What is smog? What are the hazards to the human body? How to prevent it?

From the meteorological point of view, fog and haze are two different weather phenomena. The main feature of fog is the near-surface layer, which is about 400 meters high and consists of tiny water droplets in the gas layer below it. The existence of fog will reduce air transparency and worsen visibility. If the horizontal visibility of the target drops below 1000 m, the weather phenomenon of water vapor condensation (or condensation) suspended in the air near the ground is called fog (fog), and the phenomenon that the horizontal visibility of the target is below 1000- 10000 m is called light fog or haze (fog). When fog forms, the atmospheric humidity should be saturated. As far as its physical essence is concerned, fog and cloud are the products of condensation of water vapor in the air, so fog becomes a cloud when it rises off the ground, and it is called fog when it falls to the ground or moves to the mountains. Generally, the thickness of fog is relatively small, and the thickness of common radiation fog is between tens of meters and one hundred and two hundred meters. Fog, like clouds, has obvious boundary with clear sky area, and the concentration distribution of fog droplets is uneven. The diameter of fog droplets is relatively large, ranging from a few microns to 100 micron, with an average diameter of about 10-20 micron. The naked eye can see the droplets floating in the air. Because the light scattered by fog composed of liquid water or ice crystals has little to do with wavelength, the fog looks milky white or bluish white.

The main component of smog is a kind of dust, usually called dust, such as sulfuric acid and nitric acid. The thickness of haze is relatively thick, which can reach about 1-3 km. The difference between haze and fog is that the relative humidity is not large when haze occurs, but the relative humidity in fog is saturated. Generally speaking, the visibility deterioration caused by atmospheric haze blurred vision is caused by haze when the relative humidity is less than 80%, while the visibility deterioration caused by atmospheric haze blurred vision is caused by fog when the relative humidity is more than 90%. The visibility deterioration caused by atmospheric haze blurred vision is caused by a mixture of haze and fog when the relative humidity is between 80 and 90%, but its main component is haze. Haze is different from fog and clouds, and there is no obvious boundary between haze and clear sky. The distribution of smog particles is relatively uniform, and the diameter of smog particles is relatively small, ranging from 0.00 1 micron to 10 micron, with an average diameter of about 1-2 micron. Floating particles are invisible to the naked eye. Because the smog is composed of dust, sulfuric acid, nitric acid and other particles, the longer the scattering wavelength, the more the light ratio, so the smog looks yellow or orange-gray.

With the deterioration of air quality, the smog phenomenon increases and the harm is aggravated. Therefore, in many areas of China, the phenomenon of haze weather is combined with fog as an early warning and forecast of disastrous weather, which is collectively called "haze weather".

Second, the main harm of smog weather to human body

As the saying goes, "the poisonous fog in autumn and winter kills the knife." The "smog" that we can see and can't catch actually has a great impact on the body, especially on the elderly group with high incidence of cardiovascular and cerebrovascular diseases and respiratory diseases.

1. Effects on respiratory system. The composition of smog is very complex, including hundreds of atmospheric chemical particles. Among them, aerosol particles smaller than 10 micron are harmful to health, such as mineral particles, sea salt, sulfate, nitrate, organic aerosol particles, fuel, automobile exhaust, etc., which can directly enter and adhere to human respiratory tract and alveoli. In particular, submicron particles will be deposited in the upper and lower respiratory tract and alveoli respectively, causing acute rhinitis and acute bronchitis. For patients with chronic respiratory diseases such as bronchial asthma, chronic bronchitis, obstructive emphysema, and chronic obstructive pulmonary disease, smog weather will make the condition acute or acute. Staying in this environment for a long time will also induce lung cancer.

2. Influence on cardiovascular system. There are many pollutants in the air in foggy days, and the air pressure is low, which is easy to induce acute attacks of cardiovascular diseases. For example, when the fog is heavy, the water vapor content is high. If people exercise outdoors, the sweat of human body is not easy to be discharged, which causes people to feel chest tightness and blood pressure to rise.

3. Hazy weather will also lead to the weakening of ultraviolet rays in the surface layer, which can enhance the activity of infectious bacteria in the air and increase infectious diseases.

4. In foggy days, due to the decrease of sunshine, children's ultraviolet radiation is insufficient, vitamin D production in the body is insufficient, and the absorption of calcium is greatly reduced, which will seriously cause rickets in infants and children, and slow down the growth and development of children.

5. Affect mental health. The gloomy and foggy weather is prone to mental laziness, depression and pessimism due to the weak light and low air pressure, and even it is easy to get out of control at the slightest sign of trouble.

6. Affect traffic safety. In foggy weather, the visibility of the visual field is low and the air quality is poor, which is easy to cause traffic jams and traffic accidents.

Third, how to prevent diseases in foggy days?

Haze weather is caused by natural and man-made environmental pollution. Faced with this bad weather, we have to take various measures to avoid the harm it brings to people's normal life and health.

1. Reduce going out. The elderly, children and people susceptible to respiratory diseases with weak resistance should try to reduce going out or outdoor activities, and wear masks to protect their bodies when going out to prevent pollutants from invading the lungs through the nose and mouth. After returning from going out, you should immediately wash your face and expose your skin.

2. Reduce outdoor sports. Patients with chronic respiratory diseases, such as bronchial asthma, chronic bronchitis, obstructive emphysema, chronic obstructive pulmonary disease, etc., should avoid outdoor exercise as much as possible to avoid the onset or aggravation of chronic diseases. Similarly, the foggy weather is low, and patients with chronic diseases such as hypertension and coronary heart disease should not do outdoor exercise to avoid inducing angina pectoris and heart failure. Moderate and severe smog weather can easily stimulate the human respiratory and circulatory system, especially in the morning when the air quality is poor. Generally speaking, if there is no cold air activity, rain, snow, strong wind and other weather, it is best to choose the exercise time from morning to evening with good air quality and high visibility, and it is a place with many trees and grass. In foggy weather, the amount and intensity of exercise should be moderately reduced.

3. Close the doors and windows. Because the pollutants in the air are difficult to dissipate in foggy days, doors and windows should be closed in foggy days to avoid outdoor fog entering the room to pollute the indoor air and induce acute respiratory and cardiovascular diseases.

4. Pay attention to your diet. Patients with chronic respiratory diseases, especially the elderly, should keep scientific life rules, avoid overwork and drink plenty of water. Pay attention to a light diet, eat less irritating food, eat more tofu, milk and other foods, and supplement vitamin D when necessary.

You should be more careful when driving and walking. Moderate and severe haze weather, low visibility and poor line of sight. People who drive, ride and walk should be more careful, especially when passing through intersections and unguarded railway crossings, to slow down and obey traffic rules to avoid traffic accidents.