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What is involved? (including coding of cases) SABRE Case Studies and Information
| i. Silicosis (Pneumoconiosis due to silica exposure) Silicon is the second most abundant element, following oxygen, in the earth's crust and when combined with oxygen forms silica or silicon dioxide (SiO2). Silicosis refers to the disease that develops following inhalation of the crystalline forms of silica i.e. quartz, cristobalite or tridymite. Silicosis has been divided into two forms of the disease as follows:
(Graham, 1998) Acute Silicosis (also known as silicotic alveolar proteinosis or silicotic alveolar lipoproteinosis) Acute silicosis is the most severe form of silicosis and may develop following massive exposures to free silica, predominantly quartz, for as little as a few months. Death may occur within 1 to 2 years after these initial exposures. Due to the strict regulation of maximum exposure levels to various crystalline forms of silica, acute silicosis is now extremely rare. Sporadic isolated incidences have been documented in recent times and reflect poor work practices within these workplaces for e.g. tunnelling projects. Chronic Silicosis The two forms of chronic silicosis are as follows:
The simple form of chronic silicosis is characterised by the formation of discrete nodules of collagen fibres with a maximum diameter of 1 cm. The diagnosis of simple silicosis is based on an individuals history of exposure and the observation of nodules on a chest X-ray or CT scan. Nodules are normally found throughout the upper lobes and in the regional lymph nodes (Graham, 1998). The lower lobes may be involved in more advanced cases of disease (Weill et al 1994). There are no changes in lung function as a result of simple silicosis and patients presenting with simple silicosis are often asymptomatic. Complicated silicosis results when nodule formation progresses to such an extent that the nodules fuse together and are greater than 1 cm in size. These masses of collagenised and hyalinised tissue may invade or totally replace normal lung tissue (Graham, 1998). The conglomerate masses that form during this disease process are also known as "progressive massive fibrosis" (PMF). The International Agency for Research on Cancer (IARC) has listed crystalline silica as a definite carcinogen in humans stating that there is sufficient evidence that crystalline silica in the form of quartz or cristobalite from occupational sources induces cancer. Silica exposure has been associated specifically with lung cancer, tuberculosis, nonmalignant renal disease, and auto-immune diseases such as systemic sclerosis and rheumatoid syndrome. References:
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