New Delhi: Ground-level ozone emerged as one of Delhi’s most widespread air pollution challenges this May, with nearly half of the city’s air quality monitoring stations recording violations of national standards and several locations experiencing sustained exposure throughout the month.According to an analysis by Centre for Research on Energy and Clean Air (CREA), 24 of the city’s 45 monitoring stations recorded at least one exceedance of standards for ozone.The analysis identified five major ozone hotspots across the city. The highest concentration was recorded at Pusa (IITM), where the maximum eight-hour ozone average touched 292ug/m3, nearly three times the national standard of 100ug/m3. This was followed by NSUT Jaffarpur (229ug/m3), Commonwealth Sports Complex (208ug/m3), Delhi University North Campus (207ug/m3) and Chandni Chowk (178ug/m3). Pusa recorded ozone exceedances on 25 days during May, the highest in Delhi. Several other locations also witnessed persistent ozone exposure.The findings are notable because the affected stations span institutional, residential and urban-background areas, suggesting that ozone pollution is not restricted to traffic-heavy corridors or industrial clusters.Unlike particulate matter, ozone is not emitted directly from any source. “Delhi’s ozone hotspots reflect the science of how ozone forms: it is not directly emitted, but produced in the atmosphere when sunlight drives reactions between nitrogen oxides and volatile organic compounds, with transport and local chemistry shaping where it builds up most,” said Manoj Kumar, India analyst at CREA.The findings add to growing evidence that ozone is becoming a year-round concern in Delhi. Earlier analysis of Central Pollution Control Board data showed ozone emerging as the lead pollutant in the daily air quality index on 16 of the 28 days this Feb, eight days in March and two days in Jan. In contrast, ozone was the lead pollutant on nine days in Feb 2025 and did not emerge as the dominant pollutant in Feb 2023.The increasing prominence of ozone has prompted greater regulatory attention. Last Dec, the Union environment ministry informed National Green Tribunal that it would constitute an expert panel to study ground-level ozone pollution, mitigation strategies and associated health impacts.
