On October 17, 2013, the International Agency for Research on Cancer (IARC) issued by the World Health Organization issued a report identifying the first time that air pollution is carcinogenic to humans, and the main substance of air pollution is particulate matter.
The most important particle in the air is the inhalable particle, which refers to the particle whose aerodynamic equivalent diameter is less than 10μm, that is, PM10 that we often hear, and PM2.5 is a particle smaller than 2.5μm. When the air enters the human respiratory tract, nose hair and nasal mucosa generally block most of the particulates, but the following PM10 cannot be blocked. PM10 can accumulate in the upper respiratory tract, and PM2.5 can directly enter the bronchioles and alveoli.
In the natural environment, particulates in the air mainly include dust from the wind, volcanic ash from volcanic eruptions, smoke and dust from forest fires, sea salt from sunlight-irradiated seawater, and pollen from plants. With the development of human society and the expansion of industrialization, human activities also emit large amounts of particulate matter into the air, such as dust emitted by various industrial processes such as power generation, metallurgy, petroleum, and chemical industries, cooking fumes, and automobile exhaust fumes. Smoking and so on.
Because of its small size, the particulate matter has a large specific surface area and is more likely to adsorb other substances. Therefore, the cause of the disease is complicated, but the most important thing is that it can cause cardiovascular and respiratory diseases and lung cancer.
The proportion of PM2.5 that we usually care about is actually small in the proportion of respirable particles, but why do we pay more attention to PM2.5? Of course, the first is the reason for media propaganda. On the other hand, because PM2.5 is finer, it is easier to adsorb organic pollutants such as polycyclic aromatic hydrocarbons and heavy metals, which increases the chance of causing carcinogenic, teratogenic, and mutagenic effects.