Silicosis

Silicosis is a type of pneumoconiosis, meaning a diffuse interstitial lung disease caused by the accumulation of previously inhaled inorganic dust in the lungs, specifically crystalline silica particles. It is the most common occupational lung disease in developing countries. Its nature is irreversible, and in many cases, debilitating.

Crystalline silica is a metal oxide that is abundant in nature. The most common forms are quartz, cristobalite, and tridymite. Quartz is present in most rocks and sands on the Earth’s surface, while the other two are found in volcanic rocks.

Depending on its progression, several types of silicosis are distinguished:

• Chronic silicosis: the most common form, which develops slowly and appears decades after the initial exposure to silica.
• Accelerated silicosis: occurs in patients with high levels of exposure and progresses more quickly, with the disease appearing five to ten years after the initial exposure.
• Massive progressive silicosis, conglomerate or complicated: the advanced form of the two previous ones.
• Acute silicosis or acute silicoproteinosis: caused by very intense exposure to silica dust over short periods, generally from six months to two years. It may manifest weeks or years after exposure. It is rare but very severe.

Symptoms

The symptoms of silicosis are usually chronic and progressive, although in many cases, it remains asymptomatic. The main sign, common to all pneumoconioses, is the formation of pulmonary nodules of varying sizes composed of collagen and silica particles. In the most severe forms of the disease, these nodules grow in size, merge into clusters, and cause progressive fibrosis, which can become massive.

Visible symptoms include the following:

• Cough.
• Sputum production.
• Shortness of breath that worsens with exertion.
• Fatigue.
• Rapid breathing.
• Chest pain.
• Loss of appetite and weight.

In more severe forms, the following can be observed:

• Cyanosis: a bluish tint to the skin due to a lack of oxygen in the tissues.
• General pallor.
• Pulmonary crackles: abnormal sounds while breathing (detected by auscultation).
• Cor pulmonale: enlargement and thickening of the right ventricle of the heart. It may present with swelling in the legs, dizziness, and increased fatigue and shortness of breath.
• Respiratory failure.

Causes

As mentioned, the cause of silicosis is crystalline silica particles. Once inhaled, the small particles (less than five microns) reach the lung parenchyma and settle in the respiratory bronchioles and alveoli, where they are engulfed by alveolar macrophages, immune system cells. These cells, in turn, release enzymes (cytokines) and radicals that promote inflammation and the formation of nodules. Depending on the intensity and duration of silica exposure, the nodules may remain separate and not compromise lung function, or, conversely, they may merge, causing fibrosis and respiratory dysfunction.

Risk Factors

The primary risk factor is exposure to crystalline silica dust. This exposure primarily occurs in the workplace. The industrial sectors associated with silicosis include:

• Mining and quarrying.
• Construction and public works.
• Rock cutting and polishing.
• Glass, porcelain, ceramics, or precious stone manufacturing.
• Foundry work.
• Abrasive and detergent powder manufacturing.
• Iron and steel industries.
• Paper industry.
• Paint, plastic, and rubber manufacturing.

Additionally, the duration and intensity of exposure, as well as the size of the silica particles and their concentration levels, influence the development of the disease. The individual's immune predisposition is also a risk factor.

Complications

Like other pneumoconioses, silicosis often leads to severe lung damage and can have very serious consequences, in addition to reducing the patient’s life expectancy. The most common complication is the development of chronic obstructive pulmonary disease (COPD), characterized by respiratory failure and reduced pulmonary diffusion capacity (the exchange of oxygen and carbon dioxide).

Furthermore, chronic silicosis can cause increased pressure in the lungs (pulmonary hypertension) or spontaneous lung collapse (pneumothorax). Both conditions pose a risk to life. The rapid progression of acute silicosis can also be fatal.

In addition, silicosis patients, or those exposed to silica even without showing the disease, are more susceptible to developing tuberculosis, as silica-filled macrophages lose their ability to eliminate mycobacteria. Silicosis also increases the risk of lung cancer and certain autoimmune diseases, such as rheumatoid arthritis, scleroderma, and systemic lupus erythematosus (especially the acute and accelerated forms of silicosis).

Prevention

Primary preventive measures for silicosis aim to limit exposure to silica in the workplace and promote early detection of the disease:

• Water sprinkling to make the particles settle.
• Aspiration and ventilation systems.
• Use of special masks and other personal protective equipment.
• Frequent medical check-ups for workers exposed to silica, even after they leave the workforce.

To prevent complications of silicosis, it is also recommended to quit smoking and get vaccinated against pneumococci, COVID, and the flu.

What doctor treats silicosis?

Silicosis is diagnosed and treated by specialists in pulmonology.