Environmental Engineering Reference
In-Depth Information
(lining and coverings of the chest cavity) and cancers of the lung, pleura,
peritoneum (lining and coverings of the abdominal cavity), and possibly
other sites.
1.
Asbestosis
Asbestosis is a progressive, debilitating disease of the lungs characterized
by multisite fibrosis (scarring). Asbestosis has only been reported in asbestos
workers, and it appears that high-concentration, long-term exposures are
necessary for the development of clinical disease. Asbestosis, as a conse-
quence, is not a major health risk for exposures that occur in building envi-
ronments. As a result, occupants and those service personnel who occasion-
ally disturb ACBM are highly unlikely to develop asbestosis.
2.
Pleural disease
Exposure to asbestos fibers can result in physical changes in the lining and
coverings of the chest cavity (pleura). Such changes are described as pleural
plaques and diffuse thickening of pleural tissue. Pleural plaques are distinct
areas where pleura have developed a fibrotic thickening. Pleural plaques
impair lung function and produce respiratory symptoms. They are causally
related to asbestos exposure but do not appear to contribute to cancer
development.
Fibers from all asbestos minerals appear to cause pleural disease. The
development of plaques requires a latency period of more than 15 years.
Their prevalence increases with dose (number of fibers inhaled) and number
of years since initial exposure.
Radiological studies of building service workers, including carpenters,
sheet metal workers, and school custodians, have shown that these workers
are at risk of developing pleural plaques. This risk appears to be associated
with disturbing ACBM and/or resuspending asbestos fibers.
3.
Cancers
Exposure to asbestos fibers increases the incidence of bronchogenic carci-
noma, i.e.,
lung cancer. Tumors, however, are indistinguishable from those
caused by exposure to tobacco smoke or radon decay products. Asbestos-
associated lung cancer has been reported in both smokers and nonsmokers.
Combined exposures to tobacco smoke and asbestos fibers result in a syn-
ergistic response. On average, smokers have a lung cancer risk that is 10
times greater than that of nonsmokers; the lung cancer risk in nonsmokers
heavily exposed to asbestos fibers is approximately 5 times greater than in
nonsmoking, nonexposed workers. A smoker exposed to high levels of asbes-
tos has an increased risk of lung cancer that is approximately 50 to 55 times
greater than that of a non-asbestos-exposed, nonsmoking worker.
The risk of developing lung cancer from asbestos fiber exposure is dose
dependent, with risks greater for those with greater exposure. The latency
period is typically 20 years or longer.
