According to an analysis conducted by the Center for Science and Environment (CSE), the summer of 2022 – one of the hottest in history – saw widespread ozone depletion, making Delhi-NCR’s air more toxic. The green think tank’s assessment is based on publicly available granular real time data (average 15 minutes) from the Central Control Room for Air Quality Management, the official online portal of the CPCB. The researchers obtained data from 58 official stations in Delhi-NCR.
The analysis tracked the excess at each station. Violation of the standard by a single station is considered more than a city. Days with multiple stations higher than the norm indicate the severity of the endemic spread and the number of people exposed. The green thinktank said this year, due to the initial onslaught of heatwaves, the endemic spread of ground-level ozone, which began in March itself, has been the worst ever.
Dangerous build-up of ground-level ozone can occur at any time during the year, but it usually occurs in small areas. For its wide endemic spread, warm and sunny climates are usually present in summer, especially during May. But this year, the frequency and spread of ozone depletion started early – in the month of March. Every year in some places in Delhi-NCR, ground-level ozone generally exceeds the safety standard during all summer days. But the spatial spread (number of stations exceeding the norm across the city) has been much higher this year.
On an average, 16 stations have exceeded the standard daily in this March and April, an increase of 33 per cent from March and April 2021. During 2020, when the lockdown reduced the precursor gases needed for the formation of ground-level ozone, the number was up to 10 stations per day, the report said. Dr KS Shooting Range in South Delhi is the worst affected in Delhi-NCR. The ground level ozone concentration at this location exceeded the norm for 85 days this March-May.
JLN Stadium, RK Puram and Nehru Nagar followed behind. Greater Noida is the major hotspot outside Delhi. It said that Faridabad has the least number of cases of ozone depletion at the ground level in the region. Patparganj in East Delhi recorded the highest increase in the number of days above the norm as compared to the average of the last three years. It registered a dramatic jump of 68 additional days with excesses. This is followed by Sector 116 of Noida and Mandir Marg next to Rashtrapati Bhavan.
Siri Fort and Bawana in Delhi recorded the largest reduction in the frequency of overdose as compared to the average of the last three years. This year his growth was reduced by more than 40 days. Gurugram Sector 51, Dwarka Sector 8 and Najafgarh were the other places where maximum improvement occurred. After Delhi-NCR, which recorded ozone excess on almost all days of this summer, Mumbai was the second most affected metro with 75 days of excess.
Kolkata-Howrah and Hyderabad each recorded an excess of 43 days. Even though the number of days in Kolkata-Howrah has been less than in Mumbai, its citywide concentration is 30 percent higher than in Mumbai this summer. CSE said ozone’s complex chemistry makes it a difficult pollutant to track and mitigate. Ambient ozone at ground level is not emitted directly from any source. It results from the complex interaction between NOx and volatile organic compounds (VOCs) that are emitted from vehicles, power plants, factories and other combustion sources.
These undergo cyclic reactions in the presence of sunlight to generate ozone at the ground level. VOCs can also be emitted from natural sources, such as plants. This highly reactive gas has serious health consequences. Children and older adults with respiratory disease, asthma, chronic obstructive pulmonary disease, and especially those with prematurity, are at serious risk.
It can cause inflammation and damage to the airways, making the lungs more susceptible to infection, exacerbating asthma, emphysema and chronic bronchitis, and increasing the frequency of asthma attacks leading to hospitalization. .