The harm of PM2.5: PM2.5, also known as respirable particulate matter, refers to particles smaller than 2.5 microns in diameter, which can directly enter the alveoli and enter the circulatory system through the walls of blood vessels, endangering our health. We didn’t know this concept before. Some people say PM2.5 was brought to China by Gary Locke, which makes sense to me. I think most people understand this concept from two years ago when the U.S. consulate released PM2.5 data. Recently the International Agency for Research on Cancer (IARC), a research institute affiliated with the World Health Organization, published data showing that air pollution has become an important cause of human tumors and has been classified as a class I carcinogen. It is estimated that more than 220,000 people died from lung cancer caused by air pollution in 2010. It is generally believed that there is a latency period of 10-15 years from exposure to carcinogenic substances to the onset of cancer, which means that this figure reflects the air pollution situation almost from 1995-2000. What’s worse is that air pollution causes cancer not only for lung cancer, but there is evidence of carcinogenic effects on bladder cancer and other tumors. The health risks of PM are not limited to tumors; its most direct and rapid effects are directed at the respiratory and cardiovascular systems. Some data show that more than 800,000 people die each year from COPD, asthma and cardiovascular disease caused by air pollution. The harm of respirable particulate matter to humans can also be speculated from another perspective: viable particulate matter is produced at a certain stage in the development of human industrial civilization, nature does not exist in large quantities of this type of material, the human organism is unlikely to evolve a targeted defense system in the short term, unlike ultraviolet light, although also very harmful, but in the evolution of life evolutionary process of ultraviolet light has always existed, the living organism has the opportunity In fact, lower organisms such as E. coli have a strong DNA repair system against UV radiation. Therefore, I speculate that humans have no defense against PM2.5, and the continuation of such pollution would be catastrophic to human health. PM2.5 can block the alveoli and make the lung function more loaded, reducing the life of the lung. PM0.3 can cross the air-blood barrier of the lung and enter the blood directly, because the smallest cell platelet diameter is about 2.5 microns. It has a great impact on human health. PM0.3, a general term for solid particles or droplets in the air with a diameter less than or equal to 0.3 microns, is also known as lung-accessible particulate matter. PM0.3 has a small particle size, is rich in a large number of toxic and harmful substances and has a long residence time in the atmosphere. Particle sources The main source of PM0.3: more than 90% is the exhaust from power plants, factories and automobiles, which contains heavy metals such as mercury, cadmium and lead. In general, 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, PM0.3 is mainly from the burning of fossil fuels (such as, coal burning), volatile organic compounds, etc.. These harmful substances are a root cause of lung cancer, liver cancer, lymphoma; some other is the air bacteria, viruses, it is also the main root cause of influenza A, bird flu; indoor is mainly from decoration, furniture paint and adhesives, etc., which release formaldehyde, benzene, these are a root cause of leukemia, nasal cancer, colon cancer, brain tumors, including fetal malformations. Some information shows that in the past 20 years, the incidence of lung cancer in China has increased at a high rate, and has been the number one malignant tumor causing death in men, and is also in the forefront among women. From 1975 to the early 1990s, the incidence of lung cancer in China increased by 120.9% for men and 90.4% for women; in 2005, it was estimated that there were 285,000 men and 143,000 women with lung cancer in China. If no measures are taken, by 2025, the number of lung cancer patients in China will exceed 1 million. Why are there more and more lung cancer patients? In a sense, lung cancer is a man-made tumor. The high incidence of lung cancer is mainly caused by human’s own behavior. In ancient times, esophageal cancer was discovered in Han Dynasty and breast cancer was discovered in ancient Egypt, but lung cancer was almost non-existent until the 16th century, and after the 20th century, its incidence was like a “wild horse”, rapidly climbing from outside the top 10 to the top of the world. There are three main reasons for this. The primary cause is smoking. Statistics show that 9 out of 10 people who die of lung cancer are smokers. The survey shows that in 2002, smokers over 15 years old accounted for 35.8% of the total population in China, and the total number of smokers accounted for 1/3 of the world. this directly leads to the increasing incidence of lung cancer. Although the number of male smokers has begun to decline in major cities such as Beijing, the incidence rate will continue to grow due to the long incidence cycle of lung cancer. The second is lifestyle. For example, in the alpine mountains of Xuanwei, Yunnan, the residents use smoky coal for heating, resulting in serious indoor air pollution and an alarming incidence of lung cancer among locals, especially women in households. In addition, the large amount of oil smoke produced when cooking, etc., may lead to an increased chance of lung cancer. Lung diseases, as well as intrinsic factors such as immunity and heredity, are also direct triggers of lung cancer. Finally, there is environmental pollution. Epidemiological survey shows that the incidence pattern of lung cancer is that areas with developed industries and heavy pollution are higher than those with less developed industries, and urban areas are higher than rural areas. This has a lot to do with the emission of exhaust gases from industries and automobiles.