New Delhi: Delhi's air quality deteriorated sharply on Wednesday, with the capital's average Air Quality Index climbing to 377, its worst reading in nearly ten months, as pollution levels edged closer to the severe category just days before Diwali. With 22 of the city's 59 monitoring stations recording severe air quality, and forecasts warning of a further decline over the coming days, residents of the national capital region are facing another hazardous winter spell.
The average reading of 377 was the highest since January 20, when the index had settled at 378, making Wednesday the worst day for Delhi's air in 288 days. The figure sits at the top end of the very poor category. According to the Central Pollution Control Board, an AQI between zero and 50 is classified as good, 51 to 100 as satisfactory, 101 to 200 as moderate, 201 to 300 as poor, 301 to 400 as very poor, and 401 to 500 as severe.
Delhi, at 377, was therefore only 24 points away from severe, and several individual stations had already crossed that threshold.
The station-level picture was stark. IIT Delhi recorded the highest reading at 458, followed by Jahangirpuri and Punjabi Bagh at 448 each, while Mundka recorded 439. Of the 59 monitoring stations across the city, 22 recorded severe air quality, 32 were in the very poor category, and five recorded poor air quality.
Not a single station reported air that could be described as moderate, satisfactory or good. On Thursday morning, the situation had not eased. India Gate recorded an AQI of 399, just two points below the severe threshold, according to Central Pollution Control Board data reported in the morning, while Anand Vihar recorded 296, in the poor category.
The trend over the past week shows how rapidly conditions have worsened. After an unusually clean October, in which Delhi recorded its lowest average AQI for the month in eight years, the index rose steadily through the start of November. The average stood at 117 on October 31 and just 60 on October 30, before climbing to 261 on November 1, 324 on November 2, 350 on November 3 and 377 on November 4.
That steady climb reflects a familiar winter pattern: falling temperatures, slowing winds, and a rising contribution from crop-residue burning in neighbouring states, all combining to trap pollutants close to the ground.
The sources of Wednesday's pollution were quantified by the Decision Support System. Transport emissions contributed 15.5 per cent of Delhi's pollution, while stubble burning accounted for 20.2 per cent. Other contributing sectors included industries at 2.9 per cent, waste burning at 1.3 per cent, construction at 2.2 per cent, road dust at 1.1 per cent, residential sources at 3.8 per cent and other sectors at 1 per cent.
Among neighbouring districts, Ghaziabad contributed 7 per cent, Rohtak 3.8 per cent, Gurugram 2.7 per cent, Sonipat 2.2 per cent, Jind 1.8 per cent and Bhiwani 1.3 per cent, with other sources accounting for 28.5 per cent. The picture is therefore not one of a single culprit, but of many sources converging at the worst possible time of year.
Satellite data underlined the scale of farm fires. On November 4 alone, 467 farm-fire incidents were detected across six states, including 151 in Punjab, 10 in Haryana, 33 in Uttar Pradesh, 111 in Rajasthan, five in Uttarakhand and 157 in Madhya Pradesh, with none detected in Delhi itself.
Between September 15 and November 4, a total of 4,800 residue-burning events were detected across seven states and union territories, including Delhi, according to the Consortium for Research on Agroecosystem Monitoring and Modeling from Space at the Indian Agricultural Research Institute.
The Ministry of Earth Sciences has forecast that the contribution of farm fires will rise further, from 8.5 per cent on November 2 to 22.2 per cent by November 5, as the burning season peaks.
The dominant pollutant also shifted on Wednesday. PM10 emerged as the dominant pollutant, marking a change from the previous three days when PM2.5 had dominated. PM10 refers to coarser particulate matter, including road dust and construction dust, while PM2.5 refers to finer particles that can penetrate deep into the lungs and enter the bloodstream.
Both are harmful, but the shift towards PM10 suggests that dust from roads, construction sites and dry surfaces is playing a growing role alongside smoke from farm fires and vehicle exhaust. The maximum temperature at Safdarjung, Delhi's base weather station, settled at 29.8 degrees Celsius, 0.7 degrees below the seasonal normal, while Palam recorded 27.2 degrees, 3.6 degrees below normal, and Lodhi Road recorded 29.6 degrees, 0.4 degrees below normal.
Cooler air and calm winds reduce the atmosphere's ability to disperse pollutants, allowing them to accumulate over the city.
Authorities have already moved to the second stage of emergency restrictions. The Commission for Air Quality Management invoked Stage II of the Graded Response Action Plan across the National Capital Region on Monday, with immediate effect, following the sharp deterioration in air quality.
The measures include more intensive road cleaning, higher parking charges to discourage private vehicle use, increased public transport services, and restrictions on dust-emitting construction activities and older commercial vehicles. Delhi Metro has introduced 20 additional weekday train trips, and authorities have been directed to stagger government office timings to ease traffic congestion.
These curbs sit alongside the existing Stage I measures, with civic bodies, traffic police and pollution control authorities across Delhi, Haryana, Uttar Pradesh and Rajasthan directed to step up enforcement.
The forecast offers little comfort. According to the Air Quality Early Warning System, Delhi's air quality is likely to remain in the very poor category on Thursday and to deteriorate further to the severe category between November 6 and 7. That timing coincides with the Diwali weekend, when the festival of lights is celebrated with lamps, lights and fireworks.
Diwali falls on Sunday, and the use of firecrackers traditionally adds a sharp spike in fine particles and harmful gases to air that is already hazardous. The Supreme Court on Monday allowed the manufacture, sale and use of certified green firecrackers in Delhi and neighbouring areas for a limited period, citing a lack of data to determine whether a complete ban would solve Delhi's annual pollution problem.
The court said the crackers could be set off only between 6 am and 7 am and between 8 pm and 10 pm on November 7 and 8, and it banned fireworks within 300 metres of hospitals, care homes, schools and other designated silence zones.
Health experts have long warned that prolonged exposure to very poor and severe air can aggravate asthma and other respiratory conditions, irritate the eyes and throat, and increase the risk of heart and lung problems, particularly for children, the elderly and people with existing illnesses.
During such spells, doctors typically advise residents to limit outdoor exertion, keep windows closed during the worst hours, use air purifiers indoors where possible, and wear masks when venturing out. For daily-wage workers, traffic police, street vendors and others who cannot avoid the outdoors, the advice is of limited comfort, and the pollution spell becomes an occupational hazard as much as an environmental one.
Delhi's winter pollution crisis is not new, but the speed of this year's deterioration has surprised many residents. October was unusually clean, aided by heavy rainfall and favourable wind patterns, and the city recorded its cleanest October in eight years. The contrast with early November could hardly be sharper.
Within days, the same city that had enjoyed relatively clear skies was blanketed in thick smog, with visibility dropping and the smell of smoke hanging over neighbourhoods. That swing illustrates how fragile Delhi's air quality gains can be when the seasonal factors turn against the city.
Neighbouring cities in the national capital region are also affected. Ghaziabad recorded an AQI of 257, in the poor category, while Noida recorded 330, Greater Noida 309 and Gurugram 322, all in the very poor category. The regional nature of the problem means that action confined to Delhi alone is unlikely to be enough.
Farm fires in Punjab, Haryana, Uttar Pradesh and Rajasthan, industrial emissions across the region, and vehicle exhaust from millions of daily commuters all contribute to a shared airshed, and lasting improvement requires coordinated action across state boundaries.
As Diwali approaches, the immediate question is whether the severe forecast for November 6 and 7 will materialise, and how much firecrackers will add to the burden. The limited hours and green-cracker conditions imposed by the Supreme Court are designed to contain that spike, but enforcement on the ground, and public compliance, will determine whether they work.
For now, Delhi's residents can only watch the index, limit their exposure where they can, and hope that wind and weather offer some relief before the festival weekend arrives.
(Reporting based on The New Indian Express, BBC, Outlook India and The CSR Journal.)