Types of Smog

Dr. Henry Antoine Des Voeux first used the term smog in a paper in 1905 to describe the combination of smoke and fog that had been plaguing London at the time. Since then, London has enacted strict air pollution regulations, which have drastically reduced smog incidents in the region; however, London-type smog remains a major problem in areas of the world that burn large amounts of coal for heat. Smog is most commonly associated with the Los Angeles Basin of Southern California and its photochemical smog in the United States. A combination of orographic features, abundant sunlight, and a dense population in Los Angeles results in some of the worst air quality in the United States.

What is Smog?

Smog pollutes the air throughout the community. Its composition varies. The term is derived from the words smoke and fog, but it is commonly used to describe the pall that hangs over many cities due to automotive or industrial emissions.

H.A. Des Voeux most likely coined the term in 1905 to describe atmospheric conditions over many British towns. Des Voeux’s report to the Manchester Conference of the Smoke Abatement League of Great Britain in 1911 on the over 1,000 “smoke-fog” deaths that occurred in Glasgow and Edinburgh during the autumn of 1909 popularised the term.

Types of Smog

There are at least two types of smog: sulphurous smog and photochemical smog. 

1. Sulfurous smog

Sulfurous smog, also known as “London smog,” is caused by a high concentration of sulphur oxides in the air, which is caused by the use of sulfur-containing fossil fuels, particularly coal. Dampness and a high concentration of suspended particulate matter in the air aggravate this type of smog.

2. Photochemical smog

Photochemical smog, also known as “Los Angeles smog,” is most prevalent in urban areas with a high concentration of automobiles. It does not necessitate the use of smoke or fog. The nitrogen oxides and hydrocarbon vapours emitted by automobiles and other sources cause this type of smog, which then undergo photochemical reactions in the lower atmosphere. 

The highly toxic gas ozone is formed when nitrogen oxides react with hydrocarbon vapours in the presence of sunlight, and some nitrogen dioxide is formed when nitrogen oxide reacts with sunlight.The resulting smog causes the atmosphere to turn a light brownish colour, reduces visibility, damages plants, irritates the eyes, and causes respiratory distress. 

Surface-level ozone concentrations are considered unhealthy when they exceed 70 parts per billion for eight hours or more; such conditions are fairly common in photochemical smog-prone urban areas.

Sources of Smog

Smog is a persistent problem for cities located in river basins and surrounded by mountains because trapped smog in the valley cannot be carried by the wind. Primary pollutants are those that cause smog and are emitted directly from the source. 

Secondary pollutants are formed in the atmosphere as a result of chemical interactions between primary pollutants and normal environmental conditions. The primary pollutants that contribute to air pollution are nitrogen oxides, particularly nitrogen oxides and nitric oxides, which are released into the atmosphere by the combustion of fossil fuels from coal power plants and factory emissions and car exhausts.Nitrogen dioxide is a dangerous air pollutant that, when inhaled, causes pulmonary edema (an accumulation of excessive fluid in the lungs). 

Furthermore, it contributes to photochemical smog, causing serious environmental damage.

Effects of Smog

• Inversion, which traps pollution close to the ground, raises the pollution levels in Los Angeles, Beijing, Delhi, Mexico City, and other cities.
• It is typically highly toxic to humans, causing severe illness, shortening of life, or death.
• Smog is a mixture of particulate matter in the air, such as soot, and invisible toxic gases such as ozone (O3), carbon monoxide (CO), and sulphur dioxide (SO2), all of which are carcinogens (cancer causing agents).
• Temperature inversions are emphasised, and precipitation is reduced.
• Pollution-related Haze reduces visibility.

How is the Smog formed?

Smog is created when certain chemicals in our atmosphere interfere with sunlight, contributing to visible air pollution that we call smog. It is primarily caused by the emission of nitrogen oxides from vehicles, but it is also caused by the use of solvents or paints that release volatile organic compounds.

Conclusion

Smog is most commonly associated with the Los Angeles Basin of Southern California and its photochemical smog in the United States. Des Voeux’s report to the Manchester Conference of the Smoke Abatement League of Great Britain in 1911 on the over 1,000 “smoke-fog” deaths that occurred in Glasgow and Edinburgh during the autumn of 1909 popularised the term. There are at least two types of smog: sulphurous smog and photochemical smog. Sulfurous smog, also known as “London smog,” is caused by a high concentration of sulphur oxides in the air, which is caused by the use of sulfur-containing fossil fuels, particularly coal. Photochemical smog, also known as “Los Angeles smog,” is most prevalent in urban areas with a high concentration of automobiles. The nitrogen oxides and hydrocarbon vapours emitted by automobiles and other sources cause this type of smog, which then undergo photochemical reactions in the lower atmosphere.