Silicosis - Causes, Types, Symptoms, and Treatment

Introduction:

Silicosis is a chronic (long-term) lung disease caused by breathing in tiny particles of silicon dioxide in the form of free crystalline silica (quartz) or rarely by inhaling silicates, minerals containing silicon dioxide bound with other elements, such as talc. Silica is a naturally occurring substance in certain rocks, stones, clay, and sand. Working with silica-containing materials over many years can cause easy inhalation of very fine silica dust particles. Once silica dust enters the lungs, it causes lung inflammation (swelling) and scarring (fibrosis), leading to loss of lung function.

Who Is at Higher Risk of Silicosis?

The workers who blast rock and sand in mines, quarries, and cutting stones, sandblasters, glassmakers, ceramic workers, foundry workers, gemstone workers, and potters (who use silica-containing rocks and sand abrasives) are at higher risk of this condition. Coal miners are also at increased risk of both silicosis and coal worker pneumoconiosis.

What Are the Risk Factors Involved?

Various risk factors that are involved in the development of silicosis include:

• Based on the form of silicon (exposure to the crystalline form of silica has an increased risk than the bound form).

• Depending on the duration and intensity of exposure.

• Depends on the surface characteristics.

• Speed of inhalation after the dust is fractured and converted into airborne.

What Are the Complications of Silicosis?

Several complications occur as a result of this condition. These include:

• Chronic kidney disease.

• Nocardiosis (a bacterial disease that affects the brain, lungs, and skin).

• Lung cancer.

• Tuberculosis.

• Systemic sclerosis (refers to a rare condition characterized by the hardening of the connective tissues).

• Rheumatoid arthritis.

• Other complications that possibly occur include- spontaneous pneumothorax (collapsed lung), airway obstruction, and broncholithiasis (calcifications in the windpipe branches).

• Emphysema (a lung disease that damages the air sacs and causes shortness of breath) is also common in areas of progressive massive fibrosis.

• People not affected by silicosis but exposed to silica have three times the risk of developing tuberculosis compared to the general population.

What Are the Different Types of Silicosis?

There are three types of silicosis classified based on the exposure and manifestation of symptoms:

• Acute Silicosis- It is also referred to as silicoproteinosis. The cause of acute silicosis includes exposure to intense silica dust within a short span of time. It shows positive stains of periodic acid -Schiff (PAS) due to the infiltration of mononuclear cells in alveolar septa and spaces filled with a proteinaceous material which can also be seen in pulmonary alveolar proteinosis. The occupational history associated with acute exposure to silica particles differentiates silicoproteinosis from pulmonary alveolar proteinosis.

• Chronic Silicosis- It is the most common disorder, which only manifests or develops after exposure over decades.

• Conglomerate Silicosis- It is also referred to as complicated silicosis or progressive massive fibrosis. It is the progressed or advanced form of chronic or acute silicosis. It is characterized by masses of fibrosis spread widely, especially in the upper lung zones.

What Are the Signs and Symptoms of Silicosis?

• Acute Silicosis- Patients with acute silicosis present with rapid progression of dyspnea, weight loss, bilateral crackles, and fatigue. Respiratory failure occurs within two years.

• Chronic Silicosis- Chronic silicosis mostly presents with no symptoms, usually asymptomatic, but many patients show dyspnea during exertion, which progresses to dyspnea even at rest. Other manifestations are productive cough and bronchitis. Breath sounds decrease as the disorder progresses, pulmonary hypertension, pulmonary consolidation, respiratory failure, and right ventricular failure are other conditions associated with the progression of the disease.

• Conglomerate Silicosis- This type of silicosis is associated with severe and long-term respiratory complications.

What Are the Diagnostic Approaches for Silicosis?

A detailed occupational history with short-term or long-term exposure to silica and physical examination assist in diagnosing this condition.

Various other tests are performed to rule out the diagnosis -

Imaging Test:

1. Chest X-Ray-

• This test can reveal the presence of scar tissue. Small white spots appear on X-rays which are known as silica scars.

• This test is preferable as it is more sensitive for detecting and recording the transition from simple to conglomerate silicosis. The findings from a chest X-ray can help to differentiate asbestosis from silicosis.

• Calcified hilar and mediastinal lymph nodes resembling eggshells are the typical characteristic distinguishing feature from other pulmonary disorders.

• A diffuse alveolar basilar opacity demonstrates fluid-filled alveoli is the diagnostic finding of acute silicosis.

• In conglomerate silicosis, opacities more than 10 millimeters in diameter are observed.

2. Adjunctive Tests:

• Specific Tests: Sputum culture and cytology, bronchoscopy, and positron emission tomography help distinguish silicosis from other pulmonary complications like tuberculosis or cancer. Antinuclear antibodies and elevated rheumatoid factor are noticed in a few patients, suggesting coexisting connective tissue disorder.

• Pulmonary Function Tests: In conglomerate silicosis, this test reveals decreased lung volumes, reduced levels of diffusing capacity for carbon monoxide, and airway obstruction. In the early stages of chronic silicosis, reduced lung volume with normal functional residual capacity and residual volume are observed. In the case of conglomerate silicosis, this test reveals reduced lung volume capacity, decreased diffusion capacity for carbon monoxide, and airway obstruction.

• Bronchoscopy: In bronchoscopy a thin, flexible tube is passed down the throat, where a camera is attached to the tube to view the lung tissue. Through this technique, tissue and fluid samples can be taken.

How Is Silicosis Treated?

The treatment of silicosis can be aimed at reducing the progression and relieving the symptoms of this disease. Avoidance of further exposure to silica particles should be avoided.

• Oxygen therapy is recommended in the case of patients suffering from difficulty in breathing and low levels of oxygen in the blood.

• Bronchodilator medicines are recommended to widen the airways and make breathing easier.

• Antibiotics are prescribed in case of bacterial chest infections.

• In advanced or severe cases, a lung transplant is the only choice of treatment. There are some health limitations to meet before this procedure is carried out.

• In the case of acute silicosis, whole lung lavage is recommended.

• Whole lung lavage reduces the total mineral dust load in the lungs. The use of oral Corticosteroids is also recommended in case of acute silicosis.

Conclusion:

Silicosis is a serious lung disease that does not have a cure, as lung damage cannot be reversed. However, the symptoms can be relieved with treatment, and the patient's quality of life can be improved. The prevalence of silicosis has been reduced over time due to improvements in workplace safety measures. However, reports suggest that more than a hundred people die yearly from silicosis. The long-term outcome depends on the severity of the condition.