Delhi AQI falls to ‘poor’ ahead of Diwali, likely to deteriorate further this week — pollution-control curbs kick in

As the temperature dropped to 18 degrees Celsius on November 1, Delhi's air quality plummeted into the 'poor' category, undoing the brief respite brought by last week's rains.

Typically, low temperatures and fog slow down dispersion by trapping pollutants near the surface.

With less than a week for Diwali, the air quality is expected to worsen in the coming days, dipping into the “very poor” category by the second half of this week.

Quick answers to key questions

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QUESTIONS

Delhi recorded a 24-hour average AQI of 261, which is in the ‘poor’ category. This was up from 117, classified as ‘moderate’, a day earlier.

Lower temperatures and fog can slow the dispersal of pollutants, trapping them near the surface. Stubble burning’s estimated contribution to Delhi’s pollution also rose to 18.57% on Sunday.

The Air Quality Early Warning System forecast ‘poor’ air quality on Monday and Tuesday, with a possible deterioration to ‘very poor’ by Wednesday. Its outlook for the following six days was ‘poor’ to ‘very poor’.

Measures include restrictions on certain outside-Delhi vehicles, a ban on dust-generating outdoor construction, doubled parking charges and a 50% cap on physical attendance in government and private offices. The measures apply for varying periods between November 1 and February 28.

Yes. The restrictions cover certain vehicles registered outside Delhi that do not meet the applicable emission standards. The articles state that BS-VI, CNG and electric vehicles are allowed under the rules, subject to applicable exemptions.

The city recorded a 24-hour average AQI of 261, “poor”, according to the Central Pollution Control Board (CPCB)’s bulletin, worsening over 144 points from a day earlier when it registered 117, “moderate” category.

On Sunday, Sameer app recorded an Air Quality Index (AQI) of 277. Of the 54 monitoring stations in the city, 18 recorded 'poor' air quality, while 25 recorded 'very poor' air quality.

According to the Central Pollution Control Board (CPCB), an AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

Delhi AQI to nosedive this week

Delhi AQI is likely to remain in the “poor” category on Monday and Tuesday, and may further deteriorate to the “very poor” category by Wednesday, according to the Centre’s Air Quality Early Warning System (AQEWS).

“The outlook for the subsequent six days is that the air quality is likely to be in the very poor to poor category,” the AQEWS bulletin added.

Delhi records lowest Nov 1 minimum temperature since 2023

Delhi recorded its lowest minimum temperature for November 1 since 2023, with the mercury settling at 18 degrees Celsius, 1.9 degrees below the season's average, according to the weather department.

The minimum temperature on 1 November 2023 was 16.4 degrees Celsius.

The maximum temperature settled at 29 degrees Celsius, the lowest for the date since 2021, when it recorded 27.2 degrees Celsius.

The India Meteorological Department (IMD) forecast mainly clear skies for Monday, with the maximum and minimum temperatures expected to reach 29 and 17 degrees Celsius, respectively.

Anti-pollution restrictions kick in

The deterioration in air quality coincided with the implementation of a series of special winter pollution-control measures, including restrictions on vehicles registered outside Delhi that conform to BS-IV or older emission standards, a ban on dust-generating outdoor construction activities, doubling of parking charges and a 50 per cent cap on physical attendance in government and private offices.

The restrictions, which will remain in force for varying periods between November 1 and February 28, are aimed at reducing vehicular emissions, dust pollution and traffic congestion during the winter months.

‘Smog season begins’

Stubble burning was contributing to 18.57% of Delhi’s air pollution on Sunday, up from 5.33% on Saturday, according to the Decision Support System (DSS) for air quality management in Delhi.

Past data show that farm fire contributions typically peak in the first week of November, making it an important time of year to capture data.

Jinitha Varghese, programme manager at EnviroCatalysts, told Hindustan Times (HT) that two-thirds of the fine particles in Delhi’s air came from outside the city, including NCR industries and traffic, while its own traffic is still its biggest single source.

“About 40% of the particles form in the air from gases released in the airshed, so the smoke from coal, fuels and stubble shows up as ‘secondary’ pollution and is easy to undercount,” he said.

“Smog season begins now...” noted meteorologist Navdeep Dahiya, adding that most AQI sensors across Delhi NCR are now reporting AQI levels above 300 and many are climbing into the 400-500 range. “The flow of winds are from north west with calm conditions. All emissions will persist in the atmosphere for longer duration.”

Traffic snarls as Delhi's AQI turns 'poor'

The first day of Delhi's new anti-air pollution restrictions saw heavy traffic snarls at the city's borders on Sunday, with vehicles queuing up for checks, even as air quality deteriorated to the poor category, marking the worst reading of the season so far and the highest in 198 days.

Heavy congestion was observed at several entry points, particularly along the Delhi-Gurugram and Delhi-Noida borders, as traffic police and enforcement personnel conducted vehicle checks entering the national capital.

Long queues of vehicles were reported near the MCD toll booths and other NCR entry points, with commuters facing bumper-to-bumper traffic as officials stopped vehicles that did not meet the prescribed emission standards.