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Centre for Science and Environment issues alert on the
high ozone build up this summer in Delhi. Ozone is a deadly
pollutant and so far an unknown threat in Delhi. If this trend
worsens ozone can emerge as a silent killer.
Delhi must act now and effectively
New Delhi June 14, 2007:
A new analysis of the latest available air quality data in
Delhi carried out by the Centre for Science and Environment has
exposed that ground level ozone, known to be extremely hazardous
for human health and unheard of in Delhi so far, has begun to
raise its ugly head in the city. This is the result of the
deadly combination of high pollution levels and the soaring
mercury during this unusually hot summer.
Ozone is not emitted directly from any source. But other
pollutants primarily nitrogen oxides (NOx) and hydrocarbons that
are spewed by the growing number of vehicles and other sources
in the city react in the atmosphere under the influence of
sunlight and high temperature to form ozone. High dose of NOx,
volatile organic compounds, heat and sunlight are its deadly
recipe. When ambient temperatures and sunlight remain high for
several days as it has happened this summer and the air is
relatively stagnant ozone builds up fast in the air.
What has CSE found?
CSE has assessed ozone data that is generated by the Central
Pollution Control Board in its automatic monitoring stations in
Sirifort in South Delhi, and Delhi College of Engineering in
Bawana at the outskirts of city. The CSE analysis shows the
following:
- More frequent violation of ozone standards as the temperature rises: While ozone levels in Siri Fort did not exceed the WHO guidelines of 100 microgramme per cum (for daily maximum eight hourly average) for a single day during the winter month of January, the trend changed in the subsequent months. The number of days violating the WHO guidelines began to increase from February onwards when the climate warmed up --- around 11.5% of days in February, and 35.7% in April. This peaked in May when 43.3% of days reported violation of the WHO guidelines (see graph). The levels remained particularly elevated from May 20 to June 10 2007. This clearly coincides with the trend in the ambient temperature that increased to uncommonly high levels this summer – touching the range of 38 to 47 degree Celsius.
- The ozone levels recorded this summer are not common in Delhi: Though normally ozone levels are expected to be comparatively higher during summer, uncommonly high levels have been recorded this year. The maximum level in Siri Fort has scaled to 184.4 microgramme per cum on June 10. Bawana at the periphery of the city is taking the full brunt of this deadly pollution generated in the city. The levels touched a high of 197.7 microgramme per cum. While ozone is forming in the city it is also drifting to the periphery – that is the nature of ozone.
Why are we worried about ozone?
Ozone is very harmful as even short term exposure can trigger
serious health problems. It worsens the symptoms of asthma,
leads to lung function impairment and damages the 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 visits and hospital
admissions related to respiratory disease. Studies conducted in
other countries have found strong association between ozone and
daily premature deaths count.
Due to its high short term trigger effect ozone is included in
the daily smog and health alert programmes in other countries
such as Mexico city, the US cities among others. In Mexico city
elderly, children, and those suffering from respiratory and
cardiac problems are advised to stay indoors at the time of
elevated levels of ozone.
Delhi must act immediately at these early signs of the
impending doom. As the climate vagaries are expected to
increase, immediate steps are needed to control the pollutants
that help to form ozone in the air:
- The government must put in place control strategies for ozone forming gases especially NOx which is an important catalyst for ozone formation.
- Introduce daily health alert system to inform the sensitive population (children, elderly, and those suffering from respiratory and cardiac problems) about the high daily levels and enforce emergency pollution control measures such as restricting traffic, allowing only clean fuel and vehicles and public transport in affected areas till the time the high levels dissipate.
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