Silicosis is a progressive disease that belongs to a group of lung disorders called pneumoconioses. Silicosis is marked by the formation of lumps (nodules) and fibrous scar tissue in the lungs and is caused by exposure to inhaled particles of silica, mostly from quartz in rocks, sand, and similar substances.
Silicosis is the oldest known occupational lung disease. It was first described in 1705 in stonecutters. An estimated 2 million workers in the United States are employed in occupations at risk for the development of silicosis. These include miners, foundry workers, stonecutters, potters and ceramics workers, sandblasters, tunnel workers, and rock drillers. Risk of developing silicosis increases with increasing years of exposure.
Silicosis is mostly found in adults over 40 years of age. It has four forms:
The precise mechanism that triggers the development of silicosis is still unclear. What is known is that particles of silica dust get trapped in alveoli in the lungs where air exchange takes place. White blood cells called macrophages enter the alveoli, ingest the silica, and die. The resulting inflammation attracts other macrophages to the region. The nodule forms when the immune system forms fibrous tissue to seal off the reactive area. The disease process may stop at this point or speed up and destroy large areas of the lung. The fibrosis may continue even after the worker is no longer exposed to silica.
Diagnosis of silicosis is based on the following:
There is no cure for silicosis. Therapy is intended to relieve symptoms, treat complications, and prevent respiratory infections. It includes careful monitoring for signs of TB. Respiratory symptoms may be treated with bronchodilators, increased fluid intake, steam inhalation, and physical therapy. Patients with severe breathing difficulties may be given oxygen therapy or placed on a mechanical ventilator. Acute silicosis may progress to complete respiratory failure. Heart-lung transplants are the only hope for some patients.
Patients with silicosis should call their doctor for any of the following symptoms:
Patients with silicosis should be advised to quit smoking, prevent infections by avoiding crowds and persons with colds or similar infections, and receive vaccinations against influenza and pneumonia. They should be encouraged to increase their exercise capacity by keeping up regular activity and to pace themselves with their daily routine.
Silicosis is currently incurable. The prognosis for patients with chronic silicosis is generally good. Acute silicosis, however, may progress rapidly to respiratory failure and death.
Silicosis is a preventable disease. In the United States, the National Institute for Occupational Safety and Health (NIOSH) standard for exposure to inhalable silica is 0.05 mg/m3, whereas the Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit slightly higher at 10 mg/m3. These workplace rules have substantially decreased the number of cases of silicosis in American workers.
Other preventive occupational safety measures are:
Coworkers of anyone diagnosed with silicosis should be examined for symptoms of the disease. The state health department and OSHA or the Mine Safety and Health Administration (MSHA) must be notified whenever a diagnosis of silicosis is confirmed.
See also Fibrosis ; Smoking .
Rosner, David, and Gerald Markowitz. Deadly Dust: Silicosis and the On-going Struggle to Protect Workers' Health. Ann Arbor: University of Michigan Press, 2006.
Tarlo, Susan, Paul Cullinan, and Benoit Nemery, eds. Occupational and Environmental Lung Diseases: Diseases from Work, Home, Outdoor and Other Exposures. Hoboken, NJ: Wiley, 2010.
National Center for Biotechnology Information. “Resources for Silicosis.” http://www.ncbi.nlm.nih.gov/sites/ga?disorder=Silicosis (accessed September 18, 2012).
National Institute for Occupational Safety and Health (NIOSH). “Silica.” Centers for Disease Control and Prevention. http://www.cdc.gov/niosh/topics/silica (accessed September 18, 2012).
Varkey, Basil. “Silicosis.” Medscape Reference. http://emedicine.medscape.com/article/302027-overview (accessed September 18, 2012).
Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30333, (404) 639-3534, (800) 232-4636; TTY: (888) 232-6348, firstname.lastname@example.org, http://www.cdc.gov .
Mine Safety and Health Administration, 4015 Wilson Blvd., Arlington, VA, 22203, (877) 778-6055, MSHAhelp email@example.com, http://www.msha.gov .
National Center for Biotechnology Information, 8600 Rockville Pike, Bethesda, MD, 20894, (301) 496-2475, http://www.ncbi.nlm.nih.gov .
Occupational Safety & Health Administration, 200 Constitution Ave. NW, Washington, DC, 20210, http://www.osha.gov .
Revised by Tish Davidson, AM