Diwali under toxic skies as Delhi gasps under thick smog

Delhi's air quality remained in the 'very poor' category on Sunday, with the city's average Air Quality Index (AQI) settling at 376 on Diwali, as a thick layer of smog enveloped several areas and reduced visibility. Pollution levels were expected to deteriorate further following evening celebrations, with forecasters warning that the capital could slip into the 'severe' category on Monday.

The city's average AQI increased from 369 on Saturday to 376 on Sunday, remaining close to the severe threshold of 401. The deterioration came despite Stage III restrictions under the Graded Response Action Plan (GRAP) being in force across Delhi-NCR.

Of the 59 monitoring stations that recorded data on Sunday, 12 reported air quality in the severe category and 22 in the very poor category, according to the latest figures. Jahangirpuri recorded the highest AQI at 463, indicating particularly hazardous pollution levels in the locality.

The Air Quality Early Warning System (EWS) for Delhi forecast severe air quality on November 9, citing unfavourable atmospheric conditions that could prevent pollutants from dispersing effectively. The forecast indicated that pollution would remain elevated in the following days, although subsequent daily conditions could fluctuate between the severe and very poor categories.

Delhi had already witnessed widespread pollution on Sunday morning. The city recorded an AQI of around 383, while several monitoring stations, including Jahangirpuri, RK Puram, Punjabi Bagh and Bawana, registered readings exceeding 400.

𝗙𝗶𝗿𝗲𝗰𝗿𝗮𝗰𝗸𝗲𝗿𝘀 𝗮𝗱𝗱 𝘁𝗼 𝗽𝗼𝗹𝗹𝘂𝘁𝗶𝗼𝗻

The deterioration coincided with Diwali celebrations, raising concerns that firecracker emissions would add substantially to the particulate pollution already present in the atmosphere.

PM2.5 emerged as the predominant pollutant across much of the capital on Sunday. These fine particles can penetrate deep into the lungs and are associated with respiratory and cardiovascular health risks, particularly among children, elderly people and those with pre-existing illnesses.

The Supreme Court had permitted the use of certified green firecrackers during specified hours on November 7 and 8, allowing bursting between 6 am and 7 am and between 8 pm and 10 pm. The limited permission was accompanied by restrictions intended to reduce emissions during the festival.

However, pollution levels had already reached concerning levels before the main evening celebrations, suggesting that any additional emissions could aggravate the situation.

Apart from firecrackers, emissions from vehicles, road dust, industrial activities and agricultural residue burning in neighbouring states continued to contribute to Delhi's pollution burden.

𝗨𝗻𝗳𝗮𝘃𝗼𝘂𝗿𝗮𝗯𝗹𝗲 𝘄𝗲𝗮𝘁𝗵𝗲𝗿 𝗰𝗼𝗻𝗱𝗶𝘁𝗶𝗼𝗻𝘀

Meteorological conditions were expected to play a significant role in the anticipated deterioration.

According to the EWS, a ventilation index below 6,000 square metres per second, combined with average wind speeds below 10 kilometres per hour, is considered unfavourable for the effective dispersion of pollutants.

Weak winds and reduced atmospheric mixing allow particulate matter and other pollutants to accumulate near the ground, resulting in prolonged exposure for residents.

The official forecast for November 9 indicated a partly cloudy sky, with temperatures ranging between 15 and 30 degrees Celsius and an atmospheric mixing depth of around 1,600 metres. Ventilation conditions were expected to remain unfavourable for pollutant dispersion.

The forecast pointed to severe air quality on Monday, followed by very poor conditions on Tuesday and Wednesday, although these projections remain subject to changes in weather and emissions.

𝗩𝗲𝗵𝗶𝗰𝘂𝗹𝗮𝗿 𝗲𝗺𝗶𝘀𝘀𝗶𝗼𝗻𝘀 𝗿𝗲𝗺𝗮𝗶𝗻 𝗺𝗮𝗷𝗼𝗿 𝗳𝗮𝗰𝘁𝗼𝗿

According to the Decision Support System (DSS) for Delhi, the transport sector was projected to be the largest individual contributor to the city's pollution on Sunday, accounting for approximately 19 per cent.

Stubble burning was estimated to contribute around 3.5 per cent, with its share forecast to decline marginally to 2.99 per cent on Monday.

These estimates indicate that local emission sources remain significant even during the agricultural residue-burning season. The contribution of stubble burning can vary depending on the number and location of farm fires, wind direction and atmospheric conditions.

Experts have repeatedly emphasised that Delhi's winter pollution crisis results from the combined effects of multiple emission sources rather than a single activity.

𝗚𝗥𝗔𝗣-𝗜𝗜𝗜 𝗰𝘂𝗿𝗯𝘀 𝗿𝗲𝗺𝗮𝗶𝗻 𝗶𝗻 𝗳𝗼𝗿𝗰𝗲

The Commission for Air Quality Management (CAQM) had invoked Stage III of GRAP across Delhi-NCR on November 6 after the capital's air quality approached severe levels.

The restrictions include curbs on specified dust-generating construction and demolition activities, alongside restrictions on BS-III petrol and BS-IV diesel four-wheelers in designated parts of the National Capital Region.

Authorities have also been directed to strengthen pollution-control measures, including dust suppression, road cleaning and enforcement against activities contributing to deteriorating air quality.

The restrictions are intended to prevent further deterioration, particularly when weather forecasts indicate that pollution could remain trapped over the region.

The CAQM is expected to continue reviewing pollution levels and meteorological forecasts before deciding whether additional measures are necessary.

Under the Central Pollution Control Board's classification, AQI readings between 301 and 400 fall in the very poor category, while readings between 401 and 500 are classified as severe.

With several monitoring stations already reporting severe pollution, the capital faces the prospect of another difficult post-Diwali period. The immediate concern remains whether restrictions on emissions and changes in weather conditions will be sufficient to prevent a further deterioration in air quality.