Question

Which of the following is not a criteria air pollutant under the National Ambient Air Quality Standards (NAAQS)?

• A. CO2
• B. CO
• C. O3
• D. Pb

Answer 1

The Correct Option is A

In the context of the National Ambient Air Quality Standards (NAAQS), several criteria air pollutants are identified. These include: 

• Carbon Monoxide (CO): A colorless, odorless gas produced from vehicle emissions and industrial processes.
• Ozone (O₃): A reactive gas formed when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx).
• Lead (Pb): A metallic air pollutant released from industrial emissions and historically from leaded gasoline.

The question asks which of the given options is not a criteria air pollutant. Among the provided options—CO₂ (Carbon Dioxide), CO, O₃, Pb—only Carbon Dioxide (CO₂) is not categorized as a criteria air pollutant under the NAAQS.

Correct Answer: CO₂

Answer 2

The gas that is not a criteria air pollutant under the National Ambient Air Quality Standards (NAAQS) is CO2 (Carbon Dioxide).

Additional Context:

• Criteria Pollutants under NAAQS (India):
  • PM2.5/PM10: Particulate Matter
  • O₃ (Ozone): Ground-level ozone
  • CO (Carbon Monoxide): Incomplete combustion product
  • Pb (Lead): From industrial processes and legacy fuels
  • NO₂: Nitrogen Dioxide
  • SO₂: Sulfur Dioxide
• About CO₂:
  • Classified as a greenhouse gas, not criteria pollutant
  • Not directly harmful at ambient levels but drives climate change
  • Monitored separately under climate agreements
• Key differences:
  • Criteria pollutants have:
    • Immediate health impacts at low concentrations
    • National standards for permissible limits
    • Mandatory monitoring requirements
• Regulatory framework:
  • NAAQS established under Air (Prevention and Control of Pollution) Act, 1981
  • Revised standards issued by CPCB in 2009 and 2018
• Emerging considerations:
  • While CO₂ isn't a criteria pollutant, India monitors it under:
    • National Carbonaceous Aerosols Programme
    • Paris Agreement commitments

Correct Answer: (1) CO₂.