Pneumology & Occupational Medicine & Family Medicine
Silicosis
Silicosis is the most common pneumoconiosis worldwide and one of the most serious occupational lung diseases—characterized by progressive and irreversible nodular pulmonary fibrosis caused by prolonged inhalation of free crystalline silica particles (primarily quartz—SiO₂—in its alpha-cristobalite and alpha-tridymite forms) with an aerodynamic size of less than 10 µm (the respirable fraction that penetrates into the alveoli). Once deposited in the alveoli, silica particles are phagocytosed by alveolar macrophages—but unlike other inert mineral dusts, crystalline silica is cytotoxic to macrophages: it ruptures lysosomal membranes + releases hydrolytic enzymes + kills the macrophage + and the released particles are re-phagocytosed in a vicious cycle of macrophage activation + production of pro-fibrotic cytokines (TGF-β + TNF-α + IL-1) → activation of fibroblasts → collagen deposition → formation of silicotic nodules (pathognomonic histological lesion: concentric fibrous nodules of hyalinized collagen surrounded by a ring of silica-laden macrophages and lymphocytes) in the lung parenchyma and the hilar and mediastinal lymph nodes. The occupations most at risk in Quebec include miners (gold + silver + copper + asbestos + granite mines) + quarry workers + stonemasons + construction workers (cutting granite, concrete, and bricks) + foundry workers + potters + ceramic and glass workers + and, increasingly, workers cutting artificial marble (artificial silica—quartz kitchen countertops), who develop accelerated and severe silicosis. Silicosis is incurable—no treatment can reverse established fibrosis—and can progress even after exposure has ceased. Primary prevention (reducing dust concentrations through engineering controls + personal respiratory protection + periodic medical monitoring) is therefore the only truly effective strategy.
Clinical presentations based on exposure
| Shape | Exposure duration + concentrations | Clinical and radiological presentation |
|---|---|---|
| Simple chronic silicosis (classic form) | Prolonged exposure > 10–20 years + to moderate concentrations of silica + the most common form | Often asymptomatic at the beginning + progressive exertional dyspnea + cough + bilateral silicotic nodules predominantly in the upper lobes on radiography (well-defined rounded opacities of 1-3 mm — type q + r + p according to ILO) + hilar adenopathy with «eggshell» calcifications (pathognomonic) + PFTs: restrictive pattern + or obstructive pattern |
| Massive progressive fibrosis (MPF — complication) | Progression of simple silicosis to confluent masses > 1 cm (type A + B + C according to ILO) + can progress even after cessation of exposure | Bilateral fibrotic masses in the upper lobes + disabling dyspnea + progressive respiratory failure + pulmonary arterial hypertension + cor pulmonale + increased risk of tuberculosis ++ + spirometry: mixed syndrome (restrictive + obstructive) + collapsed DLCO |
| Accelerated silicosis | Intense exposure over 5–10 years + very high concentrations + common among workers who cut artificial marble (quartz kitchen countertops — silica > 90%) | Rapid progression + table similar to chronic silicosis but much faster progression + high risk of IPF + death within a few years + increasing cases in Quebec and North America |
| Acute silicosis (silicoproteinosis) | Massive and brief exposure (weeks to a few months) + extremely high concentrations + rare + ex.: intensive unprotected sandblasting + pure quartz grinding | Severe rapid dyspnea + hypoxemia + alveolar filling (PAS-positive proteinaceous material similar to alveolar proteinosis) + radiography: diffuse alveolar opacities (≠ nodules) + fatal course in a few months to 2 years + therapeutic bronchoalveolar lavage (like alveolar proteinosis) |
Complications and Associated Diseases
- Pulmonary tuberculosis (silicotuberculosis): 3–5 times higher risk than the general population + Silica-laden macrophages have reduced bactericidal activity + Annual QuantiFERON-TB Gold screening in silica-exposed workers + Standard tuberculosis treatment but often prolonged duration
- COPD and bronchial obstruction: airway obstruction due to peribronchiolar fibrosis + smoking often associated → exacerbates COPD + spirometry mandatory in periodic monitoring
- Autoimmune diseases: Increased risk of systemic scleroderma + rheumatoid polyarthritis (Caplan's syndrome - rheumatoid nodules in the lungs of miners with RA) + systemic lupus erythematosus
- Lung cancer: Crystalline silica is classified as a Group 1 carcinogen (IARC) + risk x 2–3 + potentiated by smoking + screening by low-dose chest CT scan according to the same criteria as smokers
- HTAP and right heart failure (cor pulmonale): in advanced forms with FMP + chronic hypoxemia + annual echocardiography in severe forms
Diagnosis
- Diagnostic Criteria: documented occupational history of crystalline silica exposure + sufficient latency (generally > 5 years for chronic form) + compatible radiological image (bilateral nodules predominantly in the upper lobes +/- eggshell calcified lymph nodes) + exclusion of other differential diagnoses
- Chest radiography (ILO 2011 classification): International Classification of Pneumoconioses + profusion of opacities (0/0 to 3/3) + size and shape of opacities (p + q + r for small rounded opacities) + large opacities (A + B + C for PMF) + pleural abnormalities + eggshell lymphadenopathy (pathognomonic)
- Thoracic HRCT scan more sensitive than radiography for detecting early nodules + FMP evaluation + lung cancer screening
- Pulmonary function tests Spirometry + DLCO + plethysmography → restrictive syndrome + or mixed depending on the stage + longitudinal follow-up of progression
- Additional report Arterial blood gas if significant dyspnea + QuantiFERON-TB + CBC + ESR + ANA if suspicion of associated autoimmunity + echocardiogram if PAH is suspected
ℙ️
Silicosis from artificial marble (engineered quartz stone - high silica quartz kitchen countertops) is an emerging form of severe accelerated silicosis affecting young workers (20–40 years old) after 5 to 10 years of exposure to extremely high silica concentrations during dry or wet cutting without adequate protection. Cases have been documented in Spain, Australia, Israel, and Canada. These workers develop very severe, rapidly disabling, and fatal forms; several have undergone lung transplants. Prevention (wet cutting, source extraction, and FFP3 respiratory PPE) is imperative in this sector.
Treatment and care
- No curative treatment: Silicotic fibrosis is irreversible, meaning no medication can reverse established lesions. Therefore, treatment is symptomatic, aimed at preventing complications, and for compensation.
- Withdrawal from exhibition cessation of silica exposure + recommended at diagnosis to slow progression + but disease can progress even after cessation of exposure (especially IPF)
- Symptomatic treatment: bronchodilators (associated COPD) + respiratory rehabilitation + long-term oxygen therapy if chronic hypoxemia (SpO2 < 88 % (at rest or during exercise)
- Tuberculosis Treatment: Annual screening + standard treatment if active tuberculosis + prophylactic treatment for latent tuberculosis (isoniazid + pyridoxine × 9 months or rifampicin × 4 months) if QuantiFERON positive
- Acute silicosis: iterative therapeutic bronchoalveolar lavage (BAL) + such as alveolar proteinosis + may temporarily improve survival
- Lung transplantation: last resort in terminal stages (severe IPF + respiratory failure) + comparable post-transplant survival to other indications
- Declaration to the CNESST: Silicosis is a compensable occupational disease in Quebec (Act respecting occupational accidents and occupational diseases - RAOOD) → mandatory declaration by the physician + claim for compensation by the worker → work stoppage + disability pension + medical care covered
Medical consultation recommended
Any worker exposed to crystalline silica (mining + quarrying + stone cutting + ceramics + quartz countertops) who develops progressive shortness of breath + chronic cough + or has abnormalities on a chest X-ray should consult a doctor for silicosis evaluation. The disease is a work-related illness eligible for compensation by the CNESST in Quebec — a medical report is required. For clinical and respiratory evaluation, including chest X-ray + spirometry + QuantiFERON, and referral to pulmonology and occupational medicine, Clinique Omicron offers consultations at its service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's Physician Assistants (PAs) and Nurse Practitioners (NPs) evaluate workers exposed to silica through detailed occupational history, chest X-ray (ILO classification), spirometry, and latent tuberculosis screening (QuantiFERON-TB). They diagnose silicosis and its complications, initiate the CNESST compensation process, refer to pulmonology and occupational medicine for advanced cases, and provide periodic medical surveillance for exposed workers. Consultations are available at several service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and does not replace the advice of a doctor or a pulmonologist specializing in occupational diseases. Silicosis is an incurable occupational disease that must be reported to the CNESST in Quebec. Primary prevention through the reduction of crystalline silica exposure is the only effective strategy to prevent this disease.
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