Question

Which of the following pollutants are responsible for the cause of SMOG?

• A. From incinerators
• B. Emissions from vehicles
• C. Both incinerators and emissions from vehicles
• D. Bioreserves

Hint:

(P) \textbf{Smog} is air pollution reducing visibility, caused by smoke, fog, and chemical pollutants.
(Q) \textbf{Classical Smog:} Caused by SO$_2$ and particulates (from coal burning, industry).
(R) \textbf{Photochemical Smog:} Caused by reactions of NOx and VOCs in sunlight, forming ozone and other secondary pollutants.
(S) \textbf{Sources of Smog Precursors:}
(T) \textbf{Vehicular emissions:} Major source of NOx, VOCs, CO, PM.
(U) \textbf{Industrial emissions (including incinerators):} Source of SO$_2$, NOx, VOCs, PM.
(V) Both sources listed contribute to the pollutants that cause smog.

Answer 1

The Correct Option is C

Smog is a type of air pollution, originally named for the mixture of smoke and fog. There are two main types:
(F) Classical Smog (London Smog / Industrial Smog / Sulfurous Smog): Typically occurs in cool, humid conditions. Main pollutants: Sulfur dioxide (SO$_2$) and particulate matter (soot, smoke) from burning fossil fuels, especially coal (e.g., in industrial processes, power plants, domestic heating).
(G) Photochemical Smog (Los Angeles Smog / Summer Smog): Typically occurs in warm, sunny, dry conditions. Formed by complex photochemical reactions involving:
(H) Primary pollutants: Nitrogen oxides (NOx = NO + NO$_2$) and Volatile Organic Compounds (VOCs).
(I) Sunlight: Acts as a catalyst for the reactions. Main secondary pollutants formed include ozone (O$_3$), peroxyacetyl nitrate (PAN), aldehydes, and fine particulate matter. Primary sources of NOx and VOCs are vehicular emissions, industrial emissions, and solvent use. The question asks which pollutants are responsible for causing smog. The options refer to sources of pollutants.
(J) (a) From incinerators: Incinerators (for waste disposal) can release pollutants like particulate matter, SO$_2$, NOx, VOCs, and heavy metals if not equipped with adequate pollution control devices. These pollutants can contribute to both classical and photochemical smog.
(K) (b) Emissions from vehicles: Vehicular exhaust is a major source of NOx, VOCs, carbon monoxide (CO), and particulate matter. These are key precursors for photochemical smog and also contribute to particulate pollution in classical smog.
(L) (c) Both incinerators and emissions from vehicles: Since both sources can release pollutants that contribute to smog formation, this option is plausible if both are significant contributors.
(M) (d) Bioreserves: Bioreserves (protected natural areas) are generally sinks for pollutants or sources of clean air, not primary sources of smog-causing pollutants (unless, e.g., forest fires occur). Both incinerators and vehicular emissions are significant anthropogenic sources of air pollutants that cause or contribute to smog.
(N) Incinerators can release SO$_2$, Particulates (for classical smog) and NOx, VOCs (for photochemical smog).
(O) Vehicles are major sources of NOx, VOCs (for photochemical smog) and Particulates. Therefore, pollutants from both incinerators and emissions from vehicles are responsible for causing smog. \[ \boxed{\text{Both incinerators and emissions from vehicles}} \]