A Novel Approach to Understanding Delhi’s Complex Air Pollution Problem

With rising concerns about the steep increase in air pollution in the National Capital Territory of Delhi, several factors—particularly motorised transportation, construction, and stubble burning in neighbouring states—are being identified as contributing to this hazard. However, in order to make effective policy decisions, there is a need for a holistic approach that identifies the root causes of the problem. The use of system dynamics simulation offers a novel systems thinking approach to understand Delhi’s air pollution, taking into account the dynamic nature of the air pollution system as well as the complex interdependencies among the various factors and sources of air pollution.

The authors express special gratitude to the anonymous referee for the useful inputs and constructive feedback which helped in improving the quality of the paper significantly.

The National Capital Territory (NCT) of Delhi has seen rapid growth in its industrial, transportation, and housing sectors over the past decades. The population of Delhi has increased from 1.378 crore in 2001 to 1.678 crore in 2011, a decadal growth of 21.2% against a national growth rate of 17.7%. The total area of Delhi is 1,483 square kilometres (km²). Its population density was recorded as 11,320 persons per km² in 2011, compared to a density of 9,340 persons per km²in 2001 (Directorate of Economics and Statistics 2017). This rapid growth in population, along with the increased rate of industrialisation and urbanisation and the rise in motorised transport, have resulted in an increased concentration of various air pollutants such as nitrogen oxides, sulphur dioxide, suspended particulate matter, respirable suspended particulate matter (RSPM/PM₁₀), carbon monoxide, ozone, lead, benzene, hydrocarbons, and the like (Goyal et al 2006).

PM₁₀ includes all particulate matter (PM) with an aerodynamic diameter less than 10 micrometres (µm). These particles have the highest tendency to penetrate human lungs and may cause aggregated respiratory and cardiovascular diseases, often leading to premature deaths (Seaton et al 1995). PM_2.5, included within the PM₁₀ volume, refers to the particles that are less than 2.5 µm in aerodynamic diameter. More than 95% of combustion-related emissions from petrol, diesel, and natural gas constitute PM_2.5, and thus PM₁₀ as well. Apart from emissions, a good percentage of PM₁₀ pollution also comes from dust sources such as construction sites, vehicular movements on poorly built and broken roads, and seasonal dust storms. Nearly 80% of the dust commonly found on roads falls between the range of 2.5 µm and 10 µm and is consequently accounted within the PM₁₀ measurement. PM₁₀ was the only size fraction measured in India until 2009, when PM_2.5 was added to the criteria.