(See also Overview of Environmental Lung Diseases.)
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.
Asbestos can also cause lung cancer. Lung cancer due to asbestos is related in part to the level of exposure to asbestos fibers. Among people with asbestosis, lung cancer occurs most commonly in those who also smoke cigarettes, particularly those who smoke more than a pack a day.
Although the public has become alarmed about the risks of asbestos, people who have no occupational exposure have a very low risk of developing asbestos-related lung disease. The asbestos must be broken into tiny pieces to be inhaled into the lungs. Workers who demolish buildings that have insulation containing asbestos are at increased risk. People who regularly work with asbestos are at greatest risk of developing lung disease. The more a person is exposed to asbestos fibers, the greater the risk of developing an asbestos-related disease.
Symptoms of asbestosis appear gradually only after large areas of the lungs become scarred. The scarring causes the lungs to stiffen. The first symptoms are a mild shortness of breath and a decreased ability to exercise. Smokers who have chronic bronchitis (longstanding inflammation of the large airways) along with asbestosis may cough and wheeze. Gradually, breathing becomes more and more difficult. In about 15% of people with asbestosis, severe shortness of breath and respiratory failure develop.
People with asbestosis usually have abnormal lung function, and a doctor listening with a stethoscope placed over the lungs can usually hear abnormal sounds called crackles. In people who have a history of exposure to asbestos, doctors sometimes can diagnose asbestosis with a chest x-ray or high-resolution computed tomography (CT) of the chest that shows characteristic changes. A lung biopsy is rarely needed to make the diagnosis.
Diseases caused by asbestos inhalation can be prevented by minimizing asbestos dust and fibers in the workplace. Because industries that use asbestos have improved dust control, fewer people develop asbestosis today. Asbestos-containing materials in a home are typically only a concern if the materials are going to be removed or the home renovated, in which case they should be removed by workers trained in safe removal techniques.
Smokers who have been in contact with asbestos can reduce their risk of lung cancer by giving up smoking and should probably have a chest x-ray annually.
Most treatments for asbestosis ease symptoms. Oxygen therapy relieves shortness of breath. Drugs and other measures, including limiting salt intake and losing weight if necessary, can help relieve heart failure.
Pulmonary rehabilitation may help people cope with lung symptoms and improve quality of life.