What is the role of "air killer" pm2.5 that affects health?

In the past few days, smog weather has frequently appeared in many places in China, and the orange warning of fog continues to sound, making people pay attention to the air pollution around them again.

What exactly is PM2.5?

For environmentalists, PM2.5 is no stranger. It 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. It is an important index to monitor the degree of air pollution internationally.

Scientists pointed out that the main sources of PM2.5 are man-made, industrial waste gas generated by the combustion of minerals such as coal and oil, tail gas emission generated by motor vehicles, including particles dispersed in the air such as dust, sulfuric acid, nitric acid and organic hydrocarbons, and secondary pollutants formed through a series of photochemical reactions.

Some experts say that the concentration of PM2.5 will increase in large vehicles using diesel engines, roadsides, bus stops, street barbecues and restaurant cooking. There is also PM2.5 indoors, which is widely found in smoke generated by smoking, dust generated by air conditioning systems and printers, and fine particles entering the outdoor.

PM2.5, a common atmospheric environmental quality standard in developed countries, has not been included in the compulsory monitoring scope in China, nor has it been announced to the public. It is understood that the monitoring of PM2.5 is currently only piloted in a few cities such as Beijing, Shanghai, Nanjing and Wuhan. According to the news from Wuhan Environmental Protection Bureau, Wuhan is one of the first cities in China to start PM2.5 monitoring. PM2.5 monitors were installed at five air quality monitoring stations in Dongxihu District, such as Wuchang, Zhuankou and Wujiashan, to capture ultrafine dust particles. All the current monitoring data are uploaded to the Ministry of Environmental Protection as a reference for determining the new standard. However, the debugging time of this special monitor needs at least 1 year, and it will not be officially announced until the data is calibrated.

PM2.5 can directly enter alveoli.

Professor Zhong Nanshan, an academician of China Academy of Engineering, president of Chinese Medical Association and a leading figure in the treatment of respiratory diseases in China, has made it clear that he absolutely advocates publication. Zhong Nanshan is outspoken. PM2.5-sized particles can directly enter alveoli, which has an all-round impact on human body. Alveola is used for gas exchange. Those particles are swallowed by macrophages and remain in alveoli forever, which will have an impact on cardiovascular system, nervous system and other organs, not just the respiratory system.

Wang Xinrong, deputy chief physician of respiratory medicine in central hospital of wuhan, said that PM2.5 mainly harms the respiratory system and cardiovascular system, including respiratory irritation, cough, dyspnea, decreased lung function, exacerbation of asthma, chronic bronchitis, non-fatal heart disease and premature death of patients with cardiopulmonary diseases. Old people, children, people with weak resistance and poor immune function will be more vulnerable.

Meteorologists and medical experts believe that particles larger than 10 micron will be blocked out of people's noses; Particles with a particle size of 2.5 microns to 10 microns can enter the upper respiratory tract, but some of them can be excreted through sputum, which is relatively harmless to human health; The fine particles with a particle size less than 2.5 microns are invisible to the naked eye, and the diameter is equivalent to 1/20 of human hair. These substances can easily enter the lungs through the nasal cilia in the nasal cavity, even penetrate into the blood, interfere with the gas exchange in the lungs, and cause diseases including asthma, bronchitis and cardiovascular diseases.

Moreover, due to their light weight, these particles stay in the air for a long time, have a long transportation distance and are easy to spread. Once they adsorb water vapor, they will form haze weather, which is even more harmful to human health than sandstorms. The biggest harm to human body is not the particles themselves, but the chemicals adsorbed on them. In fact, the impact of particulate matter on health is essentially the impact of various chemicals adsorbed on the surface of particulate matter on health. For example, adsorption of carcinogens has carcinogenic effects, adsorption of dioxins has reproductive hazards, and adsorption of heavy metals has heavy metal hazards. The key is to see what is adsorbed.

How can we avoid PM2.5?

The human body needs to breathe 15 cubic meters of air every day, and people living in cities are equivalent to a mobile "air filter". "PM2.5" lurks in the air, which is a bit hard to prevent, but it is not impossible to prevent.

First of all, smog weather reduces going out.

PM2.5 is the chief culprit in the haze weather. Meteorologists said that the reason for the smog is that the urban diffusion conditions are not good, the cold air is not strong, and the wind speed is not strong. At this time, various pollutants in the city cannot spread in time and accumulate near the ground. If coupled with drought, lack of rain, strong sunshine and low humidity, various photochemical reactions between pollutants are easy to form smog. Automobile exhaust is an important factor in the formation of smog, so the smog situation will be particularly serious on the main roads with busy traffic, and the visibility is lower than that in other places.

Liu Xiaolin, director of Wuhan Psychological Hospital, said that due to the smog weather, there are more smog and pollutants in the air, which is not conducive to the health of patients with chronic bronchitis and asthma. After staying in this air for a certain period of time, the symptoms of patients with heart disease and lung disease will be obviously aggravated, and healthy people will also feel unwell. In addition, when smog weather appears, it is easy to make people feel depressed and depressed due to lack of light, and even induce depression.

First of all, we should pay attention to the change of the weather. Once there is foggy weather, try to reduce going out as much as possible and don't exercise in this weather. Drink plenty of water, sprinkle some water on the cement floor properly to suppress dust; Patients with heart disease and respiratory diseases should reduce physical exertion and do less outdoor activities; Pay attention to emotional adjustment. When the light is too dim, try to turn on the light to listen to music, control depression and boredom as much as possible, and prevent the occurrence of diseases.

Second, ordinary masks can't stop PM2.5

Wang Xinrong said that masks commonly used in the market have little effect on blocking PM2.5, and even ordinary masks used by most medical staff have no effect. At present, there are two kinds of medical protective masks (3M, Puweixin imported from the United States) on the market, which can block PM2.5 fine particles and infectious viruses such as avian influenza. The filtering effect is worthy of recognition, but the corresponding price is also relatively high, and a small number of people may feel uncomfortable when wearing it for the first time. Therefore, don't be superstitious about the role of masks. In the haze weather, residents should reduce unnecessary outdoor activities, moderately reduce the amount and intensity of exercise, so as to reduce the harm of haze weather to health. People in need, such as Lao Manzhi, can use protective masks when going out. When you get home, you must wash your face, hands and mouth in time. It is best to wash the nasal cavity with a cotton swab dipped in tap water or normal saline.

Third, don't do morning exercises in foggy days.

Professor Zhang Zhenxiang from the Department of Respiratory Medicine in tongji hospital said that many people have the habit of doing morning exercises, and they insist on it all year round, rain or shine. But the foggy weather is not suitable for going out for morning exercise. Because when people do morning exercises, the amount of oxygen needed by the human body increases, harmful substances in the fog will invade the respiratory tract and cause insufficient oxygen supply, resulting in dyspnea, chest tightness, palpitations and other adverse symptoms. Especially the milky fog will give people a clean feeling. In fact, a large number of pollutants have accumulated in fog, which can cause airway hyperresponsiveness (an important manifestation of bronchial asthma), and inhalable particulate matter, sulfur dioxide and other pollutants in fog are the main inducing factors of asthma and chronic bronchitis. Therefore, people with exercise habits are advised to do morning exercises after the sun comes out, and choose parks, rivers and other places with good air quality to do morning exercises.

Fourth, start from the side and reduce pollution.

Experts suggest that everyone should have environmental awareness, drive less at ordinary times, turn off the engine when there is traffic jam, and avoid idling of the car. Automobile exhaust not only harms people around the road for a long time, but also harms drivers themselves, especially in the case of long-term traffic jams and incomplete combustion of gasoline. So it's best to drive less, turn off the engine when there is traffic jam for a long time, and try to open the window less.

Residents should go to places with heavy smoke and dust less, and don't burn garbage and hay without permission. Burning without permission is the most convenient way for many farmers and enterprises to dispose of garbage. However, toxic substances such as dioxins and smoke particles produced by private burning will make the surrounding areas of the city unconsciously fall into a "poisonous fog".

Do not smoke indoors and stay away from second-hand smoke; Open the window less in foggy weather, and you can raise some flowers and plants; You can use an air purifier. 80% of air purifiers in the market mainly purify fine particles in the air, which has a good adsorption effect on PM2.5, but you should pay attention to changing the filter element frequently when using it.