In severe cases of asbestosis, scarring of both the lung and its lining tissue can occur.
Next: What is asbestosis? »
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