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What causes silicosis?

Free crystalline silica, SiO2, is one of the most common minerals in the earth's crust. It is found in sand, many rocks such as granite, sandstone, flint and slate, and in some coal and metallic ores. The three most common forms are quartz,

tridymite and cristobalite. 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. Inhaled crystalline silica (in the form of quartz or crystobalite) from occupational sources is classified by the International Agency for Research on Cancer (IARC) as a Group 1 human lung carcinogen. Particles of silica dust get trapped in the tiny sacs (alveoli) in the lungs where air exchange takes place. White blood cells called macrophages in the alveoli ingest the silica and die. The resulting inflammation attracts other macrophages to the region. The nodule forms when the immune system forms fibrous tissue to seal off the reactive area. Respirable silica dust may be invisible to the naked eye and is so light that it can remain airborne for a long time. It can thus travel long distances in the air and so affect populations not otherwise considered to be at risk. When inhaled, silica dust passes into the lungs, and scavenger cells such as macrophages engulf it. Enzymes released by the scavenger cells cause the lung tissue to scar. At first, the scarred areas are tiny round lumps (simple nodular silicosis), but eventually they may combine into larger masses (complicated silicosis). These scarred areas cannot transfer oxygen into the blood normally. The lungs become less flexible, and breathing takes more effort.

More information on silicosis

What is silicosis? - Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable crystalline silica.
What causes silicosis? - Silicosis is caused by overexposure to respirable crystalline silica. Particles of silica dust get trapped in the tiny sacs (alveoli) in the lungs.
What're the symptoms of silicosis? - Symptoms of silicosis include shortness of breath after exercising and a harsh, dry cough, chest pain, hoarseness, and loss of appetite.
How is silicosis diagnosed? - Silicosis is diagnosed when someone who has worked with silica has a chest x-ray that shows the distinctive patterns of scarring and nodules.
What is the treatment for silicosis? - There is no specific treatment for silicosis. Removal of the source of silica exposure is important to prevent further worsening of the disease.
How to prevent silicosis? - Silicosis is a preventable disease. The key to silicosis prevention is to prevent dust from being in the air.
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All information is intended for reference only. Please consult your physician for accurate medical advices and treatment. Copyright 2005,, all rights reserved. Last update: July 18, 2005