Effects of Silica

What is Silica and why is it dangerous?

Silica is a common, naturally-occurring crystal. It is found in most rock beds and forms dust during mining, quarrying, tunneling, and work with many metal ores. Silica is a main 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.

Inhaling finely divided crystalline silica dust in very small quantities (OSHA allows 0.1mg/m³) over time can lead to silicosis, bronchitis or (much more rarely) cancer, as the dust becomes lodged in the lungs and continuously irritates them, reducing lung capacities (silica does not dissolve over time). This effect can be an occupational hazard for people working with sandblasting equipment, products that contain powdered silica, and so on. But children, asthmatics of any age, allergy sufferers and the elderly, all of whom have reduced lung capacity, can be affected in much shorter periods of time.

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

Three types of silicosis are seen:

	Simple chronic silicosis -- 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.

Silica exposure remains a serious threat to nearly two million US workers. The National Institute of Occupational Safety and Health (NIOSH) reports that each year more than 250 die from silicosis and hundreds more are disabled.

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