Ozone ranges in all megacities of the nation have been excessive throughout the summer season of 2025, with Bengaluru and Mumbai recording ranges above prescribed requirements for over a 3rd of summer season days, stated a brand new Centre for Science and Surroundings (CSE) evaluation.
The brand new evaluation used information from 80 steady ambient air high quality monitoring stations throughout Mumbai, Kolkata, Bengaluru, Chennai, and Hyderabad.
When the CSE analysed Delhi’s ozone (O3) ranges final month, they had been discovered to have exceeded the prescribed customary on every summer season day between March 1 and Could 31.
Ozone ranges in Bengaluru exceeded prescribed limits 45 out of the 92-day summer season days monitored by the CSE, which was a 29 per cent enhance in comparison with final summer season, the brand new evaluation stated. In Chennai, ozone ranges exceeded prescribed ranges for 15 out of 92 days, compared to no exceedance days for the corresponding interval final yr.
Mumbai recorded ozone exceedance on 32 out of 92 days, marking a 42 per cent decline in comparison with the corresponding interval final yr. In Kolkata, about 22 out of 92 days this summer season registered an exceedance of ozone requirements, which was an enchancment over final yr by 45 p.c.
Because of its reactive nature, O3 ranges are monitored in an eight-hour common interval, as an alternative of 24-hour averages, not like different pollution. The prescribed ozone customary for an eight-hour interval is 100 micrograms/cubic metre as per the Nationwide Ambient Air High quality Requirements (NAAQ).
Anumita Roychowdhury, government director, CSE, stated, “If unchecked, this could grow to be a critical public well being disaster as ozone is a extremely reactive gasoline and may be dangerous even with short-duration exposures. In distinction to cities in north India, the place excessive summer season temperatures and intense photo voltaic radiation can result in ozone ranges exceeding the requirements, different cities in heat climates are experiencing constant ozone exceedance throughout different seasons as nicely.”
Story continues beneath this advert
“Floor-level ozone is starting to emerge as a pollutant of concern with cities experiencing days exceeding the 8-hour requirements. Whereas the extent of exceedance is predicted to be increased throughout the summer season months with sturdy sun-shine days and warmth, that is rising as a round-the-year downside within the hotter local weather. Clear air motion plans for cities and the states want to handle this multi-pollutant problem urgently,” CSE really useful in its evaluation.
Ozone will not be a main, however a secondary pollutant fashioned by means of chemical reactions between different pollution beneath daylight. Therefore, summer season months see a spike in ozone concentrations. These chemical substances embrace nitrogen oxides (Nox), risky natural compounds, and carbon monoxide (CO), pollution emitted from car tailpipes, energy crops, factories, the CSE evaluation said.
Floor-level ozone can have an effect on the airways and lungs adversely, enhance susceptibility to infections, worsen respiratory illnesses, and reduce lung operate.
