Meteorologists and medical experts believe that haze weather caused by fine particles is even more harmful to human health than sandstorms. Particles with a particle size of 10 micron or more 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, and they will also be blocked by villi inside the nasal cavity, which is relatively harmless to human health; However, fine particles with a particle size of less than 2.5 microns are equivalent to the size of110 of human hair and are not easily blocked. When inhaled into human body, it will directly enter the bronchus, interfere with the gas exchange in the lungs, and cause diseases including asthma, bronchitis and cardiovascular disease.

Everyone inhales about 1 10,000 liters of air every day, and the dust entering the alveoli can be quickly absorbed and directly distributed in the blood circulation without detoxification of 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 heart diseases such as congestive heart failure and coronary artery. In short, these particles can also enter the blood through bronchi and alveoli, and harmful gases and heavy metals are dissolved in the blood, which is more harmful to human health. The physiological structure of the human body determines that it has no ability to filter and block PM2.5, but the harm of PM2.5 to human health has gradually exposed its horrible side with the progress of medical technology.

In EU countries, PM2.5 has reduced people's average life expectancy by 8.6 months. PM2.5 can also be a carrier of viruses and bacteria, which contributes to the spread of respiratory infectious diseases. Major developed countries in the world, as well as Japan, Thailand and India in Asia, have included PM2.5 in air quality standards. The most tragic thing is that PM2.5 has not been included in China's environmental air quality indicators, so this has become the root cause of the direct conflict between the data of the US Embassy and the official government data.

Wei Fusheng, an academician of China Academy of Engineering and former chief engineer of China National Environmental Monitoring Center, also showed that the higher the concentrations of PM2.5 and PM 10, the higher the incidence of respiratory diseases in children and their parents, especially the impact of PM2.5. In Science of Total Environment, Pan Xiaochuan, a professor at peking university health science center Public Health College, and his colleagues published a new discovery: from 2004 to 2006, when the daily average concentration of PM2.5 at observation points in Peking University campus increased, the number of emergency patients with cardiovascular diseases also increased in Peking University Third Hospital, about 4 kilometers away. Although PM 10 and PM2.5 are both risk factors of cardiovascular disease, the influence of PM2.5 is obviously greater. The World Health Organization also pointed out in the 2005 edition of Air Quality Guidelines that when the average annual concentration of PM2.5 reaches 35 micrograms per cubic meter, the risk of human death will increase by 15% compared with the situation of 10 micrograms per cubic meter. According to a report from the United Nations Environment Programme, the concentration of PM2.5 per cubic meter will increase by 20 mg, and about 340,000 people will die every year in China and India.