Mega cities in India see high concentration of ozone pollution this summer

ALL mega cities in India, including Kolkata, Bengaluru, Mumbai, Hyderabad and Chennai, saw high concentration of ground-level ozone pollution this summer season, according to a new analysis by think tank Centre for Science and Environment (CSE).

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A previous analysis had shown that ozone, instead of particulate matter, was the main pollutant in Delhi's daily Air Quality Index (AQI) on several days this summer.

The new analysis by the CSE's Urban Lab highlighted that ozone, unlike primary pollutants, is not released directly from any source.

It forms through complex chemical reactions involving nitrogen oxides (NOx), volatile organic compounds (VOCs) and carbon monoxide (CO), pollutants emitted by vehicles, power plants, industries and other sources of combustion.

These substances react in the presence of sunlight, leading to the formation of ozone at the ground level.

Anumita Roychowdhury, executive director at the CSE, said: "If unchecked, this can become a serious public health crisis as ozone is a highly-reactive gas and can be harmful even with short-duration exposures."