Silicosis and Coal Workers’ Pneumoconiosis - Risk Factors, Symptoms, Diagnosis, and Treatment

What Is Silicosis and Coal Workers Pneumoconiosis?

Silicosis is a chronic, preventable disease of the lung caused by inhaling large quantities of silica. It is an occupational hazard and is found in people with prolonged exposure to silica. Silica is a naturally occurring element found in sand, glass, quartz, and rock. Long-standing exposure results in the build-up of silica in the lungs and airways, causing inflammation and scarring of the tissues and hence, difficulty breathing.

Coal workers’ pneumoconiosis (CWP) is another occupational hazard caused by the continued inhalation of coal or graphite particles. It is usually found in people working in coal mines. This disease is also known as black lung disease.

Silicosis and CWP are chronic diseases that take years to develop. Though silicosis may have a short-term onset, this disease is entirely preventable if appropriate preventive measures are taken. If not, it could result in severe lung impairment and prove fatal.

What Are the Types of Silicosis?

There are three types of silicosis. They are as mentioned below:

• Acute - Acute silicosis occurs when individuals come in contact with large amounts of silica. The symptoms may appear within a few weeks to two years.

• Chronic - This is the most common type of silicosis. It occurs when an individual is exposed to a low or fair quantity of silica continuously for a prolonged period. Initially, the symptoms are mild, only to worsen in the later stages.

• Accelerated - Symptoms appear about five to ten years after exposure and deteriorate rapidly.

What Are the Types of CWP?

There are three types of CWP:

• Anthracosis - Cause due to deposition of carbon dust. This condition is considered relatively harmless.

• Simple CWP - The dust particles cause a few spots or scar tissue in the lungs.

• Complicated CWP - Heavy scarring resulting in progressive massive fibrosis (thickening) of lung tissues.

What Are the Risk Factors for Developing Silicosis and CWP?

Both silicosis and CWP are known occupational hazards. Hence individuals working in industries associated with silica and coal are more prone. They are as mentioned below:

• Mining industry and quarrying.

• Glass manufacturing units.

• Sandblasting.

• Construction workers.

• Individuals who are working on plaster roofing and walls.

• Road repair.

• Masonry.

• Metal industry.

• Stone cutting.

What Are the Symptoms Associated With Silicosis and CWP?

The symptoms may be mild or severe depending on the condition and stage of the disease. They include the following:

• Persistent cough.

• Difficulty in breathing.

• Weakness and prominent weight loss.

• Chest pain and tightness around the chest.

• CWP has a typical symptom of coughing black color sputum.

• Severe conditions could result in respiratory collapse.

• Silicosis can increase the risk of developing other conditions such as chronic obstructive pulmonary disease (COPD), tuberculosis, pulmonary hypertension, heart failure, renal disorders, and even lung cancer.

How Can Silicosis and CWP Be Diagnosed?

Silicosis and CWP may take years to be found on any imaging modality. But individuals with positive occupational history and symptoms should undergo routine screening to avert any fatal consequences.

Chest X-Ray:

Due to overlapping features, it is challenging to differentiate silicosis from CWP on a chest X-ray. However, a chest X-ray can help establish an initial diagnosis.

1. Silicosis:

• It appears as a wide-spread nodule larger than simple CWP.

• It has well-defined margins.

• Usually predominant in the middle and upper lung zones.

• Severe cases will show larger nodules with fibrosis and loss of lung volume.

• The pathognomonic feature of silicosis is egg-shell calcification (calcification found at the periphery of the lymph nodes). It is usually seen in the hilar or mediastinal area.

2 Simple CWP:

• CWP appears on chest X-rays as small opaque round nodules. At times it may also appear in a reticulated pattern.

• The margins are not well-defined.

• The nodules have a granular appearance.

3. Complicated CWP:

• Larger opaque nodules with prominent fibrosis.

• The borders may be regular or irregular.

• Presence of associated emphysema (damage of air sacs).

4. Progressive Massive Fibrosis (PMF):

• PMF may be unilateral or bilateral.

• They have irregular, elongated opacities seen typically in the upper lobes.

• They have a distinct angel’s wing appearance (large lesion separated from the pleura by normal lung tissue).

• Massive calcification may be present.

• Severity is indicated by the presence of cavitation, ischemic necrosis, and tuberculous findings.

• Emphysema and loss of lung volume are characteristic of PMF and thus help in differentiating it from lung cancer.

Computed Tomography (CT):

• CT shows the presence of small diffuse nodules more predominantly in the upper part of the lungs.

• The nodules have a perilymphatic distribution.

• Calcifications are evident with the nodules.

• Enlargement of hilar or mediastinal lymph nodes.

• PMF appears as irregular, bilateral lentrical-shaped larger nodules. They are well-circumscribed and surrounded by emphysema.

• Extrapleural fat thickening is evident.

• Suspect associated tuberculosis if necrosis or cavitation is seen.

High-Resolution Computed Tomography (HRCT):

• HRCT is considered the top choice to detect nodules smaller than three millimeters.

• HRCT is the preferred diagnostic tool for a patient with normal chest X-ray or CT.

• However, the major drawback of HRCT is the scoring criteria and standardization protocol.

• CWP presents as ill-defined or well-defined nodules. They may also be present in a branching pattern.

• Emphysema could be seen in the center of the lung lobes (centrilobular emphysema).

• Silicosis usually has a ground-glass appearance.

• Micronodules may also be seen in the subpleural space.

Magnetic Resonance Imaging (MRI):

• CWP shows low signal intensity on MRI when compared with normal tissue.

• Contrast MRI shows an increase in peripheral uptake.

Nuclear Imaging:

• A PET-CT may prove beneficial in complications associated with CWP, such as lung cancer which may demonstrate an increase in uptake of the marker used in the PET scan. However, even a fibrotic mass in CWP may show increased marker uptake. Hence, differentiating the neoplasm from fibrosis may require additional investigation.

Pulmonary Function Test:

• A lung function test or spirometry can be done to assess the working condition of the lungs.

• Spirometry is non-invasive and the simplest form of lung function test.

• This test uses a device called a spirometer, which the patient will be asked to breathe into.

• This test can assess the severity of the breathing problem and, consequently, the damage to the lungs.

Bronchoscopy:

• Bronchoscopy is a diagnostic procedure in which a thin, flexible tube is inserted through the mouth or nose, down the throat into the lungs. The tube has a camera attached to its end that will allow the doctor to view the lungs, airways, and any structural abnormalities.

• Bronchoscopy will also aid in taking a biopsy of the tissue sample if required.

• The scarring of tissues is distinctly visible with bronchoscopy.

Sputum Test:

• A sputum test may be referred if associated complications such as tuberculosis are suspected.

Biopsy:

• A biopsy may be suggested to check for microscopic signs of silicosis or to rule out lung cancer more often. However, a bronchoscopy-guided biopsy is usually preferred, where a thin hollow needle will be guided along with the bronchoscope to obtain a tissue sample that would then be sent for laboratory diagnosis.

How Is Silicosis or CWP Treated?

For mild cases, treatment mainly involves symptomatic management; however, in advanced diseases with severe lung damage, surgical intervention will be required.

• Steroids and bronchodilators can help ease breathing.

• Oxygen therapy can be used.

• Antibiotics can be given to prevent infection.

• The patient will be advised to quit smoking.

• Rare cases may even require a lung transplant.

• More emphasis should be laid on preventive measures by cautioning the employers of the risk factors, screening them periodically, avoiding prolonged exposure, and equipping them with protective measures such as face masks, protective shields, and other safety devices.

Conclusion:

Silicosis and coal workers’ pneumoconiosis are preventable occupational hazards. The symptoms take years to develop, and early stages may not be visible on any imaging procedure. Imaging procedures should aim to identify these conditions before the lung suffers from any extensive and irreversible damage. Despite silicosis and CWP being indistinguishable on the radiographs, their treatment and preventive measures are the same. Exhaustive prevention can help prevent any fatal complications.