Do you know how harmful PM2.5 can be? Will it really block our lungs?

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 Do you know how harmful PM2.5 can be? Will it really block our lungs?


Production | Netease Science and Technology Know or not column group (public number: tech_163)

Haze is a primary carcinogen. There are 300 million alveoli in one lung and 80 PM2.5 particles can block one alveoli. When PM2.5 reaches 1155 micrograms/cubic meters in our living environment, 30 million alveoli can be blocked in one year and one third of the lungs can be blocked in three years.

We all know PM2.5 is terrible, but what kind of devil is it? Does it really block our lungs?

What is PM2.5?

PM2.5 is a small solid particle that we cant see floating in the air. Its shape is very irregular. But as long as its aerodynamic characteristics are consistent with spherical particles smaller than or equal to 2.5 microns in diameter, we call it PM2.5.

How small is this solid particle? Our hair is about 70 microns in diameter, and the largest PM2.5 particle is one-eighth of the diameter of the hair. Pulmonary particulate matter is another name. Because particles larger than PM2.5 can be intercepted by nasal hair and respiratory secretions in our nose, and most of PM2.5 can be inhaled into our lungs, once this small thing and toxic substances are combined into the lungs, it will cause us great trouble.

Scientists use PM2.5 to indicate the amount of such particles in the air per cubic meter. The higher the value, the more serious the air pollution is. PM2.5 index has become an important index to measure and control the degree of air pollution.

So how did PM2.5 come into being?

PM2.5 can be formed in three ways: 1) primary particles discharged directly in the form of solid state; 2) primary condensable particles discharged in the form of gaseous state at high temperature and condensed into solid state during the dilution and cooling of plumes (exhaust gas emission); 3) secondary particles generated by gaseous gas pollutants through atmospheric chemical reactions.

Primary particles are mainly produced by the combustion of fossil fuels (mainly petroleum and coal) and biomass fuels, while surface dust from other sources such as construction, farming and wind erosion contributes relatively little to PM2.5. Secondary particles are formed by multiphase (gas-particle) chemical reactions through which ordinary gaseous pollutants can be converted into very small particles. In most areas, sulfur and nitrogen are the main components of secondary PM2.5 observed, while secondary organic gas sol may also be an important component in some areas.

Specifically, the main sources of particulate matter are natural and man-made sources, but the latter is more harmful. Artificial sources include fixed sources and mobile sources. Fixed sources include all kinds of fuel combustion sources, such as power generation, metallurgy, petroleum, chemistry, textile printing and dyeing, heating, cooking coal and gas or fume emissions. The main source of flow is the exhaust gas discharged into the atmosphere by various vehicles when they use fuel in operation.

How harmful will PM2.5 be?

The World Health Organization believes that PM2.5 has a tremendous impact on human health. When PM2.5 years average concentration reached 35 micrograms per cubic metre, the risk of death increased by about 15% compared with 10 micrograms per cubic metre.

1) The effect of PM2.5 on respiratory health. PM2.5 entering the lungs can block the local tissues, reduce the ventilation function of the local bronchi, and lose the ventilation function of bronchioles and alveoli. PM2.5 adsorbing harmful gases can stimulate or corrode alveolar walls. Long-term effects can damage the respiratory defense function and cause bronchitis, emphysema and bronchial asthma. PM2.5 can also directly or indirectly activate oxidative stress system in pulmonary macrophages and epithelial cells, stimulate the secretion of inflammatory factors, neutrophil and lymphocyte infiltration, and cause lipid peroxidation in animal lung tissue. A large number of epidemiological studies have found that both short-term and long-term exposure to high concentrations of particulate matter can increase the incidence and mortality of respiratory diseases in the population.

2) The effect of PM2.5 on cardiovascular system health. At present, the impact of PM2.5 on cardiovascular system is more in-depth and comprehensive. PM2.5 can induce systemic inflammation and oxidative stress, resulting in vasoconstriction, dysfunction of vascular endothelial cells, release a large number of reactive oxygen species free radicals into the blood, thus promoting blood coagulation, leading to thrombosis, hypertension and atherosclerotic plaque formation. On the other hand, PM2.5 can stimulate intersection through the pulmonary autonomic nervous reflex arc. The sympathetic and parasympathetic nerve centers affect not only the blood and blood vessel systems, but also the autonomic nervous system of the heart, leading to decreased heart rate variability, increased heart rate and arrhythmia. A large number of epidemiological studies have shown that short-term exposure to high concentrations of PM2.5 (even for several hours) can significantly increase the daily visiting rate and mortality of cardiovascular events (such as coronary heart disease, myocardial infarction, heart failure, arrhythmia, stroke, etc.).

3) Carcinogenic effect of PM2.5. Many components in PM2.5 are carcinogenic or carcinogenic, such as polycyclic aromatic hydrocarbons, cadmium, chromium, nickel and other heavy metals. It was found that both organic and inorganic extracts of PM2.5 had mutagenicity and genotoxicity.

4) The effect of PM2.5 on other systems of the body. PM2.5 can cause systemic oxidative stress, inflammation, Hemorheology and dynamics changes after entering the maternal body, which can harm the fetus and cause a series of adverse reproductive problems.

Zhong Nanshan, an academician of the Chinese Academy of Engineering, pointed out: If you are above 5, you will go to the trachea and bronchus, but if you are below 5, especially 1-3 microns, you will go into the alveoli. The alveoli are used for gas exchange. When the particles are swallowed by macrophages, they will stay in the alveoli forever. They will affect the cardiovascular system and the nervous system, not just the respiratory system.

How to survive in PM2.5?

Since PM2.5 is so harmful and the air pollution index of PM2.5 is so high, how to survive in PM2.5 has become an important issue.

1) Do a good job of personal hygiene. When entering the room after going out, wash your face, rinse your mouth, clean your nasal cavity and remove the contaminated residues attached to your body in order to prevent the harm of PM2.5 to human body. When washing your face, youd better use warm water to wash away the particles on your face.

2) Do not open windows in foggy weather. If you really need to open a window to breathe, you should try to avoid the peak time of morning and evening haze. You can open a window to ventilate, and the time should be half an hour to one hour at a time. It can be planted on its balcony, balcony and indoor. Green crown plants, such as green radish, evergreen, tiger peel orchid, have relatively strong adsorption capacity because of their large leaves.

When using air purifier at home, we should pay attention to changing filter core frequently.

3) Wear a mask when you go out.

4) Reduce cooking fumes by using less hot oil to stir-fry vegetables. Eat more lung-nourishing fruit.

5) Smoking less.

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Source: Editor in charge of knowledge: Qiao Junjing_NBJ11279