Silicosis is a lung disease which is caused by the inhalation of dust containing free silica or silicon dioxide (SiO2). It is the major cause of permanent disability and mortality among the occupational disease. They are tiny crystal found in sand, rock or mineral ore. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. The incidence of silicosis depends upon the chemical composition of dust, size of the particles, duration of exposure and individual susceptibility. Higher the concentration of free silica in the dust, greater is the hazard. 

Silica or silicon dioxide (SiO2) is transparent crystals with molecular weight 60.09 g/mol and density 2.65 g/cm3. They are insoluble in water or acids, except hydrofluoric acid and very slightly soluble in alkali.  The current limit for free silica in the industrial atmosphere is 100 μg/m3.

Classification of silicosis according to the disease’s severity:

Chronic silicosis- This is most common type of silicosis. It usually occurs after long-term exposure of low concentration of silica dust (after 10 or more years of exposure). Patients with this type of silicosis may not have obvious signs or symptoms of disease, but abnormalities may be detected by X-ray.  

Accelerated silicosis- Develop after a worker has been exposed to large amounts of silica dust over a short period of time (after 5 to 10 years of exposure).

Acute silicosis- Develops after short-term exposure to very large amounts of silica (after week or months if exposure). 

Workers are at high risk in mining industry, pottery and ceramic industry, metal girding, sand blasting, building and construction work, rock mining, iron and steel industry, glass manufacture, plaster or drywall installation and several others. 

Sign and symptoms of silicosis:

  • Persistent shortness of breath (Dyspnea)
  • Rapid breathing (Tachypnea) 
  • A persistent cough
  • Weakness and cough
  • Fever
  • Chest pain 
  • Fatigue 
  • Gradual darkening of skin (blue skin) 
  • Loss of appetite and weight loss 
  • Respiratory insufficiency

Causes of silicosis:

When we inhale small silica dust, they are deposited into tiny alveolar sacs and ducts in the lungs and leads to formation of scar tissue. The lungs cannot clear the dust by mucous or cough. The particles are ingested by the phagocytes which accumulate and block the lymph channels. Pathologically, silicosis is characterized by dense “nodules” fibrosis, the nodules ranging from 3 to 4 mm in diameters. Silica particles between 0.5 to 3 micron are the most dangerous because they reach the interior of lungs with ease. The longer the duration of exposure, the greater the risk of developing silicosis.

Diagnosis of silicosis:

  • Chest CT or X-ray
  • Occupational history of exposure of silica
  • Pulmonary (lung) function test
  • Sometime tissue biopsy
  • Bronchoscopy
  • Sputum test

Chest X-ray or CT scan are done to check your lungs for scars. CT scan is more sensitive than X-ray, especially when helical CT and high-resolution techniques are used. An X-ray of the chest shows “snow-storm” appearance in the lungs field. CT scan provides a more detailed analysis of the lungs, and can reveal cavitation due to concomitant mycobacterial infection.

Pulmonary (lung) function test may be used to measure the amount of air you are able to inhale and the airflow to and from the lungs. The doctors see how much oxygen is transferred from your lungs to your bloodstream. Sputum test will to evaluate other lungs diseases like tuberculosis (TB). The doctor may run a long, thin tube with mini camera to the end into the lungs to check for damage.

Treatment of silicosis:

Oxygen therapy- Supplemental oxygen from a portable oxygen tank is often necessary for patients to reduce fatigue.

Stop smoking- Strongly advise patients to quit smoking.

Medication- Bronchodilators helps relax your breathing passages.

Lung transplant surgery- A lung transplant might be an option if your condition is severe.

Preventive measures:

Some of preventive measures include:

  • Stop additional exposure.
  • Stop smoking.
  • Wear mask and other protective clothing.
  • Use wet methods to cut chip or grid materials.
  • Use respirators that protect you from inhaling silica.
  • Don’t eat and drink near silica dust.
  • Use blasting cabinets or proper ventilation.
  • Regular physical examination of workers.
  • Biological monitoring (X-ray, lung function)