Coal Workers' Pneumoconiosis (Black Lung Disease) Workup

Updated: Dec 19, 2019
  • Author: Fatima J Wong, DO; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Imaging Studies


Chest radiography (CXR) remains the criterion standard for diagnosis of coal workers’ pneumoconiosis (CWP) (black lung disease) on the basis of the International Labour Organization (ILO) classification that describes the abnormalities and ranges of severity. [39, 40] A standard set of radiographs reflecting the amount of coal retained in the lungs is used for comparison. The scale represents a continuum of dust accumulation with nodule formation from category 0/0 to 3/4 which describes the profusion or concentration of small opacities in affected lung zones. [41] The chest radiographs are interpreted by at least two physicians who have received training or exhibited the ability to utilize the ILO pneumoconiosis classification system through the B Reader Certification Program, which is administered through the National Institute for Occupational Safety and Health (NIOSH). [42]

Opacities for simple CWP (SCWP) fall into either one of two categories based on size and shape. [41] Small opacities are divided into two types, rounded or irregular. The small, rounded opacities fall into three different size ranges and denoted as below:

  • p: Up to 1.5 mm in diameter

  • q: 1.5 to 3 mm in diameter

  • r: 3 to 10 mm in diameter

Alternatively, irregular opacities are also distinguished based on width, as follows:

  • s: Up to 1.5 mm

  • t: 1.5 to 3 mm

  • u: 3 to 10 mm

The lung zones are identified as follows:

  • RUZ and LUZ: Right upper zone and left upper zone, respectively

  • RMZ and LMZ: Right mid zone and left mid zone, respectively

  • RLZ and LLZ: Right lower zone and left lower zone, respectively/p>

Any nodular opacity larger than 1 cm in diameter on radiographs is considered complicated CWP (CCWP) or progressive massive fibrosis (PMF). Subcategories for this group according to the ILO classification are as follows [41] :

  • A: One large opacity with the longest dimension up to 50 mm, or several large opacities with the sum of their longest dimensions not exceeding about 50 mm

  • B: One large opacity having the longest dimension exceeding 50 mm but not exceeding the equivalent area of the RUZ, or several large opacities with the sum of their longest dimensions exceeding 50 mm but not exceeding the equivalent area of the RUZ

  • C: One large opacity which exceeds the equivalent area of the RUZ, or several large opacities which, when combined, exceed the equivalent area of the RUZ

Other imaging studies

The application of computed tomography (CT) scanning for the diagnosis of pneumoconiosis has received increasing attention and achieved a certain effectiveness as CXRs are not considered sensitive in early pneumoconiosis because of inter- and intrareader variabilities. [43]

In a study thatcompared findings on CXR and high-resolution CT (HRCT) scans between normal coal miners and those with early low-grade CWP, Savranlar et al demonstrated a high-discordance rate between the two imaging modalities,leading them to the conclusion that HRCT is more sensitive than CXR in evaluating coal workers with normal and early CWP. [43]

There have been several classification systems with attempts to use CT scans as a diagnostic modality for CWP. One such classification system is the Hosoda-Shida Classification, [44] which has been used mostly in Japan. This CT-based classification system displayed acceptable interreader agreement and compatibility with the ILO system. However, a drawback to this system was that the study participants included in the study were only those at risk for silicosis. [44]

Currently, both traditional radiography and CT scanning rely mainly on the lesion morphology and material density for diagnostic confirmation. Large shadows make distinguishing between pneumoconiosis and lung cancer tumors difficult. Magnetic resonance imaging (MRI) may improve the specificity and accuracy of diagnosis and reduce the false-positive rate according to a retrospective study of PMF in 25 CWP patients. [45]

In a small case series that evaluated the utility of positron emission tomography (PET) scanning with F-18-fluorodeoxyglucose (18F-FDG) in patients with CWP and suspected malignancy, Reichert and Bensadoun showed that even in patients with PMF without malignancy, the observed nodules were hypermetabolic on PET scan. [46] Therefore, the use of PET scans proved to be of limited value in the evaluation of CWP and associated malignancy, yielding a high rate of false-positive results.


Other Tests

On pulmonary function testing, persons with simple coal workers' pneumoconiosis (CWP) (SCWP) (black lung disease) do not always show significant impairment of lung function or decreased ventilatory capacity. A slight decrease in the alveolar-arterial pressure gradient can be observed, along with a minor reduction in diffusing capacity (P category) and minimal hypoxemia noted in the Internation Labour Office (ILO) classification categories 2 and 3 (secondary to physiologic shunting). If present, focal emphysema can result in a slight increase in lung compliance and an increase in residual volume. 

However, in persons with complicated CWP (CCWP), abnormalities are detected in stages B and C. Ventilatory capacity is reduced in proportion to the size of the conglomerate mass. Diffusing capacity is also decreased. If the mass is large enough to destroy significant vascularity, pulmonary hypertension ensues. Additionally, hypoxemia develops earlier and more frequently in miners who smoke. 

In their 4-year longitudinal study, Bourgkard et al determined that "worsening x-ray findings and pneumoconiosis were more often observed in coal miners with micronodules on CT [computed tomography] scans wheezing, low values of maximal midexpiratory flow (MMEF) and forced expiratory flow (FEF 25%-75%), and high dust exposure at first examination." These findings suggest that the presence of micronodules on CT scans, altered scores on pulmonary function tests, and wheezing signify a worse 4-year prognosis and increased risk of progression to progressive massive fibrosis (PMF). CT scanning, therefore, may be a helpful screening tool to monitor progression to pneumoconiosis. 

Vallyathan et al found that "in miners without coal worker’s pneumoconiosis antioxidants, cytokine and growth factors are maintained at baseline levels present in control subjects." [47] In contrast, miners with SCWP exhibit markedly elevated bronchoalveolar lavage (BAL) fluid concentrations of antioxidants, proinflammatory cytokines, and mediators, which increase fibroblast proliferation. The inability of the lungs to maintain a balance between oxidant burden and antioxidant defenses may play a crucial role in the disease genesis. Increased levels of interleukins 1 and 6, tumor necrosis factor-alpha, transforming growth factors-beta1 and 2, alpha1-proteinase inhibitor, and fibronectin were found in the BAL fluid of miners with radiographically defined CWP. 

The simple 6-minute walk test (6MWT) can be performed as an ancillary test to help quantify possible impairment due to CWP. It can be used in addition to chest imaging and pulmonary function testing. [48]




Biopsy is not typically needed for the diagnosis of coal workers’ pneumoconiosis (CWP) (black lung disease). Bilateral symmetrical, elongated mass lesions in advanced CWP are rarely malignant. If there is concern about malignancy based on clinical symptoms or in the setting of a unilateral large opacity, a biopsy may be required to resolve diagnostic uncertainty. [1]