Asbestos is a family of naturally occurring compounds whose heat-resistant and structural properties made it useful for inclusion in construction and shipbuilding materials, automobile brakes, and some textiles. Asbestos can be found in low levels in the air, water, and soil, but this low level of environmental exposure is not a significant contributor to human disease. Asbestos is composed of fibrous mineral silicates of different chemical compositions. When inhaled, asbestos fibers settle deep in the lungs, causing scars. Asbestos inhalation also can cause the two layers of membranes covering the lungs (the pleura) to thicken. These thickenings are called pleural plaques. These plaques do not become cancerous.
Inhaling asbestos fibers can occasionally cause fluid to accumulate in the space between the two pleural layers of the lungs (pleural space). This fluid accumulation is called a noncancerous (benign) asbestos effusion.
People with a noncancerous asbestos effusion may have difficulty breathing because of fluid accumulation. Pleural plaques tend to cause only mild breathing difficulty resulting from stiffness of the chest wall. Sometimes plaques cause no symptoms but decrease lung function.
(See also Overview of Environmental Lung Diseases.)
Pleural plaques that develop in many people with exposure to asbestos often contain calcium, which makes them easy to see on chest x-rays and computed tomography (CT).
If a tumor of the pleura is found on the x-ray, CT is usually done. If CT confirms that a tumor is possible, doctors must do a biopsy (remove a small piece of pleura and examine it under a microscope) to determine whether the tumor is cancerous. Fluid around the lungs may be removed with a needle and analyzed for cancer cells (a procedure called thoracentesis). However, thoracentesis is not usually as accurate as a pleural biopsy.