Q. Which of the following is/are secondary pollutant(s)?
  1. Ozone
  2. Sulphur dioxide
  3. Nitrogen oxides
  4. Carbon Monoxide
Select the correct option from codes given below:

Answer: 1 Only
Notes:
  1. Ozone (O3) is a secondary pollutant formed by the reaction of sunlight on primary pollutants like nitrogen oxides (NOx) and volatile organic compounds (VOCs).
  2. Sulphur dioxide (SO2) is a primary pollutant emitted directly from activities like burning of fossil fuels.
  3. Nitrogen oxides (NOx) are primary pollutants emitted from combustion sources.
  4. Carbon monoxide (CO) is also a primary pollutant directly emitted from incomplete combustion.
So out of the given options, ozone (O3) is the only secondary pollutant.