Ground-level ozone pollution: An emerging public health crisis in Delhi

Delhi is facing an escalating public health crisis as dangerous ground-level ozone (O3) pollution surges, displacing particulate matter as the city's dominant summer pollutant. New research from IIT Kharagpur and Kerala University highlights a critical link: heatwaves are drastically intensifying O3 formation, leading to over 26,500 associated deaths in India in 2024 from ischemic heart disease and chronic obstructive pulmonary disease (COPD) during these extreme weather events. This invisible, toxic gas, a byproduct of vehicle and industrial emissions reacting with intense sunlight, is now pervading residential areas for prolonged periods, marking a dire shift in the capital's perennial struggle for breathable air. This emerging multi-pollutant crisis has seen ozone exceed national eight-hour safety standards for an average of 14.2 hours daily across Delhi-NCR between March and May 2025, with hotspots like Pusa recording nearly three times the permissible limits in May 2026. India, already ranking third globally in ozone exposure according to the State of Global Air 2025 Report, is increasingly vulnerable as climate change accelerates the chemical reactions that produce this respiratory and cardiovascular threat. The National Green Tribunal (NGT) in September 2024 flagged inadequate, general measures by the Delhi Pollution Control Committee (DPCC), Central Pollution Control Board (CPCB), and Commission for Air Quality Management (CAQM), demanding targeted strategies. While Delhi Chief Minister Rekha Gupta launched the Air Pollution Mitigation Action Plan 2026 in April, emphasizing vehicular emission controls and dust management, experts from organizations like CREA and CSE caution that without concrete, measurable targets and robust enforcement, the plan risks merely echoing past efforts. The focus must broaden beyond particulate matter to aggressively curb nitrogen oxides (NOx) and volatile organic compounds (VOCs) regionally, as ozone drifts across the National Capital Region. Authorities are now under pressure to integrate targeted ozone-specific interventions and real-time monitoring into their broader pollution control frameworks, as summer heat promises to amplify this invisible killer.