Ozone levels exceeding permitted levels: study

Despite lockdown, more days witnessed higher and longer duration of ozone spells

Published - July 31, 2021 01:33 am IST - New Delhi

A Centre for Science and Environment study has found that ozone levels are exceeding the permitted levels even during winter in Delhi-NCR, making the smog more “toxic”.

“Ozone is now a round-the-year problem requiring urgent [action] and the situation demands refinement of clean air action plan to add strategies for ozone mitigation, with stronger action on vehicles, industry and waste burning,” says CSE Executive Director Anumita Roychowdhury.

Despite the pandemic and lockdowns, more days and locations witnessed higher and longer duration of ozone spells, the study said.

Year-round menace

Ozone, a highly reactive gas and dangerous for those suffering from respiratory conditions and asthma, is becoming more widespread in Delhi and NCR across all seasons, the CSE said.

“Contrary to the notion that ozone, produced photochemically from interaction between gases in the presence of sunlight, is predominantly a summer phenomenon, the analysis finds the gas has emerged as an equally strong concern during winter as well,” it said.

Occasional exceedance

The study was done by analysing the Central Pollution Control Board (CPCB) data. The CSE analysis found that the city-wide average largely remains within the standard with just occasional exceedance. But the ‘good’ category days have fallen to 115 days in 2020, which is 24 days less than in 2019.

“A location-wise analysis presents a different story. It shows that exceedance of the eight-hour average standard is quite widely distributed in the city. At the moment, it is not possible to compute the peak pollution in the city as the data that is available from CPCB is capped at 200 ug/m3. This also makes daily AQI reporting ineffective,” the study said.

Even smaller towns of NCR, including Bulandshahr in Uttar Pradesh and Bhiwani in Haryana, appeared in the top 20 list of ozone-afflicted towns and cities. South Delhi locations dominate the list with four mentions in top 10.

0 / 0
Sign in to unlock member-only benefits!
  • Access 10 free stories every month
  • Save stories to read later
  • Access to comment on every story
  • Sign-up/manage your newsletter subscriptions with a single click
  • Get notified by email for early access to discounts & offers on our products
Sign in


Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide by our community guidelines for posting your comments.

We have migrated to a new commenting platform. If you are already a registered user of The Hindu and logged in, you may continue to engage with our articles. If you do not have an account please register and login to post comments. Users can access their older comments by logging into their accounts on Vuukle.