New Delhi: This year, the city recorded its highest annual average of nitrogen dioxide levels since 2018. The average concentration of the toxic gas till Dec 22 was 47 micrograms per cubic metre, up from 43 µg/m³ last year. It was higher than the annual national standard of 40 µg/m³ and 4.7 times more than World Health Organisation’s annual safe guideline of 10 µg/m³. A highly reactive gas generated by burning fuel, it contains emissions from vehicles, power plants and industries.Central Pollution Control Board’s data, analysed by EnviroCatalyst, a think tank, shows that the annual average nitrogen dioxide concentration was 35 µg/m³ in 2023, 40 µg/m³ in 2022 and 2021, 39 µg/m³ in 2020, 45 µg/m³ in 2019 and 48 µg/m³ in 2018. High-traffic zones and industrial areas feature among the hotspots. The highest annual mean concentration was recorded at ITO — a traffic hotspot with long waiting hours at red lights — at 69 µg/m³, followed by 68 µg/m³ at IGI Airport’s Terminal 3. Anand Vihar and Shadipur, each at 66 µg/m³, Wazirpur at 65 µg/m³, Lodhi Road at 62 µg/m³ and Jahangirpuri (61 µg/m³ ) were the other hotspots.“Burning of waste in several localities has also contributed to its elevated levels, and that should be controlled. It means there is a need to reduce emissions from local sources within the city,” said Sunil Dahiya, founder and lead analyst at EnviroCatalyst. Areas that witnessed high nitrogen dioxide concentrations this year were IIT-Delhi (59 µg/m³), Okhla Phase-2 (59 µg/m³), Dwarka Sector-8 (56 µg/m³), Pusa (54 µg/m³), Chandni Chowk (53 µg/m³), Najafgarh (52 µg/m³), Major Dhyan Chand National Stadium (52 µg/m³), Jahangirpuri (51 µg/m³), Dr Karni Shooting Range (50 µg/m³) and Patparganj (50 µg/m³). Dipankar Saha, former head of CPCB’s air laboratory, said the gas is produced due to high temperature and high-pressure combustion of fuel. “It is the precursor gas for the formation of ground-level ozone, which is a highly harmful pollutant. Nitrogen dioxide can combine with naturally available positive ions like ammonium, sodium, potassium and magnesium, and produce secondary particulate aerosols. Thus, it also helps in the production of particulate load in the air,” said Saha. TOI reported on Dec 2 that a new analysis of early winter trends (Oct to Nov) in Delhi-NCR by Centre for Science and Environment revealed that PM2.5 rose and fell almost in tandem with the levels of nitrogen dioxide during morning (7-10 am) and evening (6-9 pm) hours, as both pollutants surged with traffic emissions and got trapped under shallow winter boundary layers.
