The heat has been unbearable and worse news follows. The summer pollution curve has taken an ugly turn as ground-level ozone, a highly reactive and harmful gas, has far exceeded the permissible limit, a report released by the Centre for Science and Environment (CSE) on Monday said.

“With heat wave raging in early June, ozone peaks to dangerous levels. Rising NOx levels and volatile gases in the air, primarily from vehicles, form the recipe for ozone when exposed to intense sunlight and high temperature. Ozone is a serious threat to those suffering from asthma and respiratory problems and can cause premature deaths if it is high even for a short duration during the day,” said Anumita Roychowdhury, executive director, research and advocacy and head of CSE’s air pollution programme.

Warning that Delhi needs to act fast to reduce the cocktail of gases that form ozone in the air, the CSE has warned that fast track action needs to be taken to ensure that pollution alert systems and next generation air pollution control measures are brought in.

This summer, a study of the real-time air quality data available from the key monitoring locations of the Delhi Pollution Control Committee for January to early June 2014, shows rapid build up of ozone and more frequent violation of standards this summer.

The CSE experts said warmer temperatures and the extreme heat waves are threatening to increase the frequency of days with unhealthy levels of ozone coupled with serious public health consequences.

Ms. Roychowdhury said: “Ozone is the new generation public health threat and a difficult challenge. It must be curbed at the early stages with stringent controls on nitrogen oxide and toxic and volatile gases.”

“This exposes worrying trends in the city. Though there is a variation in trends across months, there is a clear trend towards newer heights. While ozone levels are rising steadily with the onset of summer, it doubled up very quickly as soon as the heat wave hit Delhi in the first week of June. The average temperature has increased rapidly from 35 degrees Celsius on June 1 to more than 44 degrees Celsius on June 6. As a result, the ozone level shot up by 87 per cent in Civil Lines, 171 per cent in Punjabi Bagh, 315 per cent at Mandir Marg and 82 per cent at IGI airport within a week,’’ said the CSE note.