SILICOSIS

Silicosis is a respiratory disease caused by inhalation of silica dust which leads to inflammation and then scarring of the lung tissue.

Three types of silicosis are seen:

simple chronic silicosis -- which results from long-term exposure (more than 20 years) to low amounts of silica dust. Nodules of chronic inflammation and scarring provoked by the silica dust form in the lungs and chest lymph nodes. This disease may feature breathlessness and may resemble chronic obstructive pulmonary disease (COPD).

accelerated silicosis -- occurs after exposure to larger amounts of silica over a shorter period of time (5-15 years). Inflammation, scarring, and symptoms progress faster in accelerated silicosis than in simple silicosis.

acute silicosis -- results from short-term exposure to very large amounts of silica. The lungs become very inflamed and may fill with fluid, causing severe shortness of breath and low blood oxygen levels.

Progressive massive fibrosis may occur in simple or accelerated silicosis, but is more common in the accelerated form. Progressive massive fibrosis results from severe scarring and leads to obliteration of normal lung structures.

Silica is a common, naturally occurring crystal. It is found in most rock beds and it forms dusts during mining, quarrying, tunneling, and work with many metal ores. Silica is a principal component of sand, so glass workers and sand-blasters also receive heavy exposure to silica.

Risk factors include any work that includes exposure to silica dust. Mining, stone cutting, quarrying, road and building construction, work with abrasives manufacturing, sand blasting and many other occupations and hobbies involve exposure to silica.

Intense exposure to silica may result in disease in a year or less, but it usually takes at least 10 or 15 years of exposure before symptoms develop. Silicosis has become less common since the Occupational Safety and Health Administration (OSHA) instituted regulations requiring the use of protective equipment which limit the amount of silica dust inhaled.

Symptoms of Silicosis

chronic cough

shortness of breath with exercise, usually in patients who have progressive massive fibrosis

Additional symptoms that may be associated with this disease, especially in acute silicosis:

fever

cough

weight loss

severe breathing difficulty

Silicosis Treatment

There is no specific treatment for silicosis. Removal of the source of silica exposure is important to prevent further worsening of the disease. Supportive treatment includes cough suppression medications, bronchodilators, and oxygen if needed. Antibiotics are prescribed for respiratory infections as needed.

Other considerations for treatment include limiting continued exposure to irritants, smoking cessation, and routine tuberculosis skin testing.

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. Yearly skin testing to check for exposure to TB is recommended. Treatment with anti-TB drugs is recommended for people with a positive skin test. Any change in the appearance of the chest X-ray may indicate TB.

Types of Silica

Crystalline silica may be of several distinct types. Quartz, a form of silica and the most common mineral in the earth's crust, is associated with many types of rock. Other types of silica include cristobalite and tridymite.

Potential for Exposure During Construction

Concrete and masonry products contain silica sand and rock containing silica. Since these products are primary materials for construction, construction workers may be easily exposed to respirable crystalline silica during activities such as the following:

Chipping, hammering, and drilling of rock

Crushing, loading, hauling, and dumping of rock

Abrasive blasting using silica sand as the abrasive

Abrasive blasting of concrete (regardless of abrasive used)

Sawing, hammering, drilling, grinding, and chipping of concrete or masonry

Demolition of concrete and masonry structures

Dry sweeping or pressurized air blowing of concrete, rock, or sand dust

Even materials containing small amounts of crystalline silica may be hazardous if they are used in ways that produce high dust concentrations.

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