Daily News Analysis ‘High summer ozone levels in big cities: Study’ : 17 July

Key Findings:

A CSE analysis shows that ozone levels in Indian megacities were high during summer 2025.
Bengaluru and Mumbai exceeded safe ozone limits on over one-third of summer days.
Data was collected from 80 air quality stations across Mumbai, Kolkata, Bengaluru, Chennai, and Hyderabad.
In Delhi, ozone levels exceeded the safe limit on all summer days (March 1 – May 31).
Bengaluru exceeded limits on 45 out of 92 days, a 29% increase from last year.
Chennai had an excess of 15 out of 92 days, compared to zero days last year.
Mumbai recorded an excess of 32 days, showing a 42% decline from last year.
Kolkata had ozone exceedance on 22 days, a 45% improvement over last year.
Ozone is measured using an 8-hour average (standard is 100 µg/m³) due to its reactive nature.
Ozone is a secondary pollutant, formed by reactions between other pollutants under sunlight, especially in summer.
Health risks include: harm to airways and lungs, worsened respiratory illnesses, and reduced lung function.
CSE warns of a growing public health risk due to persistent ozone pollution, even in non-northern cities and across seasons.

Ozone pollution in major Indian cities during summer 2025 has exceeded safe limits, raising public health concerns, as reported by the Centre for Science and Environment (CSE).