New Delhi, May 1 -- As Delhi transitions from spring to the peak of summer, a silent, invisible pollutant has begun to build up in the air: Ground-level ozone.

Unlike winter smog, which is often visible and heavy, ozone pollution strikes more subtly. It forms when heat and sunlight react with nitrogen oxides (NOx) and volatile organic compounds (VOC) from vehicles, industries and other combustion sources. The result is a powerful oxidant that peaks during the warmest hours of the day - when outdoor activity is at its highest.

In under two months - between March 1 and April 25, 2025 - Delhi has recorded 56 days of ozone exceedances. This means that on every single day during this period, at least one location in the city breached the 8...