PM2.5 is actually a small solid particle that can not be seen floating in the air. Its shape is very irregular, but its aerodynamic characteristics are consistent with the shape of particles with a diameter of less than or equal to 2.5 microns. We call it PM2.5, including fine particles, fine particles and fine particles. The diameter of one of our hair strands is about 70 microns. The diameter of the largest PM2.5 small particles is 1/28 of the diameter of the hair strands. With the naked eye, it is impossible to see.
It can be suspended in the air for a long time. The higher its concentration in the air, the more serious the air pollution is. Although PM2.5 is only a small component in the earth's atmosphere, it has an important impact on air quality and visibility. Compared with coarse atmospheric particles, PM2.5 has small particle size, large area, strong activity, easy to carry toxic and harmful substances (such as heavy metals, microorganisms, etc.), long residence time in the atmosphere and long transportation distance, so it has a greater impact on human health and atmospheric environmental quality.
PM50, PM10 and PM2.5 are three critical values. There are not only particles of these three diameters in the air, but particles of any diameter and length below 50 microns or above. Particulate matter that can enter the lung is another name for it. Because particles larger than PM2.5 can be intercepted by nasal hair in our nose and secretions in our respiratory tract, most of PM2.5 is absorbed into our lungs. Therefore, once this small thing and toxic substances are combined into our lungs, it will bring us big trouble.
Once in the alveoli. Then it enters the capillaries through the alveolar wall, and then enters the whole blood circulation system. It will carry many harmful organic and inorganic molecules and is the source of disease. Bacteria are the well-known cause of disease. PM25 is comparable to bacteria. PM2 . 5 refers to fine particles with a diameter of 2.5 μ m, while bacteria are micron sized organisms, most of which are 1 μ m, a few μ m, or more than a dozen μ m, that is, pm2 5 is the same size as bacteria. When bacteria enter the blood, macrophages (a kind of immune cells) in the blood will immediately swallow it, so it can not make people sick. But if macrophages are used to swallowing bacteria, bacteria are living organisms and food for macrophages. PM25 is lifeless. Macrophages swallow it like lions swallow stones. They can't digest it and choke to death. After a large number of macrophages are reduced, our immunity will decline, and harmful substances will be released, resulting in inflammation of cells and tissues. Our immunity will decline, and the more likely we are to get sick.