Minimum duration of developing coal miner pneumoconiosis: March 2011
Ans. D: More than 10 years Simple pneumoconiosis (first phase of anthracosis) requires 12 years of exposure Coal workers' pneumoconiosis (CWP)/ Black lung disease It is caused by long exposure to coal dust. It is a common affliction of coal miners and others who work with coal, similar to both silicosis from inhaling silica dust, and to the long-term effects of tobacco smoking. Inhaled coal dust progressively builds up in the lungs and is unable to be removed by the body; that leads to inflammation, fibrosis, and in worse cases, necrosis. Coal workers' pneumoconiosis, severe state, develops after the initial, milder form of the disease known as anthracosis (anthrac - 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 (i.e. productive cough for 3 months per year for at least 2 years) associated with workplace dust exposure. Coal dust is not as fibrogenic as is silica dust. Coal dust that enters the lungs can neither be destroyed nor removed by the body. The paicles 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 impoant in the inflammation and fibrosis of CWP. Aggregations of carbon-laden macrophages can be visualised 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. Simple CWP is marked by the presence of 1-2mm nodular aggregations of anthracotic macrophages, suppoed by a fine collagen network, within the lungs. Those 1-2mm 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. 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 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 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 pa of the diagnostic criteria. Chest X-ray appearance for CWP can be viually indistinguishable from silicosis. Chest CT, paicularly high-resolution scanning (HRCT), are more sensitive than plain X-ray for detecting the small round opacities.
2-4 years
4-6 years
8-10 years
More than 10 years