Rising NOx levels and volatile gases in the air, primarily from vehicles, form the recipe for ozone
Delhi has witnessed significant ozone build-up this summer, shows a latest analysis done by the 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 standards this summer.
CSE experts say warmer temperatures and the extreme heat waves are threatening to increase the frequency of days with unhealthy levels of ozone—with serious public health consequences.
Read more on ozone pollution
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.”
What 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:
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.
Scientists inform that ozone is a powerful oxidiser, which means it can damage cells in a process akin to rusting. Children and the elderly are at special risk. International studies have also found a strong association between ozone and daily premature death counts; deaths related to ozone exposure are more likely among people with pre-existing diseases.
Ozone that gets created in the polluted environment of a city can drift, depending on the wind direction, and move towards cleaner environs in the rural periphery. Here, it can begin to accumulate as it has less chances of reacting with other pollutants. It builds up faster at the outskirts of cities and can damage crops.
What do other governments do?
Ozone is included in the daily smog and health alert programmes in countries such as Mexico, the US and China. In Mexico City, the elderly, children and those suffering from respiratory and cardiac problems are advised to stay indoors when levels of ozone go up. The US-based National Research Council, part of the National Academies of Science, has recommended that local health authorities should keep the harmful effects of ozone in mind when advising people to stay indoors on polluted days. A study carried out in the US by scientists led by the University of Southern California and reported in Lancet, has found that in high-ozone areas the relative risk of developing asthma in children playing three or more sports was more compared to children playing no sports. Outdoor heavy exercise is not recommended as with every breath taken in, by athletes in particular, 10 to 20 times as much air, and thus pollutants, as sedentary people do.
What should Delhi do?
“Delhi needs to act immediately to protect public health,” says Roychowdhury. “Explosive increase in vehicle numbers, especially diesel vehicles that spew much higher levels of NOx and volatile organic compounds, can only worsen the deadly recipe needed for formation of ozone in the city with hot and extreme climate.”
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