It refers to particulate matter (solid and liquid particles that can be suspended in the air) with an aerodynamic equivalent diameter less than or equal to 2.5 microns. Rich in a large number of toxic and harmful substances and in the atmosphere for a long residence time, long transport distance, and therefore a greater impact on human health and the quality of the atmospheric environment. It is less than 1/20th of the diameter of a human hair.December 4, PM2.5 is the main reason for the formation of hazy weather.The main source of PM2.5 is the residue emitted through combustion in the process of daily power generation, industrial production and automobile exhaust emissions, mostly containing heavy metals and other toxic substances. Generally speaking, coarse particulate matter with particle size of 2.5 microns to 10 microns mainly comes from road dust, etc.; fine particulate matter below 2.5 microns (PM2.5) mainly comes from the combustion of fossil fuels (e.g. motor vehicle exhaust, coal combustion), volatile organic compounds, etc. Impact on the environment Some researchers have determined the sources of PM2.5 in Beijing: dust accounts for 20%; sulfate, nitrate, and ammonia salts converted from gaseous pollutants each account for 17%, 10%, and 6%; coal burning produces 7%; exhaust emissions from the use of diesel and gasoline contribute 7%; biomass such as crops contribute 6%; and plant debris contributes 1%. Interestingly, smoking also contributes 1%, although this is a rough scientific estimate and not necessarily accurate]. The composition of PM2.5 in Beijing was also measured in this study: carbon containing particles, sulfate, nitrate, and ammonium together accounted for 69% of the weight. Similarly, 41.6% of Shanghai PM2.5 measured in 1999 was ammonium sulfate and ammonium nitrate, and 41.4% was carbon-containing material. Health hazards The main damage to the respiratory and cardiovascular systems include respiratory irritation, coughing, breathing difficulties, reduced lung function, aggravation of asthma, leading to chronic bronchitis, cardiac arrhythmias, non-fatal heart disease, and premature death in patients with heart and lung disease. The elderly, children, and patients with heart and lung diseases are the sensitive groups of PM2.5 pollution. health hazards of PM2.5. Hazy weather caused by fine particulate matter is even more dangerous to human health than sandstorms. Particles with a particle size of 10 microns or more will be blocked outside the human nose; particles between 2.5 microns and 10 microns can enter the upper respiratory tract, but some of them can be excreted through sputum, etc. In addition, they will be blocked by the villi inside the nasal cavity, which is relatively less harmful to human health; and fine particles with a particle size of 2.5 microns or less are less than 1/20th of the size of a human hair in diameter and are not easily They are not easily blocked. When inhaled into the human body, it will directly enter the bronchial tubes and interfere with the gas exchange in the lungs, causing diseases including asthma, bronchitis and cardiovascular disease. Each person inhales an average of about 10,000 liters of air per day, and the microscopic dust that enters the alveoli can be rapidly absorbed and directly enter the blood circulation for distribution throughout the body without detoxification by the liver; secondly, it can damage the ability of hemoglobin to transport oxygen and lose blood. For patients with anemia and blood circulation disorders, it may have serious consequences. For example, it can aggravate respiratory diseases and even cause heart diseases such as congestive heart failure and coronary artery. In short these particles can also enter the blood through the bronchi and alveoli, where the harmful gases and heavy metals are dissolved in the blood, causing even more damage to human health. The physiological structure of human body determines that there is no filtering and blocking ability for PM2.5, while the danger of PM2.5 to human health is gradually exposed its horrible side with the progress of medical technology. Causes respiratory obstruction or inflammation Studies show that 75% of particles below 2.5 microns are deposited in the alveoli. We can imagine that the eyes become inflamed when sand gets in them. Deep in the respiratory system, which is also a sensitive environment, fine particles remain as foreign bodies in the respiratory system for a long time and can also inflame the respiratory system. Epidemiological surveys have found that polycyclic aromatic hydrocarbons (PAHs) in urban particulate matter are associated with the incidence and mortality of lung cancer in the population. Most of the PAHs in the atmosphere are adsorbed on the surface of the particles, especially those below 5 mm in size, and very few on large particles. In other words, the more fine particulate matter in the air, the more exposure we have to carcinogens – PAHs Affecting fetal development causing defects There are other findings that are even more worrisome. Several reports in recent years have shown that human fertility is declining significantly, and environmental pollution is believed to be the culprit. An investigation from northern Bohemia, which studied pregnant women exposed to high levels of PM2.5, found that high levels of fine particulate pollution may affect embryonic development. Additional studies have found a correlation between concentrations of atmospheric particulate matter and increased perinatal and neonatal mortality, low birth weight, intrauterine growth retardation (IURG), and congenital functional defects. Particulate matter can enter blood vessels through air-blood exchange Evidence suggests that it is now common knowledge that these small particulate matters cause cellular damage Between 2004 and 2006, when the daily average PM2.5 concentration increased at the Peking University campus observation site, the number of emergency cardiovascular patients also increased at Peking University Hospital No. 3, about 4 km away. Using a time-series analysis study, we analyzed the collected data and found that an increase of 10 micrograms per cubic meter of PM2.5 concentration was associated with an 8% increase in hospital emergency patients in the hypertension category and an increase in cardiovascular disease. Impact on human life expectancy The World Health Organization report shows that even in Europe, where monitoring standards are most stringent, 386,000 people still die each year under the haze of PM2.5, and life expectancy per capita in EU countries is reduced by 8.6 months as a result. Diseases caused Three types of diseases caused by particulate matter deserve attention: infectious diseases: including influenza, tuberculosis and pneumonia; allergies: including asthma and alveolitis caused by natural allergens; and lung cancer. Most of the health effects are thought to be caused by the small particle size fraction PM2.5 rather than the large particle size fraction. The degree of hazard depends mainly on its composition, concentration and particle size. The risk of death begins to rise if the concentration of PM2.5 in the air is above 10 µg/m3 for a long period of time. For every 10 µg/m3 increase in concentration, the overall risk of death increases by 4%, the risk of death from heart and lung disease by 6%, and the risk of death from lung cancer by 8%. Hazards to visibility Observational studies have shown that particulate matter and gaseous pollutants do not have a significant effect on visibility at low concentrations. However, at higher concentrations, they can change the color of the sky and reduce visibility. When concentrations are particularly high, they can make the sky brownish. Both atmospheric pollutants and weather factors can reduce visibility, but visibility is reduced mainly due to scattering and absorption of light by fine particles and gaseous pollutants, which weakens the light signal from objects. The scattering effect of particulate matter in atmospheric pollutants is the main factor causing visibility reduction, and the scattering of particulate matter can cause 60-95% of visibility reduction, of which PM2.5 and its contained sulfate, nitrate and carbon black are the most important. The concentration of PM2.5 is a key factor in determining atmospheric visibility, while PM2.5 scattered light is the most important cause of atmospheric visibility reduction, where PM2.5 scattered light extinction accounts for 80% of the total extinction. The impact of particulate matter on the climate can be divided into two major areas: direct and indirect. The direct impact refers to the scattering and absorption of solar radiation and long-wave radiation from the ground by particulate matter particles in the atmosphere, thus affecting the ground and air radiation income and expenditure. At the same time, particulate matter can directly block sunlight from reaching the earth’s surface, so that the optical thickness of visible light increases, and the solar energy reaching the ground decreases, thus lowering the ground temperature and increasing the temperature at high altitude. Black carbon particulate matter in the atmosphere can absorb solar short-wave radiation, thus affecting solar radiation transmission, heating the atmosphere and lowering the surface temperature; at the same time, black carbon particulate matter can absorb and radiate infrared radiation, affecting the Earth’s long-wave radiation. Model calculations show that the increase in atmospheric particulate matter caused by human activities tends to cool the Earth’s surface, and the trend of surface cooling caused by the increase in particulate matter since industrialization can partially offset the increase in surface temperature caused by the increase in greenhouse gases. The indirect effect of particulate matter on climate is that changes in particulate matter concentration affect cloud formation, which in turn has a dramatic effect on climate, an aspect for which no quantitative results are available to date. Atmospheric particulate matter, as an organic part of the atmospheric hydrosphere cycle, mainly affects the microphysical processes of clouds and precipitation, but also the atmospheric stability and cloud albedo. Particulate matter particles can play an important role in cloud formation and growth as cloud condensation nuclei and ice nuclei, which can not only enhance or diminish the amount of rainfall, but also change the type of clouds and rain, e.g., convert non-precipitating clouds to precipitating clouds. Protection The gas quality report shows that since the beginning of 2013, 17 provinces and cities in the central-eastern region of the country have continued to haze, with PM2.5 on the verge of bursting into widespread heavy and severe pollution. The foggy days and the resulting physical discomfort have made many consumers deeply aware of the dangers of PM2.5. There is no need to be blindly nervous, as long as the daily travel, life and living to be a “mindful”, you can do a certain amount of PM2.5 prevention. When outdoor pollution is more serious, the number of ventilation should be reduced accordingly. Reducing smoking is also the most important source of pollution to reduce indoor particulate matter pollution (indoor spontaneous generation of particulate matter to improve the efficiency of stove combustion, reduce the use of solid fuels, the use of air purifiers for filtration (“air purifiers on PM2.5 purification performance and high efficiency filter performance and purifier structure design are Generally speaking, air purifiers with high-quality high-efficiency filters can purify up to 99.9% of PM2.5, which is one of the effective means to reduce PM2.5 concentration”. To prevent PM2.5, we need to start from the small things around us and pay attention to the use of scientific means in order to effectively prescribe the right medicine and double the efficiency of prevention. The first thing to do is to wear a good mask on foggy days and then go out to prevent toxic fog from invading the lungs by the mouth and nose, and people who have morning exercise habits should stop outdoor activities. For these body size of tiny particles, should wear a special N95 dust mask, dust mask for this aerosol filter rate should be more than 95%. Good personal hygiene Fog may seem mild, but it contains a variety of acids, alkalis, salts, amines, phenols, dust, pathogenic microorganisms and other harmful substances, so foggy days out should immediately wash the face and bare skin when you return. It is recommended to maintain a scientific routine, avoid overexertion, drink more water, pay attention to a light diet, eat less stimulating food, eat more tofu, milk and other foods. A variety of green plants in their own balconies, terraces, indoor a variety of green plants. In Singapore, indoor green walls are planted from balconies and windowsills to underground warehouses, and plants are planted from the 1st floor all the way to the 9th floor. But in Beijing, many upscale office buildings have no greenery. If each person planted one square meter, Beijing would have 20 million square meters of new greenery. During the interview, the reporter saw many plants both in front of Wang Xianmin’s office and indoors. From his experience, the green leafy plants such as green lilies, green lilies, tiger lilies, etc., because of their larger leaves, the adsorption capacity is relatively strong. “Quit car” is as important as quitting smoking “Quit car” is as important as quitting smoking. Some Hangzhou citizens found that smoking can lead to a 10-fold increase in indoor PM2.5 values, while in Beijing’s central city traffic jams PM2.5 will also increase by 4-6 times. The health benefits of quitting smoking are obvious, while driving less and taking public transportation more can also contribute to reducing PM2.5. In fact, protecting the environment is something every citizen should do, and starting from every little thing is the best contribution to the global village we live in.