Types of Smog 

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Smog results in intense air pollution. It derived its name from both fog and smoke. It is opaque in nature and has a typical odor. It is a mixture of nitrogen oxides, sulfur oxide, ozone, smoke and other particles. Smog is a type of man-made pollution which is caused as a result of industrial emissions, vehicle emissions etc ..

There is both winter smog and summer smog. While summer smog happens due to the photochemical formation of ozone, winter smog is often the result of combustion of coal and other fossil fuels. Hence, both primary and secondary pollutants are responsible for the formation of smog. 

‘Photochemical smog’ is among the most common types of air pollution. In recent years, major cities across the globe have been witnessing significant rise in smog pollution, due to the inversion effect of the atmosphere which traps pollution close to the ground.



Smog is basically classified into:

Photochemical Smog/Los Angeles Smog

Also known as ‘summer smog’, it is basically generated from the combustion of fuels in engines and also a result of the industrial fumes. Photochemical smog is formed as a result of the chemical reaction of sunlight, nitrogen oxides, and volatile organic compounds in the atmosphere. While Nitrogen oxides and other volatile organic compounds are regarded as the primary pollutants, peroxyacetyl nitrates (PAN), tropospheric ozone, and aldehydes are considered the secondary pollutants.

Photochemical smog causes eye irritation, shortness of breath and decreasing vision. 

Sulfurous Smog/London Smog

It is formed due to the presence of high concentration of oxides of sulfur in the air. In 1952, a smog episode in London led to the death of 4,000 people! Sulfurous smog causes irritation to human eyes, nose, and lungs. Volcanoes also emit sulfur dioxide into the atmosphere.


Factories, vehicles and several other consumer products contribute to the formation of smog. In urban areas, 50 percent of  the smog is formed as a result of vehicle emissions.

Use of coal as fuel: Combustion of coal produces high concentration of sulfur oxides. While burning, coal produces a significant amount of smoke.

Industrial and vehicular emissions: Emissions from the transport sector is a major contributor of smog. Peak traffic times’ cause some serious damage! Similarly, industries also release harmful gasses and fumes which leads to the formation of smog.

Excessive waste production: When waste is burnt, it emits harmful gasses, which later transforms into smog.

Fireworks: On most of the occasions, a single night of firework display causes enormous air pollution. For example, during diwali, a dense layer of smoke can be seen floating in the air.

Burning agricultural material: Burning of old crops leads to formation of smog. For example, every year, several farmers in Indian states like Haryana, Punjab and Uttar Pradesh burn their rice crop fields for growing wheat.

Construction activities: Large amounts of dirt and dust are produced in areas of high construction density. 

Natural causes: High concentrations of sulfur dioxide (primary constituents of smog) are produced during volcanic eruptions. Certain plants contribute towards smog formation as well


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Check your knowledge

Answer) It is mainly formed due to the chemical reaction of sunlight, nitrogen oxides, and volatile organic compounds. Basically, it is a combination of primary and secondary pollutants. 

Answer) While fog is produced due to the presence of water droplets in the air, smog is created due to the presence of particulates, smoke, and fog in the air. Fog is non-toxic, breathing smog leads to lung cancer, asthma, and breathing disorders. 

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