Extreme Air Pollution in Global Megacities

Curr Clim Change Rep (2016) 2:15–27 DOI 10.1007/s40641-016-0032-z EXTREME EVENTS (A SOBEL AND SJ CAMARGO, SECTION EDITORS) Extreme Air Pollution in Global Megacities Miriam E. Marlier 1,2 & Amir S. Jina 3 & Patrick L. Kinney 4 & Ruth S. DeFries 1 Published online: 17 February 2016 # Springer International Publishing AG 2016 Abstract Air quality in the world’s most populous cities (megacities) impacts a sizeable proportion of the global population. Projected population increases in urban areas over the coming decades underscore the importance of understanding the sources, variations, and impacts of air pollution. While some megacities experience episodic extreme events, in others, extremely degraded air quality is chronic. In this review, we assess recent findings on the impacts of extreme air pollution, which we define as concentrations exceeding international guidelines. We highlight recent research on pollution and growth trends in the most populous megacities. We then emphasize important new methods for monitoring air pollution exposure, such as satellite-based estimates, and suggest future needs, including a more comprehensive understanding of the health and economic impacts. The primary conclusion to emerge is that, globally, while the extreme air pollution This article is part of the Topical Collection on Extreme Events Electronic supplementary material The online version of this article (doi:10.1007/s40641-016-0032-z) contains supplementary material, which is available to authorized users. * Miriam E. Marlier 1 Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Ave., New York, NY 10027, USA 2 Department of Geography, University of California, Los Angeles, 1255 Bunche Hall, Los Angeles, CA 90095, USA 3 Department of Economics, University of Chicago, 5757 South University Ave., Chicago, IL 60637, USA 4 Mailman School of Public Health, Columbia University, 722 W. 168th St., New York, NY 10032, USA burden is highest in megacities in developing countries, significant gaps remain in our understanding. Keywords Megacities . Air quality . Pollution . Environmental health Introduction Megacities are defined as urban agglomerations of more than 10 million people and have increased from 10 cities with a total of 153 million people in 1990 to 28 cities with a total of 453 million people in 2014 [1]. By 2030, the total population of megacities is projected to reach 730 million people in 41 cities (Fig. 1a) [1], highlighting the urgency to better understand the influence of these population centers on their surrounding environment and the well-being of residents. For example, ambient (outdoor) air pollution is a leading risk factor according to the Global Burden of Disease [3] with more than 96 % of the global population in large cities exposed to fine particulate matter (PM2.5) above World Health Organization (WHO) air quality standards [4]. While the 30 most populated urban areas account for 7 % of the global burden from ambient air pollution (roughly equal to population share), several megacities in East and South Asia have higher per capita effects [5••]. The current knowledge base of air pollution in megacities is spread across multiple scales, ranging from global or regional assessments to individual megacities or specific locations within these cities. Here, we review the recent literature describing extreme air pollution (sporadic or chronic) in global megacities. We primarily concentrate on PM2.5 and ozone (O3) but also include research on other relevant pollutants, carbon monoxide (CO), volatile organic compounds (VOCs), and black carbon (BC). We focus on studies published since 2013 and megacities that are currently, or projected by 2030, to rank in the top 10 for 16 Curr Clim Change Rep (2016) 2:15–27 Fig. 1 a Population in the 30 most populous megacities for 2000–2030, with projected 2030 population indicated by darker colors and b % population change from 2015 to 2030 for the 10 most populous cities in both years (given overlap, this amounts to 13 cities total) [2] populations of the largest urban agglomerations defined by the U.N. World Urbanization Prospects. Given an overlap between the 2 years, this amounts to 13 megacities overall (Fig. 1b). Global Overview Recent estimates of the distribution of air quality are useful for understanding air pollution in megacities from a global perspective. Figure 2 shows the distribution of satellitederived PM2.5 over 2001–2010 (Fig. 1a) and the change in concentrations between the two timepoints (Fig. 1b) [6, 7••]. From 1998 to 2012, the most prominent trends in monthly PM2.5 were in the Eastern United States (−0.4 μg/m3/year), the Arabian Peninsula (0.8 μg/m3/year), South Asia (0.9 μg/ m3/year), and East Asia (0.8 μg/m3/year) [8]. Sources, and the extent to which they are produced locally or regionally, vary substantially and are dominated by residential energy usage in Curr Clim Change Rep (2016) 2:15–27 17 Fig. 2 Global average satellite-derived PM2.5 from 2001 to 2010 (μg/ m3), including dust (top panel) and the change from 2001 to 2010 (bottom panel). 2001 and 2010 estimates were selected from datasets as the center of a 3-year average (2000–2002 for 2001) [6, 7••]. Most populous megacities (defined for 2015 and 2030 projections) are indicated on the map India, China, and Bangladesh; power generation in the USA; biomass burning in the tropics; agricultural burning across Europe and Russia; and dust in North Africa and the Middle East [5••, 9]. At the global scale, premature mortality estimates for the past decade range from 1.6–3.3 to 0.1–0.8 million adult deaths per year from ambient PM2.5 and O3 exposure, respectively (Table 1) [5••, 9–12]. Over 1998–2012, satellite-based analysis indicates that global population-weighted PM2.5 has increased by 0.55 μg/m3, largely driven by increases in East and South Asia (3.2 and 2.9 %/year) [7••]. Future projections estimate that the contribution of urban areas (>400 people/ km2) to global mortality from ambient pollution will increase from 60 to 65 % of the total from 2010 to 2050, driven partly by population increases but also by higher per capita mortality attributable to air pollution [5••]. 18 Curr Clim Change Rep (2016) 2:15–27 Table 1 Recent global estimates of PM2.5 and O3-related health impacts for adults ≥30 years. Causes of death are chronic obstructive pulmonary disease (COPD), cardiopulmonary disease (CPD), cerebrovascular disease (CeVD), ischemic heart disease (IHD), cardiovascular disease (CVD), respiratory disease (RD), all causes (AC), and lung cancer (LC) Study PM2.5 O3 Details Evans et al. [9] 3.3E6 AC Not studied Satellite based for 2001–2006, not including dust 2.5E6 CPD 1.3E6 IHD Silva et al. [10] 2.2E5 LC 2.0E6 CPD 4.7E5 RD Model based for 2000 vs. 1850 (pre-industrial) Fang et al. [11] 1.5E5 LC 1.5E6 CPD 3.8E5 RD Model based for 2000 vs. 1860 (pre-industrial) (...truncated)