What is silicosis

Silicosis is a occupational lung disease called pneumoconiosis caused by breathing in of crystalline silicon dioxide, tiny bits of silica, a mineral that is part of sand, rock, and mineral ores such as quartz. Silicosis mostly affects workers exposed to silica dust in occupations such mining, glass manufacturing, and foundry work. Over time, exposure to silica particles causes scarring in the lungs, which can harm your ability to breathe. Silicosis is one of several well-described pulmonary complications associated with toxic exposures in the workplace, along with asbestosis, berylliosis, coal miner’s lung, hard metal pneumoconiosis, among others.

There are three types of silicosis:

1. Acute silicosis, which causes cough, weight loss, and fatigue within a few weeks or years of exposure to inhaled silica. Acute silicosis results from short-term exposure (weeks or months) of large amounts of silica. The lungs become very inflamed and can fill with fluid, causing severe shortness of breath and low blood oxygen levels. A cough, weight loss, and fatigue may also be present. Acute silicosis progresses rapidly and can be fatal within months.
2. Chronic silicosis, which appears 10 to 30 years after exposure and can affect upper lungs and sometimes cause extensive scarring. Chronic silicosis is the most common type of silicosis, results from long-term exposure (usually more than 20 years) to low amounts of silica dust. Chronic silicosis may cause people to have difficulty breathing.
3. Accelerated silicosis, which occurs within 10 years of high-level exposure. Accelerated silicosis occurs after 5 to 15 years of exposure of higher levels of silica. Swelling of the lungs and other symptoms occur faster in this type of silicosis than in the chronic silicosis.

Two forms of silicon dioxide exist in nature: amorphous and crystalline ¹⁾. The crystalline form of silicon dioxide is an abundant natural mineral, commonly found in substances such as sandstone, quartz, and granite. While inhalation of the amorphous form does not appear to cause clinically significant complications, inhalation of the crystalline compound can lead to pulmonary disease.

As silica deposits in the airways, contact with the alveolar and endobronchial surfaces generates reactive oxygen species. Smaller particles are taken up through phagocytosis into macrophages, which generate additional free radicals. Oxidative damage by activated macrophages and silica particles result in the release of inflammatory cytokines, increase in cell signaling, and apoptosis of parenchymal cells and macrophages. Fibroblast infiltration occurs in a nodular pattern as the disease progresses ²⁾.

Silicosis can develop within a few weeks to even decades after exposure. When people breathe silica dust, they inhale tiny particles of the mineral silica. This silica dust can cause fluid buildup and scar tissue in the lungs that cuts down your ability to breathe. This can lead to lung scarring and cough, weight loss, and fatigue.

Silicosis affects the lungs by damaging the lining of the lung air sacs. Once this begins, it leads to scarring and, in some situations, to a condition called progressive massive fibrosis. This condition happens when there is severe scarring and stiffening of the lung, which makes it difficult to breathe.

People with acute silicosis experience cough, weight loss, tiredness, and may have fever or a sharp chest pain. You may also have shortness of breath over time, especially with chronic silicosis. Your healthcare provider might hear crackles or wheezing when they listen to your lungs. Having silicosis increases the risk of other problems, such as tuberculosis, lung cancer, and chronic bronchitis.

Each type of silicosis affects the body somewhat differently:

• In acute silicosis, the lungs become very inflamed and can fill with fluid, which causes severe shortness of breath and low blood oxygen levels.
• In chronic silicosis, the silica dust causes areas of swelling in the lungs and chest lymph nodes, which makes breathing more difficult.
• In accelerated silicosis, swelling in the lungs and symptoms occur faster than in chronic silicosis.

Over time, lung capacity decreases, and people with silicosis may need support with oxygen and other devices to help them breathe.

Any person who works in industries with exposure to inhaled silica should get regular health checkups and be monitored for signs and symptoms of lung disease. In addition, if you have a cough, phlegm, or breathing difficulty that is not improving, you should be closely evaluated by your doctor. Some people with acute silicosis also have fever, weight loss, and fatigue.

Numerous occupations may place workers at risk for exposure to silica dust across a wide variety of industries ³⁾. High-risk occupations include road repair, concrete manufacturing, coal mining, brick working, and rock excavation. Also at risk are workers employed in stone cutting, petroleum extraction, steel working, sandblasting, and others. According to the Occupational Safety and Health Administration, there are over two million workers exposed to some form of respirable silicon dioxide on a regular basis. Improved awareness and safety measures in the workplace have led to a substantial decrease in this disease over the last several decades; however, safeguards remain imperfect and there continue to be new cases of silicosis that arise ⁴⁾.

From 2011-2013, 12 people younger than 45 years of age had silicosis listed as causing or contributing to death ⁵⁾. Although experts at the Centers for Disease Control and Prevention (CDC) do not know the details of their cases, this is concerning because silicosis deaths in these young adults may reflect higher exposures than those causing chronic silicosis mortality in older individuals.

Silicosis key facts:

• There are three types of silicosis: acute, chronic, and accelerated.
• Silicosis occurs in workers from mines, foundries, sandblasting, and glass manufacturing.
• About 2 million US workers remain potentially exposed to occupational silica.
• Silicosis can cause major lung damage and accounts for more than 100 deaths each year in the United States.
• There is no cure for silicosis, but it can be prevented.

Figure 1. Silicosis chest X-ray

Footnote: 78 year old male former coal-miner, who is a regular respiratory clinic attendee. Volume loss in both upper lobes. Bilateral apical conglomerate fibrosis. Diffuse predominently upper lobe nodularity.

[Source ⁶⁾ ]

Figure 2. Silicosis chest CT scan

Footnote: 35 year old quarry worker complaining of cough and breathlessness. Conglomerate mass like fibrotic areas are seen in bilateral upper lobes with traction prominence of bilateral hila. Multiple well defined centrilobular nodular opacities are seen in bilateral lungs more marked in upper lobes. Multifocal areas of ground glass haziness seen in both lung fields. Minimal loculated left pleural effusion with pleural thickening. Enlarged partially calcified mediastinal, bilateral hilar and supraclavicular lymph nodes. Trachea and major bronchi are normal. Heart and great vessels of mediastinum are normal. No evidence of right pleural/ pericardial effusion seen. Visualized spine is normal. Visualized upper abdomen is grossly normal.

[Source ⁷⁾ ]

Is there a cure for silicosis?

There is no cure for silicosis, but it can be prevented.

Can you get silicosis from one exposure?

Unlike coal dust deposition, the pathological features of silicosis continue to progress after exposure has ceased. People who work in jobs where they are exposed to silica dust (mining, quarrying, construction, sand blasting, stone cutting) are at risk of developing silicosis. Silicosis can develop within a few weeks to even decades after exposure. When people breathe silica dust, they inhale tiny particles of the mineral silica. This silica dust can cause fluid buildup and scar tissue in the lungs that cuts down your ability to breathe. This can lead to lung scarring and cough, weight loss, and fatigue.

Three clinical entities exist along the spectrum of silicosis disease including chronic silicosis, accelerated silicosis, and acute silicosis. Nodular or pure silicosis can occur after 20 or more years of exposure in occupations. An accelerated form of the silicosis disease occurs after a heavier exposure for 5 to 10 years ⁸⁾. Acute silicosis is an unusual reaction caused by heavy exposure over a short period to high levels of silica of small particle size ⁹⁾.

How much silica dust causes silicosis?

Intense exposure to silica can cause silicosis within a year. But it usually takes at least 10 to 15 years of exposure before symptoms occur. Silicosis has become less common since the Occupational Safety and Health Administration (OSHA) created regulations requiring the use of protective equipment, which limits the amount of silica dust workers inhale.

People who work in jobs where they are exposed to silica dust are at risk. These jobs include:

• Abrasives manufacturing
• Glass manufacturing
• Mining
• Quarrying
• Road and building construction
• Sand blasting
• Stone cutting
• 
  Removal of paint and rust with power tools
  
• Abrasive blasting of bridges, pipes, tanks, and other painted surfaces especially while using silica sand
• Grinding mortar
• Abrasive blasting of concrete (many bridges and buildings are made of concrete)
• Crushing, loading, hauling, chipping, hammering, drilling, and dumping of rock or concrete
• Chipping, hammering, drilling, sawing, and grinding concrete or masonry
• Demolition of concrete and masonry structures
• Dry sweeping or pressurized air-blowing of concrete or dust
• Jackhammering on various materials.

How long can you live with silicosis?

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

Accelerated silicosis – occurs after exposure to larger amounts of silica over a shorter period of time (5-15 years). Inflammation, scarring, and symptoms progress faster in accelerated silicosis than in simple 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.

What causes silicosis

Silicosis is caused by exposure to crystalline silica, which comes from chipping, cutting, drilling, or grinding soil, sand, granite, or other minerals. Any occupation where the earth’s crust is disturbed can cause silicosis. A long list of occupations are known that expose workers to crystalline silica that is inhaled. These include:

• Various forms of mining, such as coal and hard rock mining
• Construction work
• Tunnel work
• Masonry
• Sand blasting
• Glass manufacturing
• Ceramics work
• Steel industry work
• Quarrying
• Stone cutting

What are risk factors of silicosis?

Breathing crystalline silica causes silicosis and the main risk factor is exposure to silica dust.

You can prevent silicosis by limiting exposure. There are national guidelines on exposure limits over a lifetime of working.

If you work in a job that exposes you to silica dust, your employer must, by law, give you the correct equipment and clothing you need to protect yourself. You are responsible for using it—always—and for taking other steps to protect yourself and your family as you leave your job site and head home. NIOSH also recommends that medical examinations occur before job placement or upon entering a trade, and at least every 3 years thereafter.

Patients with silicosis have an increased risk of other problems, such as tuberculosis, lung cancer, and chronic bronchitis. If you are a smoker, quitting may help, as smoking damages the lungs.

Silicosis prevention

If you work in a high-risk occupation or have a high-risk hobby, always wear a dust mask and do not smoke. You might also want to use other protection recommended by Occupational Safety and Health Administration (OSHA), such as a respirator.

Silicosis symptoms

Symptoms of silicosis can appear from a few weeks to many years after exposure to silica dust. Symptoms typically worsen over time as scarring in the lungs occurs. Cough is an early symptom and develops over time with exposure to silica that is inhaled.

Symptoms of silicosis include:

• Cough
• Shortness of breath with exercise, usually in patients who have progressive massive fibrosis
• Weight loss
• Weakness

Other symptoms of this disease, especially in acute silicosis, may also include:

• Cough
• Fever
• Severe breathing difficulty
• Weight loss
• Night Sweats
• Chest pains

In acute silicosis, you may experience fever and sharp chest pain along with breathing difficulty. These symptoms can come on suddenly.

In chronic silicosis, you may only have an abnormal chest X-ray in the beginning and then slowly develop a cough and breathing difficulty. More than a third of people with silicosis have phlegm production and cough. Chronic bronchitis-like symptoms may occur, and the lungs have additional sounds called wheezes and crackles. As extensive scarring progresses over time, you may see signs of chronic lung disease such as leg swelling, increased breathing rate, and bluish discoloration of the lips.

Silicosis possible complications

Complications of silicosis are represented by:

• Progressive massive fibrosis
• Tuberculosis and nontuberculous mycobacteriosis: they should be suspected clinically when there is rapid enlargement of small nodules or when nodules undergo cavitation.

There are reports of an increased incidence of scleroderma in patients who suffer chronic exposure to silica but this phenomenon remains unexplained. Reports of acute glomerulonephritis are also in the literature ¹⁰⁾.

Silicosis diagnosis

If you work or have worked in an occupation with exposure to inhaled silica and have a cough, phlegm, or breathing difficulty, you should be evaluated for silicosis.

Having worked in an at-risk industry is the best clue for your doctor, and a chest X-ray is crucial to diagnose the type of silicosis. Your visit will include a physical examination – your health-care provider will listen to your lungs – and a chest X-ray. Your chest X-ray may be normal, or you may have a lot of scarring in the lungs.

There may be a series of tests, such as:

• Breathing tests
• High resolution CT scan of the chest
• A bronchoscopy to evaluate the inside of the lungs
• A biopsy of the lungs

In simple silicosis, chest X-ray shows variable features consisting mainly in well-defined opacities ranging from 1 to 10 mm in diameter, located in the upper lobe and posterior portion of the lung. CT-scan findings consist of multiple small nodules with hilar and mediastinal lymphadenopathy. Some nodules may be calcified.

In acute silicosis, chest X-ray shows bilateral consolidation associated with ground-glass opacities. CT-scan findings consist of numerous centrilobular ground-glass opacities with consolidation ¹¹⁾.

Additional tests, such as mucus (sputum) evaluation, may be needed to assess for associated diseases, such as tuberculosis (TB).

Silicosis treatment

There is no cure for silicosis. Prevention is still the best way to avoid silicosis lung disease. Once silicosis has developed, your doctor will assess the degree of lung damage with tests. Some people may need urgent treatment with oxygen and support for breathing. Others may need medicines to decrease sputum production, such as inhaled steroids. Some may need inhaled bronchodilators, which relax the air tubes.

Once the silicosis lung disease advances, the management is similar to many other chronic lung diseases and needs a multidisciplinary or team approach. To keep the silicosis lung disease from getting worse, it is important to stay away from any additional sources of silica and other lung irritants, such as indoor and outdoor air pollution, allergens and smoke. You may consider counseling to discuss changing occupations.

Treatment also includes limiting exposure to irritants and quitting smoking.

People with silicosis are at high risk of developing tuberculosis (TB). Silica is believed to interfere with the body’s immune response to the bacteria that cause TB. Skin tests to check for exposure to TB should be done regularly. Those with a positive skin test should be treated with anti-TB drugs. Any change in the appearance of the chest x-ray may be a sign of TB.

Acute silicosis may need to be treated with steroids, and a lung transplant may need to be considered.

Living with silicosis

Patients with silicosis need to maintain their health by leading an active lifestyle and avoiding further exposure. Quitting smoking, getting adequate exercise, managing your weight, and monitoring for complications are all important.

Many people with silicosis have chronic symptoms and a decrease in lifespan. However, over the last few decades, supportive care and earlier detection have improved survival significantly.

Managing the disease

Appropriate diagnosis and treatment will make life with silicosis easier. Using the proper medications and seeing an experienced specialist are important to managing the disease. Here are a few tips to manage silicosis:

• Quit smoking
• Get yearly vaccinations, such as pneumococcal and influenza
• Be vigilant about watching for the development of TB or other infections
• Avoid further exposure to silica
• Educate yourself about the disease
• Consider enrolling in clinical trials
• Have a plan to manage flare-ups of the disease.

Oxygen support or other ways to manage chronic lung failure, like the use of noninvasive ventilator devices, may be needed.

Silicosis prognosis and life expectancy

Prognosis varies, depending on the amount of damage to the lungs.

Silicosis can lead to the following health problems:

• Connective tissue disease, including rheumatoid arthritis, scleroderma (also called progressive systemic sclerosis), and systemic lupus erythematosus
• Lung cancer
• Progressive massive fibrosis
• Respiratory failure
• Tuberculosis