Silicosis

• What is Silicosis
• Statistics on Silicosis
• Risk Factors for Silicosis
• Progression of Silicosis
• Symptoms of Silicosis
• Clinical Examination of Silicosis
• How is Silicosis Diagnosed?
• Prognosis of Silicosis
• How is Silicosis Treated?
• Silicosis References

What is Silicosis

Silicosis is a respiratory disease caused by inhalation of silica dust which leads to inflammation and then scarring of the lung tissue.

Three types of silicosis are seen:

1) Simple chronic silicosis – which results from long-term exposure (more than 20 years) to low amounts of silica dust. Nodules of chronic inflammation and scarring provoked by the silica dust form in the lungs and chest lymph nodes. This disease may feature breathlessness and may resemble chronic obstructive pulmonary disease (COPD)

2) Accelerated silicosis – occurs after exposure to larger amounts of silica over a shorter period of time (4-8 years). Inflammation, scarring, and symptoms progress faster in accelerated silicosis than in simple silicosis.

3) Acute silicosis – results from short-term exposure to very large amounts of silica. The lungs become very inflamed and may fill with fluid, causing severe shortness of breath and low blood oxygen levels.

Statistics on Silicosis

With improving workplace standards, only 50-60 new cases are now diagnosed in the UK each year.

Risk Factors for Silicosis

A number of jobs require silica exposure, e.g. mining (gold, tin, copper and coal), stone quarrying, sandblasting, metal grinding, pottery and ceramic manufacturing.

Progression of Silicosis

Silicon dioxide is highly fibrogenic (scarring – more so than coal dust) and is particularly toxic to white blood cells (macrophages) in the alveoli of the lung. There is persistent pulmonary inflammation and fibrosis caused as a result of silica ingestion by lung white cells. As the white cells die due to the direct toxic effect of the silica, the particles are re-released back into the lung to perpetuate the process.

There is an increased incidence of tuberculosis and other mycobacterial disease beyond what would be expected. There is also a correlation between silicosis and squamous cell cancer of the lung (to the extent that lung cancer is now legally recognized as an occupational disease in those with silicosis in the UK).

Acute silicosis is a severe form of the disease caused by heavy exposure over a short period of time. It typically results in restrictive defects of the lung, cor pulmonale and respiratory failure.

Unlike coal dust deposition, the pathological features of silicosis continue to progress after exposure has ceased.

How is Silicosis Diagnosed?

A chest x-ray will demonstrate a signs suggestive of fibrosis, and certain characteristic signs of silicosis.

Prognosis of Silicosis

Chronic silicosis embodies a huge spectrum of disease, from asymptomatic to fulminant. Prognosis must thus be gauged on a case-by-case basis, depending on exposure and symptoms.

Acute silicosis is a very severe condition, which can be rapidly progressive, and lead to cardiorespiratory failure.

How is Silicosis Treated?

 

• As with all pneumoconioses, absolute avoidance of further exposure is needed to prevent disease progression.
• Preventative workplace evaluation is in place in most Western countries to ensure appropriate ventilation, extraction and dust suppression.

 

 

• Respiratory protection devices (e.g. face masks) also have a role to play.
• Regular screening for tuberculosis is important in those with silicosis.
• Industrial injuries compensation may be available in certain countries.
  

  Silicosis References

  [1] Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. pp734-35
  [2] Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998.
  [3] Talley NJ, O’Connor S. Clinical examination. Third Ed. MacClennan & Petty, 1996.