PM2.5 is a particulate matter with a particle size less than 2.5um (equivalent to the size of bacteria), which is considered to be the "culprit" causing haze weather. After PM 2.5 enters the human bod

PM2.5 is a particulate matter with a particle size less than 2.5um (equivalent to the size of bacteria), which is considered to be the "culprit" causing haze weather. After PM 2.5 enters the human body, PM2.5 is a particulate matter with a particle size less than 2.5um (equivalent to the size of bacteria), which is considered to be the "culprit" causing haze weather. After PM2.5 enters the human body, it will be swallowed by phagocytes, and at the same time it will lead to the change of biofilm permeability and cell death.

1, fine particles are also called fine particles. Fine particles and PM2.5 fine particles refer to particles with aerodynamic equivalent diameter less than or equal to 2.5 microns in ambient air. It can be suspended in the air for a long time, and the higher its concentration in the air means the more serious air pollution. Although PM2.5 is only a small part of the composition of the earth's atmosphere, it has an important impact on air quality and visibility. Compared with atmospheric coarse particles, PM2.5 has the advantages of small particle size, large area, strong activity and easy attachment of toxic and harmful substances (such as heavy metals and microorganisms). ), it stays in the atmosphere for a long time and has a long transportation distance, so it has a great impact on human health and atmospheric environmental quality.

2. The composition of particulate matter is very complicated, which mainly depends on its source. There are mainly natural sources and man-made sources, but the latter is the most harmful. There are two kinds: primary aerosol and secondary organic aerosol. Natural sources include soil dust (containing oxide minerals and other components), sea salt (the second largest source of particulate matter, whose components are similar to seawater), plant pollen, spores, bacteria and so on. Natural disasters, such as volcanic eruptions, release a lot of volcanic ash into the atmosphere, and forest fires or naked coal fires and sandstorms will transport a lot of fine particles into the atmosphere; Man-made sources include fixed sources and mobile sources. Stationary sources include various fuel combustion sources, such as power generation, metallurgy, petroleum, chemistry, textile printing and dyeing, heating, cooking, coal and gas or lampblack. The flow source is mainly the tail gas discharged into the atmosphere when various vehicles use fuel in operation.

3. Fine particles are more harmful to human health, because the smaller the diameter, the deeper the part that enters the respiratory tract. Particles with a diameter of 10μm are usually deposited in the upper respiratory tract, and those below 2μm can penetrate bronchioles and alveoli. Fine particles entering human alveoli directly affect the ventilation function of the lungs, making the body vulnerable to hypoxia. Long-term exposure to particulate matter can lead to cardiovascular and respiratory diseases and lung cancer. PM2.5 is easy to adsorb polycyclic aromatic hydrocarbons and other organic pollutants and heavy metals, which significantly increases the probability of carcinogenesis, teratogenesis and mutation.

4.PM2.5 will be swallowed by phagocytes after entering the human body, and at the same time it will lead to the change of biofilm permeability and cause cell death. The phagocytosis of PM2.5 belongs to the second line of defense of human immunity. Phagocytosis does not contain enzymes that decompose PM2.5, which leads to the change of biofilm permeability and cell death PM2.5 can carry germs into the human body, and the human body has an inflammatory reaction to defend against germs; When PM2.5 enters the body, lysosomes decompose PM2.5 and release hydrolase, which leads to cell death.