PM2. 5 is synonymous with fine particulate matter. PM is the full name of particulate matter in English and particulate matter in Chinese. PM2. 5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, also known as lung accessible particles. Its diameter is less than 1 / 20 of the thickness of human hair.
Meteorological and medical experts believe that the haze caused by fine particles is even more harmful to human health than sandstorms. Particles with a particle size of more than 10 microns will be blocked outside the human nose; Particles with a particle size between 2.5 microns and 10 microns can enter the upper respiratory tract, but some can be discharged from the body through sputum, etc. in addition, they will also be blocked by villi in the nasal cavity, which is relatively harmless to human health; The diameter of fine particles with a particle size of less than 2.5 microns is equivalent to 1 / 10 of the size of human hair and is not easy to be blocked. After being inhaled into the human body, it will directly enter the bronchus, interfere with the gas exchange in the lungs, and cause diseases including asthma, bronchitis and cardiovascular diseases. Each person inhales an average of about 10000 liters of air every day. The micro dust entering the alveoli can be quickly absorbed and directly enter the blood circulation and distribute throughout the body without detoxification by the liver; Secondly, it will damage the ability of hemoglobin to transport oxygen and lose blood. It may have serious consequences for patients with anemia and blood circulation disorders. For example, it can aggravate respiratory diseases and even cause congestive heart failure, coronary artery and other heart diseases. In short, these particles can also enter the blood through bronchus and alveoli, in which harmful gases and heavy metals are dissolved in the blood, which is more harmful to human health. The physiological structure of human body determines the effect of PM2 PM2.5, without any filtering ability The harm to human health has gradually exposed its terrible side with the progress of medical technology.
In EU countries, PM2 5 lead to the reduction of people's average life expectancy by 8.6 months. And PM2 It can also become a carrier of viruses and bacteria and contribute to the spread of respiratory infectious diseases. At present, major developed countries in the world and Japan, Thailand and India in Asia will PM2 5 included in air quality standards. In February 2012, the State Council issued a new air quality standard, adding PM2 5 value monitoring.
Wei Fusheng, academician of the Chinese Academy of engineering and former chief engineer of China environmental monitoring station, also showed that PM2 The higher the concentrations of PM5 and PM10, the higher the incidence of respiratory diseases in children and their parents, while PM2 The impact of 5 is particularly significant. A new discovery by Pan Xiaochuan, Professor of the school of public health of the Department of medicine of Peking University, and his colleagues, published in the supplement of science of total environment: PM2 at the observation point on the campus of Peking University from 2004 to 2006 When the daily average concentration increased, the number of cardiovascular emergency patients also increased in the Third Hospital of Peking University about 4 kilometers away. Although PM10 and PM2 5 are risk factors for cardiovascular disease, but PM2 The impact of 5 is obviously greater. The World Health Organization also pointed out in the 2005 edition of air quality guidelines that when PM2 When the average annual concentration reaches 35 micrograms per cubic meter, the risk of human death is about 15% higher than that of 10 micrograms per cubic meter. A report from the United Nations Environment Programme says PM2 If the concentration per cubic meter rises by 20 mg, about 340000 people die in China and India every year.
Less going out in haze weather
Experts remind that autumn and winter are the season with frequent smog. If there is smog, outdoor activities should be avoided as far as possible. If you go out, you'd better wear a mask. Although PM2 It is difficult to block through the mask, but the mask can at least block some large particles of floating dust, which has a certain protective effect on the respiratory system. If haze weather continues to appear, even healthy people will have discomfort symptoms, so everyone needs protection.