Being the capital city, Delhi’s worsening air quality has not only concerned the residents but also attracted significant regional and global attention. Over the last several years, PM10 and PM2.5 concentrations in Delhi have remained well above the prescribed national standards. The annual average concentrations of particulate matter (PM) generally violate the standards by about 3-4 times in the city.

With the Capital left gasping for breath yet again, a new study from The Energy and Resources Institute (TERI) presents pathways to reduce PM2.5 concentrations and models different future scenarios. The study titled Cost-effectiveness of interventions for control of air pollution in Delhi and supported by Bloomberg Philanthropies released recently also assesses the cost-effectiveness of multiple interventions and the reductions in PM2.5 concentration it can bring about.

The study makes three future projections – for 2022 in the short term, 2025 in the medium term, and 2030 in the long term for assessment of air quality and cost scenarios for different interventions.

In a BAU scenario with consideration of some existing emission control policies, the winter PM2.5 concentrations are expected to fall by 9%, 21%, and 28% in 2022, 2025, and 2030 respectively, when compared to 2019, the base year of the study. Though the PM2.5 concentrations may fall marginally over the years, the levels will continue to remain significantly above the national standards of 60μg per m³, notes the study.

In 2019, the PM2.5 concentrations in Delhi violated the annual average standards by about three times. Transport (23%), industries including power plants (23%), and biomass burning (14%) were the major contributors to prevailing winter time PM2.5 concentrations in Delhi during 2019.

The study calls for more stringent controls to curb emissions in the NCR and the rest of the airshed – a geographical area within which air is confined – if winter season PM2.5 levels are to be brought down considerably. Airshed level controls can reduce winter season PM2.5 concentrations by 35% by the year 2030 when compared to the business as usual scenario.

"Air pollution should be focused as a problem throughout the year not only during the winter season. Stringent actions are needed in the whole airshed to improve air quality in the NCR. Instead of completely banning the essential activities, it is important to switch to the cleaner options," says Dr Vibha Dhawan, Director-General of TERI.

"Air pollution levels in Delhi are worsened by regional sources which add to the local sources within the city. Airshed-based regional-scale air quality controls are required for effective control of air quality in the region," points out Dr Anju Goel, co-project investigator and fellow at TERI.

Priya Shankar, who leads India climate and environment programs at Bloomberg Philanthropies, says, "Given the severity and scale of the air pollution crisis, we need multi-level action and collaboration across government, business, civil society, and citizens. This analysis shows that progress in improving Delhi's air quality is possible with stronger and sustained mitigation efforts."

This study shows that stringent NCR level and Airshed level controls (detailed out in the report) can bring winter season PM2.5 concentrations in Delhi down to 103-119 µg/m3 and about 83-88 µg/m3, respectively between 2022-2030. This is will be a reduction of 20-27%, and 36-47% w.r.t BAU between 2022-2030.

The study estimates the emission and PM2.5 concentration reduction potentials of different policy interventions across sectors such as transport, biomass and industries. It also assesses the health and economic co-benefits of an airshed approach to address air pollution, and calculates direct and associated benefits like an additional economic benefit of Rs 430 billion ($6.2 billion), if regional PM2.5 control strategies are implemented between 2022-2030.

It is expected that with interventions including electrification of vehicles, implementation of environmental standards of thermal power plants, fleet modernization, shift to public transport etc in the airshed region, the annual average standard can be met.

However, in order to achieve national ambient air quality standards during winter, additional controls such as curbing ammonia release in farms, enforcement of full ban on refuse burning, converting coal-based power plants to clean energy, most stringent dust suppression control, shift to cleaner technology for brick kilns, use of induction cook-stoves, and stricter control of dust from construction activities, full vacuum cleaning of all kinds of roads, widespread landscaping and strictest control on refuse burning and construction activities are required.

This can bring the winter PM2.5 levels to 55 µg/m3 adhering to the daily standards. Further reductions can also be achieved through international cooperation by reducing contributions from outside of Indian boundaries. There is a need for further study of additional measures and costs on how to get levels further down closer to interim targets of WHO.

Contribution of regional-scale pollution is substantial in Delhi’s PM2.5 concentrations in Delhi and hence, regional level air quality planning and implementation is recommended for effective control of pollution in the whole region.”

Based on cost-effectiveness analysis, some of the air pollution control interventions emerge out as net negative cost strategies as they generate economic benefits (on account of efficiency gains) over a period of time. These include strategies like LPG penetration, induction cook-stoves, zig-zag brick kilns, use of agriculture residue in power plants etc.  

High cost-effectiveness has been observed for the control strategies for industrial and dust pollution with low costs per unit of PM2.5 removal observed. These include electrification of 2w and 3w vehicles, gaseous pollutant controls in power plants, fuel switches from solid to gaseous fuels in industries, vacuum cleaning of roads, and control of dust from construction activities.  

High cost-effectiveness was found for fleet modernization of heavy-duty vehicles like trucks and buses and low cost-effectiveness has been observed for fleet modernization of cars. With BS-VI emissions standards slowly penetrating in, the potential and cost-effectiveness of fleet modernization will fall. Modal shift to public transport and electrification of public transport comes out to be quite cost-effective in comparison to many other strategies.

In addition, the public transportation system provides additional social and economic benefits (that include reduced congestion, time and exposures, less expenditure on infrastructure creation and traffic management), there is a definite need for a gradual transition towards a multi-modal public transport system in the region.

Despite a reduction of 21% in PM2.5 concentration in the BAU scenario in the years 2022-2030, mortalities will increase by 7% i.e. 14,400 in 2022 to 15,500 in 2030 in Delhi due to the ageing population. Out of a total of 45000 mortalities in Delhi NCR in the BAU scenario, around 12,300 mortalities will be avoided in the year 2030 in Delhi NCR if control strategies are implemented at the airshed level over and above the BAU.

This will result in additional economic benefits of around INR 430 billion. Further, the benefits to cost ratio is estimated to be over 2 in alternative scenarios, indicating that the economic benefits of moving towards clean air will outweigh the costs of implementation.

The full report can be accessed here