Black lung disease, is the common name for anthracosis or coal worker's pneumoconiosis (CWP). It is a chronic, fibrotic lung disease of coal miners caused by the inhalation of coal dust over many years that accumulates in the lungs and forms black bumps or coal macules on the bronchioles. These lumps give the disease its common name. Lung disease among coal miners was first described by German mineralogist Georgius Agricola (1494–1555) in the sixteenth century, and it is now a widely recognized occupational illness affecting older miners.
Black lung disease occurs most often among miners of anthracite (hard) coal, but it is found among soft coal miners and graphite workers as well. The disease is characterized by gradual onset: the first symptoms usually appear only after more than ten years of exposure to coal dust. The extent and severity of the disease is related to the length of this exposure. The disease also appears to be aggravated by cigarette smoking. The more advanced forms of black lung disease are frequently associated with emphysema or chronic bronchitis. There is no real treatment for this disease, but it may be controlled or its development arrested by avoiding exposure to coal dust.
After the federal government started regulating dust levels in coal mines, the number of cases of black lung disease fell sharply until a resurgence in 2012. Following the passage of the Federal Coal Mine Health and Safety Act of 1969, average dust levels fell from 8.0 mg per cubic meter to the current standard of 2.0 mg per cubic meter. The 1969 law also set up a black lung disability benefits program to compensate coal miners who have been disabled by on-the-job dust exposure.
Despite the technology available to control the hazard, miners still run the risk of developing this lung disease. Fewer than 10% of coal miners have any x-ray evidence of coal dust deposits. Usually when there is such evidence, it shows up as only small black spots less than 0.4 in (1 cm) in diameter. This condition is called “simple CWP” and does not lead to symptoms or disability.
Black lung disease is among the best-known occupational illnesses in the United States. Although there was considerable reduction in the incidence of the disease after the mid-twentieth century, in some regions, more than 50 percent of coal miners develop the disease after 30 or more years on the job. The Federal Coal Mine Health and Safety Act (FCMHSA) of 1969 (amended in 1977) resulted in a reduction of CWP cases. The FCMHSA included provision for limits on coal mine dust and for a periodic chest radiograph program for mine workers. The Mine Safety and Health Administration (MSHA) coordinates with the National Institute for Occupational Safety and Health (NIOSH) to oversee the Coal Workers' Health Surveillance Program (CWHSP), which provides early detection and preventative measures against CWP. The rate of CWP in underground coal miners with 25 years or greater experience decreased from about 30% in the early 1970s to less than 5% in the late 1990s. Between 1995 and 2012, however, the prevalence of black lung disease in CWHSP participants doubled. Experts note the increase was especially associated with certain higher-risk or contract mining jobs, smaller mines, and mines in specific geographic areas.
Outside the United States, specifically in developing nations such as China and India, coal miners generally work in conditions with fewer regulations and health or safety precautions. Given limited data collected by some nations prior to 2012, exact figures regarding global prevalence of black lung disease are unavailable. One must be exposed to coal dust for years before infection is possible and therefore the number of global cases is calculated by taking the reported numbers of coal miners (those at risk) and applying a statistical average. Using this method, the World Health Organization estimates that more than 6 million cases exist outside the United States.
The particles of fine coal dust that a miner breathes while mining cannot be destroyed within the lungs or removed from them, so they build up over time. Eventually, this buildup causes thickening and scarring, making the lungs less efficient in supplying oxygen to the blood.
CWP occurs in two forms: simple and complicated (also called progressive massive fibrosis, or PMF). The primary symptom of the disease is shortness of breath, which gradually gets worse as the disease progresses. In severe cases, the patient may develop cor pulmonale, an enlargement and strain of the right side of the heart caused by chronic lung disease. This may eventually cause right-sided heart failure.
Some patients develop emphysema (shortness of breath, and respiratory and heart failure when tiny air sacs in the lungs become damaged) as a complication of black lung disease. When PMF is developed, damage continues in the upper parts of the lungs even after exposure to the dust has ended. The reasons for this complication were unknown as of 2012, but some scientists thought the complication arises after breathing of a mixture of coal and silica dust that is found in certain mines. Silica is far more likely to lead to scarring than coal dust alone.
Black lung disease can be diagnosed by checking a patient's history for exposure to coal dust, followed by a chest x ray to discover if the characteristic spots in the lungs caused by coal dust are present. A pulmonary function test may aid in diagnosis.
Xrays can detect black lung disease before it causes any symptoms. If exposure to the dust is stopped at that point, progression of the disease may be prevented.
Those miners with simple CWP can lead normal lives. However, patients who develop black lung disease at an early age, or who have PMF, have a higher risk of premature death.
The only way to prevent black lung disease is to avoid long-term exposure to coal dust. Employers may help prevent the condition by lowering coal dust levels and providing protective clothes to coal miners.
In a light micrograph of a human lung containing particles of inspired coal dust (anthracosis), the black masses shown are groups of coal dust particles.
See also Bronchitis ; Chronic obstructive pulmonary disease ; Fibrosis ; National Institute for Occupational Safety and Health ; Smoking .
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Mine Safety and Health Administration, 4015 Wilson Blvd., Arlington, VA, 22203, (877) 778-6055, MSHAhelpdesk@dol.gov, http://www.msha.gov .
Carol A. Turkington
Alyson C. Heimer, MA