Context: The National Green Tribunal (NGT) has taken suo motu cognisance of a report highlighting the alarming rise of ground-level ozone pollution across major Indian cities. The tribunal noted that elevated ozone levels are closely linked to vehicular, industrial, and power-sector emissions of nitrogen oxides (NOx) and directed the Central Pollution Control Board (CPCB) to conduct an expert study and frame control measures.
Understanding Ozone Pollution
Ozone (O₃) is a gas formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. It is a secondary pollutant, meaning it is not directly emitted but produced through chemical reactions in the atmosphere.
- Stratospheric ozone (“good” ozone): Forms the ozone layer that protects Earth from harmful ultraviolet (UV) radiation.
- Tropospheric ozone (“bad” ozone): Accumulates near the ground, acting as a major air pollutant harmful to human health, vegetation, and ecosystems.
Scale of the Problem
- Ozone Exceedance: Highest levels recorded in Delhi-NCR and Mumbai, frequently breaching CPCB safe limits (2025).
- Rising Trend: Urban ground-level ozone has increased by over 30% since 2018, driven by vehicular exhaust, power generation, and industrial activity (MoEFCC, 2024).
- Health Impact: Linked to ~70,000 premature deaths annually in India (WHO, 2024) due to respiratory and cardiovascular diseases.
- Emission Sources:
- Transport sector: ~40% of NOx emissions.
- Power generation: ~30% of NOx emissions.
- Environmental Impact: Reduces crop yields by 5–20%, damages forests, and contributes to climate warming by trapping heat.
Regulatory and Policy Response
- NGT Directive (2025): Seeks a CPCB-led expert study on ozone sources and regional control strategies.
- National Clean Air Programme (NCAP): Focuses on reducing particulate matter (PM₂.₅ and PM₁₀), but experts now call for integrating ozone metrics into air quality management.
- CPCB Initiatives: Expanding ozone monitoring networks and promoting real-time data sharing.
- Urban Interventions: Transition to cleaner fuels, e-mobility, renewable power, and stricter NOx emission norms for industries.
Way Forward
- Develop Ozone Action Plans under NCAP focusing on precursor emission control.
- Promote electric mobility, public transport, and low-NOx technologies in thermal plants.
- Enhance green cover and urban ventilation corridors to disperse pollutants.
- Strengthen public awareness on ozone exposure risks and adaptive health measures.