Home Impact of Development Environmental

Searing Heatwave Leads to Deadly Ozone Pollution in Delhi

  • Heatwaves in Delhi, India
    Heatwaves in Delhi, India. © Harsha K R / CSE
    Summer pollution curve takes an ugly turn as ground-level ozone, a highly reactive and harmful gas, far exceeds the permissible limit.
  • With heatwave raging in 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.
  • Delhi needs to act fast to reduce the cocktail of gases that form ozone in the air.
  • Delhi government must fast track pollution alert system and next generation air pollution control measures, says CSE.

New Delhi, IndiaDelhi has witnessed significant ozone build-up this summer, shows a latest analysis done by Centre for Science and Environment (CSE). A study of the real-time air quality data available from the key monitoring locations of the Delhi Pollution Control Committee (DPCC) for the period January to early June 2014 shows rapid build-up of ozone and more frequent violation of ozone standards this summer.

CSE experts say warmer temperatures and the extreme heatwaves are threatening to increase the frequency of days with unhealthy levels of ozone – with serious public health consequences.

Ground-level ozone is not directly emitted by any source. This is formed when oxides of nitrogen (NOX) and a range of volatile gases – primarily from vehicles and other sources – are exposed to each other in sunlight. Warm and stagnant air increases the formation of ozone, which is known to be extremely hazardous for human health.

According to Anumita Roychowdhury, Executive Director, Research and Advocacy, and Head of CSE’s Air Pollution Programme, “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 (NOx) and toxic and volatile gases, the major ingredients of ozone recipe.”

Air Pollution in Delhi, India
Rising nitrogen oxide levels and volatile gases in the air, primarily from vehicles, form the recipe for ozone.

What has CSE found?

CSE has analysed ozone data from the automatic monitoring stations of the DPCC located in R K Puram, Civil Lines, Mandir Marg and Punjabi Bagh – all residential areas – as well as the IGI airport, a heavy traffic and peripheral location. This exposes worrying trends in the city. Though there is a variation in trends across months, there is a clear trend towards newer heights.

The key highlights are:

  • Heatwave Worsens Ozone Pollution:

While ozone levels are rising steadily with the onset of summer, it doubled up very quickly as soon as the heatwave hit Delhi in the first week of June.

The average temperature has increased rapidly from 35 degree C on June 1, to more than 44 degree C on June 6, 2014. 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. The average ozone level of all locations was 73 microgramme per cubic metre on June 1 that doubled beyond the standards by June 5 (See Delhi Summer Ozone Factsheet on CSE website).

  • More Frequent Violation of Ozone Standards as the Temperature Rises this Summer:

CSE has tracked daily ozone since January 2014. This shows that frequency of days violating ozone standards has increased with the onset of summer.

For instance, in R K Puram, while 22.5 per cent of the days in January and 39.2 per cent days in February have exceeded the standards, as much as 87 per cent of days in March, 80 per cent in April and 64.5 per cent in May have exceeded the safe limit of eight-hour average of 100 microgram per cubic metre. In Civil Lines, a pollution hotspot, about 48 per cent of the days in January and 60.7 per cent in February had exceeded the standards, but this increased to 86.6 per cent in April and all 12 days analysed (100 per cent) for May. In Mandir Marg, 83.3 per cent of days in April and 83.8 per cent in May have violated the standards. In the high traffic area of IGI airport at the periphery of Delhi, the month of May has been particularly bad with 93.5 per cent days exceeding the standard. This trend could have been worse if the city had not experienced intermittent rains with cooling effect this summer.

  • Peak Ozone Levels are Very High:

While the number of days violating the ozone standards has increased during summer, the daily peaks have also hit dizzying heights. On several occasions and locations, very high peak levels have been noted, close to 2.5 to three times the standards. This is of serious concern as even short duration exposure to high ozone levels can cause great harm. This is one of the reasons why ozone standards are set for eight hours average as well as one hour average.

Why should we worry about ozone?

Ozone is an extremely harmful gas – particularly for those involved in outdoor activities. Just a few hours of exposure to it can trigger serious health problems, especially among those who are already suffering from respiratory and asthmatic problems. Ozone worsens symptoms of asthma, leads to lung function impairment and damages lung tissues. Chest pain, coughing, nausea, headaches and chest congestion are common symptoms. It can even worsen heart disease, bronchitis and emphysema. It increases emergency hospital visits and admissions related to respiratory diseases.