Silicosis is permanent scarring of the lungs caused by inhaling silica (quartz) dust.
People develop difficulty breathing during activity that sometimes progresses to shortness of breath at rest.
Some people also have a cough that may or may not produce sputum.
Diagnosis is based on a chest x-ray or chest computed tomography scan and a history of silica exposure.
Doctors may give medications to help breathing.
(See also Overview of Environmental and Occupational Lung Disease.)
Silicosis may be acute or chronic. Acute silicosis may develop after intense exposures over a few weeks or years. Chronic silicosis is the most common form and generally develops only after exposure over decades.
Causes of Silicosis
Silica is one of the most abundant minerals in the earth's crust and is widely distributed in nature. Silicosis is caused by inhalation of tiny particles of crystalline silica (usually quartz). Workers at greatest risk are those who move or blast rock and sand (miners, quarry workers, stonecutters, construction workers) or who use silica-containing rock or sand abrasives (sand blasters, glass makers, foundry, gemstone, and ceramic workers, potters). Outbreaks of severe silicosis have recently been identified in workers in the engineered stone industry.
Factors that influence the incidence and severity of silicosis include
Duration and intensity of exposure
Form and surface characteristics of the silica particles
Amorphous silica, such as glass or diatomaceous earth, does not have a crystalline structure and does not cause silicosis.
When inhaled, silica dust passes into the lungs, and scavenger cells such as macrophages engulf it (see Overview of the Immune System). Enzymes released by the scavenger cells cause the lung tissue to scar and form nodules. In low-intensity or short-term exposures, these nodules remain discrete and do not compromise lung function. With higher-intensity or more prolonged exposures, these nodules coalesce (come together) and cause progressive fibrosis and lung dysfunction, or they sometimes form large masses (called progressive massive fibrosis).
Symptoms of Silicosis
Silicosis can be acute or chronic. Chronic silicosis is more common.
People with acute silicosis experience shortness of breath, weight loss, and fatigue that progresses quickly. Respiratory failure is common.
Chronic silicosis often does not cause symptoms for years, but can progress to more severe disease. Many people with chronic silicosis develop difficulty breathing and cough over time. The lung damage can lead to lower levels of oxygen in the blood and can also strain the right side of the heart. This strain can lead to a type of heart failure called cor pulmonale, which can be fatal.
Complications
People with silicosis are at risk of other disorders:
Tuberculosis (TB)
Chronic obstructive pulmonary disease (COPD)
Lung cancer
Systemic rheumatic (autoimmune) diseases
People with silicosis have an increased risk of developing mycobacterial infections, such as tuberculosis.
Silica exposure is associated with increased risk of chronic obstructive pulmonary disease (such as emphysema or chronic bronchitis).
People with silicosis are at increased risk of lung cancer. Crystalline silica has been identified by the International Agency for Research on Cancer (IARC) as a Group 1 human lung carcinogen.
Exposure to crystalline silica is also associated with increased risk of several systemic rheumatic diseases, including rheumatoid arthritis and systemic sclerosis.
Diagnosis of Silicosis
History of silica exposure
Chest imaging (computed tomography or x-ray)
Doctors usually recognize silicosis based on what they see on chest x-ray or computed tomography (CT) in people with a history of silica exposure. Chest CT is more sensitive than chest x-ray for detecting silicosis and monitoring for disease progression.
On chest imaging, a number of disorders can resemble chronic silicosis. They include sarcoidosis, chronic beryllium disease, hypersensitivity pneumonitis, coal worker pneumoconiosis, miliary tuberculosis, fungal pulmonary diseases, and cancer that has spread to the lungs. Doctors do additional tests to distinguish silicosis from these other disorders.
Treatment of Silicosis
Removal from further exposure
Management of symptoms (for example, with bronchodilators and inhaled corticosteroids)
Management of complications
Removal from further exposure is important.
There are no proven, specific treatments for acute or chronic silicosis. Treatment is primarily supportive.
People who have difficulty breathing may benefit from use of bronchodilators, which are medications to keep the airways open and free of mucus. Doctors monitor people with silicosis for low oxygen levels in the blood and treat them if needed. Pulmonary rehabilitation may help people carry out activities of daily living. Lung transplantation is recommended for those most severely affected.
Complications are managed as needed. For example, infections, including tuberculosis, are treated promptly.
Prevention of Silicosis
Primary preventive measures begin with eliminating or reducing exposure. The most effective primary prevention is implementation of engineering controls (control of the environment) to limit exposure to silica. Properly fitted respirators provide additional protection.
Measures to prevent complications include smoking cessation and vaccinations against pneumococci, COVID, and influenza. Because people who have been exposed to silica are at risk of tuberculosis and similar mycobacterial infections, they should have regular tuberculosis screening.
Due to persistence of silicosis, the United States Occupational Safety and Health Administration (OSHA) issued an updated Respirable Silica Standard in 2016. The standard lowers the Permissible Exposure Limit (PEL) and requires pre-employment and periodic medical surveillance of silica-exposed workers. Medical surveillance includes questionnaires, lung function tests, and periodic chest x-rays.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Occupational Safety & Health Administration [OSHA]. Respirable crystalline silica. 2016. Regulations (Standards-29 CFR 1926.1153).
