Air Pollution and Health Risk Reduction

By: R B Singh, The author is a Professor, Department of Geography, Delhi School of Economics, University of Delhi.
The burgeoning mega cities, especially in developing countries are expected to experience higher levels of risk and exposure to health hazards from a combination of individual, physical and environmental factors.
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Rising levels of air pollution and alternation of atmospheric composition are largely connected to rapid industrialisation, motorisation and energy consumption. Increasing concentrations of nitrogen oxides, sulphur and carbon, especially in metropolitan cities like Delhi have started to pose major health risks in the form of physical and mental health disorders (Chen and Kan, 2008).

The Lancet Global Health Survey (2018) has found that there is a link between death from chronic respiratory diseases and air pollution in North Indian cities with as high as 8.7 per cent of chronic obstructive pulmonary disorders (COPD) being caused by air pollution. It is clear that air pollution is likely to affect human health in disastrous proportions.

There is extensive literature on links between COPDs and air pollution. Suspended particulate matter (SPM) and trace elements like benzene and ozone (Knowlton et al., 2004) are increasing in concentration in mega cities of developing countries. Frumkin (2002) and Magas et al. (2007) have shown evidence for chronic heart and lung disease, asthma and cancer, respectively. In the Indian scenario, among non-communicable diseases, cancer and cardiovascular disease—caused by exposure to polluted air—have been found to be the leading cause of mortality in urban areas. However, spatial variations and patterns in trend of air pollution have also been established. Particularly, it is the level of vulnerability that varies, with respect to gender and age (Curtis et al., 2006).

Effective mitigation needs to be brought in and this will require detailed analyses of the various environmental and socioeconomic factors in different cities affecting human health. Variability of the effects also needs to be factored in so that an accurate roadmap for mitigation and risk reduction efforts can be drawn.

Air Pollution Database

The present research relies on various secondary sources of data on air pollution and health impacts. The Central pollution control board (CPCB) under the Ministry of environment, forests and climate change is responsible for collecting pollution data for all states and union territories of India. The task, however, is decentralised under assorted agencies. In Delhi, it is controlled by CPCB, Delhi pollution control committee (DPCC) and National environmental engineering research institute (NEERI). The pollution recording stations are representative of three categories on the basis of their function—residential, industrial and traffic junctions. All the sites regularly monitor the particulate matter, or PM10, respirable suspended particulate matter (RSPM or PM2.5), sulphur dioxide (SO2) and nitrogen dioxide (NO2) levels. SPM and RSPM are monitored 8 hourly for 24 hours whereas SO2 and NO2 are monitored every 4 hours each day.

Trend of Air Pollution: Case of Delhi

The three major pollutants in India are SO2, NO2 and PM10. Under the National air quality monitoring programme (NAMP), these pollutants have been identified for regular monitoring at all stations (CPCB-ENVIS, 2016). Power sector and thermal power plants are the primary sources of SO2 although researchers have also listed transport as a source. However, Chelani and Devotta (2007) have found that following the implementation of policies for checking concentration of SO2 and NO2 and increased usage of compressed natural gas (CNG), there has been significant temporal variation between areas that were using CNG and those that were not. Similarly Datta et al. (2010) have stated that the transport sector may not be a major source of SO2 in Delhi. Hence, the lower concentrations of SO2 may be due to the policies on better quality of diesel and use of CNG in public vehicles. Goyal et al. (2006) also point out similar trends for SO2. Annual mean levels of SO2 indicate that it has mostly been lower than the prescribed limit (50 µg/m3). The levels of NO2, on the other hand, indicate an increasing trend and are much above the limit of 40 µg/m3. The massive rise in vehicular fleet is considered a major cause for this increase. The rise of NO2 is a threat to environmental and human health as the reactions of NOX in the presence of sunlight produces ground level ozone that is highly dangerous (Lo and Quattrochi, 2003).

Suspended particulate matter (SPM) and RSPM levels are soaring in the Delhi region (prescribed limits being 40 and 60 µg/m3 respectively). Incomplete combustion from industries and vehicles are major sources of particulates of varied sizes. Natural sources like road dust and meteorological conditions add to the load as well. SO2 concentration is highest in the winter season, particularly in the months of December and January owing to the stagnant stable air masses.

Jayaraman and Nidhi (2008) and Mohan and Kandya (2007) also state that SO2 is found to be highest in winters. SO2 concentration is the lowest in summer and the rainy months of July-September. This is largely due to high humidity. During the dry period of February to April, SO2 is found to be high. The highest RSPM levels are found in winter that is much above the prescribed limits (60 µg/m3). Similar findings are cited in detailed research by CPCB (2006). Pollution levels in Delhi were unexpectedly high in November 2016 (post-Diwali celebration); and schools remained closed for three days. The situation is grim as the causal factors and impacts are multi-faceted in nature. Due to variations in temperature, rainfall and humidity levels, wind direction and other climatic factors, the levels of SPM and RSPM vary across seasons. The contributing factors of high SPM are incomplete combustion in vehicles, construction works and other natural sources. Peak winter and summer are when SPM levels are the highest.

Mobile sources, like vehicles, are paramount contributors to oxides of nitrogen. While Delhi contains 1.4 per cent of India’s population, it accounts for 7 per cent of total vehicular load of the country (Sood, 2012). Das and Parikh (2004) mentioned that Delhi is the fourth most polluted city in the world and the dominant contributor to air pollution is the transport sector. The number of total vehicles in Delhi has increased from 1.92 million (1991) to 5.32 million (2010). Private cars in the city have proliferated rapidly—from 0.42 million in 1991 to 1.46 million in 2010. There is high dependence on private vehicles for transportation, which is clearly reflected by the increasing proportion of private cars to total vehicle composition. While, 22.2 per cent of the total vehicular load was of private cars in 1991, it increased to 27.4 in 2010 (Singh and Grover, 2018) and to about 30 per cent in 2017 (PTI, 2017). Considering the damaging effects of rise in private cars, especially diesel vehicles and two stroke vehicles, there is an urgent need to focus on the betterment of mass public transportation system.

Impact of Air Pollution on Human Health

It is well established that apart from disorders in the respiratory system, air pollution causes harm to eyes, skin, lungs and other respiratory organs. Air pollution may also worsen the circulatory system, making it vulnerable to failure (Singh and Grover, 2018).

Cropper et al. (1997) using the mortality data obtained from New Delhi Municipal Council established that there is a positive relationship between particulate pollution and deaths from respiratory and cardiovascular problems. Similarly, Firdaus (2010) too established a high correlation between SPM and health as did Agarwal et al. (2006) suggesting a direct bearing on the number of COPD cases in Delhi. Rizwan et al. (2013) have also reflected on the associated morbidity due to air pollution. Dry cough, wheezing, breathlessness and chest discomfort are notable health problems in the city. Hypertension was found to be positively correlated with RSPM. Delhi has shown significantly higher levels of chronic headache, eye irritation, skin irritation and various types of lung functions deficits. Oxides of nitrogen generated from power plants, electric utility boilers and vehicular emission have shown to cause airway resistance, chest tightness, lung and eye irritation and viral infections. It is clearly visible that the various orders of respiratory illness and deaths are increasing manifold.

Need for an Integrated National Assessment Based on Geo-health Study

Further study of the impact of different environmental and socioeconomic factors on human health in mega cities is required as they play a major role in shaping national health indicators. Such concepts will form the scientific basis for providing health security and carrying out locally differentiated sets of preventive measures aimed at environmental enhancement as well as at the identification of linkages between different territories’ geographic features and public health. Collection of statistical data related to the population morbidity and mortality may prove fruitful for monitoring health aspects. Development of specialised GIS designs and models for the purpose of data digitisation, visualising as well as common layer-to-layer and factor analysis, preparation of unified cartographic basis for mapping the indicators and analysis of the actual state of public health in urbanised areas for calculating the standardised geo-health indicators are some good initiatives.

Further steps can include:

 Analysis of urban environment factors through the example of cities in India as well as their impact on public health including, physiographic characteristics, demographic characteristics and socio-economic landscape.

 Probability distribution function of the ranks of cities based on mortality and urban area factors. Development of the integral indicators for the quality assessment of complex urban
life system.

 Comparative analysis of comfort conditions for health and wellbeing of urban and rural areas by studying the temporal dynamics of the bioclimatic indexes (BI). Extremes in BI and their connection with different climate extremes, particularly to estimate the relationship of climate extremes with disaster frequency for disaster risk reduction in urban areas can be studied. BI determines the comfort level and assesses the spreading out of climate-sensitive diseases using climate model data.

Policy Implications for Air Pollution and Health Risk Reduction

The government must implement policies to ensure that the benefits of urban growth are shared equitably and sustainably. Sustainable urbanisation requires competent, responsive and accountable governments charged with the management of cities and urban expansion as well as appropriate use of information and communication technologies (ICTs) for efficient service delivery. There is a strong need to put emphasis on eco-friendly vehicles for transportation and restoration of cycle lanes in congested urban spaces. Encouragement of native pollution tolerant plant communities, i.e., Mango (Mangifera indica), Peepal (Ficusre ligiosa), Neem (Azadiracta indica) and Babool (Acacia Arabic) etc., may help in maintaining a green cover, controlling pollution and also for the health, happiness, wellbeing and sustainability of cities. There is a need for maintaining a separate lane for high occupancy vehicles for their smooth flow and for encouragement to public transport vehicles. Cleaner fuels and more efficient diesel and petrol vehicles could also be introduced. In addition, the government should allocate funds for opening up of public hospitals for non-communicable diseases.


The urban atmospheric environment of Delhi is deteriorating due to rise in air pollution. The annual temporal analysis of SPM and RSPM suggests an upward trend and their presence in ambient air has been found to have exceeded the National Ambient Air Quality Standards. While interpreting the pollution concentration, most of the monitoring stations have been found to fall under the critical and high pollution category. The inter linkages between air pollution and human health in Delhi suggest that PM exerts the highest negative influence. Increasing health vulnerability and worsening air quality are closely related to urban disasters and need special attention, especially in urban areas of developing countries. The pollutant standards need to be made stricter and stringent implementation of pollution norms of vehicles and industries (small, medium and large) needs to be undertaken.


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