I. What is pneumoconiosis? Pneumoconiosis is a group of systemic diseases caused by long-term inhalation of inorganic dust during occupational activities and its retention in the lungs, mainly due to diffuse fibrosis of the lung tissue. There are many different types of inorganic dusts in the production environment and their degree of hazard varies. According to the pathological type of lung reaction to dust, dusts are classified into fibrogenic dusts (e.g. silica, asbestos), non-fibrogenic dusts (e.g. carbon, graphite, carbon black) and mixed dusts. What are the types of pneumoconiosis in the national statutory occupational diseases? In the latest “Classification and Catalogue of Occupational Diseases” issued in 2013, national legal pneumoconiosis includes silicosis, coal worker’s pneumoconiosis, graphite pneumoconiosis, carbon black pneumoconiosis, asbestos pneumoconiosis, talcum pneumoconiosis, cement pneumoconiosis, mica pneumoconiosis, potter’s pneumoconiosis, aluminum pneumoconiosis, welders’ pneumoconiosis, casters’ pneumoconiosis, and other pneumoconiosis that can be diagnosed according to the Diagnostic Criteria for Pneumoconiosis and the Diagnostic Criteria for Pneumoconiosis Pathology. III. What is the incidence of pneumoconiosis in China? Pneumoconiosis is the most common and major type of occupational disease in China. By the end of 2014, a total of 777,173 cases of pneumoconiosis were reported in China, accounting for about 90% of the total number of all occupational diseases. Pneumoconiosis not only affects a large number of people, but also poses a huge health risk, leading to reduced work capacity and quality of life, disability, and even death. Once pneumoconiosis is clearly diagnosed, patients should be discharged from dust work in a timely manner, undergo comprehensive treatment according to their condition, actively prevent and treat tuberculosis and other complications, reduce clinical symptoms, delay the progress of the disease, improve the quality of life, and prolong their life expectancy. What are the causes of pneumoconiosis? The main cause of pneumoconiosis is respirable dust with a diameter <10μm that can reach the deeper part of the respiratory tract. The onset of pneumoconiosis varies depending on the cause and the speed of onset after exposure to dust. The following factors influence the development of pneumoconiosis: (1) dust nature: the degree of fibrosis varies with the nature of the dust, with free silica dust being the most pathogenic, followed by asbestos and talc. (2) Dust diameter: dust with a diameter of 10-15μm can be blocked by the upper respiratory tract and prevented from entering the lower respiratory tract; dust with a diameter of 5-10μm can directly enter the deep part of the lungs and reach the terminal fine bronchi, alveolar tracts and alveoli, leading to inflammatory reactions in the lungs; dust with a diameter of <2.5-5μm can even cross the air-blood barrier and enter the blood circulation. (3) Dust concentration: the greater the concentration of dust suspended in the air, the higher its pathogenicity and the shorter the onset time. (4) Duration of exposure: The longer the worker is exposed to dust, the higher the chance of developing pneumoconiosis. (5) Chronic respiratory disease: People with chronic respiratory disease have weakened respiratory defenses and are more likely to develop pneumoconiosis. Smoking and dust exposure have a synergistic effect on pneumoconiosis. (6) Individual susceptibility: Pneumoconiosis is the result of the interaction of genetic and environmental factors. (7) Production process and dust control measures: Pneumoconiosis is a preventable disease. Improving production processes and dust control measures can prevent the occurrence of pneumoconiosis or prolong its onset. V. Which occupations may be exposed to dust? As many industrial production processes can produce dust, especially the following production positions, such as poor protective measures are most likely to cause pneumoconiosis. (1) Mining: various metal and non-metal mines (such as asbestos mines), coal mining, rock drilling, blasting, transportation, processing and other processes. (2) Casting, molding, sand cleaning, welding and other types of work in the machinery manufacturing industry. (3) asbestos production in the mining, crushing, screening; refractory materials, cement and other construction materials production, transportation, etc. (4) highway, railroad, water conservancy, hydropower construction in the excavation of tunnels, engineering blasting, etc. (5) Other industries: ceramics, jade, building materials and other processing, production, etc. F. What are the histopathological features of pneumoconiosis? The general pathological changes in the lungs can be divided into three types: nodular, diffuse fibrosis, and dust spot type. The nodular type is the most common and occurs mainly in workers exposed to silica dust or a mixture of silica dust-based dusts. To the naked eye, pneumoconiosis nodules are round, well-defined, grayish-black, and firm to the touch; to the light microscope, they appear as silica nodules with collagen fibers as the core; mixed dust nodules with collagen fibers intermingled with dust can also appear, in which collagen fibers account for more than half of the components; sometimes, silica nodules can also form, i.e., nodules formed by mixing silica nodules or mixed dust nodules with tuberculosis lesions. Diffuse fibrosis type mainly occurs in asbestos lung and other silicate lungs. Fibrosis is diffusely distributed throughout the lung, and diffuse collagen fibrous hyperplasia due to dust deposition can be seen in the respiratory bronchi, alveoli, lobular septa, small bronchi and around small blood vessels, and in the subpleural area, with widespread but non-focal distribution and foci of fibroblasts. 3. Dust spot type is more common in workers exposed to coal and carbon dusts and metal dusts, also seen in casters and welders. The lungs are grayish-black in appearance, and the lesions are characterized by foci of dust fibers (dust spots) and perifocal emphysema changes. The lesions are dark black, soft, and poorly defined, often with perifocal air spaces (perifocal emphysema), and the lesions are connected to the fibrotic interstitium in a stellate pattern, forming stellate nodules; fiber microscopy shows a mixture of reticulocytes, collagen fibers, and dust in the lesions, with less than 50% collagen fiber component. In addition, there is also significant interlobular hyperplasia and subpleural fibrosis, with occasional nodule formation; black spots of varying sizes are seen on the surface of the dirty pleura. VII. What are the imaging manifestations of pneumoconiosis? Chest X-ray: The lungs of pneumoconiosis on X-ray mainly show nodular shadows (generally 1-3 mm in diameter), reticular shadows and large fused shadows; followed by lung texture changes, hilar changes and pleural changes. In silicosis patients exposed to high silica dust content and concentration, round and round-like shadows are often predominant, appearing early in the inner and middle bands of the two lower and middle lungs, mostly on the right side, and then gradually expanding upward, but some may also appear first in the two upper lobes of the lungs; with low silica dust content or mixed dust, round-like or irregular shadows are predominant. Large shadows are usually seen in the outer zone of the upper lobes of the lungs, often in a symmetrical, cross-lobe figure-of-eight shape, with increased translucency in the outer lung fields; the thickened pulmonary lines may be weeping and the tracheal mediastinum may appear displaced because of the contraction of the hilum due to massive pulmonary fibrosis. The hilar changes are mainly increased shadow density, and sometimes "eggshell-like calcified" lymph nodes are seen. Pleural changes are mainly thickening, adhesions or calcifications.