Asbestos can cause cancer in the pleura (the thin, transparent, two-layered membrane that covers the lungs and lines the inside of the chest wall), called mesothelioma, or in the membranes of the abdomen. In the United States, asbestos is the only known cause of mesothelioma (see Overview of Environmental Lung Diseases). Smoking is not a cause of mesothelioma.
Asbestos is composed of fibrous mineral silicates of different chemical compositions. Mesotheliomas most commonly occur after exposure to crocidolite, one of four types of asbestos. Amosite, another type, also causes mesotheliomas. Chrysotile probably causes fewer cases of mesotheliomas than other types, but chrysotile is often contaminated with tremolite, which does. Mesotheliomas usually develop about 30 years after exposure and can occur after low levels of exposure.
Mesothelioma and other 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, but mesotheliomas are still occurring in people who were exposed as many as 30 to 50 years ago.
Persistent pain in the chest and shortness of breath are the most common symptoms of mesothelioma. If mesothelioma spreads to the chest wall or other nearby structures in the chest, the person may have severe pain, hoarseness, difficulty swallowing, a drooping eyelid, weakness and loss of sensation in an arm or hand, or swelling of the abdomen.
When doctors suspect mesothelioma, a chest x-ray is usually done. Usually a sample of fluid from the pleural space (pleural fluid cytology) is analyzed and a sample of tissue from the pleura (pleural biopsy) is examined to look for characteristic changes due to mesothelioma.
Additional testing may be needed to determine whether mesothelioma has spread outside the pleura.
Mesotheliomas are invariably fatal within 1 to 4 years after diagnosis. Most people live for only 9 to 12 months after the mesothelioma is diagnosed. Chemotherapy and radiation therapy do not work well, and surgical removal of the tumor does not cure the cancer.
However, surgery to remove as much of the tumor as possible, chemotherapy, and/or radiation therapy may be helpful to relieve symptoms. It is not clear whether combinations of different kinds of treatments can prolong life. Other treatment is focused on controlling pain and shortness of breath in an effort to preserve as much quality of life as possible (see Symptoms During a Fatal Illness). For example, draining fluid from around the lungs may make breathing easier, and analgesics can relieve pain. Other treatments for mesothelioma are being studied.