New Delhi: Delhi’s nitrogen dioxide levels, driven mainly by vehicular emissions and linked to respiratory illnesses, have risen to three times the national safe limit over the past week.

A report by Hindustan Times, citing Central Pollution Control Board data analysed by the think tank Envirocatalysts, reported that the hourly NO₂ concentration reached a peak of 240 µg/m³ at the IGI Airport (T3) monitoring station, run by the India Meteorological Department.

According to the analysis, this figure is three times higher than the Central Pollution Control Board’s safe standard of 80 µg/m³ and nearly ten times the World Health Organisation’s prescribed limit of 25 µg/m³. Several other locations in the Capital also recorded elevated levels during the same period.

ITO, one of Delhi’s busiest traffic intersections, recorded an hourly average of 221 µg/m³, while Delhi University’s North Campus registered 210 µg/m³. Stations at Lodhi Road (181 µg/m³), Mundka (178 µg/m³) and JLN Stadium also recorded high concentrations.

Elevated NO2 levels exacerbate asthma and respiratory infections, while short-term exposure can cause wheezing, coughing and difficulty breathing.

Envirocatalysts founder and lead analyst Sunil Dahiya told the newspaper that ITO consistently records high nitrogen dioxide levels due to its location next to a busy road. “The station is likely to capture a significant portion of vehicular emissions, which is what people on the roadside are also inhaling,” he said. Dahiya added that high emissions at the airport result from a combination of aircraft and vehicular exhaust.

Also read: What the Severe AQI of Delhi NCR This Week Tells Us About India’s Democracy

Experts cited in the Hindustan Times attributed the city’s high NO₂ readings to vehicular exhaust, biomass burning and industrial activity, with traffic congestion emerging as the dominant factor. They said vehicular emissions alone account for up to 81% of Delhi’s total nitrogen dioxide output.

Dahiya noted that while attention during winter months usually centres on particulate matter, gases like nitrogen dioxide can also spike sharply when meteorological conditions are unfavourable. “At intersections or near industrial areas, if winds are stagnant and temperatures remain high, hourly peaks can rise significantly,” he said.

IIT Delhi expert Mukesh Khare told the paper that while vehicles remain the main source, meteorological conditions are also a major influence. “In summer, better ventilation and dispersion keep levels lower. But in winter, poor wind movement and reduced sunlight lead to greater accumulation,” Khare said.

Khare added that nitrogen dioxide is released primarily from burning petrol (fossil fuels) and is an indicator of heavy traffic congestion. “Aircraft also release substantial quantities of NO₂, so higher readings near the airport are not surprising,” he said.

Also read: Air Pollution in India is Driven by Politics, Not Stubble Burning. Here's Why

The report said several monitoring stations recorded prolonged periods when nitrogen dioxide levels stayed above the national safe limit. Since November 1, the IGI Airport station logged 132 hours of exceedance, followed by 128 hours at North Campus, 118 at Najafgarh, 93 at Mundka and 81 at Lodhi Road. At Okhla Phase-II, the pollutant stayed above 80 µg/m³ for 75 hours, while Anand Vihar reported 71 hours.

The Hindustan Times also pointed to gaps in air quality data. Out of 155 monitored hours since November 1, Lodhi Road had missing data for 52 hours, followed by 28 hours at Sonia Vihar and 13 at Patparganj. Of the city’s 39 active ambient monitoring stations, 23 had complete data, while the rest showed at least an hour of missing readings.

A separate analysis by the newspaper on November 5 had revealed missing data and algorithmic inconsistencies in how Delhi’s average AQI is calculated, suggesting that the actual air quality may be worse than reported.

The Wire is now on WhatsApp. Follow our channel for sharp analysis and opinions on the latest developments.