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SILICA IN THE WORKPLACE 6 365-AXJ-01-iGDO © 2020, Workplace Safety & Prevention Services (WSPS) 1 877 494 WSPS (9777) | 905 614 1400 | wsps.ca WSPS.CA Silicosis is the result of the body's response to the presence of silica dust in the lung. The respirable fraction of the dust, particles generally considered to be smaller than 5µm (millionth of a metre), can penetrate to the innermost reaches of the respiratory tract. These are the alveoli or air sacs where exchange of oxygen and carbon dioxide occurs. Dust particles, which land on these surfaces, are removed by white blood cells known as macrophages. Particles of free crystalline silica cause the macrophages to break open. The result is the formation of a scar like patch on the surface of the air sac. Formation of large numbers of "scars" following prolonged exposure causes the alveolar surface to become less elastic. This reduces the transfer of gases. This is noticed as shortness of breath following exertion. Symptoms seldom develop in less than five years and in many cases may take more than 20 years to become disabling. There are three major types of silicosis: acute, chronic and accelerated. Acute silicosis Acute silicosis develops from inhaling large amounts of silica dust over a few days or months. Signs of the disease include shortness of breath, fever, cough and weight loss. Generally, people with acute silicosis have stable health, however for some it may lead quickly to death. Chronic silicosis Chronic silicosis is the most common type and occurs after many years of contact with low levels of silica dust in the air. There are two forms of chronic silicosis: simple or complicated. With simple silicosis, small solid or unclear nodules can be detected on a chest x-ray, however, individuals are asymptomatic or show no signs or symptoms of the disease. Long-term exposure to silica dust may lead to complicated silicosis. With complicated silicosis, also called progressive massive fibrosis, larger nodules can be detected on a chest x-ray. Some individuals may still be asymptomatic or initial symptoms may include shortness of breath with exercise, wheezing or sputum that causes coughing. Other lung diseases can aggravate the condition and severe complicated silicosis can result in heart disease in addition to lung disease. Other effects of exposure to silica Occupational exposure to respirable crystalline silica is associated with the development of silicosis, lung cancer, pulmonary tuberculosis, and airways diseases. These exposures may also be related to the development of autoimmune disorders, chronic renal disease, and other adverse health effects. Accelerated silicosis Accelerated silicosis is similar to the chronic type, however it forms more quickly. The lung scars can be detected sooner and nodules appear on a chest x-ray five years after the first exposure to silica dust. This type of silicosis occurs from exposure to large amounts of silica dust over a short time period and can progress quickly.

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