South Asian Cities Research Articles

Urban Heat Island and Environmental Degradation Analysis Utilizing a Remote Sensing Technique in Rapidly Urbanizing South Asian Cities

Rapid urbanization in South Asian cities has triggered significant changes in land use and land cover (LULC), degrading natural biophysical components and intensifying urban heat islands (UHIs). This study investigated the impact of LULC changes on land surface temperature (LST) and the role of biophysical indicators in enhancing urban resilience to thermal extremes. We used Landsat satellite imageries from 1993 to 2023, conducted a comprehensive analysis of LULC changes, and estimated LST variations at 6-year intervals in the Dhaka, Gazipur, and Narayanganj districts in Bangladesh. Afterward, we performed statistical analysis upon employing correlation, regression, and principal component analysis (PCA) techniques to summarize information. The results reveal that 339.13 km2 worth of urban expansion has occurred in last 30 years, with an average annual growth rate of 3.5%, accompanied by a substantial reduction in water bodies (−139.17 km2) and vegetation cover. Consequently, summer temperatures exceeded approximately 36.52 °C in dense urban areas. Also, the results highlighted the strong influence of built-up areas (BSI and SAVI) on LST, while vegetation (NDVI) and water indices (NDWI) exhibited a negative association. The findings emphasize the urgency of integrating green infrastructure and deploying sustainable urban planning policies to mitigate the potential adverse impacts of scattered urbanization in the face of climate change.

Greening South Asian cities for health: a study of urban green space usage and physical well-being

Greening South Asian cities for health: a study of urban green space usage and physical well-being

Feathers, folklore, and eco-literacy: Stories ascribe cultural keystone status to avian scavengers in South Asian cities

Abstract We examined the cultural significance of commensal avian scavenger species—vultures, kites, and crows—and their exploitation of anthropogenic resources and sentiments within Delhi’s urban landscapes. For this, we investigated the intrinsic values attributed to these birds by people, which are indicative of complex, rapidly urbanizing social-ecological systems. Semi-structured interviews revealed folk perceptions intertwined with socio-cultural narratives and traditions, shaped by observations of avian morphology, ecology, and behavior. Birds’ nesting habits, habitats, home ranges, and foraging behaviors affected people’s perceptions, while ecosystem services inspired zoomorphism and anthropomorphism via vernacular-nomenclature (e.g., chidiya collectively for songbirds, giddha for scavenging raptors). Culturally rooted perceptions, which informed ritual feeding practices and shaped prevalent attitudes towards commensal species, fostered mutual tolerance, and brought people into closer contact with urban biodiversity. Such physical and cultural proximity is a defining characteristic distinguishing tropical urban ecosystems from their Western counterparts. We also uncovered the web of social-technological influences on animal-related folk stories. The urbanization of perceptions in vulture extinction zones revealed shifts in social-ecological relationships with wildlife. It adds cultural dimensions to the currently appreciated keystone status of vultures, vital for their erstwhile coexistence at extremely high densities in South Asia. Urban transformations, technological advancements, and media exposure potentially reshaped human–animal interface, with media misinformation affecting personalized ecologies. Conflicts and health concerns arose from media narratives on garbage-consuming animals. Our findings offer insights to prevent severing of people and nature connections due to urbanization (e.g., technological applications can integrate scientific knowledge with biocultural narratives and folklore), promoting a new-age eco-literacy.

Flight initiation distance and bird tolerance to humans in rural and urban habitats.

Urbanization induces homogenization and changes the behavioural patterns of various bird species, thereby facilitating coexistence and prompting adaptations to disturbances in urban environments. However, there is limited research on the influence of how urbanization affects bird tolerance towards humans, especially in developing sub-tropical regions such as Nepal, which is undergoing rapid unplanned urbanization. This study identified the flight initiation distance (FID) as a proxy for assessing bird tolerance. We focused on evaluating the human tolerance levels of 33 bird species using their FIDs in urban and rural habitats within Kathmandu Valley, a rapidly urbanizing city in South Asia. We found higher tolerance in urban birds than in their rural conspecifics, which varies mainly with dietary guild and season. The positive impact on FID was associated with time of the day and body size, while a negative association was observed with flock size, mean population density of humans and interaction between body size and elevation. Our study highlights the increased tolerance level of birds in urban areas, probably owing to habituation, and emphasizes the imperative need to investigate the potential adverse effect on urban bird population owing to this increased tolerance level.

The urban air quality nexus: Assessing the interplay of land cover change and air pollution in emerging South Asian cities

Air quality degradation presents a significant public health challenge, particularly in rapidly urbanizing regions where changes in land use/land cover (LULC) can dramatically influence pollution levels. This study investigates the association between LULC changes and air pollution (AP) in the five fastest-growing cities of Bangladesh from 1998 to 2021. Leveraging satellite data from Landsat and Sentinel-5P, the analysis reveals a substantial increase in urban areas and sparse vegetation, with declines in dense vegetation and water bodies over this period. Urban expansion was most pronounced in Sylhet (22–254%), while Khulna experienced the largest increase in sparse vegetation (2–124%). Dense vegetation loss was highest in Dhaka (20–77%) and water bodies (9–59%) over this period. Concentrations of six major air pollutants (APTs) - aerosol index, CO, HCHO, NO2, O3, and SO2 - were quantified, showing alarmingly high levels in densely populated industrial and commercial zones. Pearson's correlation indicates strong positive associations between APTs and urban land indices (R > 0.8), while negative correlations exist with vegetation indices. Geographically weighted regression modeling identifies city centers with dense urban built-up as pollution hotspots, where APTs exhibited stronger impacts on land cover changes (R2 > 0.8) compared to other land classes. The highest daily emissions were observed for O3 (1031 tons) and CO (356 tons) at Chittagong in 2021. In contrast, areas with substantial green cover displayed weaker pollutant-land cover associations. These findings underscore how unplanned urbanization drives AP by replacing natural land cover with emission sources, providing crucial insights to guide sustainable urban planning strategies integrating pollution mitigation and environmental resilience.

High schoolers and dating issues: examining the effectiveness of an app-based mindfulness intervention

ABSTRACT This article reports a study comparing the impact of a mindfulness app in mitigating dating anxieties and promoting self-esteem, healthy relationships and school satisfaction among high schoolers vis-à-vis a relationship advice app. A pre- and post-test-design study was conducted with high schoolers in two South Asian cities. Participants of the relationship advice app cohort reported no significant changes in post-test outcomes. Participants of the mindfulness app cohort reported significantly lower post-test dating anxiety scores and higher self-esteem, perceived support and school satisfaction scores. Particularly, the mindfulness app was more effective for high school girls, Christians, middle class students, high schoolers with mothers as primary caregivers, participants whose primary caregivers had postgraduate and higher qualifications, who lived in standard family set-ups with parents and siblings, and who were regular in reading mindfulness posts and doing the recommended homework. Intervention compliance mediated the association between significant socio-demographic predictors and gains/changes in outcomes.

Contrasting nature of aerosols over South Asian cities and its surrounding environment

Cross-country assessment of aerosol loading was made over several South Asian megacities using multiple high-resolution remote-sensing database to assess how aerosols vary within the city and its suburbs. Parameters sensitive to aerosol optical and microphysical properties were processed over city-core and its surrounding, separated by a buffer. Cities across the Indo-Gangetic Plain (IGP; AOD:0.52–0.72) along with Mumbai (0.47) and Bangalore (0.46) denote comparatively high aerosol loading against non-IGP cities. City-core specific AOD was invariably high compared to surrounding, however with varying gradient having robust geographical signature. Exceptions to this general trend were in Kathmandu (ΔAOD: 0.07) and Dhaka (ΔAOD: 0.01) while strong positive AOD gradient was noted in Bangalore (+0.11), Colombo (+0.08) and in Mumbai (+0.07). While all mainland cities exhibited robust intraannual variability, distinction between city-core and its surrounding AOD exhibited varying seasonality. City-specific geometric coefficient of variation indicated insignificant association with mean AOD as opposed to European and American cities. Both pixel-based and city-specific analysis revealed a strong increasing trend in AOD with highest magnitude in Varanasi and Bangalore. Aerosol sub-types based on aerosols’ sensitivity to UV-absorption and particle size denotes higher relative abundance of carbonaceous smoke aerosols within city-core, without having significant distinction for mineral dusts and urban aerosols.

Environmental Sustainability of Food Environments: Development and Application of a Framework in 4 cities in South Asia

BackgroundFood environments, where people directly engage with broader food systems, may be an important contributor to the environmental sustainability of food systems. ObjectivesThe primary objectives of this study were to establish a new food environment framework that considers environmental indicators and to assess data availability and gaps using data previously collected as part of a food systems survey in 4 South Asian cities. MethodsThe framework was developed by conducting a structured literature review of previous food environment frameworks and in-depth interviews with content experts (n = 6). The framework and indicators were then mapped to data collected by consumer and vendor surveys using the Urban Food Systems Assessment Tool (UFSAT) in Ahmedabad (India), Pune (India), Kathmandu (Nepal), and Pokhara (Nepal). ResultsWe have expanded the sustainability domain within food environments to include consumer travel to food vendors, the presence of food delivery services, policies related to sustainability, vendor food waste, vendor plastic use, vendor utility usage, vendor recycling and waste management practices, and food packaging. Mapping the framework to existing data from 4 cities in South Asia, we found variations in food environment sustainability indicators, particularly regarding consumer transportation to food vendors, the presence of delivery services, and food waste. ConclusionsAlthough the majority of food environment research focuses on the availability and affordability of healthy foods, there is an urgent need to understand better how aspects of food environments contribute to environmental goals. When mapping the framework to existing food systems data, we found gaps in data on environmental sustainability in food environments and variation in indicators across settings.

Analysis of spatial pattern of water supply continuity in an Indian metropolis: a case study of Hyderabad

ABSTRACT Water supply continuity is a crucial indicator of service efficiency. Multiple South Asian cities have Intermittent Water Supply (IWS). Water supply equity in cities depends on the spatial patterns of intermittency. The present study used Kernel Density Estimation (KDE) to investigate the spatial pattern of water supply intermittency for 3071 localities of Hyderabad, India. Further, the relationship between population density and supply continuity has been examined in 146 wards of Hyderabad using Spatial Autocorrelation and Geographically Weighted Regression (GWR). Spatial Autocorrelation defines two distinct clusters of central wards for high continuity (12 wards) and population density (19 wards). However, the ward clusters are different for continuity and density, with only three central wards (2.06% of all wards) being common in both the high-high clusters. The results highlight that the water supply continuity in Hyderabad has minimal consideration for population density, resulting in a spatially inequitable water supply.

Measuring the Transit-Oriented Development (TOD) Levels of Pakistani Megacities for TOD Application: A Case Study of Lahore

The urbanization challenges in the megacities of Pakistan necessitate the implementation of comprehensive sustainable development practices to effectively address contemporary urban issues. Transit-oriented development (TOD) is a globally accepted device in achieving sustainable urban development through transport and land use integration. Evaluating the levels of TOD built in present conditions is essential for productive TOD planning, as it enables the prioritization of development interferences. In this context, we utilized a methodology to evaluate the levels of TOD (TOD-ness) present near transportation nodes through a TOD index. It utilizes ArcGIS and spatial multi-criteria analysis (SMCA) to determine the extent of TOD-supporting qualities around a transit node and identifies areas for potential improvements in transit orientation. The methodology was executed in the megacity of Lahore, situated in Pakistan. A TOD index was computed for areas surrounding the 26 LRT and 27 BRT stations along two existing corridors. The findings suggest that the TOD concept is feasible for Pakistani megacities, and urban decision makers can utilize the TOD index results to facilitate urban- or regional-level planning, funding, and investment policies. Furthermore, these findings offer valuable insights into the transportation obstacles and potential opportunities in similar developing cities in South Asia.

A Global Estimate of the Size and Location of Informal Settlements

Slums are a structural feature of urbanization, and shifting urbanization trends underline their significance for the cities of tomorrow. Despite their importance, data and knowledge on slums are very limited. In consideration of the current data landscape, it is not possible to answer one of the most essential questions: Where are slums located? The goal of this study is to provide a more nuanced understanding of the geography of slums and their growth trajectories. The methods rely on the combination of different datasets (city-level slum maps, world cities, global human settlements layer, Atlas of Informality). Slum data from city-level maps form the backbone of this research and are made compatible by differentiating between the municipal area, the urbanized area, and the area beyond. This study quantifies the location of slums in 30 cities, and our findings show that only half of all slums are located within the administrative borders of cities. Spatial growth has also shifted outwards. However, this phenomenon is very different in different regions of the world; the municipality captures less than half of all slums in Africa and the Middle East but almost two-thirds of all slums in cities of South Asia. These insights are used to estimate land requirements within the Sustainable Development Goals time frame. In 2015, almost one billion slum residents occupied a land area as large as twice the size of the country of Portugal. The estimated 380 million residents to be added up to 2030 will need land equivalent to the size of the country of Egypt. This land will be added to cities mainly outside their administrative borders. Insights are provided on how this land demand differs within cities and between world regions. Such novel insights are highly relevant to the policy actions needed to achieve Target 11.1 of the Sustainable Development Goals (“by 2030, ensure access for all to adequate, safe and affordable housing and basic services, and upgrade slums”) as interventions targeted at slums or informal settlements are strongly linked to political and administrative boundaries. More research is needed to draw attention to the urban expansion of cities and the role of slums and informal settlements.

City drafting: property-making and bureaucratic urbanism in South Asia

This Special Feature explores the negotiated bureaucratic politics shaping urbanization in South Asia. City drafting refers to the flexible and contextual practices, procedures and policies required to haul diverse property regimes into order and provisionally render urban land clear and settled. The drafted city, we argue, is necessarily provisional and uneven, left open to politicised remapping, redrafting and resettlement by a host of institutionally embedded brokers, bureaucrats, clerks and surveyors each wielding their own political and socio-technical vision of land. These drafting practices, not only shape a politics of uneven urbanisation in South Asian cities, but also help to explain the persistent fractal morphology of urban property in South Asia; spanning categories of public, private, non-private, commons, unauthorised, regularised, agrarian, urban and so on. While the South Asian city is commonly understood through the high-resolution imagery of masterplanners, policymakers and investors, city drafting methodologically focuses on the grounded bureaucratic struggles of the map, plot, record and title, through which claims to property rights, exclusions and access are shaped.

Exploration of intra-city and inter-city PM2.5 regional calibration models to improve low-cost sensor performance

Low-cost PM2.5 sensors often suffer from environmental cross-sensitivities, requiring regular calibration across a wide range of concentrations. This is typically achieved by co-locating LCS with regulatory stations and using statistical models. However, this approach becomes challenging in regions with limited regulatory monitoring stations or access. To address this challenge, we explored building separate calibration models for the pseudo-regional component of the total PM2.5 concentration, which represents background concentration, and the hyper-local component of the total concentration. This is based on the premise that the regional concentration is consistent across a given region and therefore direct co-location is less necessary, and the idea that the local concentration is not influenced by geographic properties and therefore can be calibrated based on co-location elsewhere. In this work, we used publicly-available PurpleAir data for 2022 from five different cities in South Asia and North America, and built city-specific calibration models for the regional concentrations using multiple linear regression. We tested the model performance in the city the model was built in (intra-city models; trained and cross-validated in the same city) and in other cities (inter-city models; trained and cross-validated in different cities). The regional calibration model reduced the normalized root mean square error (nRMSE) of both intra-city models, from 51% to 26%, and inter-city models, from 55% to 25% compared to PurpleAir reported concentrations. Overall, the results of this work demonstrate the potential for improved transferability of calibration models and provides evidence that calibration models built for regional concentration and local concentration separately may be a viable solution when deploying in places with limited regulatory monitoring or access to monitoring stations.

Multimetric socio‐ecological assessment of water hyacinth (Eichhornia crassipes (Mart) solms) invasion of an urban Ramsar wetland lake

AbstractWater hyacinth (Eichhornia crassipes (Mart) solms), a widely distributed invasive aquatic plant in Sri Lanka, has invaded the Diyawannawa wetland lake located in Colombo city, which is the first Ramsar wetland city in South Asia. The present study was conducted to assess the water quality parameters that influence the distribution of water hyacinth and to identify the environmental, economic, and social consequences of its invasion of the Diyawannawa wetland. Five sampling sites were selected from the Diyawannawa lake, and the water pH, temperature, conductivity, total dissolved solids (TDS), salinity, dissolved oxygen concentration (DO), nitrate concentration, and total phosphorus concentration were measured at monthly intervals in the rainy and dry seasons of 2020. The abundance of water hyacinth was recorded at each site at each sampling event. Interviews and focus group discussions (FGDs) were conducted with the representatives of the community associated with the wetland to assess the ecological, economic and social effects of water hyacinth invasion. Principal component analysis of the water quality parameters revealed that phosphorus and nitrate concentrations in water significantly influenced the abundance of water hyacinth. Further, the water quality index (WQI) indicated poor water quality in the sites invaded by water hyacinth. The interviews and FGDs revealed that water hyacinth invasion has adversely affected the lake's fisheries and navigation pathways and increased the frequency of flooding, resulting in an increased mosquito population. The results of the present study highlighted the importance of implementing water quality management programmes in the Diyawannawa wetland to control the invasion of water hyacinth. Further, we recommend increasing community participation in water hyacinth control programmes and providing opportunities for the community to engage in self‐employment activities associated with the uses of water hyacinth.

Flow physics of air pollutants dispersion: A case study in an urban street canyon in Baghbazar, Kathmandu

The alarming increase of hazardous pollutants in South Asian cities such as Kathmandu, Delhi, Mumbai, Dhaka, etc. risks the life of every individual there. A major source in the production of such harmful pollutants is vehicles and industries. A Computational Fluid Dynamics (CFD) approach is proposed to model the pollutants emitted by vehicles using different Reynolds Averaged Navier Stokes (RANS) turbulence models in the street canyon setup. The primary aim of the study is to understand the effect of turbulence on the transport of gaseous pollutants in the street canyon. RNG k − ϵ model performed best among other turbulence models with mean FB -0.105, NMSE 0.045, FAC2 0.915 and R 0.93 which is validated with the experimental data. Higher wind speeds allowed the concentration to disperse more effectively in Baghbazar’s street canyon, resulting in lower concentrations of pollutants.

Exploring the nexus between land cover change dynamics and spatial heterogeneity of demographic trajectories in rapidly growing ecosystems of south Asian cities

Rapid urbanization is a global trend that significantly alters Land Use and Land Cover Change (LULCC) patterns. Dhaka, a megacity, and Chittagong, the country’s second-largest city, have experienced substantial shifts in LULCC patterns over the past three decades. This study aims to examine the LULCC in Dhaka and Chittagong districts of Bangladesh from 1991 to 2021, focusing on identifying patterns and quantifying the effects of population growth and urbanization. Changes in LULCC patterns were identified by analyzing Landsat satellite imagery using remote sensing and geospatial techniques. The LULCC classes were classified using the Random Forest model and an inconsistency diagram, demonstrating high precision with an overall accuracy rate exceeding 85 %. The study’s findings reveal significant transformations in LULCC patterns across Dhaka and Chittagong districts from 1991 to 2021. A notable increase in built-up areas was observed in both districts, with Dhaka division witnessing a 129 % increase in built-up areas while Chittagong district saw a 515 % increase. This was due to transforming water bodies and barren land into built-up areas. However, the study also highlighted a promising increase in vegetation cover in both districts, indicating successful ecological restoration efforts. Chittagong and Dhaka saw increments of 597.95 km2 and 252.15 km2 in vegetation cover, respectively. Despite these positive changes, the study identified decreased surface water bodies in both regions. The results show a significant positive correlation between population growth/density and the built-up class, while a significant negative correlation with the barren land was observed in both districts. The findings could potentially guide policymakers in making informed decisions regarding land use, land cover, and urban sprawl management from an ecological restoration perspective. This could contribute to achieving sustainable development goals by promoting resilience ecological restoration practices.

Hot climates in urban South Asia: Negotiating the right to and the politics of shade at the everyday scale in Karachi

Although the climate has admittedly always been hot and humid in cities like Karachi, increasingly hotter temperatures are exacerbating the impact of heat on informal, precariously employed outdoor workers such as street vendors, guards and rickshaw drivers, who must negotiate their right and access to shade at the everyday scale. Recalling Mike Davis’ radical, political claim that shade is an inalienable human right, this paper proposes that few people working in the outdoor spaces of the South Asian city today understand or experience shade in these terms. Rather shade is something that must be claimed, alongside other rights and entitlements. Moreover, shade alone is insufficient as it cannot reduce the exposure of bodies to harmful ambient radiations and overall thermal discomfort. This paper makes three broad propositions for outlining a theory for the social study of shade in the South Asian city. By paying closer attention to the ways that outdoor workers negotiate shade in Karachi, this paper opens up for analysis a wider spectrum of claims-making activity in changing South Asian urban climates. It places workers’ search for shade in the broader context of shade policing and urban management aimed at creating spatial as well as social order. Finally, this article emphasises key directions and questions for future research.

Morphological, Mineralogical, and Biochemical Characteristics of Particulate Matter in Three Size Fractions (PM10, PM2.5, and PM1) in the Urban Environment.

Air pollution in megacities is increasing due to the dense population index, increasing vehicles, industries, and burning activities that negatively impact human health and climate. There is limited study of air pollution in many megacities of the world including Pakistan. Lahore is a megacity in Pakistan in which the continuous investigation of particulate matter is very important. Therefore, this study investigates particulate matter in three size fractions (PM1, PM2.5, and PM10) in Lahore, a polluted city in south Asia. The particulate matter was collected daily during the winter season of 2019. The average values of PM1, PM2.5, and PM10 were found to be 102.00 ± 64.03, 188.31 ± 49.21, and 279.73 ± 75.04 μg m-3, respectively. Various characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) were used. FT-IR and XRD techniques identified the minerals and compounds like quartz, peroxides, calcites and vaterite, feldspar group, kaolinite clay minerals, chrysotile, vaterite, illite, hematite, dolomite, calcite, magnesium phosphate, ammonium sulfate, calcium iron oxide, gypsum, vermiculite, CuSO4, and FeSO4. Morphology and elemental composition indicated quartz, iron, biological particles, carbonate, and carbonaceous particles. In addition, various elements like C, O, B, Mg, Si, Ca, Cl, Al, Na, K, Zn, and S were identified. Based on the elemental composition and morphology, different particles along with their percentage were found like carbonaceous- (38%), biogenic- (14%), boron-rich particle- (14%), feldspar- (10%), quartz- (9%), calcium-rich particle- (5%), chlorine-rich particle- (5%), and iron-rich particle (5%)-based. The main sources of the particulate matter included vehicular exertion, biomass consumption, resuspended dust, biological emissions, activities from construction sites, and industrial emissions near the sampling area.

Who owns the city? Neoliberal urbanism and land purchases in Gurgaon, India

Increasing purchases of valuable real estate for storing capital have contributed to the soaring prices of modest housing in many global cities and in several South Asian cities such as Mumbai, Delhi and Bangalore. Saskia Sassen has drawn attention to the phenomenon of underutilisation of purchased properties existing alongside the acute demand for housing by low- and moderate-income households in the same cities. Despite the gravity of this issue, empirical analyses of urban land transactions remain rare, especially because such purchases often tend to be piecemeal and obscure, involving a multitude of smaller land deals and a variety of actors. This paper examines corporate purchases of urban land in Gurgaon, a city adjacent to New Delhi that has embraced neoliberal economic policies. By creating a land database for the upcoming sectors in the city, the study makes sharply visible: (1) the radical changes in property ownership patterns from agricultural land to luxury gated communities, (2) the growing corporate investments, extreme concentration of land ownership and deeply unequal distribution of urban land and (3) the use of various illicit practices by market-leading companies in land banking.

Global PM2.5 and secondary organic aerosols (SOA) levels with sectorial contribution to anthropogenic and biogenic SOA formation

This study estimates global PM2.5 and anthropogenic and biogenic Secondary Organic Aerosols (a-SOA and b-SOA) and sources contributing to their formation. The global landscape was divided into eleven domains (North America (NAM); South America (SAM); Europe (EUR); North Africa and Middle East (NAF); Equatorial Africa (EAF); South of Africa (SAF); Russia and Central Asia (RUS); Eastern Asia (EAS); South Asia (SAS); Southeast Asia (SEA) and Australia (AUS)) and 46 cities based on varying populations. Three inventories for global emissions were considered: Community Emissions Data System, Model of Emission of Gases and Aerosol, and Global Fire Emissions Database. WRF-Chem model coupled with atmospheric reactions and the secondary organic aerosol model was employed for estimating PM2.5, a-SOA, and b-SOA for 2018. No city attained WHO's annual PM2.5 guideline of 5 μg/m3. Delhi, Dhaka, and Kolkata (63–92 μg/m3) in south Asia were the most polluted, and seven cities (mostly in EUR and NAM) met the WHO target IV (10 μg/m3). The highest SOA levels (2–9 μg/m3) were in the cities of SAS and Africa, but with a low SOA contribution to PM2.5 (3–22%). However, the low levels of SOA (1–3 μg/m3) in EUR and NAM had a higher contribution of SOA to PM2.5 (20–33%). b-SOA were consistent with the region's vegetation and forest cover. The SOA contribution was dominated by residential emissions in all domains (except in the NAF and AUS) (maximum in SAS). The non-coal industry was the second highest contributor (except in EAF, NAF, and AUS) and EUR had the maximum contribution from agriculture and transport. Globally, residential and industry (non-coal and coal) sectors showed the maximum contribution to SOA, with a-SOA and b-SOA being nearly equal. Ridding of biomass and residential burning of solid fuel is the single most action benefiting the PM2.5 and SOA concerns.