What is PM2.5?

PM2.5 is toxic waste in the air, referred to as "air medicine" for short, and it is particulate matter with aerodynamic equivalent diameter less than or equal to 2.5 microns (solid and liquid particulate matter that can be suspended in the air). PM2.5 is not a single component air pollutant, but a complex and changeable air pollutant composed of a large number of different chemical components produced by many different man-made or natural pollution sources. As far as the production process is concerned, PM2.5 can be directly emitted by pollution sources (called primary particulate matter), or it can be generated by condensation or complex chemical reaction of gaseous pollutants emitted by various pollution sources in the atmosphere (called secondary particulate matter). Most of the atmospheric particulates are sulfuric acid, ammonium bisulfate, ammonium sulfate, ammonium nitrate, elemental carbon (NP) and organic carbon (BP). There are three ways to form PM2.5: 1, and the primary particles are directly discharged in solid form; 2. Gaseous emission at high temperature, which condenses into solid primary condensable particles during plume dilution and cooling (tail gas emission); 3. Secondary particles produced by gaseous pollutants through atmospheric chemical reaction. The primary particles in PM2.5 are mainly produced by the combustion of fossil fuels (mainly oil and coal) and biomass fuels, while other sources, such as building surface dust, farmland cultivation and wind erosion, have relatively small contributions to environmental PM2.5. Secondary particles are formed by multi-phase (gas-particle) chemical reactions, through which ordinary gaseous pollutants can be transformed into extremely fine particles. In most areas, sulfur and nitrogen are the main components of secondary PM2.5 observed, and secondary organic aerosols may also be important components in some areas. The effects of PM2.5 on human health mainly include increasing the mortality rate of patients with severe and chronic diseases, aggravating chronic diseases, aggravating respiratory and heart diseases, changing lung function and structure, affecting reproductive capacity and changing human immune structure. Three diseases caused by particulate matter deserve attention: infectious diseases: including influenza, tuberculosis and pneumonia; Allergy: including asthma and alveolitis caused by natural allergens; Lung cancer and so on. Most health effects are considered to be caused by the small particle size fraction of PM2.5 rather than the large particle size fraction. The degree of harm mainly depends on its composition, concentration and particle size. PM2.5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, also known as particles that can enter the lungs. Its diameter is less than 1/20 of the thickness of human hair, which can only be found by electron microscope. 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. The PM2.5 index has become an important indicator to measure and control the degree of air pollution. PM2.5 is the residue discharged by combustion in the process of daily power generation, industrial production and automobile exhaust emission, most of which contain toxic substances such as heavy metals. Generally speaking, fine particulate matter (PM2.5) below 2.5 microns mainly comes from the combustion of fossil fuels (such as automobile exhaust and coal burning) and volatile organic compounds. The World Health Organization (WHO) believes that PM2.5 has a great impact on human health. When the average annual concentration of PM2.5 reaches 35 μ g/m3, the risk of human death is about 10 μ g/m3 higher than 15%. Zhong Nanshan, an academician of China Academy of Engineering, pointed out: "Above 5, it goes to trachea and bronchus, below 5, especially 1 to 3 microns, it enters alveoli. The alveoli are used for gas exchange. Those particles will stay in the alveoli forever after being swallowed by macrophages, which will have an impact on the cardiovascular system and nervous system, not just the respiratory system. " Netizen survey: "Looking at the turbid air in the city and the pedestrians running on the road in Dai Yue, I especially envy my parents. They can live leisurely in the countryside, breathe fresh air and taste fresh vegetables, "said Fu, a netizen. Some netizens said that they would go to those masks "for sale by the roadside!" Masks have become a hot commodity on Taobao for a while, with prices ranging from 2 yuan to 30 yuan, and some sellers are even out of stock. The relationship between smog and PM2.5, and is the smog weather caused by air pollution? Actually, fog and haze are two concepts. Fog is a natural phenomenon when the relative humidity is high, while haze is a phenomenon that a large number of extremely fine dry dust particles float evenly in the air under certain weather conditions, which makes the air with horizontal visibility less than 10 km generally turbid. Although PM2.5 has nothing to do with fog, it is one of the fine particles that cause smog. The high incidence period of smog in China is 10 to March of the following year. During this period, citizens should strengthen their precautions and reduce going out. Pregnant women, children and the elderly should stay indoors as much as possible to avoid affecting their health. Therefore, wear a mask when you go out. Advanced medical masks have excellent barrier to particles and liquids, ensuring the breathability of wearing in precise working environment. It can also deodorize. Sources of toxic particles in cities: first, automobile exhaust, medical masks imported from the United States, and Puwei server, which have good filterability and prevent both particles and fog drops. The filtration efficiency is 99.8% for particles as small as 0. 1 micron, and 99.9% for bacteria or virus carriers as small as 0.3 micron (common in droplets). SecureFit patented technology is adopted to adapt to different face shapes and achieve a high degree of fit. For the health of you and your family, wear a mask when you go out.