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 macrophages and remain in the lungs, residing in the connective tissue or pulmonary lymph nodes. 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 lesions within the lungs. The centers of dense lesions may become necrotic due to ischemia, 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 bronchioles. The coal macule is the basic pathological feature of CWP and has a surrounding area of enlargement of the airspace, known as focal emphysema.
Focal emphysema extends into progressive centrilobular emphysema. Less commonly a variant of panacinar emphysema 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) 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), 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.