The primary access path for asbestos exposure is the respiratory system. Fibers released into the air are inhaled by the subjects where they are carried into the deepest recesses of the lungs. Asbestos fibers that are locked into heavier particles of plaster, concrete or paint are often expelled through coughing and rarely reach deeply enough into the lungs.
“Clearing of Lungs” and the Development of Mesothelioma
From studies conducted in the early to mid-20th century, most of which were post-mortem examinations, it became apparent that pleural asbestos disease tended to accumulate near the bottom lobes of the lungs, in the gutter of the thoracic cavity and on the surface of the diaphragm after exposure to asbestos.
Microscopic examination of biopsy or autopsy tissue samples revealed that in many cases the asbestos fibers were no longer located in the alveoli of the lungs but rather in the intrapleural space or within the mesothelial lining of that space. This was described by many physicians as a “clearing” of the lungs, but despite the benign sounding label, this process held serious and potentially fatal implications for the subject. It has also been hypothesized that asbestos exposure can occur through fibers being swallowed or entering directly by piercing the skin. It is not known why some patients develop peritoneal mesothelioma rather than the more common pleural based disease.
Two Theories about the Development of Mesothelioma from Asbestos Exposure
The clearing of the lungs is directly connected to the two primary theories about how injury is caused by asbestos exposure. The first theory postulates that the asbestos fibers pierce the tissue walls of the pleural space (and sometimes the peritoneal space via the stomach or the diaphragm) and cause tissue damage which creates an inflammatory immune response. The second theory states that the asbestos fibers are so small that they begin to interact with mesothelial cells at a molecular level, interrupting cell replication and/or damaging the cellular DNA during mitosis, or cell division.
Do you have specific questions or concerns about the causes of mesothelioma, including details on the risks of asbestos exposure? The Mesothelioma Applied Research Foundation is here to offer support guidance and help. Talk to a mesothelioma expert for the latest information on research and clinical trials.
