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Coal workers' pneumoconiosis (CWP), also known as black lung disease or black lung, is an
occupational Employment is a relationship between two party (law), parties Regulation, regulating the provision of paid Labour (human activity), labour services. Usually based on a employment contract, contract, one party, the employer, which might be a co ...
type of pneumoconiosis caused by long-term exposure to
coal dust Coal dust is a fine powdered form of which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form ...
. It is common in coal miners and others who work with coal. It is similar to both silicosis from inhaling
silica dust Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
and
asbestosis Asbestosis is long-term inflammation and pulmonary fibrosis, scarring of the human lung, lungs due to asbestos, asbestos fibers. Symptoms may include shortness of breath, cough, wheezing, and chest pain, chest tightness. Complications may include ...
from inhaling asbestos dust. Inhaled coal dust progressively builds up in the
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s and leads to
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
,
fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
, and in worse cases,
necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
. Coal workers' pneumoconiosis, severe state, develops after the initial, milder form of the disease known as anthracosis (from the Greek , or —coal, carbon). This is often asymptomatic and is found to at least some extent in all urban dwellers due to air pollution. Prolonged exposure to large amounts of coal dust can result in more serious forms of the disease, ''simple coal workers' pneumoconiosis'' and ''complicated coal workers' pneumoconiosis'' (or progressive massive fibrosis, or PMF). More commonly, workers exposed to coal dust develop industrial bronchitis, clinically defined as
chronic bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
(i.e. productive cough for 3 months per year for at least 2 years) associated with workplace dust exposure. The incidence of industrial bronchitis varies with age, job, exposure, and smoking. In nonsmokers (who are less prone to develop bronchitis than smokers), studies of coal miners have shown a 16% to 17% incidence of industrial bronchitis. In 2013 CWP resulted in 25,000 deaths globally—down from 29,000 deaths in 1990. However, a later 2018 study by the National Institute of Occupational Safety and Health shows a resurgence, recording the highest rate of CWP in roughly two decades.


Pathogenesis

Coal dust is not as fibrogenic as silica dust. Coal dust that enters the lungs can neither be destroyed nor removed by the body. The particles are engulfed by resident alveolar or interstitial
macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
s and remain in the lungs, residing in the connective tissue or pulmonary
lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...
s. Coal dust provides a sufficient stimulus for the macrophage to release various products, including enzymes, cytokines, oxygen radicals, and fibroblast growth factors, which are important in the inflammation and fibrosis of CWP. Aggregations of carbon-laden macrophages can be visualized under a microscope as granular, black areas. In serious cases, the lung may grossly appear black. These aggregations can cause inflammation and fibrosis, as well as the formation of nodular
lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...
s within the lungs. The centers of dense lesions may become necrotic due to
ischemia Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...
, leading to large cavities within the lung.


Appearance

Simple CWP is marked by the presence of 1–2 mm nodular aggregations of anthracotic macrophages, supported by a fine collagen network, within the lungs. Those 1–2 mm in diameter are known as ''coal macules'', with larger aggregations known as ''coal nodules''. These structures occur most frequently around the initial site of coal dust accumulation—the upper regions of the lungs around
respiratory bronchiole The bronchioles or bronchioli (pronounced ''bron-kee-oh-lee'') are the smaller branches of the bronchial airways in the lower respiratory tract. They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start o ...
s. The coal macule is the basic pathological feature of CWP and has a surrounding area of enlargement of the airspace, known as
focal emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alv ...
. Focal emphysema extends into progressive
centrilobular emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alv ...
. Less commonly a variant of
panacinar emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alve ...
develops. Continued exposure to coal dust following the development of simple CWP may progress to complicated CWP with progressive massive fibrosis (PMF), wherein large masses of dense fibrosis develop, usually in the upper lung zones, measuring greater than 1 cm in diameter, with accompanying decreased lung function. These cases generally require a number of years to develop. Grossly, the lung itself appears blackened. Pathologically, these consist of fibrosis with haphazardly-arranged collagen and many pigment-laden macrophages and abundant free pigment. Radiographically, CWP can appear strikingly similar to silicosis. In simple CWP, small rounded nodules (see
ILO Classification The ILO International Classification of Radiographs of Pneumoconioses is a system of classifying chest radiographs (X-rays) for persons with a (or, rarely, more than one) form of pneumoconiosis. The intent is to provide a standardized, uniform metho ...
) predominate, tending to first appear in the upper lung zones. The nodules may coalesce and form large opacities (>1 cm), characterizing complicated CWP, or PMF.


Diagnosis

There are three basic criteria for the diagnosis of CWP: #Chest radiography consistent with CWP #An exposure history to coal dust (typically underground coal mining) of sufficient amount and latency #Exclusion of alternative diagnoses (mimics of CWP) Symptoms and pulmonary function testing relate to the degree of respiratory impairment but are not part of the diagnostic criteria. As noted above, the chest X-ray appearance for CWP can be virtually indistinguishable from silicosis. Chest CT, particularly high-resolution scanning (
HRCT High-resolution computed tomography (HRCT) is a type of computed tomography (CT) with specific techniques to enhance image resolution. It is used in the diagnosis of various health problems, though most commonly for lung disease, by assessing t ...
), are more sensitive than plain X-ray for detecting the small round opacities.


Treatment

There is no cure or discovered treatments for pneumoconiosis. Some patients are given oxygen to help with their breathing and are advised to stop smoking to prevent further decline in lung function. In the most extreme cases a lung transplant could be done to help prolong the patient's life expectancy.


Prevention of pneumoconiosis

The main way to avoid contracting coal worker's pneumoconiosis is to avoid the inhalation of coal dust. Some of the ways to prevent this disease include: not smoking, wearing ventilated masks when coming in contact with potentially dangerous airborne particles, regular pulmonary exams, and becoming educated about the risks of lung diseases in your work environment.


Epidemiology

In 2013 CWP resulted in 25,000 deaths down from 29,000 deaths in 1990. Between 1970 and 1974, prevalence of CWP among US coal miners who had worked over 25 years was 32%; the same group saw a prevalence of 9% in 2005–2006. In Australia, CWP was considered to be eliminated in the 1970s due to strict hazard control measures. However, there has been a resurgence of CWP in Australia, with the first new cases being detected in May 2015. From 1999 to 2016, the average years of life lost due to CWP increased from 8.1 to 12.6 years, most likely due to the increased severity and progression of CWP.


History

Black lung is actually a set of conditions and until the 1950s its dangers were not well understood. The prevailing view was that silicosis was very serious but it was solely caused by silica and not coal dust. The miners' union, the
United Mine Workers of America The United Mine Workers of America (UMW or UMWA) is a North American labor union best known for representing coal miners. Today, the Union also represents health care workers, truck drivers, manufacturing workers and public employees in the Unit ...
, realized that rapid mechanization meant drills that produced much more dust, but under
John L. Lewis John Llewellyn Lewis (February 12, 1880 – June 11, 1969) was an American leader of organized labor who served as president of the United Mine Workers of America (UMW) from 1920 to 1960. A major player in the history of coal mining, he was the d ...
they decided not to raise the black lung issue because it might impede the mechanization that was producing higher productivity and higher wages. Union priorities were to maintain the viability of the long-fought-for welfare and retirement fund, which would be sustained by higher outputs of coal. After the death of Lewis, the union dropped its opposition to calling black lung a disease and realized the financial advantages of a fund for its disabled members. In the
Federal Coal Mine Health and Safety Act of 1969 The Federal Coal Mine Health and Safety Act of 1969, U.S. Public Law 91-173, generally referred to as the Coal Act, was passed by the 91st United States Congressional session and enacted into law by the 37th President of the United States Richard ...
, the US Congress set up standards to reduce dust and created the Black Lung Disability Trust. The mining companies agreed to a clause, by which a ten-year history of mine work, coupled with X-ray or autopsy evidence of severe lung damage, guaranteed compensation. Equally important was a "rate retention" clause that allowed workers with progressive lung disease to transfer to jobs with lower exposure without loss of pay, seniority, or benefits. Financed by a federal tax on coal, the Trust by 2009 had distributed over $44 billion in benefits to miners disabled by the disease and their widows. A miner who has spent 25 years in underground coal mines has a 5–10% risk of contracting the disease.


21st century

After the Federal Coal Mine Health and Safety Act of 1969 became law in the United States, the percentage of American miners with black lung disease decreased by about 90 percent. More recently, however, rates of the disease have been on the rise. The
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH) reported that close to 9 percent of miners with 25 years or more experience tested positive for black lung in 2005–2006, compared with 4 percent in the late 1990s. New findings have shown that CWP can be a risk for surface coal miners, who are 48% of the workforce. Data from the Coal Workers' Health Surveillance Program of NIOSH, which examined chest X-rays from more than 2,000 miners in 16 US states from 2010 to 2011, showed that 2% of miners with greater than one year of surface mining experience developed CWP. 0.5% of these miners had PMF. Most of these workers had never worked in an underground mine prior to surface mining. A high proportion of the X-rays suggested that these miners had developed silicosis. NIOSH, with support from the
Mine Safety and Health Administration The Mine Safety and Health Administration (MSHA) () is a large agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 (Mine Act) to enforce compliance with mandatory safe ...
(MSHA), operates a Mobile Health Screening Program, which travels to mining regions around the United States. Miners who participate in the Program receive health evaluations once every five years, at no cost to themselves. Chest x-rays can detect the early signs of and changes in CWP, often before the miner is aware of any lung problems. A 2016-17 investigation by
National Public Radio National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from other n ...
found that the
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
had under-reported cases of progressive massive fibrosis (a complication of black lung) by at least a factor of 20. NPR identified over 2,000 cases at certain clinics in Kentucky, Virginia, West Virginia, Pennsylvania, and Ohio, compared to 99 that NIOSH reported. NIOSH confirmed in 2018 the largest cluster of PMF ever scientifically documented, despite near-elimination of the disease in the 1990s. The causes of the spike are believed to include longer working shifts, mining of thinner coal seams (which causes mining machines to put more non-coal
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
dust in the air), and retirements and layoffs that have prompted more former employees to visit health clinics. New U.S.
Mine Safety and Health Administration The Mine Safety and Health Administration (MSHA) () is a large agency of the United States Department of Labor which administers the provisions of the Federal Mine Safety and Health Act of 1977 (Mine Act) to enforce compliance with mandatory safe ...
rules took effect in August, 2016, that lowered maximum allowed dust concentrations for surface and underground mines, and exposure by miners who have been found to be developing pneumoconiosis.


Research

Work to investigate the relationship between respirable dust exposure and coal worker's pneumoconiosis was carried out in Britain by the
Institute of Occupational Medicine The Institute of Occupational Medicine (IOM) was founded in 1969 by the National Coal Board (NCB) as an independent charity in the UK and retains this charitable purpose and status today. The "Institute" has a subsidiary, IOM Consulting Limited, whi ...
. This research was known as the Pneumoconiosis Field Research (PFR). The research underpinned the recommendations for more stringent airborne dust standards in British coalmines and the PFR was ultimately used as the basis for many national dust standards around the world.


See also

*
Black Lung Benefits Act of 1972 The Black Lung Benefits Act (BLBA) is a U.S. federal law which provides monthly payments and medical benefits to coal miners totally disabled from pneumoconiosis (black lung disease) arising from employment in or around the nation's coal mines. Th ...
* Caplan syndrome


References


External links

*
NIOSH Mining Topic: Respiratory Diseases



Mine Safety and Health Administration


* ttps://web.archive.org/web/20110615171149/http://www.iom-world.org/solutions/commentary1.php Institute of Occupational Medicine's pneumoconiosis research {{DEFAULTSORT:Coal Worker's Pneumoconiosis Lung diseases due to external agents Occupational diseases Coal mining