Can a “Blue Sky” Return to Indian Megacities?

Deterioration of air quality in Indian megacities (Delhi, Mumbai or Kolkata) is much more significant than that observed in the megacities of developed countries. Densely packed high-rise buildings restrict the self-cleaning capabilities of Indian megacities. Also, the ever growing number of on-road vehicles, resuspension of the dust, and anthropogenic activities exacerbate the levels of ambient air pollution, which is in turn breathed by urban dwellers. Pollution levels exceeding the standards on a regular basis often result in a notable increase in morbidity and mortality. This article discusses the challenges faced by Indian megacities in their quest for sustainable growth, without compromising the air quality and urban way of life. Main Text: India has the largest number of megacities (3 out of ~25) in the world. Together, Delhi, Mumbai and Kolkata house approximately one–fifth of the total worldwide megacities population (UN, 2010). The year 1991 saw the opening of the Indian economy and markets that resulted in rapid urbanisation. One outcome was the increase in use of private vehicles using limited road space, often leading to congestion and public health concern over the prolonged exposure to greater emissions from road vehicles (Nel, 2005; Patankar and Trivedi, 2011). The sky over Indian megacities is rarely blue nowadays. While the blue color itself is not a direct indication of the cities air quality level, the absence of it is a visible warning sign of a serious problem related to air pollution. Recent estimates suggest that exposure to vehicle-emitted nanoparticles (Kumar et al., 2011a) and other pollutants (suspended particulate matter, SPM; sulphur dioxide, SO2; and nitrogen dioxide, NO2; Gurjar et al., 2010) cause ~11250 and ~10500 excess deaths in Delhi every year, respectively. Reports by the Central Pollution Control Board (CPCB) suggest a high correlation between increased outpatient visits to hospitals and elevated pollution levels in Delhi (CPCB, 2008a, b). In fact, ~1/3 of Delhi adults have been shown to carry one or more respiratory symptoms due to poor air quality, which surges to ~2/3 in children (CPCB, 2008a, b). Findings of the “six cities” Cite this article as: Kumar, P., Jain, S., Gurjar, B.R., Sharma, P., Khare, M., Morawska, L., Britter, R., 2013. New Directions: Can a “Blue Sky” return to Indian megacities? Atmospheric Environment 71, 198-201. http://dx.doi.org/10.1016/j.atmosenv.2013.01.055 Page 2 of 8 study (NSR, 2010) indicate that, in 2007, 24-h average ambient concentrations of SPM, PM10, PM2.5 and NO2 in residential areas of Delhi and Mumbai were much higher than the CPCB standards (Table S1). The indoor environment does not safeguard against outdoor pollution, because outdoor air penetrates easily indoors (Hoek et al., 2008) where Indian city dwellers spend more than 80% of their time (Massey et al., 2012) as in most countries around the world (Heinrich, 2011; Wallace and Ott, 2011). Even in the absence of additional indoor source contributions, indoor concentrations of PM10 and PM2.5 can reach between 50 and 100% of their outdoor counterparts inside naturally ventilated buildings (Morawska and Salthammer, 2003). Given this fact, “clean air” in the context of megacities, and whether it is available to the residents of Indian megacities, needs to be explored. “Clean air” is referred to here as air with pollutant levels that fall below the WHO (2006) standards (Table S2) or the “low concentration” category of the CPCB (i.e. <50% of those set as national standards). This leads to the question: what is needed to achieve “clean air” objectives in Indian megacities? Fig. S1 presents an interesting overview of annual mean PM10 levels in Indian cities and the megacities worldwide (WHO, 2011). At par with Karachi, Delhi shows ~10-fold pollutant concentration levels over the WHO limits or the levels in New York which appears to be the cleanest megacity. Clearly, taking PM10 as a metric, all three Indian megacities are among the top polluted cities in developing countries and up to 10-times more polluted than the megacities in developed world. Inter-comparison of PM10 levels in various Indian cities suggests that even the cleanest cities contained ~2-times higher annual PM10 concentrations (with the dirtiest being 13-times higher) over the WHO guidelines. About eight of these burgeoning cities show equal or more concentrations than those in the three Indian megacities. Although such growing Indian cities are not the focus of this article, their inhabitants are paying identical or even larger health penalties compared to those residing in megacities (Banerjee et al., 2012; Salvi, 2011). The “six city” study (NSR, 2010), which included Delhi and Mumbai, suggested that road vehicles are the principal source for most pollutants, except PM10 and SPM (largely produced by resuspension from paved and unpaved road dust), therefore lowering their levels should be the first priority. Mitigation actions such as better maintenance of existing roads using innovative environmental friendly road construction materials (e.g. polymers with improved bitumen quality) as well as paving of unpaved roads and footpaths could help controlling the resuspension of PM10 and SPM. On the other hand, limiting the emissions from combustion sources such as road vehicles, refuse burning and diesel generator sets could work well in minimising the emissions of other pollutants. For instance, introduction of compressed natural gas (CNG) in all public modes of road transport and light duty commercial vehicles in Delhi during 2001-2006 resulted in reduction in PM concentrations, in addition to CO, NOx and SO2 levels. Further reduction in ambient pollutant concentrations by targeting the combustion-derived emissions is possible given the past success stories, such as the downward trend of SO2 and lead emission levels following the policy decisions regarding the lead and sulphur content in fuels (from 10,000 ppm in mid-1990s to 500 ppm within 4 years and to 50 ppm in 2010). However, this is still about 5 times higher than the ultra-low-sulphur diesel used in Europe (Jones et al., 2012). Despite the above efforts, the current levels of some of the combustion-derived air pollutants such as PM2.5 are up to ~7.5 times above the 24-h average standards in Delhi (NSR, 2010; WHO, 2011). These will require great efforts to reduce them, if “clean air” targets are to be achieved. The ineffectiveness of the policy interventions to meet the air quality goals is attributed to increase in the number of private vehicles in addition to other factors discussed above. A modal shift from private to public mode is likely to improve the effectiveness of various interventions. Moreover, any solution Cite this article as: Kumar, P., Jain, S., Gurjar, B.R., Sharma, P., Khare, M., Morawska, L., Britter, R., 2013. New Directions: Can a “Blue Sky” return to Indian megacities? Atmospheric Environment 71, 198-201. http://dx.doi.org/10.1016/j.atmosenv.2013.01.055 Page 3 of 8 must firstly reduce emissions at the source. Court-mandated measures applied in public transport of Mumbai and Delhi have resulted in improvements in air quality, although the case in Kolkata is less encouraging, since older vehicles are yet to be phased out or changed to CNG. Besides the timely implementation of progressive emission norms and improvement in fuel quality, adoption of successfully applied emission reduction methods elsewhere, such as the installation of over 100 million non-polluting e-bikes by Chinese cities during the past decade (Shuguang et al., 2011), hydrogen fuel based clean vehicles (Kumar et al., 2009) or the use of subsidised electric vehicles in the UK and Europe, can also be of value. However, the question remains as to whether India's air pollution problem would disappear if vehicle emissions were significantly reduced. The same “six city” study (NSR, 2010) showed that emissions from power plants, industries, domestic biomass burning, building and construction activities are also of concern. Both short and long distance trans-boundary pollution from surrounding areas can also increase the ambient air concentrations in India's megacities. For example, Delhi and Kolkata are surrounded by suburban areas where unregulated anthropogenic sources of domestic biomass burning and local diesel generators (for continuity of electricity supply) are common. As recently shown, “unorganised industry” is the main contributor to airborne metals in Delhi (Pathak et al., 2012). This indicates the magnitude of the problem and the need for an emissions reduction to clean the air over these megacities. Moreover, there is yet another mega pollution source that must be addressed: the cities themselves! Through the buildings’ high energy consumption, the cities themselves are indirect pollution sources. It has been estimated that urban areas account for over 70% of energy related greenhouse gas (GHG) emissions worldwide (CPCB, 2008a, b; Hoornweg et al., 2011). The actual amount of emissions varies significantly between cities and countries. For instance, Delhi was responsible for 1.5 tCO2 e/capita of GHG emissions in the year 2000 (the year when the data was available), Sydney, Australia contributed much higher emissions in 2006, at 20.3 tCO2 e/capita (Hoornweg et al., 2011). These emissions contribute to global atmospheric pollution and, thus, to the background pollution in the cities. Megacities in developed countries tend to consume much more energy than those in developing countries (the difference between Delhi and Sydney is of the order of 20 times!), which indicates that future emissions in the latter will increase in line with their economic progress. Therefore, when addressing urban sustainability, the issue of urban and building design, as well as human behaviour should be brought into the picture, as this is where huge gains can be made in energy reduction and air pollution (Fig. 1). This is of particular importance for megacities which will grow into super megacities in the next one or two decades, as is the compounding problem of global climate change and the impact this will have on indoor and outdoor air quality and energy consumption. For example, temperature increases will drive even more energy consumption and higher air pollution emissions for air conditioning in already hot climate of India. So can Indian megacities have a sustainable future growth without compromising on air quality and urban life? A positive answer is possible through the proper management of pollution, reduction of vehicle emissions, and regulation of “unorganised” industries (Fig. 1). This should be underpinned by scientifically evaluated air pollution dispersion modelling and forecasting systems that are fit for local use and capable of predicting the sudden occurance of “extreme” pollution levels due to unfavourable meteorology and poor dispersal capacity at busy traffic-intersections, in order to allow time for mitigation plans to be drafted and implemented (Gokhale and Khare, 2007). For instance, modelling studies for the long range Cite this article as: Kumar, P., Jain, S., Gurjar, B.R., Sharma, P., Khare, M., Morawska, L., Britter, R., 2013. New Directions: Can a “Blue Sky” return to Indian megacities? Atmospheric Environment 71, 198-201. http://dx.doi.org/10.1016/j.atmosenv.2013.01.055 Page 4 of 8 transport of pollutants could objectively apportion the contribution from background and remote sources to the pollution load in city centres (Wagstrom and Pandis, 2011). This would help to identify appropriate control points, which can be prioritised in order to reduce pollution levels in the cities. Lessons can still be learned from the developed world to ensure the future of India's megacities and to manage future megacities. One such concept applied in developed world is establishing sustainability metrics for cities. These metrics have been successfully developed for growing cities such as Boston, Seattle and Chicago, to monitor environmental, social and economic impacts (Fitzgerald et al., 2012). Conceputal framework for sustanability metrics is also available for growing cities in India but requires comprehensive evaluation and a protocol for its effective implementation (JNNURM., 2005). Emission control measures and policies have helped in reducing the level of air pollutants in Indian megacities over the past decade. Consequently, the air is cleaner, but it is still not close to the “clean air” goal. PM10 levels are still unacceptably high and continue to be above air quality standards (Sharma et al., 2013). PM2.5, which has recently attracted the attention of regulatory authorities in India, is a concern, after being introduced as a standard in 2009. So far, measured data show up to 7.5 and 2.5 times higher levels in Delhi and Mumbai, respectively, than those prescribed by the CPCB (NSR, 2010). NOx levels continue to exceed the standards at most monitoring stations (NSR, 2010). Nanoparticles, potentially the most harmful of all pollutants (Heal et al., 2012; Kumar et al., 2013) as they can penetrate straight into the lungs and blood stream (Donaldson et al., 2005), are not currently in the regulatory picture (Kumar et al., 2011b). Preliminary investigations on nanoparticle measurements in Indian megacities indicate roadside concentrations 10's of times higher than in European megacities (Kumar et al., 2011a; Kumar et al., 2012). Limited efforts are made thus far to bring together issues of sustainable living and air pollution. Better foresight is needed if Indian cities are to reduce and maintain air pollution levels within the standard limits, including plans to develop regulatory guidelines for pollutants that are currently not in the list (e.g. nanoparticles, indoor air pollutants). Meeting the “clean air” goals – and returning to a “blue sky” – in existing megacities may appear to be a distant dream, but this could well be achieved for new and growing cities, if a holistic approach combined with a futuristic vision is adopted.