Delhi's air quality remains 'very poor' for fourth day; likely to turn 'severe' ahead of Diwali

New Delhi: Delhi's air quality remained in the 'very poor' category for the fourth consecutive day on Thursday, with forecasts indicating a likely deterioration to the 'severe' category from Friday, days ahead of Diwali.

The 24-hour average Air Quality Index (AQI) stood at 369 at 4 pm on Thursday, compared to 377 recorded at the same time on Wednesday, according to the Central Pollution Control Board (CPCB).

The city's average AQI was recorded at 350 on Tuesday and 324 on Monday.

Delhi records first 'very poor' air quality of season, three stations report 'severe' category

Of the 59 active air quality monitoring stations in the national capital, 18 recorded 'severe' air quality, with Jahangirpuri registering the highest AQI of 454 at 4 pm, according to CPCB data.

As per CPCB standards, an AQI between 0 and 50 is classified as 'good', 51-100 as 'satisfactory', 101-200 as 'moderate', 201-300 as 'poor', 301-400 as 'very poor' and 401-500 as 'severe'.

The Air Quality Early Warning System (AQEWS) has forecast that Delhi's air quality will remain in the 'very poor' category on Thursday before deteriorating to 'severe' from Friday to Sunday.

"The outlook for the subsequent six days is that the air quality is likely to be in the severe to very poor category," the AQEWS bulletin said.

Forecasts by the Decision Support System (DSS) for Air Quality Management in Delhi indicate that the contribution of stubble burning to the city's pollution is expected to decline sharply on November 7, while the share of vehicular emissions is projected to rise.

The DSS, under the Ministry of Earth Sciences, estimated the contribution of stubble burning at 15.601 per cent on Thursday, which is expected to rise to 19.201 per cent on Friday before dropping sharply to 1.575 per cent on Saturday.

The DSS forecast for the contribution to Delhi's PM2.5 levels over the next few days is based on climatological data on fire counts and emissions, rather than real-time farm fire activity.

The contribution of transport emissions is projected to increase from 17.913 per cent on Thursday to 18.291 per cent on Friday and 21.108 per cent on Saturday.

Sunil Dahiya, founder and lead analyst at EnviroCatalysts, said the expected decline in the share of stubble burning was primarily due to changing weather conditions and did not indicate a reduction in farm fires.

"As a western disturbance moves in, the north-westerly winds that carry smoke from Punjab and Haryana into Delhi are forecast to weaken and turn easterly around Diwali," he said.

Dahiya said Punjab had recorded 2,347 farm fires this season, with more than 700 reported on November 3 and 4 alone.

A lower contribution from stubble burning would not necessarily translate into cleaner air, as slower winds and morning mist could trap local emissions from vehicles, industries, waste burning and firecrackers, he said.

He added that the early warning system had already forecast 'severe' air quality for November 6 and 7, and warned that pollution from farm fires could return once north-westerly winds resumed.