Indian Cities, New Study Warns
Ozone used to disappear when winter ended. Not anymore. A six-year study finds toxic ozone now blankets Indian cities through most of the year — and Delhi-NCR has it worst. The Centre for Science and Environment (CSE) tracked ozone levels from 2021 to 2026. Heat, strong sunlight and rising emissions are pushing readings far above safe limits, even in cities once seen as only mildly polluted. Ozone forms when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in sunlight and heat. Unlike smoke or dust, it cannot be seen. It damages lungs, crops and the climate. “Rising ground-level ozone and prolonged exposure windows are transforming India’s localised, winter-time particulate problem into a year-round, transboundary crisis that peaks during the summer,” said Anumita Roychowdhury, executive director of CSE and the study’s lead author.
