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| | __NOTOC__ |
| {{DiseaseDisorder infobox | | | {{DiseaseDisorder infobox | |
| Name = Silicosis | | | Name = Silicosis | |
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| '''For patient information click [[{{PAGENAME}} (patient information)|here]]''' | | '''For patient information click [[{{PAGENAME}} (patient information)|here]]''' |
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| {{CMG}} | | {{CMG}}{{AE}}{{AV}} |
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| ==[[Silicosis overview|Overview]]== | | ==[[Silicosis overview|Overview]]== |
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| ==Diagnosis== | | ==Diagnosis== |
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| [[Silicosis diagnostic criteria|Diagnostic Criteria]] | [[Silicosis history and symptoms|History and Symptoms]] | [[Silicosis physical examination|Physical Examination]] | [[Silicosis laboratory findings|Laboratory Findings]] | [[Silicosis electrocardiogram|EKG]] | [[Silicosis chest x ray|Chest X ray]] | [[Silicosis CT|CT]] | [[Silicosis MRI|MRI]] | [[Silicosis echocardiography or ultrasound|Echocardiography or Ultrasound]] | [[Silicosis other imaging findings|Other Imaging Findings]] | [[Silicosis other diagnostic studies|Other Diagnostic Studies]] | | [[Silicosis diagnostic criteria|Diagnostic Criteria]] | [[Silicosis history and symptoms|History and Symptoms]] | [[Silicosis physical examination|Physical Examination]] | [[Silicosis laboratory findings|Laboratory Findings]] | [[Silicosis chest x ray|Chest X ray]] | [[Silicosis CT|CT]] | [[Silicosis MRI|MRI]] | [[Silicosis other imaging findings|Other Imaging Findings]] | [[Silicosis other diagnostic studies|Other Diagnostic Studies]] |
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| ==Treatment== | | ==Treatment== |
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| ==Case Studies== | | ==Case Studies== |
| [[Silicosis case study one|Case #1]] | | [[Silicosis case study one|Case #1]] |
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| ==Pathology==
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| When small silica dust particles are inhaled, they can embed themselves deeply into the tiny alveolar sacs and ducts in the lungs, where oxygen and carbon dioxide gases are exchanged. There, the lungs cannot clear out the dust by mucous or coughing.
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| When fine particles of silica dust are deposited in the lungs, [[macrophage]]s that ingest the dust particles will set off an [[inflammation]] response by releasing tumor necrosis factors, [[interleukin-1]], [[leukotriene B4]] and other [[cytokines]]. In turn, these stimulate [[fibroblast]]s to proliferate and produce collagen around the silica particle, thus resulting in [[fibrosis]] and the formation of the nodular lesions.
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| Furthermore, the surface of silicon dust can generate silicon-based radicals that lead to the production of [[hydroxyl]] and oxygen radicals, as well as [[hydrogen peroxide]], which can inflict damage to the surrounding cells.
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| Characteristic lung tissue pathology in nodular silicosis consists of fibrotic nodules with concentric "onion-skinned" arrangement of [[collagen]] fibers, central hyalinization, and a cellular peripheral zone, with lightly birefringent particles seen under polarized light. In acute silicosis, microscopic pathology shows a periodic acid-Schiff positive alveolar exudate (alveolar lipoproteinosis) and a cellular infiltrate of the alveolar walls.
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| ==Prevalence==
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| Silicosis is the most common occupational lung disease worldwide, it occurs everywhere but is especially common in developing countries.<ref>{{cite paper
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| | author =Steenland K, Goldsmith DF
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| | title =Silica exposure and autoimmune diseases
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| | version =
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| | publisher =National Institute for Occupational Safety and Health, Cincinnati, OH 45226, USA
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| | date =Nov 1995
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| | url =http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&list_uids=8561170&dopt=Citation
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| | format =
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| | accessdate = 2007-05-29}}</ref> From 1991 to 1995, China reported more than 24,000 deaths due to silicosis each year.<ref name="WHO">{{cite web
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| | last =
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| | first =
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| | authorlink =
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| | coauthors =
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| | title =Silicosis Fact Sheet
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| | work =
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| | publisher =World Health Organization
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| | date =May 2000
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| | url =http://www.who.int/mediacentre/factsheets/fs238/en/
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| | format =
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| | doi =
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| | accessdate = 2007-05-29}}</ref> In the United States, it is estimated that over one million(two million<ref>{{cite web
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| | last =
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| | coauthors =
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| | title =Safety and Health Topics Silica, Crystalline
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| | work =
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| | publisher =Occupational Safety and Health Administration
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| | date =March 2007
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| | url =http://www.osha.gov/SLTC/silicacrystalline/index.html
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| | format =
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| | doi =
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| | accessdate = 2007-05-29}}</ref>) workers are exposed to free crystalline silica dusts and 59,000 of these workers will develop silicosis sometime in the course of their lives.<ref name="WHO"/>
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| According to CDC data<ref>http://www2.cdc.gov/niosh-chartbook/ch2/ch2-10-3-5.asp</ref>, silicosis in the United States is relatively rare. The incidence of deaths due to silicosis declined by 84% between 1968 and 1999, and only 187 1999 deaths had silicosis as the underlying or contributing cause.<ref>http://www2.cdc.gov/niosh-chartbook/imagedetail.asp?imgid=234</ref> Additionally, cases of silicosis in Michigan, New Jersey, and Ohio are highly correlated to industry<ref>http://www2.cdc.gov/niosh-chartbook/imagedetail.asp?imgid=232</ref> and occupation<ref>http://www2.cdc.gov/niosh-chartbook/imagedetail.asp?imgid=232</ref>.
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| Although silicosis has been known for centuries, the industrialization of mining has led to an increase in silicosis cases. Pneumatic drilling in mines and less commonly, mining using explosives, would raise rock dust. In the United States, a 1930 Hawk's Nest incident (epidemic of silicosis) due to the construction of the Hawk's Nest Tunnel near Gauley Bridge, West Virginia caused the death of more than 400 workers. The prevalence of silicosis led some men to grow what is called a miner's mustache, in an attempt to intercept as much dust as possible.
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| There is some concern that a batch of cannabis contaminated with silica found in the UK may cause silicosis in some users. <ref>[http://www.ukcia.org/library/contam/default.php Cannabis contamination in the UK]</ref>
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| Also, the mining establishment of Delamar Ghost Town, Nevada was ruined by a dry-mining process that produced a silicosis-causing dust. After hundreds of deaths from silicosis, the town was nicknamed ''The Widowmaker''. The problem in those days was somewhat resolved with an addition to the drill which sprayed a mist of water, turning dust raised by drilling into mud, but this inhibited mining work.
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| Silicosis is an occupational hazard to mining, sandblasting, quarry, ceramics and foundry workers, as well as grinders, stonecutters and those continually exposed to silica dust.
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| Protective measures such as respirators have brought a steady decline in death rates due to silicosis in Western countries. Unfortunately, this is not true of less developed countries where work conditions are poor and respiratory equipment is seldom used. For instance, life expectancy for silver miners in Potosí, Bolivia is around 40 years due to silicosis.
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| Recently, silicosis in Turkish denim sandblasters was detected as a new cause of silicosis due to recurring, poor working conditions.
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| Silicosis is seen in horses associated with inspiration of dust from certain cristobalite-containing soils in California.
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| ==Symptoms==
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| Because silicosis is progressive, signs of it may not appear until years after exposure.<ref name="WHO"/> Symptoms include:
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| * [[Tachypnea]] or shortness of breath after physical exertion
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| * Dry or severe cough, often persistent and accompanied by hoarseness of the throat
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| * Fatigue or tiredness
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| * Changes in breathing pattern (rapid breathing or shallow breathing)
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| * Loss of appetite
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| * Chest pain
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| * Fever
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| * Gradual dark shallow rifts in nails eventually leading to cracks
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| In advanced cases, the following may also occur:
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| * [[Cyanosis]]
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| * [[Cor pulmonale]]
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| * Respiratory insufficiency
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| Patients with silicosis are particularly susceptible to [[tuberculosis]] (TB) infection - known as silicotuberculosis. The reason for the increased risk - 10-30 fold increased incidence - is not well understood. It is thought that silica damages pulmonary [[macrophages]], inhibiting their ability to kill mycobacteria.
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| ==Types of Silicosis==
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| Classification of silicosis is made according to the disease's severity, onset, and rapidity of progression. These include:
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| * ''Chronic silicosis''
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| Occurs after 15-20 years of exposure to moderate to low levels of silica dust. Chronic silicosis itself is further subdivided into simple and complicated silicoses. This is the most common type of silicosis. Patients with this type of silicosis may not have obvious symptoms, so a chest X-ray is necessary to determine if there is lung damage.
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| * ''Asymptomatic silicosis''
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| Early cases of the disease do not present any symptoms
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| * ''Accelerated silicosis''
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| Silicosis that develops 5-10 years after high exposure to silica dust. Symptoms include severe shortness of breath, weakness, and weight loss.
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| * ''Acute silicosis''
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| Silicosis that develops a few months to 2 years after exposure to very high concentrations of silica dust. Symptoms of acute silicosis include severe disabling shortness of breath, weakness, and weight loss, often leading to death.
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| ==Diagnosis==
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| Patient history should reveal exposure to silica dust due to occupation. Physical check up will reveal decreased chest expansion and abnormal breath sounds. Pulmonary function test will reveal reduced lung capacity.
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| Chest x-ray will confirm the presence of nodules in the lungs, especially in the upper lobes. Typically, it will also reveal eggshell [[calcification]] of the [[lymph node|hilar lymph node]]s. In rare cases, pulmonary nodules may also be calcified. In advanced cases of silicosis, coalescence of nodules may show up as large masses.
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| A computed tomography or [[CT scan]] can also provide a mode detailed analyses of the nodules, and can reveal cavitation due to concomitant mycobacterial infection.
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| ==Treatment==
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| Silicosis is an irreversible condition with no cure. Treatment options currently focus on alleviating the symptoms and preventing complications. These include:
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| * Stopping further exposure to silica and other lung irritants, including [[tobacco smoking]].
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| * [[cough medicine|Cough suppressants]].
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| * [[Antibiotic]]s and antitubercular agents to prevent [[tuberculosis]]. These include [[isoniazid]], [[rifampin]], and [[pyrazinamide]].
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| * Chest [[physiotherapy]] to help the bronchial drainage of [[mucus]].
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| * [[Oxygen]] administration to avoid [[Hypoxia (medical)|hypoxemia]].
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| * [[Bronchodilator]]s to facilitate breathing.
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| * [[Lung transplantation]] to replace the damaged lung tissue is the most effective treatment, but is associated with severe risks of its own.
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| Experimental treatments include:
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| * Whole-lung lavage (see [[Bronchoalveolar lavage]])
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| * Inhalation of powdered aluminium, d-penicillamine and polyvinyl pyridine-N-oxide.
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| * [[Corticosteroid]] therapy.
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| * The herbal extract tetrandine may slow progression of silicosis.<ref>{{cite paper
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| | author =Chao, D.H. ; Ma, J.Y.C. ; Malanga, C.J. ; Banks, D.E. ; Hubbs, A.F. ; Rojanasakul, Y. ; Castranova, V. ; Ma, J.K.H
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| | title =Multiple emulsion-mediated enhancement of the therapeutic effect of tetrandine against silicosis
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| | version =
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| | publisher =West Virginia University School of Pharmacy
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| | date =July 1996
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| | url =http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=463739
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| | format =
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| | accessdate =
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| | quote = Previously it was shown that the action of tetrandrine is attributed to its ability to inhibit the release of reactive oxygen metabolites and inflammatory cytokines by alveolar macrophages, and that targeted delivery of tetrandrine to alveolar macrophages using a multiple emulsion system minimizes drug toxicity, maintains the drug's pharmacological activity, and enhances tetrandrine distribution in the lungs while reducing systemic drug distribution. This study provides ''in vivo'' evidence of emulsion-mediated enhancement of drug action in the lungs against silica-induced lung injury using a rat model. }}</ref>
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| ==Prevention==
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| The best way to prevent silicosis is to identify work-place activities that produce crystalline silica dust and then to eliminate or control the dust. Water spray is often used where dust emanates. Dust can also be controlled through dry air filtering.
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| ==See also==
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| * [[Pneumoconiosis]]
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| * [[Asbestosis]]
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| * [[COPD]]
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| * [[Philip D'Arcy Hart]]
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| * [[Hawk's Nest incident|Hawk's Nest Incident]]
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| * [[John Haldane]]
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| * ''[[The Citadel (novel)|The Citadel]]''
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| == External links ==
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| * [http://www.breader.com/articles/silicosis-coal-workers-pneumoconiosis-article.htm Imaging Findings in Silicosis by Daniel Powers, MD]
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| ==Notes== | | ==Notes== |
| <div class="references-small"> | | <div class="references-small"> |
| | {{reflist|2}} |
| </div> | | </div> |
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| [[Category:Pulmonology]] | | [[Category:Pulmonology]] |
| [[Category:Occupational diseases]] | | [[Category:Occupational diseases]] |
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| {{Respiratory pathology}} | | {{Respiratory pathology}} |
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| [[bg:Силикоза]]
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| [[de:Silikose]]
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| [[es:Silicosis]]
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| [[fr:Silicose]]
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| [[it:Silicosi]]
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| [[nl:Silicose]]
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| [[pt:Silicose]]
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| [[simple:Silicosis]]
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| [[sl:Silikoza]]
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| [[uk:Силікоз]]
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