We searched Medline, Embase, and the Cochrane databases for studies from between Jan 1, 1991, and July 31, 2011, with the search term “silicosis” alone, or with “silica” or “silicon dioxide” in combination with “tuberculosis”, “lung function”, “airway obstruction”, “carcinogen”, or “cancer”. We focused mainly on reports from between 2006 and 2011, but older publications were also included when they covered essential aspects of silicosis. We also searched the reference lists of selected reports
SeminarSilicosis
Section snippets
Epidemiology
Silicosis is caused by the inhalation of crystalline silicon dioxide or silica1 and is one of the most important occupational diseases worldwide.2, 3 Although prevention efforts have been made for many decades, silicosis is a problem worldwide.2, 3 The disorder occurs everywhere, but is especially prevalent in countries of low and middle income, where the burden is often under-reported because of poor surveillance. China has the most patients with silicosis, with more than 500 000 cases
Causes
Worldwide, silicon dioxide or silica is the most abundant mineral and occurs in crystalline and amorphous forms.16 The most common free crystalline forms of silica in workplaces are quartz, tridymite, and cristobalite. Quartz can occur naturally and at varying concentrations in rocks such as sandstone (67% silica) and granite (25–40% silica).2 Cristobalite and tridymite occur naturally in lava and are formed when quartz or amorphous silica is subjected to very high temperatures. They can also
Associated disorders
Silica exposure has been associated with several disorders (panel). Only tuberculosis, airway obstruction, and lung cancer will be discussed further in this Seminar. Tuberculosis risk increases with severity of silicosis, and in acute and accelerated silicosis.37, 38, 39 Silica exposure increases tuberculosis risk even without silicosis.37, 38 In developing countries, mineral mining (particularly gold mining) might contribute to tuberculosis rates at a country level.57 Tuberculosis risk remains
Pathophysiology
Pathological varieties of silicosis include simple (nodular) silicosis, progressive massive fibrosis, silicoproteinosis, and diffuse interstitial fibrosis.1, 62 Gross pathological examination of the lung identifies discrete hard nodules, usually with upper-lobe predominance. Hilar and peribronchial lymph nodes are frequently enlarged. Microscopically, the distinguishing silicotic nodules are in hilar lymph nodes and lung parenchyma (figure 1). Under polarised light microscopy, birefringent
History
Diagnosis of silicosis generally relies on a history of substantial exposure to silica dusts and compatible radiological features, together with exclusion of other competing diagnoses, such as miliary tuberculosis, fungal infections, sarcoidosis, idiopathic pulmonary fibrosis, other interstitial lung diseases, and carcinomatosis. The diagnosis of an occupational lung disease depends on a thorough occupational history, without which the diagnosis of silicosis could easily be missed in the
Management
No proven curative treatment for silicosis exists. An investigation101 showed that particles coated with aluminium did not produce fibrosis in the lungs of rabbits, leading to the hypothesis that inhalation of aluminium powder might prevent or halt progression of silicosis in people. However, inhalation of aluminium dust did not have any definite effect on the symptoms or radiological progression in one trial.102 No sustained benefits in objective parameters of disease status have been reported
Prevention
Silicosis is a major cause of morbidity and mortality in both developed and developing countries. Further efforts are therefore needed to recognise and control silica hazards worldwide. In 1995, the Global Program for the Elimination of Silicosis was established by a joint International Labour Organization and WHO committee. In the past decade, outbreaks of silicosis have been reported in some small-scale companies or mines in developing countries, mainly caused by poor hazard recognition and
Search strategy and selection criteria
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