An Overview of Black Lung Disease

Coal workers pneumonconiosis is increasing both in incidence and severity

In This Article

Black lung disease, also known as coal worker's pneumonoconiosis (CWP) is an occupational condition that—while once declining—is now increasing in both incidence and severity in the United States. Most often occurring in coal miners, the greatest increase has been seen in central Appalachia, though the disease is increasing in other regions as well. The disease is caused by the inhalation of fine dust particles that cause scarring, which is followed by the development of scar tissue (fibrosis). It can be divided into two categories, simple or complex (progressive massive pulmonary fibrosis). Since the condition is irreversible, treatment is focused on managing symptoms and preventing further lung damage. When severe, a lung transplant may be considered. Prevention is key, and those who are exposed should be monitored regularly.

Basics

Black lung disease gets its name from the appearance of the lungs in miners who have inhaled coal dust particles—black. The medical term for black lung disease is coal worker's pneumoconiosis (CWP) which is actually a spectrum of diseases.

Definitions and Types

Black lung disease is caused by the inhalation of dust particles during coal mining. It begins with a mild condition known as anthracosis that does not have symptoms (is asymptomatic). Evidence of anthracosis related to air pollution can be found in many people who live in urban areas, not just coal miners.

Black lung disease or coal mine dust lung disease (CMDLD) can be divided into two categories:

  • Simple: Simple black lung disease is most common, with the development of inflammatory nodules in the lung.
  • Complex: Complex disease, or progressive massive pulmonary fibrosis, is more severe. It can lead to severe disability and death.

History

The connection between black pigment in the lungs and coal miners was first made in 1831 by Dr. Craufurd Gregory. After chemical analysis of the material, he was the first to consider black lung disease an occupational disease related to coal dust and alerted physicians to watch for the disease in miners.

Symptoms

Early on, many people will have no symptoms of black lung disease. When symptoms begin, shortness of breath only with activity (exercise intolerance) may easily be dismissed as being simply due to age.

With time, shortness of breath may worsen and include a sensation of chest tightness. A persistent cough may also occur which can be either dry or wet (productive of mucus).

The particular symptoms a person experiences can vary based on the make-up of the dust at their particular place of employment, other medical conditions, and general health.

Complications

One of the most serious complications of severe black lung disease is right heart failure. Due to extensive fibrosis in the lungs, the blood pressure in the pulmonary artery (blood vessel that carries blood from the right side of the heart to the lungs) increases. This increased pressure subsequently leads to enlargement of the right side of the heart and right-sided heart failure (cor pulmonale).

Tissue death (necrosis) in the periphery of the lungs sometimes occurs in people with rheumatoid arthritis who have black lung disease (Caplan syndrome).

An older study also noted an increased risk of lung cancer (specifically squamous cell carcinoma of the lungs) with simple black lung disease. Lung cancer does appear to be more common among coal mine workers (after controlling for smoking) even without black lung disease.

Other Lung Diseases Caused by Coal Dust Exposure

Coal dust exposure is also associated with other lung diseases that may have their own symptoms. In addition to fibrosis (a restrictive airway disease), coal miners are at risk for developing obstructive lung diseases such as emphysema and chronic bronchitis, and it's estimated that at least 15% of coal miners have chronic bronchitis due to dust exposure (industrial bronchitis).

Incidence

The incidence of black lung disease had actually declined to record lows in the 1990s due to the Coal Act. Since that time, the prevalence of black lung disease (combining both simple and complex) has increased significantly according to a 2018 study reported in the American Journal of Public Health. At the current time, black lung disease is present in over 10% of miners who have worked in or near the mines for 25 or more years. This number is higher in central Appalachia, with 20.6% of long term miners having black lung disease. (Central Appalachia includes Kentucky, Virginia, and West Virginia). (In this study, black lung disease or CWP was defined as the presence of small opacities or the presence of an opacity larger than 1 centimeter on imaging.)

The prevalence of severe (complex) black lung disease, or progressive massive fibrosis has also increased significantly since the mid- to late- 1990s. The average annual prevalence of progressive massive fibrosis in the mid-to-late 1990s was 0.37%. This rose to 3.23% (an 8.6-fold rise) between 2008 and 2012. Data was derived from the Coal Workers' Health Surveillance Program in Kentucky, Virginia, and West Virginia.

A cluster of cases of progressive massive fibrosis not discovered through the surveillance program was reported by a single radiology practice in eastern Kentucky. The single practice found 60 cases of progressive massive fibrosis in current and former coal miners between January of 2015 and August of 2016.

The proportion of people with progressive massive fibrosis who have claimed federal black lung benefits has also increased considerably since 1996, especially in Virginia.

Why Are the Incidence and Severity Increasing?

The increase in black lung disease may be partly linked to the recent increase in coal mining, but this does not explain the worsening severity and the finding of severe black lung disease even in young miners. There are a number of factors that may be contributing, such as mining thin coal seams (with greater exposure to silica), the depth of mining, and more.

The Problem Persists After Exposure Is Done

Of great importance is that negative health effects persist even after a person is no longer exposed to coal mine dust. A 2015 study compared the prevalence of black lung disease in former and active miners. The former miners had a greater prevalence of black lung disease than the current miners.

Causes and Risk Factors

Many coal miners are at risk for black lung disease, with some exposures to coal dust posing more risk. For example, stone cutters have very high exposure rates, as do people who work downwind from dust-generating equipment.

Pathophysiology

When coal dust enters the lungs, it settles in the small airways where it cannot be removed or degraded. Immune cells called macrophages (essentially the "garbage trucks of the immune system") engulf "eat" the particles, where they remain indefinitely. The presence of these particles in macrophages causes the lungs to appear black, hence the name black lung disease.

It is actually the substances released by macrophages (such as cytokines) that leads to inflammation. Inflammation, in turn, leads to the formation of scar tissue (fibrosis).

Black lung disease differs from some lung diseases in that it is primarily a disease of the small airways. Due to the small size of the dust particles, they "land" in the distal bronchioles near the sacs where the exchange of oxygen and carbon dioxide takes place (alveoli). (Larger particles are often caught in the cilia in the large airways where they can be moved upwards in the airways and coughed up or swallowed.)

Genetic differences may play a role in who is most at risk as well. Genome-wide association studies (studies that look for common variants in the entire genome) in China have show associations that may increase the risk as well as associations that may be protective.

Surprisingly, unlike conditions such as asbestosis, cigarette smoking doesn't increase the chance a person will develop black lung disease (though it can worsen lung function and compound the symptoms in those who have the disease).

Where Are People Most at Risk?

Though coal miners in central Appalachia appear to have the highest risk of black lung disease, the disease occurs in all U.S. mining regions across the country (and roughly 57% of coal miners work in regions outside of central Appalachia). A 2017 study reported in the American Journal of Industrial Medicine found that that, overall, 2.1% of miners had black lung disease. The prevalence was highest in the East (3.4%), and lowest in the interior (0.8%), with a prevalence between these in the West (1.7%)

Diagnosis

The diagnosis of black lung disease begins with a careful history to evaluate risk factors and a physical exam.

Imaging

A chest X-ray is most often the first test, but a CT scan is usually needed to find smaller abnormalities. Findings may include "coal macules," or tiny nodules 2-5 millimeters (mm) in diameter scattered diffusely in the upper lobes of the lungs. (Of note is that a chest X-ray cannot usually detect nodules less than 10 mm in diameter).

Progressive massive fibrosis is diagnosed if there are lung nodules larger than 1 centimeter in diameter (roughly 0.4 inches), or 2 centimeters (0.8 inches) depending on the criteria of different organizations.

Other studies (such as an MRI or PET scan) may be needed at times, primarily to rule out other diagnoses.

Procedures

Pulmonary function tests are commonly done, but due to the presence of disease in the small airways may not show significant changes until the disease is fairly advanced. A bronchoscopy and/or lung biopsy may be needed, again to rule out other diagnoses.

Differential Diagnosis

There are a number of conditions that need to be considered in the differential diagnosis of black lung disease. Some of these include:

  • Silicosis: Silicosis also occurs in miners and can appear quite similar to progressive massive fibrosis.
  • Asbestosis
  • Berylliosis
  • Chronic bronchitis: Chronic bronchitis can occur along with black lung disease, but symptoms may also mimic the disease.

Treatment

At the current time, there is no cure for black lung disease and the goal of treatment is to prevent worsening of the disease and control symptoms.

Medications such as inhalers may be needed, especially for those who also have chronic bronchitis. Oxygen may be needed, especially with progressive massive pulmonary fibrosis. Pulmonary rehabilitation can be helpful in providing breathing techniques, and teaching people how to cope with the symptoms of black lung disease.

A lung transplant is the only option with end-stage black lung disease, and the rate of lung transplants that are done for black lung disease has been increasing. The increasing rate of lung transplants also supports the rising prevalence of severe black lung disease.

Measures to prevent worsening or complications are critical in managing black lung disease. This includes not only reducing exposure to coal dust, but exposure to other metal dusts. Smoking cessation and avoidance of secondhand smoke are, of course, important. The pneumonia vaccine and flu vaccinations are important to reduce the risk of pneumonia.

Prognosis

The prognosis of black lung disease depends on the extent of the disease (simple or complex) as well as further exposures. Simple black lung disease can progress slowly over a long period of time, whereas progressive massive pulmonary fibrosis can progress rapidly.

Years of potential life lost (YPLL), a measure of the toll the disease takes, has been increasing, likely due to the increased severity of black lung disease in recent years.

Prevention

Prevention encompasses both primary prevention, meaning preventing exposure in the first place, and secondary prevention, or preventing further damage once evidence of black lung disease is present.

Primary prevention includes better methods of dust control, limits on exposure, and the use of protective equipment (such as respirators) when indicated. The Federal Coal Mine Health and Safety Act of 1969 (amended in 1977) defined dust limits and created the Coal Workers' Health Surveillance Program (NIOSH).

In 2014, new rules (Lowering Miners' Exposure to Respirable Coal Mine Dust) reduced the maximum allowable exposure and added protections to previous guidelines.

Surveillance

Surveillance, or attempting to diagnose black lung disease in the early, simple stage of the disease is also very important. At the current time, The National Institute for Occupational Safety and Health has guidelines that recommend miners have imaging studies done every five years to look for evidence of coal mine dust related disease. These are only guidelines, and some people may need to be monitored more frequently. These guidelines are also in place for people who do not have symptoms. Those who have symptoms or findings on imaging studies that suggest black lung disease will need further evaluation.

A Word From Verywell

Black lung disease is increasing in both prevalence and severity, which is disheartening as it is, in a sense, a preventable disease. Efforts to increase surveillance are vital. Fortunately, studies are in place attempting to determine why progressive massive fibrosis is increasing so that measures can be taken to reduce risk.

Was this page helpful?

Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Katabami M, Dosaka-Akita H, Honma K, et al. Pneumoconiosis-related lung cancers: preferential occurrence from diffuse interstitial fibrosis-type pneumoconiosis. American Journal of Respiratory and Critical Care Medicine. 2000. 162(1):295-300. doi:10.1164/ajrccm.162.1.9906138


  2. Blackley DJ, Halldin CN, Laney AS, et al. Continued Increase in Prevalence of Coal Workers’ Pneumoconiosis in the United States, 1970–2017. American Journal of Public Health. 2018. 108(9):1220–1222. doi:10.2105/AJPH.2018.304517


  3. Blackley DJ, Halldin CN, Laney AS. Resurgence of a debilitating and entirely preventable respiratory disease among working coal miners. American Journal of Respiratory and Critical Care Medicine. 2014. 190(6):708-9. doi:10.1164/rccm.201407-1286LE


  4. Blackley DJ, Crum JB, Halldin CN, Storey E, Laney AS. Resurgence of Progressive Massive Fibrosis in Coal Miners - Eastern Kentucky, 2016. Morbidity and Mortality Weekly Report. 2016. 65(49):1385-1389. doi:10.15585/mmwr.mm6549a1


  5. Almberg KS, Halldin CN, Blackley DJ, et al. Progressive Massive Fibrosis Resurgence Identified in U.S. Coal Miners Filing for Black Lung Benefits, 1970-2016. Annals of the American Thoracic Society. 2018. 15(12):1420-1426. doi:10.1513/AnnalsATS.201804-261OC


  6. Halldin CN, Wolfe AL, Laney AS. Comparative Respiratory Morbidity of Former and Current US Coal Miners. American Journal of Public Health. 2015. 105(12):2576-7. doi:10.2105/AJPH.2015.302897


  7. Wang T, Li Y, Zhu M, et al. Association Analysis Identifies New Risk Loci for Coal Workers' Pneumoconiosis in Han Chinese Men. Toxicological Sciences. 2018. 163(1):206-213. doi:10.1093/toxsci/kfy017


  8. Reynolds LE, Blackley DJ, Laney AS, Halldin CN. Respiratory morbidity among U.S. coal miners in states outside of central Appalachia. American Journal of Industrial Medicine. 2017. 60(6):513-517. doi:10.1002/ajim.22727


  9. Blackley DH, Halldin CN, Laney AS. Continued increase in lung transplantation for coal workers' pneumoconiosis in the United States. American Journal of Industrial Medicine. 2018. 61(7):621-624. doi:10.1002/ajim.22856


  10. Mazurek JM, Wood J, Blackley DJ, Weissman DN. Coal Workers' Pneumoconiosis-Attributable Years of Potential Life Lost to Life Expectancy and Potential Life Lost Before Age 65 Years - United States, 1999-2016. Morbidity and Mortality Weekly Report. 2018. 67(30):819-824. doi: 10.15585/mmwr.mm6730a3


Additional Reading