Delhi Air Pollution

The World Health Organization (WHO) estimates  seven million premature deaths every year  caused due to air pollution, considered to be the largest health and environmental threat in recent times.  Nearly nine out of ten people in the world  live in places where annual mean PM2.5* levels exceed the recommended WHO value. A few studies have concluded the direct correlations between exposure to PM2.5 particles and to  acute lung and chronic heart problems.  Therefore, it serves as a proxy to understand the different sources of air pollution to assess local and regional air quality. In the recent past, there is evidence on the increasing transmission of Covid-19 infection being exasperated by air pollution, creating a grave public health crisis in India.

*PM2.5 - Particular Matter is a mixture of microscopic particles with diameter size of less than 2.5 micro-meters/ 2.5x10^-6 meter/ 20 times smaller than a human hair strand.

The Changing Trend of Air Quality in Delhi-NCR

Air quality in India has deteriorated significantly over the past two decades, owing to population growth, increasing numbers of vehicles, use of fossil fuels, inefficient transportation systems, poor land use patterns, industrialization, and ineffective environmental regulations. Ever since the  1991 Industrial policy , environmental pollution has worsened, specifically in North India. 

The recurrent air-pollution in the winter months of the capital region has become an annual distress phenomenon. Over the past two decades, the satellite-derived long-term trend of PM2.5 concentration of Delhi (Figure 1) indicates the pollution hotspots, where the levels were almost 12 times the  WHO Ambient Air Quality Guidelines  (10µg/m³) and 4 times the  National Air Quality Standards  (40µg/m³).

64% increase of PM2.5 emissions in the last 2 decades

Two noticeable dips are observed in the trend which are assumed to be the result of the intervention policies formulated at regional and local levels through  clean air programs    and actions made to cut down emissions through necessary policy reforms. The first-era reforms to control air pollution, suggested by the  Environment Prevention & Control Authority (EPCA), 2003  to the Delhi government, such as the large-scale transition to cleaner alternative fuels (CNG and Euro II Diesel) and a systemic phasing out of the old diesel vehicles had a positive impact on the city's air quality between 2004 and 2006. 

The second-era of reforms include local and regional interventions. The closure of coal-based thermal power plants at Rajghat and Badarpur, the imposition of environmental compensation charge on heavy and commercial vehicles entering Delhi territory, and the introduction of BS IV Standards led to the lower emissions in the city. Despite the implementation of various emergency measures, the dangerous levels of PM2.5 emissions have been steadily rising since 1998.

PM2.5 emissions for 2013-2018 indicate high concentration in the central cores of Delhi than its urban periphery. This could be a result of the large-scale infrastructure projects and traffic congestion being reported within the core areas such as Dwarka, Hauz Khas, Saket, Dakshin Puri, and Rohini (Figure 5). The area of investigation consists of the most critical wards of Delhi with the highest PM2.5 concentrations in the past 5 years. The automated air-quality monitoring station at Sirifort operated by  Central Pollution Control Board (CPCB)  provides valuable insights into the long-term trends of air pollution in the area.

Impact of COVID

A comparative analysis of daily PM2.5 concentrations indicate the peaks during the winter months of 2018, 2019, 2020 (Figure 6) due to trapping of fine particles under cool air. The COVID-19 pandemic lockdown provided a temporary respite before picking pace with the ease of lockdown measures from September-October, 2020. For more than 207 days in 2019, the residents of Sirifort were exposed to unhealthy PM2.5 levels.

Hazardous conditions observed during early morning hours and late nights peaking in winter months

The hourly PM2.5 concentrations from Sirifort gives us a better understanding of the emission levels that vary across different times of the day and various months in the area. The hazardous conditions were specifically prevalent during the nights and early morning hours of winter months (Figure 7).

Strategic local interventions must be prioritized to protect the region's most vulnerable residents. The short and long-term exposure to these toxic PM2.5 levels increases the risk of respiratory and chronic cardiovascular diseases.

Way Forward

A multi-pronged approach at regional, local and sectoral levels, including governments, SMEs, concerned citizens and other relevant stakeholders, is necessary to drastically reduce the current PM2.5 levels in Delhi and NCR. The stupendous task for the  National Clean Air Programme  and the Commission for Air Quality Management for Delhi-NCR to lower emissions in the coming years is challenging, but feasible. Collective action on a long-term strategy can improve the air quality in Delhi, maintaining – and improving – the city’s livability.  

Views expressed are authors’ own.