3.1 - Asbestosis
3.2 - Lung Cancer
3.3 - Mesothelioma
Asbestos is a term that encompasses a number of non-metallic minerals sharing a certain fibrous form. Amphiboles are species of asbestos that are formed in iron-ore host rock. As opposed to chrysotile, or "white asbestos," amphibole fibres are straight and stiff. Commercially, amphiboles were valued for their tensile strength and have been most commonly used as a component of cement. Crocidolite or "blue asbestos" is one of two types of amphiboles that were mined in South Africa. Once inhaled, all types of asbestos can cause lung disease. There are three major diseases caused by the inhalation of asbestos fibres: asbestosis, lung cancer and mesothelioma. Disease occurs when asbestos fibres interact with the cells in a patient's lungs, and is affected by the intensity and duration of exposure, size of fibres and type of exposure. Other modifying factors also affect disease, as not everyone with identical asbestos exposure will develop the same disease; some will not get sick at all. It is also suggested, although not well documented, that asbestos can cause stomach cancer when ingested and intestinal cancer if fibres migrate from the lungs.
3.1 -
Asbestosis
Asbestosis is scarring, or fibrosis, of the lung. When asbestos fibres are breathed
in and enter the lung, they are taken up by cells of the immune system. The
activation of immune cells results in scarring. Asbestosis diminishes the ability
of the patient to work and, at advanced stages, prevents those affected from
exerting even minimal effort without becoming breathless. The development of
asbestosis is related to dose, and generally takes 10-20 years for the individual
to become symptomatic.
3.2 -
Lung Cancer
Although no one has determined the mechanism of disease, lung cancer
as caused by asbestos is identical to lung cancer caused by smoking. The synergistic
relationship between smoking and asbestos exposure in the development of lung
cancer has been well documented: smoking increases the risk of contracting lung
cancer from asbestos exposure 50-fold. The latency period for lung cancer is
10-30 years.
3.3
- Mesothelioma
Caused exclusively by asbestos, mesothelioma is a cancer of the cells that line
the pleura, which surrounds the lungs. Mesothelioma is characterised as an aggressive
tumour, but the mechanism of disease is an active area of research. Asbestos
fibres migrate through the lungs to the pleura, where they interact with mesothelial
cells and cause a growth. The tumour can take up to 40 years to develop after
exposure, but once it forms it can quickly spread to other tissues. The disease
is usually fatal within 18 months of diagnosis. Unlike asbestosis, mesothelioma
does not appear to be dose-related-developing the disease is not related to
the amount of asbestos exposure.