What are the hazards of particulate matter in the air?

What are the hazards of particulate matter in the air?
 
 
On October 17, 2013, the International Agency for Research on Cancer under the World Health Organization issued a report, identifying for the first time that air pollution is carcinogenic to humans, and the main substance of air pollution is the particulate matter.
 
The most important thing to pay attention to is the inhalable particulate matter in the air, which refers to the particulate matter with an aerodynamic equivalent diameter of less than 10μm, which is what we often hear of PM10, and PM2.5 is the particulate matter less than 2.5μm. When air enters the human respiratory tract, nasal hair and nasal mucosa can generally block most of the particles, but those below PM10 cannot. PM10 can accumulate in the upper respiratory tract, while PM2.5 can directly enter the bronchioles and alveoli.
 


In the natural environment, the particulate matter in the air mainly includes sand and dust caused by wind, volcanic ash from volcanic eruptions, smoke and dust caused by forest fires, sea salt evaporating from seawater irradiated by sunlight, pollen of plants, etc. With the development of human society and the expansion of industrialization, human activities also emit a large amount of particulate matter into the air, such as smoke and dust from various industrial processes such as power generation, metallurgy, petroleum, and chemistry, cooking fumes from cooking, exhaust from automobiles, Smoking and so on.
 
Due to the small size and large specific surface area of ​​particulate matter, it is easier to adsorb other substances, so the cause of its disease is more complicated, but the most important thing is that it can cause cardiovascular disease, respiratory disease and lung cancer.
 
PM2.5, which we are usually more concerned about, actually occupies a small proportion of inhalable particulate matter, but why pay more attention to PM2.5? Of course, one is the reason for media propaganda, and the other is because PM2.5 is finer and easier to absorb organic pollutants such as polycyclic aromatic hydrocarbons and heavy metals, which significantly increases the probability of carcinogenesis, teratogenesis, and mutagenesis.