Pleural Disease Risk Factors

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The pleura, or pleural lining is a membrane that covers both the inner chest wall and the surface of the lungs; the narrow space between these layers is known as the pleural cavity. They are part of what is called in medical terms the mesothelium, which consists of all similar membranes that cover and provide protection and lubrication for most of the bodily organs.

Any infections or adverse conditions that affect this space or the membranes – whether bacterial, viral or cancerous – are called pleural diseases. As with all diseases, there are associated risk factors that can affect one’s chances of being affected.


Mesothelioma Lung CancerOf course, the pleural disease that gets the most attention is mesothelioma, or cancer of the mesothelium. This is a highly aggressive, malignant cancer that commonly spreads to nearby organs, and has even been found in distant areas such as the gastro-intestinal tract and the brain.

It has been demonstrated that malignant mesothelioma is caused by prolonged and/or heavy exposure to asbestos fibers, thereby making it an asbestos cancer. These fibers are inhaled deep into the lungs, where they literally burrow into the inner tissues of the alveoli, or air sacs. Eventually, they go straight through to the outer surface of the lung and the pleura, where their interactions with living cells somehow cause mutations at the level of the DNA. This is what causes them to become cancerous, although medical researchers are not completely certain of the exact mechanism – or why some people exposed to asbestos develop mesothelioma, particularly pleural mesothelioma, and many do not.

It is believed by some medical researchers that part of the risk factor may be connected to a contaminated polio vaccine administered to children between 1957 and 1963. The contaminant was a virus called SV40. This virus has been reported found in human mesothelioma tissues and has been known to induce mesothelioma in laboratory animal subjects; it is also associated with other types of cancer. A definite link between human mesothelioma and SV40 alone has not yet been proven. There is evidence that SV40 may trigger the formation of mesothelioma cells in the presence of asbestos fibers, however.

Mesothelioma Diagnosis RatesThe amount of asbestos to which one is exposed appears to have a great deal of bearing on whether or not mesothelioma develops. However, this factor seems to vary widely from one individual to another. Some people who have worked around asbestos for years never develop the disease; others contract mesothelioma after only brief exposure. In general however, the chance of contracting mesothelioma is proportionate to the amount and length of asbestos exposure.

One risk factor that increases the chances exponentially is tobacco use. According to several studies, a cigarette smoker exposed to asbestos has a chance 90 times greater of obtaining a mesothelioma diagnosis than a non-smoker.


Asbestosis is caused by the build-up of scar tissue on lung surfaces. This scar tissue is fibrous, causing the lung and pleural tissues to become stiff. As the scar tissue builds up, pressure is put on the lungs, and they are increasingly unable to expand.

This occurs because antibodies, known as macrophages, recognize microscopic asbestos fibers as a foreign (exogenous) pathogen and attempt to attack them. Because these fibers are silicon, not carbon-based however, the caustic acids produced by macrophages that would normally destroy organic viruses and bacteria have little effect. Instead, the macrophages are shredded on the sharp extrusions of asbestos fibers. This releases their digestive acid and allows it to attack healthy tissues. As these chemical burns heal, scar tissue forms and builds up over time.

Again, the risk factor is exposure to asbestos fibers, and is dependent on the length of time and amount of exposure.

Occupational Risk Factors

Because asbestos was so aggressively marketed as a “miracle mineral” so widely for so long, it is difficult to find an occupation in which substantial asbestos exposure risk has not been a factor.

At the top of the list are those who have worked in asbestos mining and manufacture. These workers were working with asbestos directly, and therefore had the heaviest ongoing exposure.High Risk Occupations

Also at risk are family members of these workers. The reason is that asbestos fibers were frequently lodged in the hair and clothing of these workers, and were subsequently carried into the home.

Beyond asbestos mining and manufacture, almost anyone who has worked in industrial manufacturing and/or production, as well as construction sites and building and/or demolition has almost certainly been exposed to asbestos to some degree. In general, if there was fireproofing or danger from extreme heat was a factor in any way, there was asbestos somewhere.

Other Risk Factors

There are genetic and pathogenetic factors as well as elements of a person’s health history that and make one more predisposed to pleural disease. One of these is the existence of pleural plaques.

Pleural plaques are areas of the inner rib cage and the diaphragm that have become fibrous and calcified – in other words, the tissue becomes stiff and inflexible. This is usually caused by genetic factors, but can be attributed to environmental factors, such as asbestos exposure.

Mesothelioma DiagnosisA study conducted in Uppsala, Sweden between 1963 and 1980 indicated that people with pleural plaques ran an increased risk of lung cancer. Unfortunately, the study did not provide controls for smoking, and therefore the results have been questioned.

Regardless of whether mesothelioma or other pleural diseases are connected with pleural plaques caused by disease or the environment, it is clear that such plaques by themselves do not cause mesothelioma or lung cancers by themselves; invariably, there is a history of asbestosexposure.

Non-Asbestos Pleural Disease

Pleural conditions not due to environmental factors and occupational asbestos exposure are actually common. These involve infections and fluid build-up in the pleural cavity, but are not in fact diseases, but rather symptoms of bacterial and/or viral infections. They include pneumonia, pleurisy, and pleural effusion as well as empyema.

While these symptoms can be life-threatening and require professional medical attention, they are usually quite treatable with antibiotics and other medications.


‘Pleural Disease Risk Factors’ Resources:


  1. Bowker, Michael. Fatal Deception, pp. 116 – 121.
  2. Lee, Y.C. “SV40 As a Causative Agent in Mesothelioma.”
  3. Bocchetta, M., et. al. “Human Mesothelial Cells are Unusually Susceptible to Simian Virus 40.”
  4. Carrier, Delos D., MD. “Asbestosis & Asbestos-Related Pleural Disease.”
  5. Reinhartz, Abe. “Fact Sheet on Pleural Plaques.”