Pleural Plaque and Asbestos Exposure

Asbestos is a naturally occurring mineral that was once used very prominently in the fields of manufacturing, insulation, and fireproofing. The strong and incombustible qualities of this mineral made it a perfect choice for many products like insulation and wall and ceiling panels. These products were readily used to wrap and insulate pipes, water lines, boilers, and electrical wires, and were used in the manufacturing of valves, gaskets, and other pieces of equipment that needed to be heat resistant.  However, when these products were installed, repaired, maintained, or removed the process disturbed the asbestos material and resulted in the release of asbestos dust.

Asbestos dust contains microscopic particles of asbestos fiber that travel through the air and can be inhaled by workers or other individuals near the asbestos-containing product. This dust can enter the body through the airways (mouth and nose) or cling to the clothing of working and later be inhaled or ingested by family members. The dust includes both types of asbestos- straight (amphiboles) and curly (chrysotile). Chrysotile asbestos is the most popular type of asbestos used in manufacturing, but because it is water-soluble its fibers clear the body faster after inhalation (1). Amphibole fibers, on the other hand, enter the body, lodge in the membranes and organs, and eventually cause inflammation.

Once these asbestos fibers have entered the body they can travel through the lymphatic system or the blood stream and lead to the development of many different types of asbestos-related diseases and conditions. Asbestos exposure has been proven to cause asbestosis, mesothelioma, lung cancer, pleural disease, pleural thickening, benign pleural effusion, and pleural plaques (2,3). Of all of the asbestos-related thoracic diseases the most common condition is pleural plaques.

Pleural plaques develop in exposed individuals within 20 to 40 years of initial asbestos exposure. This development is thought to be related to the body's immune system reaction to the fibers once they become imbedded in the membranes or organs. Pleural plaques develop after many years of exposure even if the exposure was low and intermittent. If the long-term exposure was high-level and continuous pleural plaques can still be found but the most common asbestos-related condition is then asbestosis.

Pleural plaques are distinguished from other asbestos-related diseases and conditions by their appearance. These plaques can be described as white, smooth, raised areas of fibrosis collagen tissue that are found on the inner surfaces of the ribcage, diaphragm and pleura. In addition these plaques are usually calcified and can range in size from small to large. 

Almost everyone who has ever been exposed to asbestos will suffer from pleural plaques. This is because the asbestos fibers work their way into the pleural lining (outer lining of the lung) where they cause chronic inflammation and eventual scarring from that inflammation. The plaques are a direct result of the pleural scarring. Thankfully these plaques are always benign in natural, and will not ever change from plaques to cancer. However, there is some current scientific evidence that suggests that any individuals that are plagued by pleural plaques do have an increased risk for developing mesothelioma (4,5).

Although the rate of pleural plaque development for anyone experiencing asbestos exposure is high, the number of individuals who know they are suffering from the condition is low. This is because the disease known as pleural plaques does not produce any symptoms. With a lack of side effects and symptoms, the condition can go undiagnosed until another possibly unrelated condition produces symptoms. It is usually when the individual seeks medical attention for another condition that the pleural plaques are found in the pleural lining.

Most individuals become aware that they suffer from pleural plaques once they undergo a chest x-ray for the diagnosis of another condition, such as pneumonia or chest pain. Pleural plaques show up on regular x-rays as forms of shadowing. The shadowing is a result of the calcification of the plaques.

Although an x-ray can pinpoint areas of abnormality and promote suspicion of plaques, a chest CT scan is the diagnostic tool of choice for confirming a diagnosis.  CT scans offer higher resolution images and better showcases the areas of pleural calcification in the pleural lining (6).

Once pleural plaques are diagnosed the condition does not call for any type of treatment. Since the plaques do not cause symptoms and their formation is non-life threatening their removal is pointless and no current treatment exists. However, patients that are diagnosed with pleural plaques are encouraged to schedule regular check-ups. These regular physicals can help doctors monitor the growth of the plaques or scarring. As part of the regular check-up patients are encouraged to undergo pulmonary (breathing) tests to monitor lung function.  Pulmonary tests, along with other routine tests, can be used to evaluate the patient's condition and rule out the development of other asbestos-related diseases.

Any history of asbestos exposure puts an individual at greater risk for developing life-threatening diseases later in life. Pleural plaques are not serious but many of the other asbestos-related conditions are. If you have ever worked around or been exposed to asbestos containing products you are urged to see a doctor as soon as possible. Although many of the asbestos-related diseases are not curable, such as mesothelioma, early detection can help increase the chances of a positive outcome to treatment and help prolong life once a diagnosis has been made.

'Pleural Plaque and Asbestos Exposure' Resources:
  1. Hillderdal, G: Asbestos, Asbestosis, Pleural Plaques and Lung Cancer; Scand J Work Environ Health; 1997; 23:93-103
  2. Peacock C, Copley SJ, Hansell DM: Asbestos-related benign pleural disease. Clin Radiol 2000 Jun; 55(6): 422-32
  3. Bolton C, Richards A, Ebden P: Asbestos-related disease. Hosp Med 2002 Mar; 63(3): 148-51
  4. Bianchi, C: Pleural Plaques as Risk Indicators for Malignant Pleural Mesothelioma: A Necropsy-Based Study; Am J Ind Med 32:445-449 (1997) 
  5. Hillderdal, G: Pleural Plaques and Risk for Cancer in the County of Uppsala; Europ J Respir Div Suppl 107 Vol 61, 1980 pp 111-117
  6. berle DR: High-resolution computed tomography of asbestos-related diseases. Semin Roentgenol 1991 Apr; 26(2): 118-31