Health Effects
of Exposure to Asbestos
General Information
Significant exposure
to any type of asbestos will increase the risk of lung cancer,
mesothelioma and nonmalignant lung and pleural disorders, including
asbestosis, pleural plaques, pleural thickening, and pleural effusions.
This conclusion is based on observations of these diseases in
groups of workers with cumulative exposures ranging from about
5 to 1,200 fiber-year/mL. Such exposures would result from 40
years of occupational exposure to air concentrations of 0.125
to 30 fiber/mL. See Detecting Asbestos for typical levels of concentration.
The conclusion is supported by results from animal and mechanistic
studies.
Diseases from asbestos
exposure take a long time to develop. Most cases of lung cancer
or asbestosis in asbestos workers occur 15 or more years after
initial exposure to asbestos. Tobacco smokers who have been exposed
to asbestos have a "far greater-than-additive" risk
for lung cancer than do nonsmokers who have been exposed, meaning
the risk is greater than the individual risks from asbestos and
smoking added together. The time between diagnosis of mesothelioma
and the time of initial occupational exposure to asbestos commonly
has been 30 years or more. Cases of mesotheliomas have been reported
after household exposure of family members of asbestos workers
and in individuals without occupational exposure who live close
to asbestos mines.
Asbestos Facts:
• When asbestos fibers are inhaled, most fibers are expelled,
but some can become lodged in the lungs and remain there throughout
life. Fibers can accumulate and cause scarring and inflammation.
Enough scarring and inflammation can affect breathing, leading
to disease.
• People are more likely to experience asbestos-related
disorders when they are exposed to high concentrations of asbestos,
are exposed for longer periods of time, and/or are exposed more
often.
• Inhaling longer, more durable asbestos fibers (such as
tremolite and other amphiboles) contributes to the severity of
asbestos-related disorders.
• Exposure to asbestos, including tremolite, can increase
the likelihood of lung cancer, mesothelioma, and non-malignant
lung conditions such as asbestosis (restricted use of the lungs
due to retained asbestos fibers) and changes in the lung lining.
• Changes in the lining of the lungs (pleura) such as thickening,
plaques, calcification, and fluid around the lungs (pleural effusion)
may be early signs of asbestos exposure. These changes can affect
breathing more than previously thought. Pleural effusion can be
an early warning sign for mesothelioma (cancer of the lining of
the lungs).
• Most cases of asbestosis or lung cancer in workers occurred
15 years or more after the person was first exposed to asbestos.
• Most cases of mesothelioma are diagnosed 30 years or more
after the first exposure to asbestos.
• Mesothelioma has been diagnosed in asbestos workers, family
members, and residents who live close to asbestos mines.
• Health effects from asbestos exposure may continue to
progress even after exposure is stopped.
• Smoking or cigarette smoke, together with exposure to
asbestos, greatly increases the likelihood of lung cancer.
Health Risks of Asbestos Exposure
Chronic exposure to asbestos may increase the risk of lung cancer,
mesothelioma, and nonmalignant lung and pleural disorders. Evidence
in humans comes from epidemiologic studies as well as numerous
studies of workers exposed to asbestos in a variety of occupational
settings. Tremolite asbestos exposure has been associated with
an increased incidence of disease in vermiculite miners and millers
from Libby, Montana. This evidence is supported by reports of
increased incidences of nonmalignant respiratory diseases, lung
cancer, and mesothelioma in villages in various regions of the
world that have traditionally used tremolite-asbestos whitewashes
in homes or have high surface deposits of tremolite asbestos and
by results from animal studies.
Risk Factors
Various factors determine how exposure to asbestos affects an
individual:
• Exposure concentration - what was the concentration of
asbestos fibers?
• Exposure duration - how long did the exposure time period
last?
• Exposure frequency - how often during that time period
was the person exposed?
• Size, shape and chemical makeup of asbestos fibers:
Long and thin fibers are expected to reach the lower airways and
alveolar regions of the lung, to be retained in the lung longer,
and to be more toxic than short and wide fibers or particles.
Wide particles are expected to be deposited in the upper respiratory
tract and not to reach the lung and pleura, the sites of asbestos-induced
toxicity. Short, thin fibers, however, may also play a role in
asbestos pathogenesis. Fibers of amphibole asbestos such as tremolite
asbestos, actinolite asbestos, and crocidolite asbestos are retained
longer in the lower respiratory tract than chrysotile fibers of
similar dimension.
• Individual risk factors, such as a person's history of
tobacco use (smoking) and other pre-existing lung disease, etc.
Note, cigarette smoke and asbestos together significantly increase
your chances of getting lung cancer. Therefore, if you have been
exposed to asbestos you should stop smoking. This may be the most
important action that you can take to improve your health and
decrease your risk of cancer.
Additional Asbestos
and Mesothelioma information can be found by visiting
http://www.help-for-mesothelioma.com .
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