Silicosis is the most common type of pneumoconiosis, a progressive lung condition caused by inhalation of foreign substances or dust and is characterized by nodular lesions. Left untreated, pneumoconiosis can lead to fibrosis, where a condition marked by the formation of excessive fibrous tissue, even after there is no more exposure to the silica dust.

Silicosis - nodules on chest x-ray
Silicosis showing as nodular mass on a chest x-ray.


When silica particles are deposited in the lungs, a type of immune system cell called alveolar macrophages will ingest the compound in order to get rid of it. However, since macrophages cannot process the silica compound, they will die instead.

Dying macrophages release proteolytic or protein-degrading enzymes into the surrounding tissue thus causing inflammation, which then attracts other macrophages and a type of cell called fibroblast. Fibroblasts are specialized type of cells that produce fibrous tissues to isolate and wall off the inflammation, thus causing nodules to develop in the lungs.

In silicosis, nodules typically develop in the upper lobes of the lungs, near the terminal and respiratory bronchioles.

In most cases, silicosis only involves formation of the nodules, which has no symptoms and is of no physiological significance. However, in cases where there is a lot of fibrous tissue formation or fibrosis, large areas of the lung can be destroyed.

Cause of Silicosis

Silicosis is the result of inhalation of silica dust, mainly from industrial sources such as:

  • Flint Ceramics
  • Sandstone Building Material, Cement
  • Silica Flour Materials in paint, porcelain, scouring soaps, wood fillers
  • Quartz Gold, lead, coal, and zinc mining

Silica dust
Electron microscopy of silica dust.

People who are most likely to develop silicosis are those who are continually exposed to silica dust due to their working environment. These include:

  • Foundry workers
  • Miners
  • Stonecutters
  • Grinders
  • Boiler scalers
  • Sand blasters
  • Tunnel workers


Silicosis is classified according to its severity, onset and rapidity of progression of the disease. It usually begins as an asymptomatic (with no symptoms) condition, which can then develop into:

  • Acute silicosis
    This form of the disease develops after 1 to 3 years of exposure to very high concentration of silica dust.

  • Accelerated silicosis
    This form develops at an average of 10 years of lower concentration of silica.

  • Chronic silicosis
    Simple and complicated silicoses develop after 20 years or longer of exposure to lower levels of silica.

Symptoms of Silicosis

In early stages, there may be no symptoms of silicosis. The disease can then progress to develop the following symptoms:

  • Dyspnea (air hunger) or difficulty in breathing, especially after physical exertion
  • Tachypnea or rapid breathing
  • Persistent dry cough
  • Hoarseness
  • High blood pressure or pulmonary hypertension
  • Confusion
  • Tiredness, lethargy, or malaise
  • Difficulty in sleeping
  • Changes in breathing characteristics (decrease in rate and depth of breaths)
  • Heart failure
  • Cor pulmonale or enlargement of the right-side of the heart


In addition to confirming the patient’s current and past occupation as a risk factor, diagnosis of silicosis include:

  • Physical checkup
    Chronic silicosis reveal decreased chest expansion, diminished intensity of breath sounds, crackling, and rapid breathing.

  • Chest x-ray
    Small and discrete nodules are present in chest x-ray of simple silicosis. In advanced cases, large masses of dense, fibrous tissue are seen.

  • Pulmonary function tests
    These tests will reveal reduced lung capacity in silicosis patients.


There is no cure for silicosis, instead treatments of this condition focus on supportive or palliative measures. These include:

  • Limiting exposure to lung irritants and smoking cessation

  • Cough suppressant

  • Inhaled bronchodilators to make breathings easier

  • Chest physiotherapy
    To help with coughing and bronchial drainage of mucus, physiotherapy techniques such as chest percussion or vibration (gentle tapping of the chest) can be done.

  • Increased drinking water consumption (at least 3 quarts or liters per day)

  • Oxygen administration
    To avoid hypoxemia or insufficient oxygenation of the blood, oxygen can be administered by cannula or mask. Patients with severe silicosis may require mechanical ventilation.

  • Antibiotics in cases of respiratory infections


Silicosis can develop into more serious conditions, such as pulmonary tuberculosis (TB) and fibrosis, which can cause respiratory insufficiency and cor pulmonale.

Patients with silicosis are at high risk for developing TB. This is probably caused by silica’s interference with the body’s ability to ward off the bacteria that cause tuberculosis.


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