Diwali Delhi pollution: AQI drops to 'very poor' at 329, study reveals local sources responsible not stubble burning

Delhi woke up to ‘very poor’ air quality on Thursday, coinciding with the ongoing Diwali celebrations. The Air Quality Index (AQI) recorded at 7:45 am stood at 329, indicating a shift from 'very poor' to 'poor' air conditions.

Although there has been a decrease in farm fires, local pollution sources remain significant contributors to the declining air quality, which has lingered between 'poor' and 'very poor' for several days, according to a study conducted by the Centre for Science and Environment (CSE).

The CSE report emphasises the increasing impact of local pollution, particularly from the transport sector, which is responsible for over half of the pollution generated from local sources. Anumita Roychowdhury, CSE's executive director for research and advocacy, noted that while farm fires have dominated discussions traditionally, this year they contributed only 1 to 3 per cent of Delhi's pollution during most of the evaluation period, peaking at 8-16 per cent on certain days. “This highlights the urgent necessity to address local pollution sources,” she stated.

She further revealed that the contribution of vehicular emissions to the city's pollution is alarming and called for immediate and strict measures to curb local pollutants in Delhi and its surrounding areas. This discussion comes as the region prepares for a potential spike in pollution levels due to stubble burning and the use of firecrackers during Diwali.

Shambhavi Shukla, programme manager of CSE's clean air initiative, expressed concern over current PM2.5 levels, which are comparable or even higher than in previous winters, indicating stagnant or regressive air quality. The worsening traffic congestion has exacerbated the situation, causing idling vehicles to release greater emissions.

Key findings from the CSE study include:

- Rising PM2.5 levels: The air quality in Delhi has been on a steady decline, with PM2.5 levels exceeding 100 µg/m³ in mid-October. Although these levels are lower than in prior years, a sharp rise is expected as winter approaches, with a recorded peak PM2.5 level of 213 µg/m³ on October 23, partially linked to farm fires.
  
- Increase in 'Poor' air quality days: This winter has seen the highest number of 'very poor' air days in three years, counting 11 days categorized as 'very poor' alongside five 'poor' days. In contrast, the days rated as 'good' air quality have plummeted from 11 days in 2022 to merely two in 2024.

- Local and external pollution sources: An assessment by the Indian Institute of Tropical Meteorology highlighted that Delhi's PM2.5 composition is influenced by 29 different sources, with vehicles identified as the primary local contributor responsible for over half of the pollution emissions in the city.

(With inputs from Kumar Kunal)