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Bending Delhi’s Air Pollution Curve

Learnings from 2020 to Improve 2021

L. S. Kurinji, Adeel Khan, Tanushree Ganguly
June 2021 | Risks & Adaptation


Suggested citation: Kurinji, L. S, Adeel Khan, and Tanushree Ganguly. 2021. Bending Delhi’s Pollution Curve: Learnings from 2020 to Improve 2021. New Delhi: Council on Energy, Environment and Water.

Overview

The study intends to support the Delhi government, the Central Pollution Control Board (CPCB), and the Delhi Pollution Control Committee (DPCC) in identifying priority areas of interventions needed in controlling air pollution in Delhi during the winter season of 2021. It establishes the primary drivers of Delhi's winter air pollution during the different phases of the season. It considers meteorological parameters, source activity levels, and its contributions to investigate how winter 2020 was, if at all, different in the pandemic circumstances compared to the previous years.

Key Highlights

  • Delhi residents were exposed to air that does not meet the National Ambient Air Quality Standards (60 µg/m3) for more than half of 2020 despite low economic activity levels for close to eight months (March to November) due to the pandemic-induced lockdown.
  • Delhi’s air quality in winter 2020 was worse than winter 2019 with 92 severe and very poor air quality days in the winter of 2020 compared to 80 such days in 2019.
  • Relative contribution from farm fires was the highest (~30 per cent) between 15 October and 15 November 2020. In the following months, the contribution from household emissions (including domestic cooking, space heating, water heating, and lighting) primarily drove poor air quality in Delhi.

Source: Author’s analysis

  • Calmer winds in October and November amplified the impact of farm fires on Delhi’s air quality. The stubble burning phase (15 October to 15 November) in 2020 experienced 172 hours (70 per cent higher) of calm and light winds (<5 km/h) compared to 101 hours in 2019.
  • Activity levels were low at the start of the winter. But most activities, including vehicular traffic and power generation, bounced back to the previous year’s levels (proxied by indicators such as congestion and electricity generation levels) as the season progressed.
  • Adverse meteorological conditions in Delhi intensified the impact of local and regional emissions on Delhi’s air quality. While meteorological conditions cannot be controlled, sustained air quality gains can be realised only by steeper emission cuts across sectors.

How can Delhi’s air pollution be controlled?

Delhi needs a dedicated air quality forecasting cell to facilitate the rollout of preventive measures

Some cities, such as Beijing, roll out emergency measures in response to air quality (AQ) forecasts and not after air quality dips to dangerous levels. In contrast, the Delhi government orders execute emergency measures under the Graded Response Action Plan (GRAP) ex-post after air quality concentrations reach a certain threatening level. However, such responsive measures cannot prevent the occurrence of high pollution episodes.

  • Integrate air quality forecasts with a decision support system to enable the local regulatory agencies to implement on-demand emission control interventions targeting prominent sources during forecasted high-pollution episodes.
  • The Delhi government, the CPCB and the DPCC should use the air quality forecasts developed by the Indian Institute of Tropical Meteorology (IITM) to issue public health warnings and take pre-emptive actions in the national capital.
  • Move from a system that enforces the GRAP as an ex-post measure to one that prevents the occurrence of high pollution episodes through pre-emptive emission control measures.
Calmer winds in October and November amplified the impact of farm fires on Delhi’s air quality. The stubble burning phase (15 October to 15 November) in 2020 experienced 172 hours (70 per cent higher) of calm and light winds (<5 km/h) compared to 101 hours in 2019.

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