Megacities and Atmospheric Pollution

Abstract

About half of the world's population now lives in urban areas because of the opportunity for a better quality of life. Many of these urban centers are expanding rapidly, leading to the growth of megacities, which are defined as metropolitan areas with populations exceeding 10 million inhabitants. These concentrations of people and activity are exerting increasing stress on the natural environment, with impacts at urban, regional and global levels. In recent decades, air pollution has become one of the most important problems of megacities. Initially, the main air pollutants of concern were sulfur compounds, which were generated mostly by burning coal. Today, photochemical smog-induced primarily from traffic, but also from industrial activities, power generation, and solvents-has become the main source of concern for air quality, while sulfur is still a major problem in many cities of the developing world. Air pollution has serious impacts on public health, causes urban and regional haze, and has the potential to contribute significantly to climate change. Yet, with appropriate planning, megacities can efficiently address their air quality problems through measures such as application of new emission control technologies and development of mass transit systems.This review is focused on nine urban centers, chosen as case studies to assess air quality from distinct perspectives: from cities in the industrialized nations to cities in the developing world. While each city-its problems, resources, and outlook-is unique, the need for a holistic approach to the complex environmental problems is the same. There is no single strategy in reducing air pollution in megacities; a mix of policy measures will be needed to improve air quality. Experience shows that strong political will coupled with public dialog is essential to effectively implement the regulations required to address air quality problems.

Nitrogen dioxide measurement by cavity attenuated phase shift spectroscopy (CAPS) and implications in ozone production efficiency and nitrate formation in Beijing, China

“…The roles of megacities in regional air pollution, such as photochemical smog and haze, have been extensively investigated in previous works [Guttikunda et al, 2003[Guttikunda et al, , 2005Kanakidou et al, 2011;Lawrence et al, 2007;Madronich, 2006;Molina et al, 2010;Molina and Molina, 2004;Ran et al, 2012]. Beijing, one of the largest cities in China and one of the top 25 world megacities, has a resident population of more than 20 million in 2012 (http://www.…”

Climate change and its effects on urban spaces in Chile: A summary of research carried out in the period 2000-2012

“…In particular, the following are analyzed: behaviour of water run-off in drought periods (Müller and Reinstorf, 2011); the current state and expected evolution of mountain glaciers (Bodin et al, 2010); the effects of high temperatures on the population (Bell et al, 2008); the consequences of the reduction in respirable particulate matter associated with the mitigation of greenhouse gases (Cifuentes et al, 2001;Bell et al, 2006;Grass and Cane, 2008); an assessment of the effect produced by cities on the atmosphere (Molina and Molina, 2004); and the incorporation of the risk focus in megacities (Kopfmüller, 2009).…”

“…Consider heat waves as a public health problem, thereby generating policy programs intended to prevent the consequences of these phenomena in the vulnerable population (ONU-HABITAT, 2012). Indications for urban planning Molina and Molina (2004). Literature review (case study) Los Angeles, (U.S.), Mexico City (Mexico), Toronto (Canada), Delhi (India), Beijing (China), Santiago (Chile), São Paulo (Brazil), Bogotá (Colombia) and Cairo (Egypt)…”

Urban Road Transportation Externalities: Costs and Choice of Policy Instruments

“…The existing literature (for example Molina and Molina 2004) suggests that externalities from urban transportation cannot be solved through one specific policy instrument; instead it requires a portfolio of policy measures that best suit each city's specific circumstances. For example, local air pollutants (such as SPM, CO, VOCs, and lead) require substantial reduction to avoid their effects on human health.…”

“…For example, commuter rail produces almost half as much CO 2 emissions as an average car trip per passenger kilometer of travel in the United States (ABA 2007). Similarly BRT is considered to be one of the more environmentally friendly modes of urban transportation as it leads to reduced travel duration, improved air quality, increased pedestrian space and bike use, and less private Timilsina and Dulal vehicle use (Molina and Molina 2004). The TransMilenio BRT project in Bogota, Colombia is estimated to have reduced: the emission of CO 2 by 14.6 million metric tonsduring the first 30 years of its operation; 93 percent of traffic fatalities; 40 percent of local air pollutants; and 32 percent of travel time as compared to the transportation that would have been implemented otherwise (Lee 2003).…”