What Are Pneumoconioses?

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Pneumoconioses are lung diseases caused by inhaling dust and fibers that result in fibrosis (scarring) in the lung. Most often due to workplace or occupational exposures, the most common diseases include black lung disease (coal miner's pneumoconiosis), silicosis (due to silicone), and asbestosis (due to asbestos inhalation).

Man in protective gear working outdoors

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Early on, symptoms are usually absent, but as the condition progresses people may develop exercise intolerance, shortness of breath, and a persistent cough. Diagnostic tests may include pulmonary function tests, imaging studies such as computerized tomography (CT), and more.

Unfortunately, there is no treatment available that reverses the fibrosis seen with pneumoconioses, and treatment is aimed at reducing symptoms and preventing further damage to the lungs. For this reason, prevention is the goal.

Occupational Lung Diseases

There are a number of occupational lung diseases of which pneumoconioses are only one type. Other work-related lung conditions include hypersensitivity pneumonitis, lung cancer, and obstructive airway disorders such as chronic obstructive pulmonary disease (COPD). Some of these conditions may occur even with short-term or brief exposures on the job.

With pneumoconioses, there is usually a very long latency period before symptoms appear, meaning that someone may be exposed to a type of dust for decades before experiencing symptoms. An exception is with silicosis, in which some people can develop rapidly progressive disease even after short term exposures.

Incidence/Prevalence

The mortality from pneumoconioses decreased from 1968 to 2000, with the exception of asbestosis. However, the recent finding of rapidly progressive coal worker's pneumoconiosis in Appalachia, as well as new sources responsible for silicosis, makes an understanding and awareness of these conditions as important as ever.

Due to the long latency period of pneumoconioses, people who were exposed decades ago may only now begin to develop symptoms.

Types of Pneumoconioses

Pneumoconioses are most often caused by exposure to nonorganic dusts and fibers such as coal, silica, asbestos, beryllium. and other hard metals. It's important to note that while the risk is usually discussed in regard to workers, family members may also be exposed (and develop the conditions) due to factors such as handling clothes that were near the dusts (laundry).

Asbestos

Asbestos is perhaps best known as being the primary cause of a rare type of cancer called mesothelioma and a risk factor for lung cancer. More commonly, however, it is associated with interstitial lung disease (asbestosis). While asbestos use has been banned in some settings, and limited in others, exposures still occur today.

The term asbestos actually includes six different minerals that occur in nature. Asbestos has been used in a broad range of products due to its unique properties such as resistance to heat and chemicals, electrical resistance, and having significant strength while also being flexible.

Some products that may contain asbestos include:

  • Brakes in vehicles
  • Insulation
  • Cement
  • Fireproofing

Some occupations in which exposures may occur include:

  • Construction
  • Mining
  • Insulation work
  • Shipbuilding

Outside of the workplace, exposures may occur with gardening in areas contaminated by asbestos or household activities that may disturb asbestos.

The amount of asbestos that gets into the air people breathe depends on many factors, including:

  • Location
  • Type of material or soil the asbestos is in
  • Age and characteristics of that material
  • Weather conditions and moisture
  • Intensity of the activity disturbing the asbestos

Silica

Silicosis is another type of pneumoconiosis (fibrotic lung disease) caused by free silica (silicon dioxide) exposure. Silica is found most commonly in quartz, and is abundant on the planet. Silicosis is very common and is currently the most prevalent occupational lung disease globally. Respirable silica is also found in granite, shale, sandstone, and sand.

In addition to causing silicosis, the inhalation of silica is associated with emphysema, lung cancer, kidney disease, autoimmune diseases, and an increased risk of contracting tuberculosis.

There are many occupations in which people may be exposed to silica, a few of these being:

  • Stone work, such as drilling, tunneling, cutting, chipping, polishing, mining
  • Stone fabrication for countertops
  • Concrete work, such as drilling, grinding, and polishing
  • Construction
  • Brick and tile work
  • Sandblasting
  • Demolition
  • Foundries
  • Pottery work

While workplace environments have certainly improved, a 2020 review found that some workers in areas of risk were exposed to concentrations of silica more than 10 times the upper limit of what is currently allowed. Most of the people exposed to the excess levels worked in construction of some form.

The risk of silicosis in workers who prepare stone slabs for countertops has also resulted in a more recent outbreak, with the first two deaths related to this practice reported in 2019.

Black Lung Disease

Black lung disease or coal worker's pneumoconiosis had once been decreasing, but at the current time is increasing both in incidence and severity in the United States.

Overall, the prevalence of coal worker's pneumoconiosis in coal workers who have worked in the industry for 25 years or more is 10%, with a prevalence of over 20% among workers in Virginia, West Virginia, and Kentucky.

Coal worker's pneumoconiosis can be either simple or complex (progressive massive fibrosis), and the incidence of progressive massive fibrosis relative to simple disease is also increasing (an increase from 0.37% to 3.23% between 2008 and 2012 alone).

Coal mining is the leading cause, but urban exposure to pollution has also been shown to cause black lung disease.

Beryllium

Less commonly, exposure to beryllium dust can also lead to pneumoconiosis. Beryllium is found in the aerospace, electronics, and nuclear industry, jewelry making, and dental alloy construction. Similar to the other pneumoconioses in many ways, berylliosis also causes granulomas in the lungs.

Other Substances

A number of other hard metals may also result in pneumoconioses. Some of these include:

  • Talc (magnesium sulfate): Exposures occur in occupations such as insulation work, mining, shipbuilding, and construction
  • Iron (siderosis) involving either metallic iron or iron oxide: Occupations where exposures may occur include mining, foundry work, and welding.
  • Tin (stannosis), involving tin or tin oxide: Exposures are found in occupations such as smelting, mining, and tin working.
  • Barium: Exposures are found in occupations such as glass and insecticide manufacturing.
  • Kaolin (sand, mica, and aluminum silicate): Exposures are seen in pottery and clay workers, cement workers.
  • Antimony
  • Mica
  • Aluminium
  • Cobalt
  • Artificial stone: In addition to natural occurring stone, previously unseen cases of pneumoconiosis have been arising due to exposures to artificial stone. Studies have been reported in Australia, the UK, and Belgium, but being so new, the precise impact or incidence of these exposures is unknown.

Pneumoconiosis Symptoms

The symptoms of pneumoconiosis can vary depending on the particular exposure, but are often not present for an extended period of time (there is usually a long latency period).

When present, symptoms may include:

  • Shortness of breath: Early on, shortness of breath may only be present with activity. As the condition progresses, however, difficulty breathing may occur while resting as well.
  • Persistent cough: A cough is very common and may or may not be productive of sputum depending on the particular inhaled dust.
  • Exercise intolerance: Exercise may become more difficult, something that may easily be dismissed as due to normal aging.
  • Fatigue: A vague sense of fatigue may be present as well. Since the conditions usually have a very gradual onset, however, this may be missed or attributed to something else such as normal aging as well.
  • Chest wall pain: Pain that is felt in the chest wall may occur, and may be related to the underlying condition or due to coughing.
  • Other symptoms may include head congestion, a runny nose, sinus pressure, or wheezing.
  • Night sweats (with berylliosis)

Complications

Restrictive lung disease may result in secondary complications, and sometimes these are the first symptoms of the condition.

As the right side of the heart attempts to pump blood through the scarred lung tissue, the pressure in the pulmonary artery increases. Unlike the left side of the heart, the right ventricle is thinner and not as strong, and eventually, blood backs up due to the pressure.

Right heart failure (cor pulmonale) often declares itself with severe shortness of breath and fatigue. Swelling can be present just as with left heart failure, but can involve not only the ankles, but also the chest and abdomen. Differentiating symptoms related to right heart failure and the underlying lung disease can then become challenging.

Causes

The lung damage seen with pneumoconioses begins with inflammation caused by the accumulation of inhaled particles in the lungs. This inflammation is the body's normal attempt to eliminate the dust particles present in the lungs.

As inflammation persists, it can lead to scarring (fibrosis) of the lungs. Scarring (fibrosis) is a permanent condition, and at this point, the disease is irreversible. The degree of inflammation (and subsequent fibrosis) depends on several factors, including the particle size, the length of exposure, amount of exposure, and more.

Particle Size

The size of the offending particles is very important in both causing disease and determining where in the lungs the disease will occur.

Large particles tend to be "caught" in the upper airways (the bronchi) where clearance mechanisms can effectively remove them. These particles become trapped in mucus which is then moved up and expelled via the action of the cilia, the tiny hairs lining the airways that move foreign material up and away from the lungs.

Intermediate-size particles usually land in the bronchioles. Particles considered intermediate in size are usually greater than 2 microns but less than 10 microns in diameter. In the larger bronchioles, the combination of mucus and ciliary action can sometimes remove the particles.

Small particles (those less than 2 microns in diameter) may make it all the way to the smallest of airways, the alveoli. In this location they have bypassed normal clearance mechanisms and are "eaten" (phagocytosed) by immune cells called macrophages present in the lungs.

With silica, most inhaled particles are from 0.3 to 5.0 microns.

Inflammatory Response

When cells in the body (such as macrophages, lymphocytes, and epithelial cells) encounter dust particles that have not been cleared by the mucociliary system, they release a number of inflammatory substances (such as TNF-alpha, matrix metalloproteinases, interleukin-1-beta, and transforming growth factor-beta).

These substances in turn stimulate cells called fibroblasts to grow and divide. As the fibroblasts increase in numbers, they surround the dust particles in the lungs to form nodules, and eventually, progressive fibrosis.

Fibrogenicity

Some dust particles are more likely than others to cause fibrosis. Of the dusts discussed, beryllium is considered the most fibrogenic, followed by silica and asbestos, with coal dust being least fibrinogenic.

Interstitial Fibrotic Lung Disease

Many people are familiar with lung diseases such as COPD, but these lung diseases, referred to as obstructive lung diseases, differ from restrictive lung diseases such as pneumoconiosis in several ways.

Diagnosis

The diagnosis of pneumoconiosis may include a number of steps and can vary depending on the particular dust exposure. With some dusts, such as coal dust, specific protocols are in place for screening and monitoring.

History

A very careful history and physical examination are important with any medical condition, but particularly so with pneumoconioses. Your doctor will want to know about the length and amount of any known exposure. Other factors, such as a history of smoking, asthma, or other lung conditions are important to note.

In addition to exposure history, a family history may be helpful. Genome-wide association studies suggest that genetics may play a role in who develops pneumoconiosis as well as the severity.

Physical Exam

As part of a general physical examination, your doctor will pay particular attention to your:

  • Lungs: The doctor will check for evidence of crackles as well as any discomfort you appear to have with breathing. Respiratory rate is an important viral sign, especially with severe disease.
  • Skin: Your doctor will check for any sign of cyanosis, a blueish discoloration of the skin caused by insufficient oxygen in the bloodstream.
  • Fingers: Your doctor will look for nail clubbing, in which fingernails take on the appearance of upside-down spoons. Clubbing can be caused by a number of lung conditions, including lung cancer, and is a normal finding (genetic) in some people.
  • Weight: Unintentional weight loss is common, but usually more remarkable in the advanced stages of pneumoconioses.

Laboratory Exams

Arterial blood gases (ABGs) may be done to determine the oxygen concentration in your blood.

Procedures

Pulmonary function tests can be very helpful not only in diagnosing and determining the severity of pneumoconiosis, but also in determining if other lung conditions such as COPD are also present.

While with obstructive lung diseases (such as COPD) forced expiratory volume in one second (FEV1) is usually decreased, this can be normal with restrictive lung diseases such as pneumoconioses.

Total lung capacity may be decreased. With obstructive lung diseases, expiration is usually most problematic and can lead to air trapping and an increase in lung capacity. In contrast, with pneumoconioses there is more difficulty with inhalation (the lungs are stiffer or less compliant), and lung volumes are often lower.

Other tests that can be helpful include lung plethysmography and diffusing capacity (DLCO).

If berylliosis is suspected, a bronchoalveolar lavage may be performed as well as a beryllium lymphocyte proliferation test (BeLPT).

Imaging

Imaging tests are often done and may begin with a chest X-ray. Chest CT can reveal more detail and help distinguish the different forms of pneumoconioses.

With black lung disease, disease is more prominent in the upper lungs. With silicosis, disease is usually scattered throughout the lungs and calcification may be seen in the lungs as well as lymph nodes (eggshell calcification).

Other Tests

Since silicosis is associated with an increased risk of tuberculosis, tuberculosis testing may be done.

Treatment

There is no treatment available that can reverse pneumoconioses, so treatment focuses on addressing symptoms and avoiding worsening of the condition.

Avoidance of Further Exposure

Avoidance of further exposure to the offending dust is very important, and whether a person will be able to continue in his or her occupation will depend on findings during the evaluation.

Medications

There are no medications that "treat" pneumoconioses, but medications such as inhalers may be needed to manage the symptoms or to manage co-existing conditions such as COPD or asthma.

Pulmonary Rehabilitation

Pulmonary rehabilitation is underutilized but extremely important to maximize quality of life. A rehab program may include endurance training, strength training, and exercise training. Many of these programs are holistic, and also include nutritional education, further education about the disease, and emotional support for coping with the condition.

A comprehensive pulmonary rehabilitation program has been found to benefit people with pneumoconiosis with regard to their physical functioning, knowledge of their disease, and emotional well-being.

Immunizations

As with other lung diseases, vaccinations for flu and pneumonia may help prevent further damage or complications due to these infections.

Oxygen

Oxygen therapy may be needed as symptoms progress, and can significantly improve quality of life when needed.

Lung Transplantation

With severe disease, a lung transplant may be considered in those who are otherwise generally healthy and is the only true "cure" for the disease. At least 62 lung transplants for coal worker's pneumoconiosis were performed between 2008 and 2018 alone. The procedure is improving with regard to success and complications.

Smoking Cessation

For those who smoke, quitting is imperative. While smoking does not increase the risk of developing pneumoconiosis, it can compound the complications and lessen quality of life.

Prevention

The saying "an ounce of prevention is worth a pound of cure" was never more appropriate than with pneumoconioses. These conditions should, in theory anyway, but completely preventable.

For those who are exposed to dust at work, education is critical. There are many guidelines in place (too in-depth to discuss here), and following these guidelines can reduce your risk. These may include time limits for potential exposures, the use of personal protective equipment (such as respirators), and more.

There are currently rulings on exposure limits for different dusts, but these are subject to change over time. For example, with silica, a recommended average exposure limit of 50 micrograms per cubic meter for inhalation of dust containing crystalline silica for a 10-hour workday was proposed.

With beryllium, an eight-hour exposure limit of 0.2 micrograms of beryllium per cubic meter of air with short term exposures up to 2.0 micrograms was proposed.

A Word From Verywell

Pneumoconioses are important lung diseases to be aware of as they should theoretically be entirely preventable. That said, even when protocols are followed flawlessly, those who were exposed in the past are still at risk.

In addition, rapidly emerging new sources of pneumoconiosis are just now being reported (such as in workers who prepare stone countertops). If you are potentially exposed to any of these dusts on the job, take some to learn about your risks and what you can do to make sure you are safe on the job.

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