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 lyumph 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 (4-8 years).  Inflmation, 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.

Causes and Risks

Silica is a common, naturally occuring 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.

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