The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention.
Advances in technology over the last century, as well as the exportation of many high exposure jobs, nearly eliminated lung diseases caused by occupational exposure to respirable dust (the pneumoconioses) in the United States. One such example of this near elimination is black lung, or coal workers' pneumoconiosis (CWP), following the 1969 Federal Coal Mine Health and Safety Act. The Act established permissible exposure limits to respirable dust, designed to prevent the most severe forms of CWP from occurring, and a national respiratory health screening program for underground coal miners. Between 1970 and the mid-1990s, disease prevalence plummeted from nearly 35% to less than 5% prevalence among longer tenured miners, and from 3% to less than 1% in miners with less than 10 years of mining tenure (Hall NB, et al. Curr Environ Health Rep. 2019;6:137).
Many assumed that this was the last we'd hear of black lung - that the cases of disease existing in the 1990s were likely caused by exposures that occurred prior to the 1969 Act, and within a few years, no further cases would be detected. This appeared to be an entirely reasonable assumption in the 1990s given the 30 years of declining prevalence and the continuous technological advances designed to continue reductions in dust exposures. In fact, the precipitous decline in black lung was briefly viewed as a public health triumph, as the most severe forms appeared to be near eradication in the United States just 2 decades ago (Attfield MD, et al. Am J Public Health. 1992;82:971; Attfield MD, et al. Am J Public Health. 1992;82:964). However, what has since been observed is a strong and ongoing resurgence of the potentially deadly fibrotic interstitial disease starting in the early 2000s (Figure 1), with the most striking increase observed in the Central Appalachian states of Kentucky, Virginia, and West Virginia (Blackley DJ, et al. Am J Respir Crit Care Med. 2014;190:708; Blackley DJ, et al. Am J Public Health. 2018;108:1220).
Of great concern is the resurgence of complicated Black Lung (progressive massive fibrosis [PMF]), which is completely disabling and leads to premature mortality. The prevalence of PMF is higher today than when NIOSH started formally tracking the disease in the 1970s, especially among specific populations.
Since the mid-2000s, NIOSH and others have described the following(Hall NB, et al. Curr Environ Health Rep. 2019;6:137):
· Increasing prevalence and severity of CWP both nationwide and specifically in Central Appalachia.
· Rapid progression of CWP.
· Increases in the frequency of lung transplantation for CWP.
· Severe disease among surface coal miners with no underground mining tenure.
· Increased severity of disease among former and retired miners.
· Hundreds of cases of PMF among coal miners seeking care at clinics in eastern Kentucky and southwestern Virginia.
· Increasing numbers of miners with PMF filing for federal black lung compensation.
· Radiologic and pathologic indications of increased respirable silica exposure among coal miners.
· Premature mortality in miners diagnosed with CWP.
· Underutilization of a secondary prevention worker removal program designed to reduce the exposure of miners with disease.
· Former miners with severe disease describing extreme pressure to operate. outside of applicable protective federal standards in order to increase productivity
In our surveillance work, we have talked to many miners who, after having months or years' worth of extensive workups for pneumonia, sarcoidosis, lung cancer, and/or diseases other than the pneumoconioses, have eventually learned that they actually had dust-induced lung disease attributable to their work. Additionally, through our evaluation of the transplantation data, it has become clear that dust-related lung disease is likely underreported or underrecognized among those receiving lung transplants. Finally, through analysis of mortality data, it is apparent that CWP is also underreported as a cause of death among miners with black lung. We mention these points to emphasize how important it is to document a full occupational history for proper diagnoses, early intervention, and improved public health information to inform primary and secondary disease prevention efforts.
Resources for clinicians
CWP is most commonly identified using plain posterior-anterior chest radiography and presence/severity of fibrotic change is described using an international standard established by the International Labour Office (International Labour Office. Guidelines for the use of the ILO international classification of radiographs of pneumoconioses. Geneva: International Labour Office; 2011). In the United States, NIOSH operates the B Reader Training and Certification Program, which offers a free self-study syllabus, https://www.cdc.gov/niosh/topics/chestradiography/breader.html, and in-person training courses on occasion, to assist physicians in learning and demonstrating continuous competency in classifying chest radiographs of dust-exposed workers according to the ILO Standards (Halldin CN, et al. J Occup Environ Med. 2019;61:1045). The B Reader Program and ILO Standards are currently undergoing a decade-long revision process where both will feature digitally acquired chest radiograph images. This process should be fully complete in the following months.
To educate miners, mine operators, and others about the risks of respirable dust, NIOSH produced an educational video, Faces of Black Lung, in 2008 that featured two miners in their 50s and 60s who had complicated Black Lung. Because of the resurgence of disease and particularly severe cases being identified among much younger miners, NIOSH recently released an updated version of the video, Faces of Black Lung II, where three Kentucky underground miners, ages 39, 42, and 48, describe the incredible disability and quality of life lost due to a disease caused by gross overexposure of respirable coal mine dust.
Unfortunately, the 42-year-old miner died from complications stemming from Black Lung less than a year after filming his part in the video, and the other two miners have been advised to be evaluated for lung transplantation. We hope that these men's stories will help younger miners relate to the risks of respirable coal mine dust and help others understand the severity of disease as all three of these men struggled to breathe just describing their day to day tasks.
No one should ever have to consider a lung transplant at the age of 40 because they went to work attempting to provide for their family. No one should ever be faced with end-of-life planning while their kids are in grade school because of a disease they acquired at work. Respirable coal mine dust is the only cause of black lung, and the coal mining industry has the necessary technology and tools to prevent harmful exposures to respirable dust, and, together with miners, must successfully and consistently implement dust suppression controls. There is no cure for black lung; it's irreversible and can be first recognized and continue to progress even after a miner has left exposure. However, early identification and appropriate intervention can prevent progression to the most disabling manifestations. The role of the clinician is to be part of the early identification of black lung through including CWP in the differential diagnosis for unusual or unexpected respiratory illness in otherwise healthy primarily working aged miners. The public health community must continue to monitor disease prevalence in working populations and implement policies and recommendations to support the efforts of those on the frontline - the miners, industry, and health-care workers.
The Energy Information Agency projects that coal will continue to be a substantial source of U.S. energy production and consumption well into the mid- to late-century. Unfortunately, Black Lung has made a resurgence and is killing miners, and each of us has a role to play in eliminating it once and for all. We will continue to carry out our mandate to screen working coal miners for respiratory disease; however, given the continued contraction of the coal mining industry, it's much more likely for cases of disease to be recognized in the clinic setting. Therefore, we reiterate our previous plea to clinicians: when identifying an individual with interstitial fibrosis consider their full occupational history.
Dr. Halldin and Dr. Laney are from the Surveillance Branch, Respiratory Health Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV.