Occupational Medicine
A Basic Guide

08: Industry Specific Pearls

Dan Mirski, MD, MPH

In the early 1900s, coal mine deaths in the United States exceeded 2,000 annually.1 In 1907, 362 miners were killed in the worst single coal mine disaster in U.S. history— an explosion at the Monongah Mines in West Virginia.2 As is typically the case, large-scale disasters were the impetus for legislative change, and in 1910, Congress established the Bureau of Mines under the Department of the Interior with the goal of conducting research and reducing accidents in the coal mining industry.


The industry’s unique federal oversight is relevant to the issue of mining-specific diseases and accidents. Although the primary care provider need not know the nuances of mining laws and regulations, it is important to have some background, because it can play into everyday medical care.


The mining industry is not governed by OSHA, but by a separate federal regulatory body, the Mine Safety and Health Administration (MSHA). OSHA and the National Institute for Occupational Safety and Health (NIOSH) were created in 1970. NIOSH was established as part of the Centers for Disease Control within the U.S. Department of Health and Human Services to ensure safe working conditions. OSHA was established under the Department of Labor (DOL) as the federal authority responsible for prescribing and enforcing regulations affecting occupational health or safety. Both OSHA and MSHA are managed by the DOL, which specifies that when “the provisions of the Mine Act either do not cover or do not otherwise apply … then the OSHAct will be applied to those working conditions.”3 Therefore, although the two statutes differ and employer reporting differs, treatment by the provider is basically unchanged regardless of the federal entity overseeing the industry. Interestingly, whereas NIOSH merely advises OSHA on its standards, it actually develops the health standards for MSHA to prevent occupational disorders.4


Mining-Related Disorders

Occupational disorders seen in miners include respiratory diseases, traumatic and repetitive or cumulative musculoskeletal injuries, and noise-induced hearing loss (NIHL). A few of these disorders are specific to the mining industry, but the majority are also seen in numerous occupational and non-work settings. Pulmonary ailments tend to be more mining-specific because they are often caused by inhalation of occupational dust such as coal, silica, and asbestos as well as diesel particulates and welding fumes.


Coal Workers’ Pneumoconiosis

The classic and quintessential occupational disease associated with mining is coal workers’ pneumoconiosis (CWP). Pneumoconiosis is an alteration of pulmonary structure from dust inhalation (usually coal, silica, or asbestos) that is non-neoplastic and non-asthma, emphysema, or bronchitis in classification.


CWP, also known as “black lung,” is caused by coal dust, which is primarily made up of carbon. One- to two-millimeter macrophage-laden macules deposit in the alveolar ducts and cause cough and phlegm production. These deposits can result in a reduction in the first second of the Forced Expiratory Volume (FEV1) on spirometry and can be seen on chest X-rays. CWP can sometimes progress rapidly from minor simple pneumoconiosis to advanced pneumoconiosis disease with severe reduction in pulmonary function and expiratory flow.


Although CWP is not always aggressive, it can progress very rapidly and without much warning. NIOSH therefore, in 1974, created a radiology “B reader” initiative as part of its Coal Workers’ X-ray Surveillance Program. The B stands for black lung. The program was meant to eliminate inter-reader variability when interpreting chest X-ray abnormalities caused by prolonged dust inhalation. At this writing, there are just under 200 NIOSH-certified B reader radiologists in the United States. Although B readers document chest X-ray findings on all pneumoconiosis cases, it was the need to follow the progression of CWP that prompted the initiative.


B reader findings describe parenchymal abnormalities as well as pleural changes in a systemic and reproducible manner. Chest X-ray findings are described as p, q, or r if they are small, rounded opacities and s, t, or u if small and irregular. Concentrations of these opacities are also documented on a 0/- to 3/+ 12-point scale. Lung zones as well as large opacities, referred to as categories A, B, or C, are also recorded. This NIOSH-sponsored United Nations International Labour Organization (ILO) classification produces standardized and reproducible chest X-ray pneumoconiosis documentation, which aids in individual patient screening and surveillance as well as epidemiology and research.


Apart from CWP, although often confused with it, is a pneumoconiosis caused by silica. Silica is silicon dioxide, and along with oxygen it is the most abundant element in the earth’s crust. It comes in various forms, but crystalline silica—of which quartz is the most common type—is ideal for industrial use because of its very high melting point, hardness, and chemically inert property. Nearly every type of rock contains quartz and thus silicosis is the most common type of pneumoconiosis worldwide. Silicosis caused by the inhalation of crystalline silica dust is non-reversible and progresses in a predictable fashion based on the intensity and duration of exposure. Although there is a likely 10- to 20-year latency period, silicosis can progress even when the worker is no longer exposed. This is important because it can progress while a patient is retired or no longer working as a miner, and thus the work history may be missed. Progression is slow because the dust is toxic to macrophages, and therefore it takes years for bronchiolar clearance of silica to occur.



Inhalation of crystalline silica causes an intense cellular reaction and production of “silicotic nodules” of various sizes that form granulomas in the upper- and mid-lung zones. These grow and conglomerate over time, especially if exposure continues, and thus progress from “simple silicosis” to what is known as PMF: progressive massive fibrosis. PMF is also known as “conglomerate silicosis” and can have a butterfly-like appearance several centimeters wide on X-ray. Prior to conglomeration, simple silicosis rarely produces impaired pulmonary function. However, once conglomeration occurs, pulmonary function deterioration is common and can be rapid from then on.


Recurrent bacterial infections, respiratory failure with cor pulmonale, and an increased risk of lung cancer are associated with PMF. There is also a strong association with tuberculosis and a stronger association in rheumatoid arthritis patients who can develop necrobiotic nodules (Caplan’s syndrome). It is therefore wise to obtain a rheumatoid factor and to have a high suspicion for potential concurrent TB.


The main clinical difference of which the physician must be aware between silicosis and CWP is that the latter can be much more rapidly aggressive, whereas silicosis is more common but progresses in a steadier fashion over the years. In 2017, OSHA published new regulations—based on updated data on complications from silica dust exposure—that streamline silicosis-prevention  standards across all industries. The new regulations include two respirable crystalline silica standards—one for construction and the other for general industry and maritime. They also mandate exposure-control measures and other requirements such as worker training and medical exams, with chest X-rays and lung function tests every three years, for anyone required to wear a respirator due to silica exposure for more than 30 days a year. OSHA estimates that the new rules will save nearly 700 lives and prevent 1,600 new cases of silicosis per year.


Pneumoconioses are the quintessential mining associated group of diseases; however, miners are affected by other pulmonary disorders as well.


Other Mining-Related Disorders

Major improvements in dust control through practical engineering means have resulted in a significant decline in all miner-associated respiratory diseases, especially in the last four decades. Still, mining remains a dangerous occupation. Until 2002, it was listed under the U.S. Bureau of Labor Statistics as the most dangerous industry (now surpassed by commercial fishing and roofing). Beyond producing poor air quality, mine drilling and haulage employ diesel-powered equipment that produces diesel particulate. When inhaled, these diesel particulates (IARC Group 2A) have been linked to an increased risk of lung cancer.


Besides facing the risk of pulmonary disorders, miners are susceptible to the obvious dangers of such a physically demanding profession. Potentially fatal and permanently disabling physical hazards arise from moving machinery, falls from height, flooding, explosions, rock falls, bulkhead collapses, and fires. Less easily identified occupational hazards occur from cumulative trauma. It is important to associate these other, perhaps more subtle, injuries to their occupational origins to ensure that individuals can be cared for under workers’ compensation programs. Workers’ compensation allows health care to be provided to people who would not otherwise have access to care and enables them to maintain a percentage of their income while undergoing treatment and recovery. It also allows for better overall reporting of industrial risks for future engineering and prevention programs.


Musculoskeletal Injuries. Miners are especially prone to back injuries resulting from heavy lifting and shoveling, along with slips and falls. Among other causes, the latter can result from an uneven ground environment, which also produces ankle and knee injuries. Overhead work is common in underground tunnels, resulting in rotator cuff and other shoulder injuries. Repetitive upper-extremity motions can also result in lateral and medial epicondylitis and carpal tunnel syndrome. Use of heavy mobile equipment such as rock drills can also produce hand-arm vibration syndromes and repetitive whole- body vibration. This physical stress can further exacerbate musculoskeletal ailments, especially spinal disorders. Despite the mechanical automation of many mining operations, the industry continues to remains heavily dependent on physically demanding manual labor.



Isolation and Shiftwork: Besides addressing the industry-specific and common occupational pathology that providers encounter, the health care worker also has to remember that miners frequently work in isolated environments that operate 24 hours a day. The resulting shiftwork provokes a unique range of occupational maladies, from fatigue to severe regular sleep deprivation and accompanying cognitive and motor impairments. Such an environment also lends itself to unhealthy dietary intake and other social stressors. Underground mines obviously do not have cell phone or wireless reception, and miners are often closed off from family members and events aboveground during their shifts. Such closed communities can be prone to significant psychological stressors whenever an injury occurs and can lead to increased drug and alcohol use as well as posttraumatic stress disorder.


Skin Disorders: In deep underground mines, Miliaria rubra (“mucker’s mange”) is a prevalent skin disorder due to the hot environment, low ventilation, and perspiration, all exacerbated by the miner’s clothing and personal protective equipment. The condition, which frequently occurs in overheated patients, is also known as heat rash or “prickly heat,” as the occlusion of eccrine sweat ducts results in papules and vesicles that patients describe as stinging instead of itching. It is generally self-limiting, but treatment involves moving the patient to a cooler environment and applying desonide or other anti- inflammatory lotion. Most patients adapt over time, but some do not and are not well suited for work in a hot underground mine.


Noise-Induced Hearing Loss: The proximity of heavy machinery exposes the mining-industry worker to a substantial amount of unwanted noise and resultant noise-induced hearing loss. NIHL, the single most common work-related illness, is discussed next in detail in the manufacturing section of this guide.


When dealing with miners, it is important for the provider to think about generalized disorders that are encountered in other work environments as well as industry-specific diseases, such as CWP. Furthermore, obtaining an entire work history is crucial because some mining diseases, such as silicosis, may not appear until decades after the person has been removed from the exposure.




  1. MHSA – An Exhibit on Mining Disasters; msha.gov/Disaster
  2. https://cnn.com/2013/07/13/us/u-s-mine-disasters-fast-facts/index.html
  3. osha.gov/laws-regs/mou/1979-03-29
  4. McCunney, , A Practical Approach to Occupational and Environmental Medicine, 2nd ed, pgs 43, 151-154