NEW DELHI — The Central Pollution Control Board (CPCB) has informed the National Green Tribunal (NGT) that the Delhi-National Capital Region (NCR) and the Mumbai Metropolitan Region recorded the highest exceedances of ground-level ozone concentration compared to other urban regions in India.
The CPCB report submitted on September 25, 2025, analyzed ozone levels across 178 monitoring stations, applying the 2 per cent exceedance criteria of the National Ambient Air Quality Standards (NAAQS).
Causes and Committee Formation
Tropospheric ozone a harmful pollutant, is formed from complex photochemical reactions involving precursors such as Volatile Organic Compounds (VOCs) and Nitrogen Oxides typically under conditions of high heat and sunlight. The report attributes elevated summer ozone levels primarily to emissions from the transport sector, power plants, and industrial activities.
In light of the persistent threat, the NGT was updated on existing governmental efforts:
• Expert Committee: The Union Ministry of Environment, Forest and Climate Change has recommended the constitution of an expert committee to study and recommend specific measures for controlling the sources of ozone and its precursors.
• NGT Directive: The NGT has granted the time until November 12, 2025, to submit the proposed Terms of Reference and the names of experts for this high-level committee.
The CPCB submission was made in response to a March 2025 NGT directive regarding a previous report that highlighted a “dangerous increase in ozone pollution across urban India.”