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City sees spike in ozone pollution as winter recedes
Gurugram: With the winter chill subsiding and concentrations of particulate matter (PM) pollutants dropping to less-than-extreme levels, the city has begun seeing
Gurugram: With the winter chill subsiding and concentrations of particulate matter (PM) pollutants dropping to less-than-extreme levels, the city has begun seeing a spike in the concentration of another pollutant — ozone.
According to the Central Pollution Control Board’s daily air quality index (AQI) bulletin, the city did not witness a single day in January when ozone was the primary pollutant. However, since February 1, Gurugram has recorded five days when ozone overtook PM2.5 as the city’s most prominent atmospheric contaminant.
As per data from the air quality monitor at Vikas Sadan, Sector 11, the 24-hour average concentration of ozone for January was 34.3 µg/m³, which rose to 53.4 µg/m³ in February. While these numbers are not a cause for alarm (the ‘safe’ threshold of ozone as per India’s air quality standards is 100 µg/m³ over eight hours), experts said they indicate further spikes as summer meteorology takes over.
On Monday, ozone levels in the city touched as much as 180 µg/m³ at 4pm, the highest reading in at least two months. HT had reported, on June 25 last year, of a spike in ozone levels while PM pollutants remained at a season-low during the summer. At the time, ozone levels had spiralled to 268 µg/m³ over an eight-hour period.
A senior scientist at the CPCB’s air quality lab in Delhi explained, “Presence of sunlight has a direct impact on formation of ground level ozone. Given the intense heat waves that occurred last year, the spike in ozone is plausible. Ozone levels tend to spike when winter conditions subside, and its presence is felt most during the day. At night, ozone levels tend to deplete, before spiking again during the afternoon, when sunlight is available.”
Polash Mukherjee, an air quality expert with the National Research Development Corporation (NRDC), said, “Ozone is a composite, or a secondary pollutant, which is formed due to chemical reactions undergone by other pollutants, such as nitrogen oxides (NOx). Heat, which is a catalyst, facilitates these reactions. Hence, higher concentrations of ozone are seen during the summer months.”
Ozone pollution is thus also a clear indicator of vehicular pollution, which results in higher concentration of NOx.
Official data indicates that ozone pollution affects Gurugram’s urban centre more than the city’s peripheral areas. In Gwal Pahari, where the CPCB gathers data from a second air quality monitor at the National Institute for Solar Energy, the daily average concentration of ozone increased from 22.3 µg/m³ in January to 29.1 µg/m³ in February. The experts said the difference can be attributed to more primary emissions from vehicles in the vicinity of Vikas Sadan, but that further study is required for a conclusive explanation.
Sumit Sharma, director at TERI’s climate change division, said, “After PM2.5 and PM10, ozone poses the greatest health risk among common pollutants. However, the issue is largely neglected at a policy level, perhaps because particulate matter is seen as a bigger threat, and emerges as an issue when air quality visibly deteriorates in the winter. Several developed countries that have launched successful campaigns against primary emissions, the policy focus has shifted to ozone. We are yet to see this in India.”
Niranjan Raje, a former member of the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority (EPCA) and a Gurugram resident, said that the health risk associated with ozone pollution is high because of its invisibility. “One cannot see ozone, which is a gaseous pollutant. But one can feel ozone. It causes irritation of skin, tightening of chest, and other issues. In summer months, people tend to ascribe these symptoms as a direct result of heat. This is only partly true,” Raje said.
Unlike the ‘good’ ozone present in the earth’s ozone layer, which protects us from harmful ultraviolet (UV) radiation, ground level ozone is highly reactive and can have adverse impacts on human health, severely exacerbate respiratory ailments such as asthma and bronchitis, Raje added.
Kuldeep Singh, regional officer, HSPCB, said, “We have prepared an air quality action plan for Gurugram, which will tackle about 12 different parameters as per a 2009 state notification. The plan is designed to maintain all round wholesomeness of air quality and will bring down concentrations of all pollutants, gaseous and particulate, in a phased and sustained manner over a period of time.”
Taking note of the severity of ozone pollution, a 2018 report by the Centre for Science and Energy had recommended that governments take active steps to mitigate primary pollutants, which lead to its formation. These steps involved curbing private vehicle usage, increasing electric mobility, scaling up public transport and pedestrian infrastructure, deploying citywide parking management, and aggressively controlling industrial emissions.
