Silicosis

SILICOSIS

Silicosis is a chronic fibrotic pulmonary disease caused by in-halation of silica dust (crystalline silicon dioxide particles). Ex-posure to silica and silicates occurs in almost all mining, quarrying, and tunneling operations. Glass manufacturing, stone-cutting, the manufacture of abrasives and pottery, and foundry work are other occupations with exposure hazards. Finely ground silica, such as that found in soaps, polishes and filters, is extremely dangerous.

Pathophysiology

When the silica particles, which have fibrogenic properties, are inhaled, nodular lesions are produced throughout the lungs. With the passage of time and further exposure, the nodules en-large and coalesce. Dense masses form in the upper portion of the lungs, resulting in the loss of pulmonary volume. Restrictivelung disease (inability of the lungs to expand fully) and ob-structive lung disease from secondary emphysema result. Cavi-ties can form as a result of superimposed TB. Exposure of 15 to 20 years is usually required before the onset of the disease and shortness of breath are manifested. Fibrotic destruction of pul-monary tissue can lead to emphysema, pulmonary hypertension, and cor pulmonale.

Clinical Manifestations

Patients with acute silicosis present with dyspnea, fever, cough, and weight loss and have a rapid progression of the disease. Symp-toms are more severe in patients whose disease is complicated by progressive massive fibrosis. More commonly, this disease is a chronic problem with a long latency period. The patient may have slowly progressive symptoms indicative of hypoxemia, se-vere air-flow obstruction, and right-sided heart failure. Edema may occur because of the cardiac failure.

Medical Management

There is no specific treatment for silicosis, because the fibrotic process in the lung is irreversible. Supportive therapy is directed at managing complications and preventing infection. Testing is performed to rule out other lung diseases, such as TB, lung can-cer, and sarcoidosis. If TB is present, it is aggressively treated. Additional therapy might include oxygen, diuretics, inhaled beta-adrenergic agonists, anticholinergics, and bronchodilator therapy.