Rising pollution and sunny days have taken the concentration of ground-level ozone-a harmful gas-to alarming levels in Delhi's air, making children and the aged vulnerable to the pollutant.
Ground-level ozone is formed when sunlight reacts with oxides of nitrogen, oxygen and hydrocarbons emitted from vehicles. Against an eight-hourly standard of 100 micrograms per cubic meter (ug/m3), residential areas like RK Puram and IGI Airport have clocked as high as 382. Most days in April so far have breached this standard, as per air-monitoring data by government agencies.
Breathing ozone can trigger many health problems including chest pain, coughing, throat irritation, and congestion, says the US Environment Protection Agency. Ground-level ozone also can reduce lung function, inflame the lung lining and permanently scar lung tissue, it says.
Controlling the rise of this pollutant is hard as it does not have a direct source of emission.
"We think the rise could be because more oxides of nitrogen are able to react with oxygen freely in the absence of particulate matters (fine particles) because we managed to reduce that (particulate matters) by introducing CNG and stricter emission norms. Increase in NOx gases is a tradeoff while capping the emission of fine particles," said Prof S.P. Gautam, chairman, CPCB. "It makes sense to monitor ozone more and bring out pollution alerts."
This month, the eight-hourly average has breached the standard by several notches on most days, sometimes clocking 166 ug/m3 and sometimes crossing even 300 in Civil Lines, Mandir Marg, Punjabi Bagh, IGI, ITO, Siri Fort and other places where air is being monitored 24X7 by the Delhi government and the CPCB. Summer worsens the rise in ozone levels due to the lethal mix of sunlight and vehicular pollution.
"Ozone is included in the daily smog and health alert programmes in countries such as Mexico and the US. Delhi must introduce a daily pollution alert system to inform people, especially those suffering from respiratory and cardiac problems about the high daily levels," said Anumita Roychowdhury, associate director of Centre for Science and Environment.