Global Megacities Research Articles

Ozone trends and their sensitivity in global megacities under the warming climate

Tropospheric ozone formation depends on the emissions of volatile organic compounds (VOC) and nitrogen oxides (NOx). In megacities, abundant VOC and NOx sources cause relentlessly high ozone episodes, affecting a large share of the global population. This study uses data from the Ozone Monitoring Instrument for formaldehyde (HCHO) and nitrogen dioxide (NO2) as proxy data for VOC and NOx emissions, respectively, with their ratio serving as an indicator of ozone sensitivity. Ground-level ozone (O3) reanalysis from the Copernicus Atmosphere Monitoring is used to assess the O3 trends. We evaluate changes from 2005 to 2019 and their relationship with the warming environment in 41 megacities worldwide, applying seasonal Mann-Kendall, trend decomposition methods, and Pearson correlation analysis. We reveal significant increases in global HCHO (0.1 to 0.31 × 1015 mol cm−2 year−1) and regionally varying NO2 (−0.22 to 0.07 × 1015 mol cm−2 year−1). O3 trends range from −0.31 to 0.70 ppb year−1, highlighting the relevance of precursor abundance on O3 levels. The strong correlation between precursor emissions and increasing temperature suggests that O3 will continue to rise as climate change persists.

Navigating the Challenges of Urbanization: A Case Study of Tokyos Developmental Issues and Strategic Solutions

Abstract: Tokyo, as a leading global metropolis, exemplifies the complex interplay between rapid urban expansion and associated challenges. This paper explores Tokyo's developmental issues since 1950, focusing on population density, land resource shortages, agricultural land decline, waste management, and disaster preparedness. Despite its status as Japans economic, cultural, and administrative center, Tokyo's limited land area and unique geographical constraints present significant hurdles. The study evaluates the city's responses to these challenges through urban planning and policy making, assessing both the effectiveness of existing solutions and areas for improvement. The paper highlights the need for a multifaceted approach involving strategic planning, innovative solutions, and collaborative efforts to enhance Tokyos resilience and sustainability. While providing valuable insights into Tokyos urbanization challenges, the study acknowledges limitations such as inconsistent data availability and the difficulty in measuring policy impacts. Future research should include comparative studies with other global megacities to identify universal and unique urbanization challenges and investigate the long-term effects of specific policies and practices on urban sustainability and quality of life.

Priority Intervention Evaluation of Community Regeneration in Megacities Based on the Business Improvement District (BID) Model: A Case Study of Tianjin, China

This study aims to start from the macroscale of the megacity, explore a top-down operational technical path from the identification of community regeneration units as the evaluation objects to the BID priority intervention evaluation, and then propose differentiated community regeneration strategies based on the BID model. In the post-epidemic era, it is necessary for global megacities to take new measures in urban regeneration to respond to worldwide changes and challenges. As an innovative tool to promote central city revitalization, the BID model has played an important role in community transformation. In the context of the continuous decentralization of population and industry in China’s megacities, it is urgent to explore the technical path to apply the BID model to local community regeneration. Given the shortcomings of existing studies in the method to identify the scope of BID implementation and evaluate intervention priorities, this study takes Tianjin, a megacity in China, as an example and uses DBSCAN (density-based spatial clustering of applications with noise) and service area analysis to define the community regeneration units with commercial agglomeration characteristics as the objects. Then, the BID priority intervention evaluation system is constructed from the two measurement aspects of the intervention potential and the necessity of community regeneration to classify the BID intervention priorities of community regeneration units. The main conclusions are as follows: 1. When the DBSCAN analysis parameters take the minimum number of elements as 30 and the search distance as 120 m, the result is most suitable for identifying community units with commercial agglomeration of the study area; 2. Population vitality, especially working and residential population density, is the key factor affecting BID intervention potential, while road network density is an important indicator for determining the necessity of community regeneration; 3. Community regeneration units with high BID priority levels need to develop differentiated regeneration strategies combining their BID intervention potential, regeneration necessity characteristics, and location attributes. These conclusions can provide references for the governments of megacities to screen and establish BIDs.

Identifying the Central Business Districts of global megacities using nighttime light remote sensing data

ABSTRACT The Central Business Districts (CBDs) are important hubs for urban economic activities. In the context of globalization, a unified CBD boundary would greatly facilitate the study of global CBD comparative analysis, urban socio-economic development, urban transport and commuting mode. However, previous studies have encountered challenges in developing a practical method for global CBD identification due to limitations in data sources and methodologies. In this study, we selected 32 global megacities as research objects and used the open-access Black Marble nighttime light (NTL) products to construct indicators with the intensity and angular effects of NTL. Clustering and decision tree were then employed to derive rules for CBD identification. Results show that combining Z-score indicators and the strategy of clustering 32 cities before decision tree classification could improve the accuracy of CBD identification, which achieved a producer accuracy of 85%. The 32 cities were clustered into three types, i.e. U.S.A.-like, the mixed type, and China-like. The rules for CBD identification became more complex in the above order, but the accuracy decreased in turn. This study provides a new CBD identification method for cities lacking reference data, allowing for the delineation of unified and comparable CBD boundaries on a large scale.

Transforming Megacities: Value and Impacts of Mixed-Use Developments with Multi-Criteria Decision-Making

Abstract This research article explores the valuation of mixed-use developments and their impact on urban planning and city regeneration. The study introduces a Multi-Criteria Decision Making (MCDM) methodology to analyze complex buildings developed in Shanghai from 2009 to 2019. Two MCDM appraisals are offered in different developments using three groups of key indicators that served as benchmarks for other Chinese clusters and global megacities. The article addresses two primary research questions: how mixed-use assets can be assessed using MCDM, and what the key performance indicators and factors contributing to the success of mixed-use developments are. The findings highlight the importance of connectivity, previous real estate experience, ESG strategies, international branding, architectural design, financial metrics, and adaptability of the real estate industry in evaluating mixed-use assets. The study provides insight to stakeholders involved in real estate development, including urban planners, developers, and investors, enabling them to make informed decisions and improve sustainable practices. The research also highlights the importance of considering ESG principles, community benefits, and long-term strategies when assessing mixed-use developments to drive social change and contribute to urban regeneration.

Getting citizens to conserve water: A comparison of crisis responses in Bogota and Mexico City

How can global megacities respond to increased threats from natural hazards? Looking at hazard events that produced drinking water crises in Bogota, Colombia, and Mexico City, Mexico, we compare these cities’ efforts to decrease potable water consumption. We ask how and why the socioeconomic and biophysical contexts shape city policymakers’ responses to water crises and consider the immediate and lasting impacts of technical and behavioral interventions. Leveraging our 2 case studies in Latin America, we identify how the unique policy contexts affected the interventions used and helped determine their outcomes. Four factors are identified as particularly relevant as follows: the differential roles of scientific and technical perspectives in each context, the role of ideology, the complexity of the environmental policy problems in each setting, and the varied roles of policy entrepreneurs in Bogota and Mexico City.

Exploring the spatiotemporal evolution dynamic and influencing factor of green ecology transition for megacities: A case study of Chengdu, China

Global climate change, rapid urbanization, and economic development have brought many challenges and threats to human production and lifestyles, increasing the necessity for sustainable human development, urban ecological governance, and low-carbon energy transformation. The current research on the green ecological transition model of global megacities is relatively scattered, with most studies focusing on the green ecological transition of a single dimension of ecological or social value. Based on the panel data of the economic, social, and ecological of Chengdu from 2010 to 2020, we measure the level of green ecological transition of Chengdu and its regions using the entropy weight method and TOPSIS method and then utilize exploratory spatial data analysis to explore the spatiotemporal evolution dynamic of green ecological transition in Chengdu city, and finally use the spatial Durbin model to analyze the key factors of green ecological transition in Chengdu park city. The results showed that: (1) the overall green ecological development level of Chengdu Park City showed an obvious upward trend, and the spatial region presents the characteristics of the circle structure of decreasing from the inside to the outside; (2) the green ecological transformation of Chengdu park cities has shown a positive spatial autocorrelation since 2015, and Jinjiang and Qingyang districts have become the green ecological transformation; (3) the adjustment of energy structure and the improvement of market freedom had a significant positive impact on the development of park cities, with a contribution of 8.3% and 10.9%, respectively. These results and findings will help to provide references for academic research and urban area planning on the green and low-carbon development transition and regional sustainable development of megapark cities.

Climate Change, Extreme Heat, and South Asian Megacities: Impact of Heat Stress on Inhabitants and Their Productivity

Abstract Of the 33 global megacities, 10 were situated in South Asia. Extreme heat waves have become an annual phenomenon due to climate change in South Asian megacities, causing severe health issues and even deaths. In this study, we evaluated 29 years (1990–2019) of historical data on heat stress in ten selected megacities (existing and prospective)—New Delhi, Dhaka, Mumbai, Kolkata, Ahmedabad, Chennai, Bengaluru, Hyderabad, Chittagong, and Pune—in India and Bangladesh. We used heat index (HI) and environmental stress index (ESI) analyses to evaluate stress and vulnerability. Our results showed New Delhi, Mumbai, Kolkata, Ahmedabad, and Chennai in India; Dhaka and Chittagong in Bangladesh were already experiencing an elevated number of hours of “danger” levels of heat stress, which may lead to heat cramps, exhaustion, stroke, and even death. Furthermore, the frequency of “danger” levels of heat stress and vulnerable levels of ESI has increased significantly since 2011 in the selected megacities, which elevated the heat-related vulnerability among the millions of inhabitants in terms of work hours lost for light, moderate, and heavy work due to heat stress. The vulnerable population in the studied megacities might have to reduce annual work hours by 0.25–860.6 h (light work), 43–1595.9 h (moderate work), and 291–2402 h (heavy work) due to extreme heat in 1990–2019. We also discussed the implication of the work-hour loss on productivity, income, gross domestic product, and sustainable development goal progress because of heat stress and its causes and suggested recommendations to reduce its impact.

Study on the Spatiotemporal Evolution of the “Contraction–Expansion” Change of the Boundary Area between Two Green Belts in Beijing Based on a Multi-Index System

In serving as a pivotal strategy for curbing urban sprawl, large-scale urban green belts, being a significant constituent of the urban green space, have been ubiquitously employed in the scheming and fabrication of green space systems in global megacities. Nevertheless, the disregard for research into the independent alteration mechanism of urban green space, coupled with the reactive approach of planning and construction and the singularity of quantitative indices, has engendered challenges in the creation of urban green belts. This paper presents an investigation into the juncture zone of two green belts in Beijing as a case study, erecting a “contraction–expansion” flux model of its green space and gauging the transformational traits of the green space in light of its spatial–temporal evolution with regards to its quantity, space, and connectivity among others. Findings reveal that between 2005 and 2012, the green space in Beijing underwent an approximately 20% alteration, with the green belt intersection zone’s green space area experiencing a dual trajectory shift of “expansion-contraction”. This shift was primarily characterized by expansion before 2015 and contraction from 2015 onwards. Concerning spatial attributes, patterns of expansion and aggregation were discernible in scattered distribution, whereas contraction and aggregation were evident in mass and spaced distribution. Spatial stability was influenced by the change model, marked by a shift in the center of gravity from a “north-south-east” orientation to a “northwest-southeast” direction. At the connectivity stratum, noticeable variations were witnessed in both the overall and local connectivity levels pre- and post-2015. Regarding individual connectivity, three vital nodes of stable linear connectivity were identified, playing a decisive role in defining the dispersion of crucial corridors within the area of study.

Spatial gradients of urban land density and nighttime light intensity in 30 global megacities

The spatial agglomeration of urban elements results in the center-periphery urban structure, but the difference in spatial gradients of socioeconomic and physical elements is unclear. This study investigates how urban land density (ULD) and nighttime light intensity (NLI) decline with the distance to center(s) using the inverse-S function. Taking 30 global megacities as examples, we acquired their urban land and nighttime light in 2020 to represent urban physical and socioeconomic elements, respectively. ULD and NLI in concentric rings have been calculated to compare their spatial gradients from the city center(s). Results show that both ULD and NLI decrease slowly around city centers, followed by a relatively quick decline to suburban areas, and then decrease slowly again to a background level, showing an inverse-S shape. This spatial gradient can be well-fitted by the inverse-S function, whose parameters reflect disparities in urban extents and urban forms. NLI decreases faster than ULD, resulting in smaller radii (extents) of NLI, which shows the spatial agglomeration of socioeconomic elements is more obvious than that of physical space. This gap requires balanced development of socioeconomic and physical elements in megacities to avoid low-density urban sprawl and promote sustainable urban development.

Future population exposure to heatwaves in 83 global megacities

Global warming leads to more frequent and intense heatwaves, putting urban populations at greater risk. Previous related studies considered only surface air temperature or one or two Shared Socioeconomic Pathways (SSPs) and were limited to specific regions. Moreover, no research focused on heatwave exposure in highly-populated global megacities facing severe threats. This study is the first to project future population exposure to heatwaves in 83 global megacities by 2100 using fine-resolution data, suitable indices reflecting human comfort in heatwaves by incorporating temperature and humidity, and a future population exposure projection and analysis framework. The results show that (1) the global frequency of extreme heatwave events and average change rate in each megacity sequentially increase from SSP1-2.6 to SSP5-8.5, and the change rate is generally larger in megacities in the Southern Hemisphere; (2) the increases in heatwave exposure are greatest under SSP370, and the change rates are generally larger for megacities in Southern Asia; (3) there is a high degree of inequality (Gini of 0.6 to 0.63) in future heatwave exposure globally, with the highest inequality under SSP5-8.5 and the lowest under SSP3-7.0; (4) the average exposure, increase rate, and change are highest in low-income megacities and lowest in high-income megacities. The distribution of exposure is the most balanced in middle-income megacities and the least balanced in high-income megacities; and (5) population growth contributes more to the change in exposure than total warming in high-income megacities under SSP1-2.6, and total urban warming contributes much more than population growth in all other cases. Every effort should be made to avoid the SSP3-7.0 scenario and pursue sustainable and rational urban economic development. Mumbai, Manila, Kolkata, and Jakarta warrant particular attention due to their rapid exposure growth. Additionally, policymakers and urban planners must focus on improving sustainable development planning for megacities in southern Asia and low-income megacities.

Feasibility, economic and carbon reduction benefits of ride-hailing vehicle electrification by coupling travel trajectory and charging infrastructure data

Ride-hailing has become a common travel choice in global megacities. However, ride-hailing fleets are facing severe challenges toward electrification owing to high travel intensity, high price sensitivity, inconvenience related to charging, and range anxiety. This study established a comprehensive feasibility–economic–environment assessment system to explore the applicability, life-cycle economic as well as carbon reduction benefits of ride-hailing electrification. For full-time ride-hailing vehicle drivers who face the greatest electrification challenges, it is found that charging station service radius of 1 km, average charging power of 37.5 kW, and state of charge of 30–70% as charging threshold are optimal for balancing the charging feasibility and driving experience. Ride-hailing electrification for full-time drivers can achieve synergetic economic and environmental benefits by saving 14000–24500 $ and reducing 47–66 t of CO2 emissions in a whole lifetime. This research suggests that developing a smart order dispatch system for ride-hailing to guide more efficient charging activities would help relieve range anxiety and further promote ride-hailing electrification.

Secondary sources of PM2.5 based on the vertical distribution of organic carbon, elemental carbon, and water-soluble ions in Bangkok

Ambient PM2.5 pollution can affect human health and the environment in global megacities. Secondary PM2.5 is produced by physical and chemical reactions of primary air pollutants. Sources of secondary PM2.5 in Bangkok have been considered in most on-target investigations for the control and management of air quality. This research aims to identify the vertical distribution of secondary PM2.5 sources in Bangkok, Thailand. Vertical distributions of PM2.5 in haze and non-haze periods were collected at different heights (30, 75, and 110 m above ground level) at the Air Pollutants Monitoring Tower, Kasetsart University (KU tower) between November 2020 and July 2021. The carbon components were analyzed by an OCEC analyzer using the IMPROVE thermal/optical reflectance (TOR) protocol, and the ionic species were determined by ion chromatography. The results showed that the organic carbon (OC) to elemental carbon (EC) ratios of PM2.5 tended to increase with altitude at 30, 75, and 110 m in the range of 2.0 - 7.7, 3.4 - 8.0 and 3.0 - 16.6, respectively. In the haze period (Jan-Feb 2021), the SOC within PM2.5 was the highest at 110 m which was 24.5%. In addition, the key components of SOC, NO3−, NH4+, and SO42− within PM2.5 were found in secondary aerosols in Bangkok. The chemical compositions indicated that secondary PM2.5 is mainly contributed by local vehicle exhaust (30 m) and long-range transported biomass burning (75 and 110 m). This research provides useful information that could be applied for urban secondary PM2.5 control and management.

Global Megacities and Frequent Floods: Correlation between Urban Expansion Patterns and Urban Flood Hazards

With climate change causing increased extreme weather events, megacities worldwide are experiencing unprecedentedly devastating floods and recurring flood damage. Investigating global megacities’ increased disposition to flooding will aid in developing sustainable flood-risk-management frameworks. Many studies have been conducted on the association between land-cover types and flood consequences, but few on investigating urban expansion patterns’ correlation with flood hazard and risk. This study examines the correlation between urban expansion patterns and increased flood hazards. Twelve megacities throughout the world were selected for this study. After exploring the possibility of the megacities having experienced flooding, we qualified their patterns of urban expansion and their potential to influence the elements of flood risk. Our results revealed that edge expansion and leapfrogging patterns had a strong positive correlation with statistical significance with flood hazard, while infilling had a weak positive correlation that showed no statistical significance with flood hazard. Further, we found that the megacities have all experienced devastating floods in the past two decades. Flood risk frameworks need to account for the impact of these patterns, and future urban planning designs and policies need to incorporate flood risk frameworks that account for patterns of urban expansion.

Leaders or laggards in climate action? Assessing GHG trends and mitigation targets of global megacities

Urban areas account for between 71% and 76% of CO2 emissions from global final energy use and between 67–76% of global energy use. The highest emitting 100 urban areas (defined as contiguous population clusters) account for 18% of the global greenhouse gas (GHG) emissions. To date there is no comprehensive study of megacities (10 million+ population) analysing their historic population, economic and emission patterns and contributions to global GHGs. A key challenge is that a majority of these megacities (33 out of 41) are located in developing countries, making it challenging to track their rapidly mounting emissions. In this research, we capitalize on recently released open-access datasets—the Global Human Settlements Database (R2019A) and the World Urbanization Prospects (2018) for analyzing megacity development and GHG trends, vis-à-vis the mitigation targets outlined in their climate action plans. We find that as leading political and economic centres in their nations, though most megacities have initiated climate action plans, the aggregate impact of megacities on global emissions is limited. Based on this evidence, we explore how rapidly growing megacities can hedgehop to effectively reduce their GHG emissions while urbanizing and developing economically.

Tri-decadal evolution of land subsidence in the Beijing Plain revealed by multi-epoch satellite InSAR observations

The persistent land subsidence in the Beijing Plain induced by the massive exploitation of groundwater caused significant decreases in ground elevation and damages to buildings and civil infrastructures. Although various satellite SAR datasets have been analyzed to monitor subsidence in the Beijing Plain, no multi-decadal scale deformation measurement has been derived from multi-sensor InSAR results, and the recent deceleration of land subsidence or even uplift remains unclear. This study retrieved land subsidence measurements over the past three decades (1992–2022) by integrating multi-sensor C-band InSAR measurements into a logistic model. The cumulative subsidence presented three major subsidence funnels surrounding downtown in the North, Northeast, and East, with the maximum vertical displacement as high as 1.98 m in the Chaoyang District. The land subsidence positively responded to the changes in groundwater depth, showing a clear deceleration since 2016. After five and half years, it became almost stagnated within the context of continuous groundwater recovery, which implied the delayed compaction of lowly draining aquitards. Only slight residual subsidence persisted in Chaoyang, Shunyi, and Daxing Districts. Meanwhile, land uplift happened in Shunyi, Huairou, and Pinggu Districts. Remarkably, a portion of the land subsidence in the Chaobai Plain reversed to uplift due to multiple artificial recharges using diverted water. Although groundwater storage could recover significantly in the next decade, most severely sunken lands and inelastically compacted aquitards are irrecoverable, leading to a permanent loss of storage capacity in the Beijing Plain. This study provides scientific data support for the local government decision-maker to better manage groundwater resources and mitigate land subsidence, which presents a typical example of monitoring long-term land subsidence in similar global megacities.

Necrosettlements: Life-threatening housing, necropolitics and the poor's deadly living in Mumbai

Global megacities are rapidly transforming through slum redevelopment and alternative resettlements of evicted poor. Resettlement is broadly seen as enabling, a basis of improved housing and even a pathway towards urban citizenship. This article offers an alternative perspective on urban resettlement, whereby the urban poor are subjected to life-threatening housing interventions. It builds on Mbembe's (2003) 'necropolitics' through an ethnographic study of Mumbai's Mahul case to theorise state powers in unleashing life-threatening housing circumstances. In doing so, this article introduces the concept of necrosettlements to account for the particularity of necropolitical-economy, material reality, unfolding subjectivities, and political possibility of life-threatening settlements. First, it theorises a political economy that extracts economic surplus and creates urban growth from poor-exclusive housing in uninhabitable places and with a life-compromising built environment against general residential developments. Second, the material details of life-threatening housing comprise of place-based, local biosphere, township's architecture, infrastructural and constrained dwelling, and their cumulative effects. Third, subjectivities of living included physiological suffering, compromised survival, socioeconomic and political vulnerability, comorbidity and death. Fourth, and finally, rather than representing absolute sovereign domination, however, these settlements also emerged as potential sites for residents to invoke their right to life, question extractive urbanism and demand settlement justice.

Air monitoring of tire-derived chemicals in global megacities using passive samplers

Pollution from vehicle tires has received world-wide research attention due to its ubiquity and toxicity. In this study, we measured various tire-derived contaminants semi-quantitatively in archived extracts of passive air samplers deployed in 18 major cities that comprise the Global Atmospheric Passive Sampling (GAPS) Network (GAPS-Megacities). Analysis was done on archived samples, which represent one-time weighted passive air samples from each of the 18 monitoring sites. The target analytes included cyclic amines, benzotriazoles, benzothiazoles, and p-phenylenediamine (PPD) derivatives. Of the analyzed tire-derived contaminants, diphenylguanidine was the most frequently detected analyte across the globe, with estimated concentrations ranging from 45.0 pg/m3 in Beijing, China to 199 pg/m3 in Kolkata, India. The estimated concentrations of 6PPD-quinone and total benzothiazoles (including benzothiazole, 2-methylthio-benzothiazole, 2-methyl-benzothiazole, 2-hydroxy-benzothiazole) peaked in the Latin American and the Caribbean region at 1 pg/m3 and 100 pg/m3, respectively. In addition, other known tire-derived compounds, such as hexa(methoxymethyl)melamine, phenylguanidine, and various transformation products of 6PPD, were also monitored and characterized semi-quantitatively or qualitatively. This study presents some of the earliest data on airborne concentrations of chemicals associated with tire-wear and shows that passive sampling is a viable techniquefor monitoring airborne tire-wear contamination. Due to the presence of many tire-derived contaminants in urban air across the globe as highlighted by this study, there is a need to determine the associated exposure and toxicity of these chemicals to humans.

Climate justice is social justice: articulating people’s rights to the city in Mumbai

Mumbai, India’s most populous city, faces rising temperatures, flooding, and pollution. Climate change is an urgent concern, yet strong disagreements divide the city’s population on the nature of appropriate responses to climate crisis. We find that urban activists in Mumbai make an explicit connection between social justice and climate justice. This paper studies three social movements working in Mumbai to secure access to housing, water and sanitation for marginalized communities. Building on the work of Nancy Fraser, Iris Marion Young and Henri Lefebvre, we argue that climate injustice in Mumbai has roots in structures of inequality based in class, gender, religion and migration status. Climate adaptation strategies run the risk of exacerbating inequalities when disasters strike. We seek design solutions that centre on inclusive justice rather than technocratic market forces. This paper opens up a conversation about global megacities, climate change and “urban climate justice from below”.

The dynamics of cardiovascular and respiratory deaths attributed to long-term PM2.5 exposures in global megacities

Exposure to ambient fine particulate matter (PM2.5) air pollution is a significant driver of premature deaths. We estimate the number of cardiovascular and respiratory (CR) premature deaths attributed to long-term exposure to PM2.5 in 33 global megacities based on long-term remotely sensed observations from 2000 to 2019. Our analysis uses high-resolution (0.01 degree) PM2.5 concentration data and cause-specific integrated exposure-response (IER) functions developed for the Global Burden of Disease Project. From 2000 to 2019, PM2.5-related CR death rates per 1000 people increased in 6 of 33 megacities, decreased in 9, and remained constant in 18 megacities. The increase in PM2.5-related CR mortality in 11 megacities located in South and East Asia during the period 2000–2019 can be attributed to the increases in PM2.5 concentrations. All 33 megacities could avoid 30,248 (9 %), 62,989 (20 %), 128,457 (40 %), 198,462 (62 %) and all of the estimated 322,515 CR deaths attributed to PM2.5 pollution in 2019 if they were to attain the World Health Organization's four interim PM2.5 targets (IT-1, IT-2, IT-3, and IT-4) and the new air quality guideline (AQG), respectively. Major improvements in air quality are needed to reduce the number of CR deaths attributed to PM2.5 in South and East Asia, in addition to ny reductions that would likely follow shifts in the population structures of these megacities moving forward.