According to figures compiled till December 22, Delhi’s average NO2 concentration stood at 47 micrograms per cubic metre (µg/m³), up from 43 µg/m³ last year. The level breaches India’s annual ambient air quality standard of 40 µg/m³ and is nearly five times the World Health Organisation’s recommended annual guideline of 10 µg/m³.
Nitrogen dioxide is a highly reactive gas released primarily through fuel combustion, with vehicles, power plants and industrial units among its main sources.
An analysis of Central Pollution Control Board (CPCB) data by think tank EnviroCatalyst shows that NO₂ levels have remained persistently high in recent years. The annual average concentration was 35 µg/m³ in 2023, 40 µg/m³ in both 2022 and 2021, 39 µg/m³ in 2020, 45 µg/m³ in 2019 and 48 µg/m³ in 2018.
Traffic-heavy junctions and industrial pockets have emerged as the city’s worst-affected zones. ITO, a major traffic bottleneck known for long signal waiting times, recorded the highest annual mean concentration at 69 µg/m³. It was followed closely by IGI Airport’s Terminal 3 at 68 µg/m³. Anand Vihar and Shadipur reported 66 µg/m³ each, Wazirpur 65 µg/m³, Lodhi Road 62 µg/m³ and Jahangirpuri 61 µg/m³.
Experts say local sources within the city need urgent attention. “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.
Several other monitoring stations also logged worrying concentrations this year. IIT-Delhi and Okhla Phase-2 recorded 59 µg/m³ each, Dwarka Sector-8 56 µg/m³, Pusa 54 µg/m³, Chandni Chowk 53 µg/m³, Najafgarh and Major Dhyan Chand National Stadium 52 µg/m³ each, Jahangirpuri 51 µg/m³, and Dr Karni Shooting Range and Patparganj 50 µg/m³ each.Beyond its direct health impact, NO₂ plays a critical role in worsening overall air pollution. Dipankar Saha, former head of CPCB’s air laboratory, explained that the gas is generated during high-temperature, high-pressure fuel combustion. “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.
Earlier this month, a Centre for Science and Environment analysis of early winter trends in Delhi-NCR (October to November) found that PM2.5 levels closely mirrored NO₂ concentrations during peak traffic hours in the morning and evening. Both pollutants spiked with vehicular emissions and were trapped near the surface by shallow winter boundary layers, compounding the city’s seasonal air quality crisis.
(With inputs from ToI)