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New Delhi, November 5, 2023: On November 2, Delhi’s pollution level – PM2.5 concentration – saw its first huge spike of this winter season: with a sudden and staggering 68 per cent jump within 24 hours, crossing 313 microgramme per meter cube (µg/m3) which was equivalent to ‘severe+’ category as per the Air Quality Index (AQI) concentration range.
Releasing a new analysis by Centre for Science and Environment (CSE) of the deadly winter pollution that has gripped Delhi-NCR these days, Anumita Roychowdhury, executive director, research and advocacy, CSE, said: “This winter season has started with a much higher pollution level compared to November last year. The combination of adverse meteorological conditions, onset of crop residue burning, and high local pollution has tilted the scale dangerously, increasing public health risk.”
“Even though the overall long-term pollution curve is stable and downward, it is still significantly above the national ambient air quality standards. This demands most stringent and sustained action on vehicles, industry, energy systems and waste management across the region,” Roychowdhury added.
The analysis has been done by CSE’s Urban Lab, whose head Avikal Somvanshi said: “This kind of rapid build-up is not uncommon during this part of the season and is generally associated with smoke-fall from farm stubble fire and meteorological factors assisting transportation of the smoke to Delhi-NCR and topping the high local pollution. But it must be kept in consideration that this rapid build-up in a short time span is able to tip air quality into severe category because baseline pollution from local sources is already very high.”
Key highlights of the CSE analysis
Massive increase within a short time-frame: The most notable trend this year is the sudden and rapid build-up of smog episode in this early phase of winter. On November 2, PM2.5 levels in Delhi crossed 300 µg/m3 or ‘severe+’ level for the first time this season. It was a very sudden escalation as the level rose a staggering 68 per cent within 24 hours.
During the previous five years, overall trends show that PM2.5 levels start to rise steadily from the beginning of October. This year, the levels started to rise from the middle of September. Illustratively, this increase was at a slower rate and by the end of October, the levels were 20-30 per cent lower than the average levels for the corresponding Octobers of the previous five winters – since 2018-19.
Early beginning of bad air quality days this year due to lower rainfall during September and October: In contrast to the previous winter of 2022-23, the smog episode has started earlier this year. The last day with “good” PM2.5 AQI before the onset of winter was observed on September 9, 2023.
It remains to be seen how many more smog episodes with varying durations may occur this winter. As is the global practice, at least three continuous days of severe AQI is considered as one smog episode. In previous winters, such episodes have been recorded lasting six-10 days; the winters between 2018 and 2021 had, on an average, experienced three smog episodes each. During the winter of 2022-23, only one smog episode was recorded from January 6-9. Also, Diwali and late December of 2022-23 did not witness a smog episode (like in the earlier winters).
High influence of combustion sources – percentage share of PM2.5 is very high: The share of PM2.5 in PM10 is an important indicator of the impact of combustion sources. While coarser PM10 comes largely from dust sources, the tinier PM2.5 come more from vehicles, industry and open burning. This year the percentage share of PM2.5 in PM10 has crossed 50 per cent, which indicates higher impact of combustion sources. On November 2, the ratio for PM2.5 stood at 60 per cent -- highest this season indicating the higher influence of combustion sources.
Farm stubble fire count has increased -- but is still much lower than the seasonal peak of previous year: SAFAR’s estimate has shown that the percentage contribution of farm stubble fire to Delhi’s PM2.5 concentration had crossed 25 per cent on November 2; it was in the 10-20 per cent range in the week leading to November 2. This is expected to rise in the coming days. The fire instances in Punjab and Haryana are yet to peak. In previous years, on the worst days, its contribution had topped 40 per cent, as generally noted during the middle of November.
Pollution hotspots remain most polluted despite implementation of action plans: About 13 pollution hotspots that were identified in 2018-10 continue to remain a challenge, while newer hotspots are emerging as well and have proliferated. Among all hotspots, Mundka and New Moti Bagh are the most polluted locations in Delhi with average PM2.5 levels exceeding 300 µg/m3. Most of the official hotspots of Delhi are exceeding the ‘severe’ level of pollution. At the same time, many non-hotspots are showing higher pollution levels.
The worst polluted new hotspots in Delhi are New Moti Bagh, Nehru Nagar, Sonia Vihar and DU North Campus. Greater Noida, Noida Sector 62, Loni and Faridabad are the most polluted locations in NCR.
Delhi in grip of multi-pollutant crisis – while particulate pollution is severe, nitrogen dioxide (NO2) levels are also rising: The levels of NO2 – which comes largely from vehicles -- are also rising in the region. This indicates high impact of vehicular pollution. City-wide average NO2 is up by 60 per cent compared to the first week of October last year. Certain high traffic locations have been reporting levels as high as three-four times the 24-hour standard.
ITO is most polluted NO2 location in Delhi, with an average of 219 µg/m3. Nehru Nagar and Siri Fort are the next most polluted NO2 locations in Delhi.
PM2.5 and NO2 hotspots can vary across the city: The official PM2.5 hotspots of Delhi are relatively less polluted with NO2. Noida Sector 125 and Sector 1, and Ghaziabad’s Sanjay Nagar and Indirapuram are the most polluted NO2 locations in the NCR.
What should be the action agenda?
Address the key policy gaps urgently: Says Roychowdhury: “While several measures have been taken over the years to clean up fuels and technology across transport and industry sectors, and control dust sources, more action is needed at a scale and speed to address the remaining policy gaps for meeting the clean air targets. Only this can prevent building up of such smog episodes endangering public health.”
Need local and regional scale multi-sector action to cut emissions from vehicles, industry, power plants, waste burning, construction and dust sources. Need transformative changes in infrastructure and systems in each of these sectors.
Need stronger control of episodic pollution like crop residue burning; stronger hyper-local action on all other pollution sources; and more effective monitoring, enforcement and compliance strategy.
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