What are the main pollutants in the air?

What are the main pollutants in the air?
 
On the earth, the normal air composition is calculated by volume fraction: nitrogen (N2) accounts for about 78%, oxygen (O2) accounts for about 21%, rare gases account for about 0.939%, carbon dioxide (CO2) accounts for about 0.031%, and Other gases and impurities account for about 0.03%, such as ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), water vapor (H2O), etc. Due to the different environments everywhere on the earth, it directly affects the air quality everywhere, and the situation is quite complicated. Therefore, only the human settlement environment is discussed here, that is, the air quality problem of a relatively closed human living space.


 
If the normal air composition changes, it will have a great impact on the human body that depends on the air for survival, that is to say, the air is polluted. In the human settlement environment, there are four main categories of air pollutants: particulate matter, planktonic bacteria, volatile organic compounds (VOCs) and inorganic matter.
 


Particulates:
When the air flows, it will carry many tiny particles, including dust, sea salt, plant pollen, spores, etc. We often hear that PM2.5 and PM10 are indicators to measure the concentration of particles of different sizes.
 
Planktonic bacteria:
Planktonic bacteria refer to fungi, bacteria, viruses, etc. suspended in the air, including mites, cockroaches, cat and dog allergens, penicillium, aspergillus, staphylococcus, cocci and so on.
 
VOCs:
VOCs include formaldehyde, toluene, xylene, styrene, benzo[α]pyrene, hydrocarbons, lipids and other volatile organic compounds. The main sources are all kinds of furniture, chemical products, coatings, adhesives, fuels, etc. in the living environment.
 
Inorganic:
Including ammonia, carbon monoxide, carbon dioxide, ozone, nitrogen oxides, sulfur dioxide and other sulfides. These substances are mainly due to environmental changes, biological excretion, air movement, etc., which have more or less impact on the human body.