Ground-level ozone – Delhi-NCR: An invisible threat

June 17, 2025

New Delhi June 13, 2025: New analysis of Centre for Science and Environment (CSE) finds higher number of days exceeding the standard for ozone and also wider geographical spread of the problem in Delhi and the National Capital Region (NCR) this summer. CSE issues the alert on the multi-pollutant crisis in in the region.

This summer, several days have recorded ozone as the lead pollutant in the daily Air Quality Index (AQI) instead of particulate matter. Out of 18 days between May 25-June 11, ozone has been the lead pollutant on 12 days. But there is no system to address this problem under the current Graded Response Action Plan for emergency action to reduce exposures or to address its sustained mitigation with longer term clean air action plan. While the policy attention are nearly fully drawn towards particulate pollution, co-control of the toxic gases from vehicles, industry and combustion sources that contribute to ozone formation in the air, are neglected. If unchecked this can become a serious public health crisis as ozone is a highly reactive gas.