On sunny and hot days, dense haze can easily be seen over large metropolitan areas. This is the so-called smog - the product of combustion of liquid and solid fuels, processed in the atmosphere.
Initially, smog was the result of condensation of air moisture on the combustion products of various types of fuel (particles of smoke, ash, dust). However, with the development of technology, since about 1950, a new type of smog has appeared - photochemical, which is the result of mixing substances such as ozone (more than 90%), nitrogen oxides, nitrate peroxides and volatile organic substances (vapors of paints, gasoline, chemicals, etc.). Under the influence of strong ultraviolet radiation, the concentration of all these substances in the air forms smog.
Sources of smog include waste gases from factories and power plants, household chemical products such as hairspray or solvents, and of course car exhaust, which is the main cause of smog in big cities.
The large amount of pollutants that accumulate in smog has a negative impact on the environment and human health. Because of it, the amount of oxygen in the air decreases, and the one that is contains toxic substances.
Smog is especially dangerous in hot and calm weather. Under such natural conditions, it sinks lower to the ground and can stay for several days. That is why it is most often seen in sunny weather.
Promotes the concentration of smog in the air and high-rise buildings, which impede the movement of air masses. And also the high humidity of the air, in which city dwellers have to breathe moisture saturated with various hazardous substances that are soluble in it.
Smog has a direct toxic effect on the lungs, aggravating asthma, exacerbating allergies and other diseases that affect the body's respiratory system. In addition, combustion products absorbed into the blood have a general negative effect on the body, weakening its immune system.