Bengaluru sees spike in toxic ozone levels: Alarming 29% rise sparks public health concern

A recent analysis by the Centre for Science and Environment (CSE) has flagged a worrying surge in ozone pollution across Bengaluru, recording 45 days of ozone exceedance between March and May 2025- a 29% increase compared to the same period last year. This significant rise signals earlier and more intense ozone formation, raising serious concerns for public health and agriculture.

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The data from the city’s air quality monitoring stations reveal that nearly half the summer days crossed the safe ozone limit. The worst-hit day was March 31, when 4 out f 14 monitoring locations breached the threshold. Hombegowda Nagar topped the list with 31 high-ozone days, followed by Bapuji Nagar. While a comparison with May 2024 shows a drop in hourly ozone peaks, it’s evident that concentrations now spike earlier in the day and dissipate faster.

Experts explain that ground-level ozone is not emitted directly but forms through sunlight-driven chemical reactions involving pollutants like nitrogen oxides (NOx) and Volatile Organic Compounds (VOCs), primarily from vehicle exhausts, factories, and power plants. Unlike primary pollutants, ozone behaves like a secondary, regional pollutant-spreading beyond urban limits and posing risks to distant areas.

Health experts warn that prolonged ozone exposure can worsen respiratory conditions such as asthma and bronchitis, particularly affecting children, the elderly, and those with pre-existing lung issues. The frequency and severity of asthma attacks are also increasing, often leading to hospital admissions.

CSE researchers note a troubling shift in ozone peaks from summer to early spring (February-April), with levels rising 31% during that window compared to last year. The shift is attributed to increasing temperatures, stronger sunlight, and changes in precursor emissions.

To combat the crisis, CSE recommends Bengaluru’s clean air action plan focus heavily on ozonc control-advocating for more zero-emission vehicles, cleaner fuels, improved industrial practices, and waste management.

The situation is not limited to Bengaluru. Cities like Mumbai, Hyderabad, Delhi, Kolkata and Chennai have also seen dangerously high ozone levels this summer, pointing to a broader national challenge