In some large cities, due to the high level of pollution that they suffer, we find a phenomenon called “smog”. This name comes from English when joining the words smoke: smoke and fog: mist. This term is used to refer to the air pollution suffered by some cities as a result of combining certain atmospheric conditions and specific air pollutants.
This dense, darkened “smog” is a mixture of fog, smoke and vapors that come from chemicals. It is a type of atmospheric pollution with concentrations of sulfur and nitrogen oxide, hydrocarbons and millions of particles of lead, manganese, copper, nickel, zinc and carbon. All these gases come from industries, cars and even homes as a result of combustion processes.
Causes: Currently two types of smog are identified: photochemical and sulfurous or reducing.
The origin of photochemical smog is in the combustion of engines, a complex mixture that is formed from the interaction of sunlight with two of the main components of exhaust gases, NOx and hydrocarbons, giving ozone as the main oxidant. . Sulfurous smog is that which contains high concentrations of sulfur oxides and particulate matter.
Smog is not an air pollutant, it is a consequence of air pollution.
Smog is especially important in cities with dry, hot and sunny climates, and in places where there are many vehicles. Currently in developed countries the fuels that cause this type of pollution are burned in facilities with better purification or dispersion systems, which is why it is rare to find this effect of pollution.
The effects of smog directly affect the health of people, plants and animals, in addition to the harmful effects they cause on nature. Air pollutants are diverse and each of them affects the body in different ways. Eye and throat irritation, cough, fatigue, anemia and in general an overload of the respiratory tract, are some of the effects of this contamination. If the victim also suffers from asthma, allergies or other lung problems, smog can kill, as has already been demonstrated with the death of thousands of people in different cities.
In 1943, the inhabitants of Los Angeles (USA) suffered the consequences of photochemical smog. Nitrogen oxides and hydrocarbons emitted from vehicle exhausts reacted by the action of the sun on hot days to form peroxyacetyl nitrate, PAN, and ozone. As a preventive measure, catalytic filters were placed in the exhaust pipes of the cars and managed to lower ozone concentrations from 0.027 parts per million (ppm) to 0.003 ppm.
Another event that impacted society was during 1952, in the city of London, England. The smog with sulfur oxides and soot particles was highly concentrated and due to the static conditions of the atmosphere that in 5 days caused the death of around 3,500 people.
In the years following these unfortunate events, pollution control measures were adopted in several European countries and the USA, and since then numerous studies have been conducted to assess the health effects of environmental pollution.