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Removal mechanism of dust particles
Origin：Hefan Hit： Time：2020-03-05
After the airborne particles are inhaled, some are re-exhausted through the respiratory tract; the other part floats on the walls of the trachea and alveoli. The factors that determine the deposition rate of particles are the size (particle size), density, and morphology of particles, which are almost independent of the composition of the particles. The mechanism of dust particle deposition is as follows.
1: Inertial impact. Most of the particles with an aerodynamic diameter of 5 to 30 μm are impacted by their own inertia (the particles in the air flow still move in the original direction when the air flow direction changes suddenly), and they sink to the walls of the nasal cavity and throat.
2: Settlement. Particles of 1 to 5 μm are mainly deposited on the trachea and bronchial wall due to gravity.
Among the deposited particles, they are soluble substances, which are absorbed by the trachea and cell walls according to the same solubility, and then enter the blood vessels to run throughout the body. Toxic substances can cause local inflammatory reactions or systemic poisoning (for example, lead particles cause lead poisoning). The insoluble particles are discharged from the respiratory organs by a cleaning mechanism of the respiratory organs after a certain period of time.
Respiratory cleaning mechanism
① Ciliary movement. Particles adhering to the airway wall are transported to the throat by the cilia and mucus of the airway epithelium and coughed up or swallowed. The cilia movement reaches 1500 times per minute. Due to this effect, the airway cleaning effect can be completed within 24 hours.
② lung food cells. Particles floating on the wall of the alveoli enter the pneumocytoma. It is then transported to the airways and excreted by ciliary movement, but some of it enters the lymph nodes. It is said that the pneumoepithelial cells are cleaned very slowly, and it takes about 60 to 120 days to clear half of the number of particles (half-life) to be excreted. In addition, if the particles are toxic particles, such as free silicic acid particles, they will break into the puff cells after entering the puff cells. As a result, lysosomal oxides in the cell flow out of the cell
3. Diseases caused by particles
Mineral dust people long-term inhalation of certain fiber dust, lung tissues and lymph nodes will produce chronic diseases mainly irreversible fibrous lesions, which will reduce lung function Different. The main mineral dusts and the diseases they cause are as follows:
② silicate compounds (talc lung, kaolin lung, diatomite lung);
③ asbestos (asbestos lung);
④ Aluminum and its compounds (aluminum lung, alumina lung, bauxite lung);
⑤ Iron compounds (iron oxide lung, iron sulfide lung);
⑥ coal powder (pneumoconiosis of coal mine workers);
Beryllium (beryllium lung);
⑧Other (graphite lung, etc.). In addition, asbestos dust caused malignant tumors of the respiratory organs (lung cancer, pleural mesothelial tumor) has also attracted people's attention.
Metal particles The main diseases or symptoms caused by some metal particles are as follows.
① Zinc. After a few hours of contact with zinc smoke, fever and dyspnea will occur, and it will disappear naturally within a few hours (zinc fever).
② Cadmium. Long-term exposure can cause emphysema or systemic renal dysfunction (characterized by low-molecular-weight proteinuria).
③ Chrome. In particular, hexavalent chromium causes nasal septum perforation.
④ Lead. Causes hematopoietic dysfunction, anemia and whiteness, thrombocytopenia (aplastic anemia). In addition, there have been many cases of peripheral neuritis (upper limb palsy).
⑤ Manganese. Acute poisoning causes diseases of the central nervous system such as pneumonia, chronic poisoning leading to degenerative changes in brain cells.
癌 Carcinogens. Obvious carcinogens and possible carcinogens are uranium (lung cancer), chromate (lung cancer), nickel carbonyl (paranasal and lung cancer), and arsenide (lung cancer).
Harmful fog
① Sulfuric acid mist. It is more irritating to the airways than sulfur dioxide, causing throat, trachea contraction, or pulmonary edema.
② Hydrofluoric acid mist. It has a strong irritating effect on the airways and can cause pulmonary edema.
③ oil mist. Irritating to airways. Symptoms similar to pneumoconiosis have also been reported.
① Cotton, linen and linen. The main symptoms are chest tightness, difficulty breathing, and some degree of bronchoconstriction. Especially on Monday after the rest day, when they are exposed to this type of dust, the symptoms are more severe. This is its characteristic. After inhaling cotton dust, it will cause pneumoconiosis symptoms.
② Sugarcane fiber. The long-term inhalation of dry sugarcane stem dust after extracting sugar juice causes symptoms such as shortness of breath and fever.
③Fungus and pollen. Among them, some are inhaled with room dust and play an important role as allergens (such as hay fever and farmers' lungs caused by hay). After contact with forage grass, it can cause fever, dyspnea (exogenous allergic pneumonia) and other symptoms. It is said that some good-temperature actinomycetes also act as antigens.
Dust from the lungs
The lungs have a self-cleaning ability to discharge inhaled dust particles. After inhaling the dust, the dust deposited in the ciliated trachea can be expelled quickly, but the fine dust particles entering the alveoli are discharged slowly. The former can be called tracheal exhaust. , Mainly by virtue of mucus secreted by the respiratory mucosa, insoluble or insoluble dust particles are expelled due to the movement of cilia; the latter is called lung clearance, which is mainly caused by macrophages in the alveoli, which swallow the dust and transport it to The end of the bronchioles is expelled from the body with sputum through the respiratory tract.
Regarding the rate of dust removal in the lungs, some people have conducted research with radio aerosols and found that most of the inhaled dust particles are cleared within 24 hours. In a work class, most of the dust deposited on the mucous membranes of the respiratory tract can be cleared within a few hours. Only the part of the dust that has not been discharged is accumulated for a long period of time. After reaching a certain amount, it can react with the lung tissue to cause disease. The rate of dust discharge from the lungs is related to the size of the dust particles and the location of the deposit.
