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Silicosis

Definition

Silicosis is a respiratory disease caused by inhaling silica dust.

Alternative Names

Causes

Silica is a common, naturally-occurring crystal. It is found in most rock beds and forms dust during mining, quarrying, tunneling, and working with many metal ores. Silica is a main part of sand, so glass workers and sand-blasters are also exposed to silica.

Three types of silicosis exist:

• Simple chronic silicosis -- results from long-term exposure (more than 20 years) to low amounts of silica dust. Swellings caused by the silica dust form in the lungs and chest lymph nodes. This disease may cause people to have trouble breathing and may be similar to chronic obstructive pulmonary disease (COPD).
• Accelerated silicosis -- occurs after exposure to larger amounts of silica over a shorter period of time (5 - 15 years). Swelling in the lungs and symptoms occur faster than in simple silicosis.
• Acute silicosis -- results from short-term exposure to very large amounts of silica. The lungs become very inflamed and can fill with fluid, causing severe shortness of breath and low blood oxygen levels.

Progressive massive fibrosis can occur in either simple or accelerated silicosis, but is more common in the accelerated form. Progressive massive fibrosis is caused by severe scarring and destroys normal lung structures.

People who work in jobs that expose them to silica dust are at risk. These jobs include:

• Mining
• Stone cutting
• Quarrying
• Road and building construction
• Abrasives manufacturing
• Sand blasting

Intense exposure to silica can cause disease within a year, but it usually takes at least 10 - 15 years of exposure before symptoms occur. Silicosis has become less common since the Occupational Safety and Health Administration (OSHA) created regulations requiring the use of protective equipment, which limits the amount of silica dust workers inhale.

Symptoms

• Chronic cough
• Shortness of breath with exercise, usually in patients who have progressive massive fibrosis

Other symptoms of this disease, especially in acute silicosis:

• Fever
• Cough
• Weight loss
• Severe breathing difficulty

Exams and Tests

Your health care provider will take a medical history that includes many questions about your jobs (past and present), hobbies, and other activities that may have exposed you to silica. The health care provider will also do a physical exam.

Tests to confirm the diagnosis and rule out similar diseases include:

• Chest x-ray
• Pulmonary function tests
• Purified protein derivative (PPD) skin test (for tuberculosis)

Treatment

There is no specific treatment for silicosis. Removing the source of silica exposure is important to prevent the disease from getting worse. Supportive treatment includes cough medicine, bronchodilators, and oxygen if needed. Antibiotics are prescribed for respiratory infections as needed.

Treatment also includes limiting exposure to irritants, quitting smoking, and having routine tuberculosis skin tests.

People with silicosis are at high risk for developing tuberculosis (TB). Silica is believed to interfere with the body's immune response to the bacteria that causes TB. People with silicosis should have skin tests to check for exposure to TB. Those with a positive skin test should be treated with anti-TB drugs. Any change in the appearance of the chest x-ray may be a sign of TB.

Support Groups

Joining a support group where you can meet other people with silicosis or related diseases can help you understand your disease and adapt to its treatments.

Outlook (Prognosis)

The outcome varies depending on the amount of damage to the lungs.

Possible Complications

• Increased risk for tuberculosis
• Progressive massive fibrosis

When to Contact a Medical Professional

Call your health care provider if you are exposed to silica at work and you have symptoms of the disease.

Prevention

If you work in a high-risk occupation or have a high-risk hobby, wear dust masks and do not smoke. You might also want to use other protection recommended by OSHA, such as a respirator.

References

American Thoracic Society. Adverse effects of crystalline silica exposure. Am J Respir Crit Care Med. 1997;155:761-765.

Murray J, Nadel J. Textbook of Respiratory Medicine. 3rd ed. Philadelphia, Pa: WB Saunders; 2000.

Pipavath S. Imaging of Interstitial Lung Disease. Radiol Clin North Am. 2005 May; 43(3); 589-599.

Noble J. Textbook of Primary Care Medicine. 3rd ed. St. Louis, Mo: Mosby; 2001:694-696

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