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Silicosis +si-lu-!kO-sus

by Lee S. Newman, MD, MA

Silicosis is permanent scarring of the lungs caused by inhaling silica (quartz) dust.

  • People develop difficulty breathing during exercise that sometimes progresses to shortness of breath even at rest, and some people also have a cough that may or may not produce sputum.

  • Diagnosis is made with a chest x-ray or computed tomography.

  • Doctors can sometimes give drugs to help keep airways clear.

Silicosis is the oldest known environmental lung disease (see Overview of Environmental Lung Diseases). It is caused by inhalation of tiny particles of silica (usually quartz) or, less commonly, by inhalation of silicates, such as talc.

Workers at greatest risk are those who move or blast rock and sand (miners, quarry workers, stonecutters) or who use silica-containing rock or sand abrasives (sand blasters; glass makers; foundry, gemstone, and ceramic workers; potters). Recently, silicosis has been identified in workers who fabricate or install countertops manufactured from engineered silicates (silica conglomerate). Coal miners are at risk of mixed silicosis and coal workers’ pneumoconiosis (see Coal Workers’ Pneumoconiosis).

Silicosis may be

  • Acute

  • Chronic

Acute silicosis may develop after intense exposures over several years or months.

Chronic silicosis is the most common form and generally develops only after exposure over decades.

Accelerated silicosis, which is rare, may develop after more intense exposures over several years or months (like acute silicosis). Silica is also a cause of lung cancer.

When inhaled, silica dust passes into the lungs, and scavenger cells such as macrophages engulf it (see Table: Overview of the Immune System). Enzymes released by the scavenger cells cause the lung tissue to scar.

Simple chronic silicosis isthe first stage of chronic silicosis. In this stage, the scarred areas are tiny round lumps.

Eventually, complicated chronic silicosis occurs when the scarred areas combine into larger masses. Sometimes these larger masses come together into even larger masses (progressive massive fibrosis). These scarred areas cannot transfer oxygen into the blood normally. The lungs become less flexible, and breathing takes more effort.

Symptoms

In acute silicosis, shortness of breath worsens rapidly. People also lose weight and have fatigue. Respiratory failure often develops within 2 years.

Chronic silicosis often does not cause symptoms for years, but many people eventually develop difficulty breathing during exercise. Sometimes the breathing difficulty progresses to shortness of breath even during rest. Some people have a cough that may produce sputum. Breathing may worsen for years after the person stops working with silica. 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 (see Pulmonary Hypertension), which can be fatal.

People with accelerated silicosis experience the same symptoms as people with chronic silicosis, but symptoms develop and worsen over a shorter period.

People with silicosis are many times more likely to develop tuberculosis or nocardiosis when exposed to the organisms that cause these disorders than are people without silicosis. They are also at risk for progressive systemic sclerosis and lung cancer.

Diagnosis

  • Computed tomography

Diagnosis is made when someone who has worked with silica has chest computed tomography (CT) that shows distinctive patterns consistent with the disease. A chest x-ray can also be done to help diagnose silicosis. When imaging findings are unclear, samples of lung tissue can help confirm the diagnosis. Additional tests are done to distinguish silicosis from other disorders.

Prevention

Controlling silica dust in the workplace is key to preventing silicosis. When dust cannot be controlled, as may be true in the sandblasting industry, workers should wear protective gear, such as hoods that supply clean external air or special masks that efficiently filter out tiny particles. Such protection may not be available to all people working in a dusty area (for example, painters and welders), so whenever possible abrasives other than sand should be used.

Workers exposed to silica dust should have regular chest x-rays so that problems can be detected early. Workers who smoke should be encouraged to stop. Other preventive measures include pneumococcal vaccine and an annual influenza vaccination to help protect against infections to which workers may be more vulnerable.

Treatment

  • Whole lung lavage

  • For acute or accelerated silicosis, corticosteroids

  • Treatments for symptoms and complications, such as drugs that open the airways and sometimes lung transplantation

Silicosis cannot be cured, but its progression can be slowed if exposure to silica is avoided, especially at an early stage of the disease.

A whole lung lavage (washing) can be used to treat both acute and chronic silicosis. During this procedure, doctors fill the lung with a salt (saline) solution and then drain it to clear material from the air spaces.

Some people with acute or accelerated silicosis benefit from taking corticosteroids.

People who have difficulty breathing may benefit from drugs to keep the airways open and free of mucus (bronchodilators—see Treatment of symptoms). Lung transplantation is a last resort.

Because people with silicosis have a high risk of developing tuberculosis, they should have regular checkups that include a tuberculosis skin test.

People should be monitored and treated for low oxygen levels in the blood. Pulmonary rehabilitation may help people carry out activities of daily living.

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