OZONE POLLUTION (Syllabus: GS Paper 3 – Env and Eco)

Context: A new study by Delhi-based think tank Centre for Science and Environment (CSE) has revealed a disturbing trend: Ground-level ozone pollution is on the rise across India’s major cities.

Ozone

• About: The ozone in the stratosphere, known as the "ozone layer," forms a natural protective barrier.
• Protection: It prevents harmful ultraviolet sunlight (UV-B) from reaching the Earth's surface, safeguarding plant and animal life.
• Termed "Good Ozone": This naturally occurring ozone is referred to as "good ozone" due to its essential protective role.

Ozone Needs Special Attention

• Formation of Ground-Level Ozone: Ground-level ozone is not directly emitted from any source; it is produced through a complex interaction between nitrogen oxides (NOx) and volatile organic compounds (VOCs) under sunlight.
• Sources: NOx and VOCs, the precursors of ozone, are emitted from vehicles, power plants, factories, and other combustion sources. VOCs can also originate from natural sources, such as plants.
• Health Risks: Ground-level ozone poses serious risks to those with respiratory conditions, such as asthma and chronic obstructive pulmonary disease (COPD), as well as children with premature lungs and older adults.

  Key Highlights of Study

  • Analysis of Metropolitan Areas: The researchers analyzed metropolitan areas of Bengaluru (Karnataka), Chennai (Tamil Nadu), Kolkata (West Bengal), Mumbai and Pune (Maharashtra). They also looked at data for Delhi-National Capital Region, Greater Ahmedabad (Gujarat), Greater Hyderabad (Telangana), Greater Jaipur (Rajasthan) and Greater Lucknow (Uttar Pradesh).
  • Exceedances: All 10 areas studied witnessed exceedances of the national ozone standard, with Delhi being the most affected.
  • Rapid Increase in Smaller Cities: Smaller cities like Ahmedabad and Pune are experiencing a particularly rapid increase in ozone pollution, the report further found.
  • Trade-Off Between Particulate Pollution and Ozone: Global experience indicates a common trade-off: as particulate pollution is reduced, issues with nitrogen oxides (NOx) and ground-level ozone increase, the report pointed out.
  • National Ambient Air Quality Standard: Due to its highly toxic nature, the national ambient air quality standard for ozone is set only for short-term exposures (one-hour and eight-hour averages), with compliance measured by the number of days that exceed these standards.