Economic and Public Health Impacts of Transportation-Driven Air Pollution in South Asia

Abstract

South Asia, a rapidly urbanizing and industrializing region, faces critical air quality challenges, with transportation emissions becoming a major source of urban pollution. These emissions contribute significantly to public health issues, including respiratory and cardiovascular diseases, while imposing substantial economic burdens on affected populations. This study aims to examine regional trends, evaluate the economic impact of transportation-driven air pollution, and offer actionable insights for policy development. Using a narrative review approach, the study synthesizes evidence on air quality, transportation emissions, and public health in major South Asian cities. Key findings reveal that in Sri Lanka, transportation emissions, driven by traffic congestion and industrial activity, worsen respiratory conditions, especially in Colombo. In India, cities like Delhi suffer from severe health risks linked to pollution from the growing transportation sector. Pakistan’s expanding transportation sector increases energy consumption and emissions, particularly in Lahore, which experiences significant health impacts. In Bangladesh, Dhaka faces intense pollution due to urbanization and vehicle growth, while Kathmandu in Nepal struggles with diesel vehicle emissions. The economic burden of transportation-driven air pollution is considerable, with rising healthcare costs and productivity losses in major cities. The study recommends cleaner transportation technologies, enhanced public transit, and regional cooperation to address pollution, urging a comprehensive approach to urban planning and sustainable transport infrastructure for improved air quality and economic resilience in South Asia’s cities.

1. Introduction

South Asia, one of the world’s fastest-developing regions, faces significant challenges due to rapid economic growth, urbanization, and industrialization coupled with a rapidly increasing population. The region heavily relies on biomass for cooking and heating, while traditional agricultural practices such as crop residue burning and waste incineration further degrade both ambient and indoor air quality. Consequently, air pollution is a pressing issue in South Asia, affecting both urban and nonurban areas, where emissions and regional transport patterns significantly impact air quality [1].

Geographically, South Asia is home to the Himalayas, the largest ice-covered region outside the poles, which plays a vital role in regulating monsoonal transport of pollution and moisture. Adjacent to the Himalayas lies the Indo-Gangetic Plain (IGP), one of the world’s most densely populated regions and a hotspot for diverse anthropogenic and biogenic emissions [1]. The region also hosts some of the most polluted cities globally, exposing nearly 25% of the world’s population to severely compromised air quality, particularly in countries like India and Bangladesh.

Urban transportation is a major contributor to air pollution in Asian cities, with its impacts intensifying over recent decades. Air pollution is a leading global health risk, often termed a “silent killer” by the World Health Organization (WHO). Globally, ambient and household air pollution together cause approximately seven million deaths annually, with South Asia contributing over two million deaths per year to this grim statistic [2,3].

Rapid and often unplanned urbanization has exacerbated air pollution in South Asia, threatening both human health and environmental sustainability. Major sources of air pollution include transportation, power generation, residential fuel combustion, industrial facilities, and agriculture. Urban centers in South Asia differ from their counterparts in North America and Europe, often sprawling into peri-urban areas while simultaneously densifying. Both trends pose unique challenges: peri-urban sprawl stretches infrastructure and transport systems, while densification intensifies congestion, vehicle emissions, and the management of urban environmental services such as waste disposal and water supply [4].

Addressing the complexities of air pollution in South Asia requires understanding the interplay between its sources, economic development, and policy measures. Comprehensive data and sectoral analysis are essential to design effective interventions and assess the costs and benefits of mitigation strategies [5].

1.1. Air Quality, Pollution, and Sustainability in South Asia

Worsening air quality and pollution present significant sustainability and environmental health challenges in South Asia, a region highly vulnerable to climate change [6]. Countries such as India, Nepal, Bangladesh, and Pakistan are among the most polluted globally. Satellite imagery reveals the phenomenon of the “brown cloud” over cities like New Delhi and Lahore, driven by carbon aerosols [7]. Contributing factors include cultural practices such as the use of cooking stoves in rural and semi-urban households, along with industrial emissions, vehicular traffic, and other sources [8,9].

The World Air Quality Report [10] highlights that 37 out of the 40 most polluted cities in the world are located in South Asia. Since 2010, nearly 700 million people—half the region’s population—have been impacted by climate-related disasters. Projections indicate that by 2050, over 800 million people in South Asia will suffer direct consequences from deteriorating air quality, leading to significant economic and public health burdens [11]. Air pollution ranks as the leading risk factor for adverse health outcomes in the region, with devastating effects on lives and livelihoods [12].

The health implications of air pollution are severe and multifaceted. Air pollution contributes to 11% of deaths in the region and accounts for 40 million disability-adjusted life years annually [12]. Studies have linked ambient air pollution to 349,681 pregnancy losses annually across Bangladesh, India, and Pakistan, highlighting its disproportionate impact on maternal and infant health [13]. Maternal health outcomes, such as breached placentas and increased infant mortality rates, further underscore the societal burden of air pollution [14]. Indoor air pollutants, including formaldehyde (CH₂O) and total volatile organic compounds (TVOCs), prevalent in urban and industrialized areas, exacerbate respiratory issues and increase the risk of certain cancers [15,16,17]. Liang [15] found that indoor formaldehyde levels in Chinese urban residences averaged 0.061 mg/m³, exceeding the recommended limit of 0.05 mg/m³. This elevated exposure increased the risk of nasopharyngeal cancer, with a lifetime cancer risk of 0.6 in 1000, higher than the acceptable level of 1 in 100,000. Research also indicates that the total lifetime cancer risk from organic hazardous air pollutants averages around 6 in 10,000, with formaldehyde being one of the top-ranking compounds.

The escalating presence of ozone, both as a greenhouse gas and a major air pollutant, also poses serious risks to human health and vegetation in the region. This is largely driven by increasing emissions of ozone precursors [1]. South Asia has recorded the largest increase in cardiovascular deaths related to ozone and PM_2.5, with India alone experiencing over 150,000 such deaths annually [18]. In Kathmandu, Nepal, PM₁₀ exposure causes approximately 1600 premature deaths annually, while Pakistan’s urban areas report 2500 premature deaths each year due to air pollution [19,20].

CO₂ emissions have risen dramatically across South Asia, with Nepal, Bhutan, and Bangladesh experiencing increases of 23.6-fold, 15-fold, and 6.6-fold, respectively, between 1990 and 2020 [11]. India not only leads the region in CO₂ emissions but also reports the most significant rise in greenhouse gas emissions. Population-weighted PM_2.5 concentrations remain critically high, with Nepal leading, followed by India and Bangladesh [11].

Sustainability challenges further compound the crisis. Access to safely managed drinking water is limited to 17.6% of the population in Nepal, 35.8% in Pakistan, and 36.6% in Bhutan. Sanitation services remain inadequate, with only 38.7% of the population in Bangladesh having access. Electricity access is also limited, particularly in Pakistan, where only 70.8% of the population has reliable electricity [11].

The multidimensional impacts of air pollution in South Asian cities underscore the urgency of addressing these issues, which is imperative to ensuring sustainability, protecting public health, and reducing the economic burden associated with declining air quality.

1.2. Research Questions and Objectives

The main research questions for this study are: What are the major sources of transportation-related air pollution in South Asian cities? How do transportation emissions affect public health in these urban centers? What are the economic implications of the health burdens caused by air pollution in these regions? These questions aim to explore the relationship between transportation emissions, public health outcomes, and the economic costs associated with air quality deterioration in major cities of South Asia. These questions aim to explore the relationship between transportation emissions, public health outcomes, and the economic costs associated with air quality deterioration in major cities of South Asia. The importance of studying this subject lies in the escalating challenges posed by urban air pollution, particularly in rapidly developing regions like South Asia, where transportation emissions are a major contributor to poor air quality. As urban populations continue to grow, transportation systems expand, and industrial activities increase, the health and economic burdens of air pollution are becoming increasingly significant.

This paper aims to review the existing literature on transportation emissions in urban areas, focusing on their economic and public health impacts. It examines the sources of pollution, evaluates the associated health risks, and explores the broader economic implications for affected populations. By synthesizing this knowledge, the study seeks to provide actionable policy recommendations that are both economically viable and effective in addressing transportation-related air pollution and its health consequences. The significance of this research lies in its potential to guide policymakers and stakeholders in implementing targeted interventions to enhance air quality, reduce health expenditures, and support sustainable urban development across South Asia.

2. Materials and Methods

This study uses a narrative review approach to examine the existing literature on air quality, transportation emissions, and public health in major South Asian cities like Delhi, Dhaka, Karachi, Colombo, and Kathmandu. By integrating sources such as peer-reviewed articles, government reports, and policy briefs, the review identifies key trends in transportation emissions, health impacts, and the economic burden of air pollution. Unlike systematic reviews, which focus on strict inclusion criteria and quantitative data, this approach allows for flexibility in addressing diverse evidence, offering a comprehensive understanding of the region’s air quality challenges and policy implications.

The review focused on studies published between 2000 and 2023. Relevant articles were selected from high-quality journals in Scopus and Web of Science, with Google Scholar used cautiously to avoid unreliable sources. Dissertations and theses were also included to gather micro-level insights from South Asia. The inclusion criteria targeted papers that discussed transportation-related air pollution and its economic, social, or health impacts, especially in urban areas.

Various search strings were used, such as “Economic impacts of transportation-driven air pollution” and “Health impacts of urban transportation”. Specific country-focused searches, like “Urban transportation in India” and “Urban transportation in Bangladesh”, helped target studies from South Asian nations. This search yielded 110 articles, of which 52 were relevant to the study’s goals. The findings were thematically organized to provide actionable insights for improving air quality and public health in the region.

3. Review Results and Discussion

3.1. Transportation Emissions, Air Quality, and Public Health Implications in Major South Asian Cities

3.1.1. Sri Lanka

Sri Lanka, a developing nation in South Asia, is increasingly grappling with urban air pollution due to rapid urbanization, industrialization, and rising vehicular emissions. Its urban transportation system, dominated by private vehicles, three-wheelers, and buses, exacerbates these challenges. Although smaller in scale compared to neighboring countries, the air quality issues in Sri Lanka have significant implications for public health, particularly in densely populated urban areas.

Air pollution has emerged as a pressing public health concern in Sri Lanka’s urban areas, driven by increasing traffic congestion and poorly regulated emissions from small- to medium-scale industries [21]. A study on children’s respiratory health revealed that urban children experience a significantly higher prevalence of wheezing compared to those in semi-urban settings. Indoor cooking with unclean fuels was identified as a key risk factor for wheezing across both settings, underscoring the combined impact of indoor and outdoor pollution on respiratory health. However, factors beyond outdoor air quality, yet to be fully explored, may also contribute to this disparity [21].

Premasiri et al. [22] emphasized that the Western Province of Sri Lanka, home to 60% of the country’s vehicular fleet, is a major contributor to air pollution. This area also hosts 70% of Sri Lanka’s industries, including high-polluting sectors such as thermal power plants, iron smelting, and petroleum refineries. As a result, approximately 85% of the nation’s fossil fuel consumption occurs in the Western Province, leading to significant air pollution from industrial emissions, transportation, and power plants. Due to rapid urbanization, population growth, and increasing industrial activity, air quality in the province has worsened, making it the most polluted region in the country.

In response, Colombo implemented the “Clean Air 2000 Action Plan” in 1992 to mitigate pollution from key sectors such as transportation and industry [23]. This initiative yielded notable improvements in air quality. For example, reductions in sulfur levels in diesel fuel led to a 7% decrease in sulfur dioxide (SO₂) levels between 2001 and 2002 and a 15% decrease from 2003 to 2004. Measures such as vehicular emission testing (VET) and road infrastructure improvements resulted in a 10–20% reduction in SO2 and particulate matter (PM) levels from 2009 to 2012. The adoption of hybrid vehicles further contributed to declining nitrogen dioxide (NO₂) levels, demonstrating the effectiveness of these interventions.

Premasiri et al. [24] also highlighted the vulnerability of other urban centers in the Western Province, including Gampaha and Kaluthara, to air pollution due to rapid urban development. Air pollution monitoring in these cities revealed that pollution levels, particularly from vehicle emissions, were significantly high. In 2014, NO₂ levels exceeded the World Health Organization’s (WHO) annual guideline values in all three cities, while SO₂ levels surpassed the 24-h guideline in some areas. However, data from 2012 to 2014 indicated a decreasing trend in pollution levels, particularly in areas with less traffic congestion. Seasonal variations also influenced pollutant concentrations, with the North-East monsoon having a stronger impact on air quality than the South-West monsoon. Overall, Colombo recorded the highest pollution levels, followed by Kaluthara and Gampaha, with pollution levels closely linked to traffic density. The study concluded that urban air pollution in these cities has become a serious environmental concern.

Weerasundara et al. [25] conducted a study in Kandy City, Sri Lanka, to evaluate health risks associated with atmospheric heavy metals in a densely populated urban area typical of developing countries. The study focused on nine commonly occurring heavy metals: Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd, and Pb. To assess non-carcinogenic health risks, the Hazard Quotient (HQ) and Hazard Index (HI) were utilized. HQ measures the risk of exposure to a single heavy metal by comparing it to a reference dose, where values above 1 indicate potential health concerns. HI provides a cumulative assessment of non-carcinogenic risks by summing the HQs of all metals under study, with values above 1 suggesting combined exposure risks. The study also evaluated cancer risks using lifetime daily cancer risk metrics.

The findings revealed high concentrations of Al and Fe, attributed to both natural and human-made sources. Elevated Zn levels were linked to vehicular emissions and the use of zinc-coated materials, emphasizing the role of urban activities in heavy metal pollution. This comprehensive approach highlights the significant environmental and health challenges posed by heavy metal exposure in urban settings. High concentrations of Al and Fe were observed due to both natural and anthropogenic sources. Zn levels were linked to vehicular emissions and the use of Zn-coated materials. The contamination factor and geo-accumulation index showed that Al and Fe remain uncontaminated, while other metals range from uncontaminated to contaminated, with potential long-term effects. The risk assessment revealed that ingestion posed the highest exposure pathway, followed by dermal contact and inhalation. Children were found to face a higher health risk than adults.

Air pollution in Sri Lanka is intensifying, primarily due to a significant rise in motor vehicles and traffic congestion. Air quality monitoring began in 1997 with stations in Colombo, showing that from 1997 to 2003, sulfur dioxide, nitrogen dioxide, and ozone levels steadily increased while carbon monoxide levels decreased. However, fine particulate matter (PM10 and PM2.5) consistently exceeded national air quality standards [26].

Kandy experiences worse air quality than Colombo, attributed to its geographical location, increased vehicle population, and traffic congestion. Between 2001 and 2005, sulfur dioxide, nitrogen dioxide, and ozone levels exceeded the standards 41%, 14%, and 28% of the time, respectively. The presence of carcinogenic polyaromatic hydrocarbons from kitchen smoke and vehicle exhausts poses a significant health risk, contributing to rising cases of respiratory diseases, such as chronic obstructive pulmonary disease, in Kandy [26].

A study by Samaradiwakara and Pitawala [27] investigated the causes of air pollution in Kandy, Sri Lanka, a UNESCO World Heritage Site, focusing on dust particles in the city and its suburbs. Eighteen road and thirteen household dust samples were analyzed for elemental concentrations and mineralogical characteristics. The study found higher concentrations of Ca, Zn, and Cu, indicating the influence of anthropogenic sources like construction and traffic. Mineralogically, dust consisted primarily of clay minerals and quartz, while fibrous materials showed minimal health impact due to short atmospheric suspension. Despite lower industrial and transportation activity compared to other cities, Kandy’s pollution levels remain notably high.

Pushpawela et al. [28] highlight the unique opportunity presented by the COVID-19 lockdown to study the effects of reduced human activities on air pollution. A study conducted in Colombo and Kandy, Sri Lanka, examined the spatiotemporal characteristics of particulate matter (PM10, PM2.5) and trace gases (NO2, O3, SO2, CO) during normal and lockdown periods. The results suggest a significant reduction in NO2, PM10, and PM2.5 concentrations during the lockdown, while O3 levels were higher. These findings demonstrate notable air quality improvements, despite the increase in O3 due to reduced fossil fuel combustion in transport and industrial sectors. The study also underscores the challenge of reducing secondary pollutants, even with stringent controls on primary emissions.

Adikaram and Arambepola [29] examined the behavioral attitudes of three-wheeled taxi drivers, or ‘tuk-tuks’, in Sri Lanka towards mitigating on-road air pollution. Given their significant role in urban mobility, understanding their attitudes is essential for addressing environmental sustainability. The study identified key factors influencing their behavior, including efforts to reduce pollution, awareness, and socio-demographic and legislative influences. The findings suggest that educating drivers, providing financial support, and encouraging behavioral change are crucial for reducing air pollution and protecting their health.

3.1.2. India

India, the most populous country in the world, has a vast transportation sector supported by over 5.6 million kilometers of roads, making the system predominantly road-based. Rail networks also play a significant role in connecting the nation [30]. India’s road density, at around 170 km per 100 square kilometers as of 2016, surpasses that of countries like China, Japan, Russia, and Brazil [30]. The flexibility and reliability of road transportation have made it the preferred mode of travel, with the sector experiencing significant growth since the 1980s, fueled by globalization and liberalization policies [31]. This robust transportation network is largely dependent on fossil fuels, particularly oil, contributing to a rise in road transport energy demand, which has grown annually by 5–6% since 1980. The transportation sector accounts for approximately 50% of India’s total energy consumption in the form of diesel, petrol, aviation fuel, and natural gas [32].

The air quality in India’s cities has become a major concern, with pollutants such as particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and ozone (O₃) often exceeding national air quality standards. According to the World Health Organization (WHO), India is home to 37 of the 100 most polluted cities in the world, with Delhi, Raipur, Gwalior, and Lucknow among the top ten [33]. In a global survey of 1600 cities in 2015, Delhi was ranked as the most polluted city, highlighting the urgent need for effective measures to improve air quality [34].

One such measure, the odd-even driving scheme implemented in Delhi from January 1 to 15, 2016, demonstrated positive results. A comparative analysis of particulate matter (PM2.5 and PM1.0) concentrations before and during the scheme showed a decrease in pollution levels along key road corridors, with PM2.5 reductions higher than those for PM1.0. This reduction in fine particulate matter is crucial for improving respiratory health, particularly in urban areas where vehicular emissions are a significant source of pollution [34].

On 1 November 2019, New Delhi and surrounding towns experienced a severe smog event, with air quality index (AQI) levels reaching 530, far above the safe threshold of 50. This “severe plus” level of pollution was driven by multiple factors, including emissions from vehicles, industrial activities, coal-based power plants, construction, open waste burning, and seasonal agricultural practices such as stubble burning in neighboring states like Haryana and Punjab. The air quality deteriorates further during the winter months, creating a recurring smog problem that has serious public health implications [35].

Air pollution in India has been linked to significant health problems, contributing to a higher disease burden than tobacco use. It is a leading cause of respiratory infections, chronic obstructive pulmonary disease, heart attacks, strokes, and lung cancer. The Energy Policy Institute at the University of Chicago estimates that residents of the Indo-Gangetic Plain will lose, on average, seven years of life expectancy due to high levels of fine particulate pollution [35].

In response to the escalating air pollution crisis, India has implemented the National Clean Air Program (NCAP), which targets a 20–30% reduction in particulate pollution levels by 2024. The program has identified 122 non-attainment cities with poor air quality, including Bengaluru, a city that suffers from significant particulate pollution due to emissions from transportation, industries, and open waste burning [36]. Of the 122 non-attainment cities identified under the NCAP, many have shown significant progress in reducing particulate pollution levels. Notably, 21 cities achieved over a 40% reduction in PM10 levels, although only a few have fully met the National Ambient Air Quality Standards (NAAQS). Bengaluru, for instance, recorded a 24% reduction in PM10 levels over six years. Despite these achievements, challenges such as underutilization of funds and ensuring sustained reductions remain key hurdles. The health impacts of air pollution are stark: long-term exposure to fine particulate matter (PM2.5) has been linked to thousands of deaths from chronic obstructive pulmonary disorder, ischemic heart disease, stroke, and lung cancer in cities like Bengaluru [37].

The transportation sector’s contribution to greenhouse gas emissions is another major concern. In Chandigarh, for example, emissions from urban road transport have risen sharply, with the potential for even higher emissions by 2020. The shift from private vehicles to public transport could reduce greenhouse gas emissions by 15–20%, highlighting the importance of sustainable transport strategies [38]. In Kolkata, the impact of regional industrial emissions, such as sulfur dioxide from coal burning in power plants, is exacerbated by local transportation and biofuel combustion, contributing to high levels of particulate pollution [39].

In an effort to improve air quality, Delhi introduced compressed natural gas (CNG) buses in the early 2000s, significantly reducing particulate and greenhouse gas emissions compared to their diesel counterparts. However, more recent analyses suggest that cleaner diesel buses might offer comparable emission reductions at a lower cost, raising questions about the most cost-effective strategies for improving urban air quality [40].

The health impacts of air pollution are not limited to respiratory issues. The WHO’s Global Burden of Disease Study estimated that India experienced 695,000 premature deaths in 2010 due to outdoor air pollution, and the situation is expected to worsen by 2030 as industrial, residential, transportation, and construction sectors grow [41].

Sustainable transportation is essential for reducing air pollution and its associated health risks. A study in Delhi has shown that promoting non-motorized transport (NMT), such as walking and cycling, can reduce mortality rates by over 40,000 cases annually, as well as lower morbidity rates. Although creating infrastructure for NMT would require significant investment, the health and economic benefits, including reduced healthcare costs, make it a compelling strategy for improving public health [42].

3.1.3. Pakistan

Pakistan, a rapidly urbanizing South Asian country, faces severe air quality challenges, particularly in major cities like Karachi, Lahore, and Islamabad. The urban transportation system, heavily reliant on private vehicles, motorcycles, and public transport such as buses and rickshaws, contributes significantly to vehicular emissions and deteriorating air quality. The transportation sector in Pakistan has experienced significant growth, with its rate increasing by about 19% from 1990 to 2015, largely driven by inefficient public transport systems [43]. In 2015, the number of registered motor vehicles in Pakistan reached 17.7 million [44]. While the railway system was once a dominant mode of freight transport, carrying 73% of freight traffic in the 1950s, its share had plummeted to less than 5% by 2015. Currently, the transport sector is responsible for 90% of passenger traffic and 95% of inland shipments [45]. This sector also makes substantial economic contributions, accounting for over 10% of the national GDP and 25–26% of federal public programs. The number of vehicles on the road surged from 2 million in the 1990s to about 17 million by 2015, with over 80% being automobiles and motorcycles. A significant portion of these vehicles consists of two-stroke engines and heavy-duty trucks and buses, which contribute heavily to roadside emissions [46,47]. The transportation sector consumes 35% of Pakistan’s energy and is responsible for 29% of the country’s total carbon emissions.

Energy consumption in transportation is projected to rise to 52% by 2040 [48]. The adoption of hybrid and electric three-wheelers has been identified as a potential solution to reduce emissions and increase economic benefits for vehicle operators. Survey results indicate that despite high initial costs, users would welcome these vehicles for their financial advantages. Regular three-wheelers typically operate over 100 km daily, providing modest monthly earnings. In contrast, hybrid or electric three-wheelers could boost earnings by 50% while significantly reducing greenhouse gas emissions—by 3–6 tons of CO₂ annually per vehicle—with a return on investment period of just over a year [49].

Air pollution is a critical issue in Pakistan, especially in urban centers, where dust and smoke particles are significantly higher than global averages and five times greater than those in developed countries [50]. Major contributors include rapid urbanization, inadequate industrial emission controls, traffic congestion, and poorly maintained vehicles. Urban centers like Lahore and Rawalpindi face particularly severe pollution levels due to these factors. Motor vehicle exhaust remains the most significant contributor to air pollution, posing a serious environmental and public health challenge [50].

Workers in urban areas, such as traffic policemen and bus drivers, are at elevated risk of exposure to soil-bound polycyclic aromatic hydrocarbons (PAHs), which are linked to respiratory issues and cancer. Studies have found high concentrations of PAHs in soil and dust samples from public transport hubs in Lahore, with traffic policemen and drivers at high risk of cancer through dust ingestion and dermal contact [50]. In Quetta, air pollution has reached alarming levels, with significant impacts on respiratory diseases and premature deaths, especially among children [51].

Road dust poses another severe health risk, particularly in urban areas like Karachi and Shikarpur. Elevated concentrations of toxic metals such as chromium, lead, cadmium, and nickel have been identified in road dust samples, with significant risks of non-cancerous and cancerous health outcomes, especially for children [52]. In Lahore, rapid population growth and urbanization have exacerbated pollution levels. Transportation and industrial emissions contribute to critically high levels of sulfur dioxide, particulate matter, and noise pollution, exceeding WHO standards. Poorly maintained vehicles, which constitute 90% of emissions, underscore the need for stricter regulatory enforcement [53].

The city of Haripur also faces severe air quality challenges, with high concentrations of particulate matter linked to industrial activities and traffic from the nearby Hattar Industrial Estate. The lack of effective monitoring and law enforcement by federal and local authorities further exacerbates the issue [54]. Across Pakistan, urban air pollution has been linked to numerous health impacts, including asthma, allergies, and chronic respiratory diseases. In Lahore alone, air pollution causes approximately 1250 deaths annually, with chronic obstructive pulmonary disease being the most prevalent among air pollution-related illnesses [55].

Studies have also highlighted the link between air pollution and life expectancy. For instance, carbon emissions have been found to negatively impact life expectancy in Pakistan, emphasizing the urgent need for carbon emission regulation [56,57]. Additionally, cities like Lahore, Faisalabad, and Gujranwala face a recurring smog crisis every winter, contributing to severe health issues and an estimated 128,000 air pollution-related deaths annually in the country [58]. These findings underscore the pressing need to address the dual challenges of transportation emissions and air pollution in Pakistan’s urban centers.

3.1.4. Bangladesh

Dhaka, a megacity with over 20 million people, faces severe challenges from rapid urbanization and vehicular growth. Between 2010 and 2015, approximately 0.42 million vehicles were added, with private cars being the largest contributors to exhaust emissions and traffic congestion, occupying over 70% of the roads [59]. Despite their low passenger capacity, car ownership remains high, worsening pollution and economic losses.

From 2009 to 2017, exhaust emission costs rose by 77.89% (from Tk 20.71M to Tk 36.84M/day), climate change costs (CCCs) by 63.96% (from Tk 18.73M to Tk 30.71M/day), and noise pollution costs (NPCs) by 101.61% (from Tk 11.20M to Tk 22.58M/day). The study, analyzing 84 road segments and 18 intersections, emphasizes the need for sustainable regulation of vehicular activities to curb emissions, costs, and congestion [59].

The transportation sector plays a crucial role in Bangladesh’s growing economy but heavily relies on fossil fuels, leading to rising CO₂ emissions. Addressing energy conservation and emission control in this sector is vital for sustainable development. A study using the Logarithmic-Mean Divisia Index (LMDI) model analyzed factors driving CO₂ emissions in Bangladesh’s transport sector from 1990 to 2017 [60]. The findings revealed a 106.94% increase in CO₂ emissions, driven primarily by economic activity (66.03%), population growth (23.56%), economic structure (7.64%), and energy intensity (6.25%). However, changes in the energy structure reduced emissions by −0.80%. Economic output emerged as the dominant contributor, accounting for 66% of the increase, highlighting the link between rapid economic growth and rising energy-driven emissions [60].

A study analyzed seasonal variation, weekly trends, spatial gradients, and pollutant levels (PM2.5, PM10, SO₂, NO₂, CO, and O₃) in Dhaka from 2013 to 2017, with diurnal cycles examined for 2017 due to limited hourly data availability [61]. Ozone showed distinct seasonal patterns compared to other pollutants, which peaked in winter and dropped during the monsoon. PM2.5 and PM10 concentrations increased five- to sixfold, while SO2, NO2, and CO rose two- to threefold during winter compared to monsoon. Particulate matter (PM2.5 and PM10) often exceeded BNAAQS limits during non-monsoon periods, unlike gaseous pollutants, which posed a lesser health risk. Despite a slight, statistically insignificant decline in PM2.5 levels from 2013 to 2017, fine particulate pollution remains dangerously high, posing significant health risks [61].

3.1.5. Nepal

Vehicular emissions significantly impact air quality in Nepal’s urban areas, causing severe respiratory health issues for commuters and pedestrians [62]. In Bhaktapur Municipality, transport emissions total 3310 tons/year, with CO₂ comprising 94.36%, followed by CO (4.39%), HC (0.72%), NOx (0.35%), and PM10 (0.18%). Strong correlations were found among pollutants, such as CO₂ and PM10 (r = 0.92) and CO₂ and NOx (r = 0.90).

Diesel fuel is a major contributor to greenhouse gas emissions, particularly CO₂, exacerbating air quality deterioration. Despite its small size (6.56 km²), Bhaktapur’s transport emissions significantly affect local air quality. Scenario analysis suggests that adopting electric vehicles could substantially reduce emissions. Given differences in population density, area size, and pollution between Bhaktapur and neighboring Kathmandu, air pollution control policies must be tailored to the unique conditions of each city [62].

A study by Bhandari et al. [63] on the effects of lockdown and mobility changes during COVID-19 in the Kathmandu Valley highlights those anthropogenic sources, particularly the transport sector, are the primary contributors to fine particulate matter (PM2.5) in the region. The study found that restricting human activities significantly improved air quality.

During the lockdown periods of 2020 and 2021, PM2.5 concentrations were lower compared to the same months in pre-pandemic years (2017–2019). However, as activities resumed, pollution levels returned to pre-lockdown levels and continued to rise after the lockdowns ended. The findings indicate that restrictions on human mobility, such as reduced walking, driving, and public transport usage, contributed to the decline in PM2.5 concentrations, demonstrating that mobility limitations can effectively reduce air pollution [63].

Dhakal analyzed the implications of transportation policies on energy demand and environmental emissions in Kathmandu Valley, focusing on pollutants like CO₂, CO, HC, NOx, SO2, total suspended particles (TSP), and lead (Pb). Using the Long-range Energy Alternatives Planning System framework, the study constructed future scenarios up to 2020, evaluating traffic improvement measures, public transportation promotion, and the adoption of electric vehicles.

From 1988 to 2000, energy demand increased over fourfold, with TSP levels rising 4.5 times—a major concern as particulate concentrations already exceeded WHO guidelines. Under a non-intervention scenario, energy demand in 2020 was projected to rise 2.7 times compared to 2000, with TSP levels increasing 2.5 times. Scenario analysis revealed that increasing vehicle speeds, promoting public transportation, and adopting electric vehicles could reduce energy demand by 28%, 28%, and 18%, respectively. However, enhancing comfort on overcrowded public transportation might increase energy demand by 10% compared to the non-intervention scenario [64].

3.2. Public Health and Economic Impacts

Urban transportation emissions in South Asia impose significant economic burdens on the region, as evidenced by the findings summarized in

Table 1. Urban transportation emissions and impacts. # is number. * is an unordered list, which has no practical meaning here.

Country/Study Area/City # of Studies	Study Type	Discussed Issues	Economic Impacts	Health Impacts
Sri Lanka
Colombo (4)	Cross section studies in the Colombo city area to measure respiratory health status	* Respiratory diseases * Risk of cancer due to diesel smoke	* Economic losses from reduced productivity and absenteeism linked to pollution-related health issues.	* Significant increase in respiratory illnesses among urban children. * Urban settings had a significantly higher prevalence of wheezing in the last 12 months compared to semi-urban children. * Potential non-carcinogenic and carcinogenic health risks, particularly from lead and cadmium. * Prolonged exposure could lead to respiratory issues and cardiovascular diseases.
Kandy (1)	A quantitative research method to evaluate the health risks associated with heavy metals in atmospheric deposition in Kandy City.
Colombo and Kandy (2)	A comparative analysis method to assess the impact of the COVID-19 lockdown on air quality in urban cities.
Colomb, Gampaha and Kalutara (1)	Air pollution levels measuring in major urban cities and descriptive method
India
Bangalore (2)	* Mixed-methods approach to analyze and compare commuting-related CO2 emissions in Xi’an, China, and Bangalore, India. * Observational study using quantitative methods; air quality data analysis and health risk assessment with AirQ+ model.	* Positive correlation between NO2 concentration and deaths * PM2.5 impacts respiratory health (coughing, teary eyes, headaches) * Long-term PM2.5 exposure linked to health issues * Environmental and economic impact of transitioning Delhi’s bus fleet from diesel to CNG to reduce emissions * Evaluation of GHG emissions and CDM technologies in Chandigarh’s urban transport * Variability of SO2, CO, and hydrocarbons in Kolkata linked to emissions and transport * Impact of electric auto-rickshaws on emissions in India’s transport sector * Potential link between vehicular NO2 emissions and increased COVID-19 fatality rates in India * Impact of emissions from anthropogenic sectors on PM2.5 and health effects in South and East Asia	* Estimated annual cost savings from morbidities and mortalities: USD 4869.8 million, benefiting Delhi’s finances * Challenges in building non-motorized transport (NMT) facilities (bike lanes, safer roads) * CNG buses more cost-effective in reducing emissions than diesel buses, leading to long-term fuel and maintenance savings * Potential GHG reduction of 520 Gg, resulting in cost savings for climate change mitigation * Projected 6.30% CO emission reduction by 2030 with a 5% shift to electric auto-rickshaws	* Long-term PM2.5 exposure caused deaths from COPD, ischemic heart disease, stroke, and lung cancer * Long-term O3 exposure led to deaths from respiratory diseases * Transition to CNG buses reduces air pollution, potentially decreasing respiratory and cardiovascular health issues * Potential improvement in air quality and reduction in health issues related to air pollution * Potential contribution to respiratory and cardiovascular health issues due to elevated pollutant levels * Potential decrease in air pollution-related health issues due to reduced emissions * Elevated NO2 levels may exacerbate respiratory conditions, potentially increasing COVID-19 severity and fatality rates * Potential reduction in health risks associated with PM2.5 exposure through the elimination of emissions from specific sectors
Delhi (4)	* Observational studies using quantitative methods; analyzed air quality data to assess the impact of the odd-even driving scheme on PM2.5 and PM1.0; emissions. * Economic evaluation using cost-effectiveness analysis; assessed emissions and costs of CNG versus diesel buses in Delhi’s public transit system.
Chandigarh (1)	Quantitative study using the VAPI model to assess GHG emissions and the potential for mitigation through CDM technologies in Chandigarh’s urban transport sector.
Kolkata (1)	Observational study measuring SO2, CO, and light hydrocarbons over Kolkata, India, to assess emissions and transport effects.
Surat City (1)	Quantitative research assessing emissions from auto-rickshaws and evaluating a 5% shift to electric models by 2030.
Many cities (all over India) (6)	* Observational study that analyzes the relationship between vehicular NO2 emissions and COVID-19 fatality rates in India. * Utilization of the WRF-Chem regional atmospheric model to assess the air quality and human health benefits of eliminating emissions from various anthropogenic sectors in South and East Asia * Development of a vehicle stock database for India from 1993 to 2018, utilizing survival functions to analyze on-road exhaust emissions
Pakistan
Overall (Many cities) (8)	* Application of the autoregressive distributed lag (ARDL) and vector error correction model (VECM) to analyze the relationship between transport energy consumption, economic growth, and CO2 emissions in Pakistan from 1990 to 2015 * Conducted a user survey to assess the adoption potential of hybrid and electric three-wheelers in Pakistan, analyzing responses from three-wheeler drivers across the country * Econometric analysis using error correction model, regression, and co-integration tests to assess the impact of economic growth, urbanization, and energy consumption on environmental degradation in Pakistan * Management of green transportation: an evidence-based approach	* Impact of transport energy consumption on CO2 emissions in Pakistan * Explored feasibility and user acceptance of transitioning to hybrid and electric three-wheelers in Pakistan’s transportation sector * Influence of economic growth, urbanization, and energy consumption on transport-related environmental degradation in Pakistan * Environmental effects of air and railway transportation in Pakistan, including carbon emissions and resource depletion * Contributions of transport and industrial emissions to elevated air pollution in Lahore, including sulfur dioxide, lead, and particulate matter * Assessment of toxic elements and particulate pollution in Lahore’s urban road dust * Health risks from heavy metals in PM2.5 road dust in two Pakistani cities * Exhaled carbon monoxide levels in urban and suburban populations * Air pollution health risks at the Kallar Kahar site in Pakistan * Prevalence of cardiovascular diseases due to industrial air pollution near IEI, Pakistan * Occupational exposure to dust-bound PAHs and carcinogenic risks in Lahore and Rawalpindi	* Economic growth, urbanization, and energy consumption increase transport-related environmental degradation * Road infrastructure boosts economic growth but worsens environmental quality, increasing SO2 emissions * A comprehensive city management plan is needed: alternative roads, traffic management, regulations, and taxes on vehicular/industrial emissions * Potential for a 50% increase in monthly earnings for three-wheeler owners through reduced fuel and maintenance costs * Health effects of smog in Gujranwala, Pakistan, identified through geo-visualization * Public awareness and willingness to pay for reducing atmospheric pollution in Pakistan	* PM10 bypasses respiratory defenses, contributing to allergic disorders * Exacerbation of asthma, allergies, and other respiratory diseases * PM2.5 linked to lung cancer mortality (ages 25+ and 30+) * PM10 concentration linked to 16.96% of infant post-neonatal mortality * NO2 exposure linked to all-cause mortality * Heavy traffic and poorly maintained vehicles increase hazardous metal concentrations in road dust * Non-cancerous health risks from Cu, Ni, and Zn exposure in Karachi, Shikarpur * Cancer risk from Pb, Cd, and Ni exceeds tolerable limits in children and adults in various cities * Excess CO emissions from Lahore’s mass transit system * Significant improvement in air quality during COVID-19 lockdown (PM2.5 drop: Karachi 62%, Lahore 62%, Peshawar 57%, Islamabad 55%) * Reduction in greenhouse gas emissions (3–6 tonnes CO2 per year per three-wheeler) leading to improved air quality and public health * Health impacts from carbon monoxide exposure among commuters and roadside vendors * Potential health benefits from reducing atmospheric pollution through public support * Smog-induced health effects in Gujranwala community * Elevated sulfur dioxide, lead, and particulate matter levels pose significant health risks in Lahore * Potential health risks from exposure to air pollution and toxic elements in road dust.
Karachi, Lahore, Islamabad, and Peshawar (1)	Impact of transport and industrial emissions on the ambient air quality of Lahore City, Pakistan
Gujranwala (1)	Geo-visualization of smog-induced health effects hotspots in Gujranwala, Pakistan, from a community perspective.
Lahore (2)	Analysis of transport and industrial emissions to assess their impact on the ambient air quality in Lahore City, Pakistan.
Haripur city (1)	Assessment of particulate matter (PM) in ambient air across different settings and its associated health risks in Haripur city, Pakistan.
Karachi (1)	Comparison of exhaled carbon monoxide levels among commuters and roadside vendors in urban and suburban populations in Pakistan.
Faisalabad (2)	Analysis of urban road dust samples from Lahore, Pakistan, to assess concentrations of potentially toxic elements and particulate pollution
Karachi and Shikarpur (1)	Health risk assessment of heavy metals accumulated on PM2.5 fractioned road dust from two cities in Pakistan.
Khyber Pakhtunkhwa Province (1)	Survey-based study assessing public awareness and willingness to pay for eliminating atmospheric pollution in Pakistan.
Kallar Kahar (Chakwal) (1)	Modeling of air pollution health risks for environmental management at an internationally important site (Kallar Kahar) in Pakistan.
Islamabad (1)	Assessment of cardiovascular disease (CAD) prevalence due to industrial air pollutants near Islamabad Industrial Estate (IEI), Pakistan.
Quetta (1)	Air pollution assessment in urban areas of Quetta, Pakistan, and analysis of its impact on human health.
Lahore and Rawalpindi cities (1)	Source profiling and carcinogenic risk assessment for cohorts occupationally exposed to dust-bound polycyclic aromatic hydrocarbons (PAHs) in Lahore and Rawalpindi cities, Punjab,
Bangladesh
Dhaka City (3)	Modeling the impact of motorized vehicles’ activities on emissions and economic losses in Dhaka, Bangladesh. Analysis of spatial gradients and time trends in air pollution in Dhaka, Bangladesh, and their implications on human health. Estimation of air pollutants from different sectors in Dhaka City using emission inventory analysis.	* Impact of motorized vehicles on emissions and economic losses in Dhaka * Spatial gradients and time trends in air pollution and their health implications in Dhaka * Air pollutant estimation from various sectors in Dhaka City * Energy-related CO2 emissions in the transport sector of Bangladesh.	* The uncontrolled rise in personal vehicles led to significant emission spikes and economic losses.	* Dhaka, Bangladesh’s capital, has become one of the world’s most polluted cities, with air pollution posing a major public health concern.
Overall (1)	Decomposition analysis of energy-related CO2 emissions from Bangladesh’s transport sector development.
Nepal
Kathmandu Valley (1)	Analysis of air quality changes in the Kathmandu Valley during COVID-19 lockdown, using mobility data and air pollution levels.	The impact of the COVID-19 lockdown and associated mobility changes on air quality. * Emission load from road transportation and its environmental impact in Bhaktapur Municipality.	* Rising motorized travel in Kathmandu Valley increases fuel imports, straining Nepal’s economy * Vehicular emissions in Bhaktapur contribute to pollution-related diseases, increasing healthcare costs.	* Potential reduction in air pollution-related health risks due to decreased emissions during lockdown* Vehicular emissions significantly deteriorate air quality in many urban parts of Nepal * Diesel fuel plays a crucial role in emitting greenhouse gases, deteriorating air quality and health.
Bhaktapur (1)	Estimation of emission load from road transportation in Bhaktapur Municipality using traffic and emission data.

. In Sri Lanka, urban centers such as Colombo experience substantial economic losses due to pollution-related health issues. Increased respiratory illnesses among urban children, partly attributed to diesel smoke exposure, lead to higher healthcare expenses and reduced productivity from absenteeism. These impacts underscore the dual economic toll of direct medical costs and lost labor contributions to the economy.

In India, urban areas like Delhi and Bangalore have seen air pollution drive up healthcare costs and productivity losses, with one study estimating annual cost savings of USD 4869.8 million if morbidity and mortality rates were reduced. The lack of non-motorized transport (NMT) infrastructure further exacerbates economic challenges by limiting sustainable urban development. Similarly, in Pakistan, vehicular emissions contribute to respiratory diseases and premature deaths, with urbanization and increased energy consumption worsening environmental quality. Poorly maintained vehicles and heavy traffic elevate hazardous metal concentrations, increasing healthcare costs and necessitating comprehensive urban planning to mitigate the economic strain.

Bangladesh and Nepal also face economic pressures from urban transportation emissions. In Dhaka, the rise in personal vehicles correlates with emission spikes and economic losses due to unregulated growth. In Nepal’s Kathmandu Valley, the dependence on imported fuel for rising motorized travel strains the national economy, while vehicular emissions increase healthcare expenses related to pollution-induced diseases. These findings collectively emphasize the need for policies addressing sustainable urban transport to reduce health and economic costs in South Asia.

While numerous studies have examined the health effects of urban transportation emissions, there remains a significant gap in the quantification of their economic impacts. Most research has focused on the direct health costs, such as increased healthcare expenditures due to respiratory and cardiovascular diseases, but the broader economic consequences -such as lost productivity, reduced worker efficiency, and the long-term burden on public health systems, have not been extensively studied. This lack of quantification is particularly notable given that urban air pollution, particularly from transportation emissions, can have wide-reaching effects on both local economies and national economic systems. The economic impacts of air pollution go beyond healthcare costs, as they can affect labor productivity, tourism, housing prices, and overall quality of life, leading to indirect economic losses. For example, studies in regions with high air pollution have shown reductions in labor productivity due to illness and absenteeism. Furthermore, poor air quality can deter investment and impact real estate values, particularly in densely populated urban areas. Integrating the economic dimension into the analysis of urban transportation emissions would provide a more comprehensive understanding of the full cost of air pollution and guide future policies to mitigate both health and economic impacts.

3.3. Additional Insights from Studies Across South Asia

Beyond the studies specifically reviewed in this paper that directly discuss urban transportation-related emissions and impacts, extensive research on air pollution across South Asia has provided critical insights into its multifaceted effects, complementing the findings in Table 1. Asia, home to over 4.5 billion people, relies heavily on transportation to connect its vast population [65]. However, transportation is a major contributor to air pollution, with significant consequences for both human health and the environment [11,66]. Common modes of transport such as private cars, buses, trains, and subways are significant pollution sources, exposing individuals to high levels of emissions during daily commutes. In congested urban areas, prolonged exposure to these pollutants increases the risk of respiratory and cardiovascular diseases [67]. Cities like Delhi and Mumbai, where the average commute exceeds 60 min, face even longer exposure times, exacerbating the impact of traffic-related pollution [68]. Public transportation users are also at risk, especially in poorly ventilated vehicles [69].

Air pollution’s health impacts are wide-ranging, including respiratory infections, chronic diseases, and premature mortality. Both acute and chronic exposure to ambient and household air pollution affects individuals across their life cycle, from prenatal development to old age. For instance, exposure during pregnancy can increase risks of fetal loss, premature birth, and low birthweight [70], while long-term effects include stunting and respiratory issues in childhood [71,72]. In adulthood, air pollution contributes to diseases such as cardiopulmonary conditions, type 2 diabetes, and mental health issues [73,74,75]. Additionally, air pollution is linked to cognitive decline, obesity, and complications from diseases like COVID-19 [76,77]. Studies indicate that mortality rates from air pollution are significantly elevated, with particulate matter exposure directly contributing to an increased death toll [78]. In high-pollution areas like South Asia, long-term exposure can reduce life expectancy by as much as 5 years [79,80].

The World Bank Group designates South Asia as a global air pollution hotspot, home to 37 of the world’s 40 most polluted cities. Approximately 60% of the population in the region is exposed to unsafe air quality that far exceeds WHO standards. Air pollution causes over 2 million premature deaths annually, with transboundary pollution playing a significant role. For example, 30% of Punjab, India’s, pollution originates from Pakistan, and similarly, 30% of Bangladesh’s urban pollution stems from India. Localized measures alone are insufficient, as even full implementation of controls in cities like Delhi would fail to meet WHO air quality targets due to regional pollution inflows. The report advocates for coordinated regional actions, showing that such initiatives are more cost-effective and impactful, saving over 750,000 lives annually while reducing healthcare costs and improving productivity. Bold political commitment and unified strategies are essential to addressing South Asia’s air pollution crisis, resulting in significant health and economic benefits [81].

Amer et al. [82] use time series and machine learning techniques, including ARIMA, exponential smoothing, and neural networks, to project the impact of air pollution on mortality and disability-adjusted life years (DALYs) in SAARC countries. The study, which spans data from 1990–2019 and forecasts trends for 2020–2030, reveals notable health disparities tied to ambient particulate matter (APM), ambient ozone pollution (AOP), and household air pollution (HAP). Bangladesh faces the highest health challenge from HAP, with deaths and DALYs showing substantial variability. Nepal bears the greatest burden from HAP, followed by India, which emerges as a hotspot for APM and HAP-related health risks. Pakistan suffers the most from HAP, while AOP outcomes remain relatively stable. Bhutan’s impacts are moderate, and the Maldives records the lowest deaths and DALYs. Sri Lanka’s health impacts are comparatively low, reflecting lower vulnerability to air pollution. These findings underscore the need for evidence-based policies across the SAARC region to mitigate air pollution and its health effects.

Pandey et al. [83] analyzed the economic and health impacts of three major types of air pollution in India: ambient particulate matter, household air pollution, and ambient ozone pollution. The study estimates economic losses due to premature deaths and morbidity at $36.8 billion (1.36% of GDP) in 2019. These losses are most pronounced in low-GDP states such as Uttar Pradesh and Bihar, while Delhi experiences the highest per-capita losses. Urban transportation contributes significantly to ambient particulate matter and ozone pollution, highlighting its critical role in the economic burden. However, household air pollution remains less influenced by urban transportation. The study emphasizes that state-level strategies for air pollution reduction could yield significant health and economic benefits, supporting India’s broader economic goals.

In Dhaka, Bangladesh, air quality has worsened dramatically, making it one of the most polluted cities globally. Industrial and traffic emissions are the primary contributors [84], leading to increased mortality from cardiovascular diseases (CVD) and respiratory illnesses [85]. Numerous studies show strong correlations between exposure to fine particulate matter (PM2.5) and increased mortality, hospitalization, and emergency visits due to CVD and respiratory diseases [61,86]. In fact, outdoor air pollution is the third leading cause of mortality in Bangladesh, following high blood pressure and smoking (IHME, 2018) [87]. A global state of air report estimated that PM2.5 exposure caused 122,400 deaths in Bangladesh in 2015 [88], and mortality attributed to air pollution has increased by 52% over the last two decades. In 2016, Dhaka experienced 9051 premature deaths due to PM2.5 exposure, accounting for 6.62% of all deaths, with ischemic heart disease, stroke, chronic obstructive pulmonary disease, lung cancer, and acute lower respiratory infections being the primary causes [89].

The impact of particulate matter (PM2.5) on air quality and human health is particularly severe in developing countries, including South Asia, due to rapid industrialization and urbanization [90]. The region, which is home to 22% of the world’s population within just 3% of its land area [91], suffers from some of the highest PM2.5 concentrations globally. Ten of the world’s twenty most polluted cities are located in South Asia [92]. Between 2010 and 2016, the region saw a significant decline in air quality, particularly during winter and dry months [93,94]. Nearly half of the South Asian population is exposed to PM2.5 levels exceeding WHO safety thresholds, contributing to 22% of all deaths in the region. In India and Pakistan, air pollution results in massive economic costs, with India’s losses estimated between 4.5–7.7% of GDP and Pakistan’s at 6% [95]. Pakistan’s major cities are experiencing worsened air quality due to increased emissions of sulfur oxides, nitrogen oxides, smoke particles, and aerosols [96,97,98].

The mean PM2.5 concentrations in Bangladesh, India, Pakistan, and Sri Lanka range from 15 to 40 µg/m³ annually and from 35 to 65 µg/m³ over 24 h, exceeding WHO-recommended air quality standards of 10 µg/m³ annually and 25 µg/m³ for 24-h exposure [99]. These levels contribute to staggering health consequences, with India alone experiencing 1.1 million premature deaths annually due to PM2.5 exposure [100]. Bangladesh, Pakistan, and Nepal suffer from approximately 163,000, 134,600, and 16,200 premature deaths each year, respectively [101]. Furthermore, air pollution significantly affects pregnancy outcomes, with an estimated 349,681 pregnancy losses annually in Bangladesh, India, and Pakistan due to ambient air pollution [13]. As a result, PM2.5 and its associated risks are gaining increasing attention from public health experts, governments, and international organizations, all striving to control PM2.5 emissions at local, regional, and global levels.

South Asia’s population is among the most heavily exposed to PM2.5 worldwide, with the 2015 Global Burden of Disease (GBD) study reporting a population-weighted mean PM2.5 concentration of 73 µg/m³, significantly higher than the global average of 44 µg/m³ [7]. The Air Quality Life Index [102] reports that countries like Bangladesh, India, Nepal, and Pakistan contribute to over half of the global life years lost due to pollution, with Bangladesh alone losing an average of 6.8 years of life per person—far more than the 3.6 months lost in the United States. The sources of ambient air pollution vary across rural and urban areas, requiring region-specific strategies to effectively control PM2.5 emissions [90,103].

4. Thematic Insights: Achieving Sustainable Urban Transportation

Achieving sustainable urban transportation is crucial for enhancing air quality, public health, and economic vitality. Policymakers must prioritize cleaner transportation systems, better integration of public transit, and regional cooperation to build resilient, healthy, and economically competitive urban environments. A long-term, holistic approach is essential for ensuring the success of these initiatives.

As illustrated in the conceptual framework (Figure 1), the link between transportation, air quality, and public health is critical. Transportation emissions significantly contribute to urban air pollution, leading to respiratory and cardiovascular diseases. Policies should focus on reducing emissions by adopting cleaner technologies and promoting alternatives such as public transit, cycling, and walking. For example, the study “Evaluation on the Development of Urban Low-Carbon Passenger Transportation Structure in Tianjin” highlights efforts like expanding public transit and promoting non-motorized transport, which have reduced carbon emissions and improved air quality Tianjin case study [104]. Such initiatives improve environmental quality, reduce healthcare costs, and enhance the quality of life, making sustainable transportation a key strategy for healthier cities.

The economic costs of inefficient transportation systems, highlighted in Figure 1, are substantial. Poor air quality results in increased healthcare expenditures, lost productivity, and decreased urban attractiveness. Investing in sustainable transportation—such as electric vehicles (EVs), expanded public transit, and carpooling—can mitigate these costs, fostering economic resilience by supporting a more productive workforce and reducing pollution-related health issues. Smart transportation systems, which utilize advanced sensors, data transmission, and energy-efficient technologies, can further optimize traffic flows, reduce congestion, and encourage the use of cleaner energy in vehicles [105,106].

These advancements lower transportation-related emissions and contribute to better urban air quality, showcasing the economic and environmental rationale for sustainable transportation as a vital component of urban policy.

Public transportation plays a key role in sustainable urban mobility. Cities that invest in efficient, low-emission transit systems can reduce reliance on private vehicles, easing congestion and improving air quality. Prioritizing the expansion and modernization of public transit, along with policies that encourage its use, will support long-term sustainability by reducing pollution and improving mobility for all urban residents. For instance, medium-sized cities that adopt multimodal approaches—integrating buses, trains, bicycles, and pedestrian-friendly infrastructure—can significantly enhance transportation efficiency, accessibility, and environmental sustainability [107].

While Figure 1 focuses on localized impacts, many cities face transboundary air pollution, necessitating regional cooperation. Policies should address both local emission reductions and cross-border collaboration to manage shared air quality challenges. Coordinated strategies for emission reductions and joint initiatives can help cities achieve cleaner air and more sustainable urban environments. For example, the Tianjin case study emphasizes the role of integrated planning and policy in achieving low-carbon transportation goals [106].

Urban areas frequently have pollution hotspots where emissions are especially high. Targeted policies should aim to reduce emissions in these regions by promoting cleaner technologies, expanding green spaces, and enforcing stricter emission standards. Urban planning must also prioritize alternative transportation options and pedestrian-friendly spaces to alleviate congestion and mitigate environmental impacts [108,109].

Sustainable urban transportation is crucial for the long-term resilience of South Asian cities, which face significant challenges related to urbanization, traffic congestion, air pollution, and public health. As South Asian cities continue to grow, transportation demand rises, exacerbating congestion, increasing pollution, and causing a range of health problems. Addressing these issues requires tailored approaches to urban development, taking into account the unique conditions, demographics, and future development goals of each city.

For instance, in Dhaka, Bangladesh, rapid urbanization and a high population density have led to severe traffic congestion and air pollution. The city has one of the highest rates of air pollution in the world, with the transportation sector being a major contributor to particulate matter and other pollutants. In this context, sustainable urban transport solutions such as expanding the public transit network, promoting the use of electric vehicles (EVs), and improving traffic management are key. However, given Dhaka’s historical infrastructure and the challenge of integrating modern systems into a densely built environment, policymakers must focus on a mix of short-term and long-term strategies that fit the city’s evolving needs.

Similarly, in Mumbai, India, transportation-related air pollution significantly impacts public health. Studies indicate that poor air quality leads to an increase in respiratory diseases, especially among vulnerable populations such as children and the elderly. Mumbai has made strides in public transport with the expansion of the metro system and initiatives like the introduction of electric buses. However, these efforts must be complemented by stricter emission regulations for vehicles, better infrastructure for non-motorized transport (e.g., cycling and walking), and initiatives to reduce traffic congestion. Mumbai’s older urban design also means that a one-size-fits-all approach to urban transportation cannot be applied, necessitating solutions that integrate both old and new systems.

In Sri Lanka, particularly in Colombo, urban transportation faces similar challenges due to rapid urban growth and a growing middle class with increasing reliance on personal vehicles. As the city struggles with traffic congestion and air pollution, a shift toward sustainable transportation options such as improved bus networks, electric taxis, and better urban planning to reduce travel demand is essential. However, like other cities in South Asia, Sri Lanka must consider the balance between economic development and environmental sustainability, ensuring that policies do not hinder job creation or economic activity.

Policymakers in South Asia must recognize that each country’s urban challenges are unique. Modern cities can integrate new technologies into their transportation infrastructure, while older, densely populated cities like Dhaka may need more gradual, adaptive approaches considering current infrastructure limitations. To effectively tackle these challenges, policymakers must engage all sectors of society—governments, businesses, and citizens—in a collaborative effort. Governments should take the lead in implementing policies that promote sustainable transport and clean technologies, but private-sector investments in green technologies and public engagement are essential for creating lasting change. Robust monitoring systems must be put in place to track the progress of these policies, providing data on air quality, traffic patterns, and public health outcomes. Only through this comprehensive and integrated approach can South Asian cities overcome the challenges posed by urban transportation, air pollution, and their associated economic and health impacts.

5. Conclusions, Recommendations, and Limitations

This study has reviewed the existing literature on transportation emissions, their public health impacts, and the broader economic consequences, with a focus on major South Asian cities. The findings underscore the critical links between transportation emissions, air quality, and public health. The economic burden of poor air quality is substantial, with healthcare costs, lost productivity, and decreased urban livability driving significant challenges for cities. Sustainable urban transportation systems, which integrate cleaner technologies, efficient public transport, and regional cooperation, emerge as key strategies for mitigating these impacts and fostering healthier, more economically resilient urban environments.

The study emphasizes the need for comprehensive, long-term policy interventions that prioritize cleaner transportation, reduce emissions, and promote sustainable urban mobility. By adopting such policies, cities can improve public health outcomes, enhance economic vitality, and build resilience against future environmental and economic stresses. Furthermore, the implementation of sustainable transportation models can mitigate the economic costs associated with air pollution, ultimately benefiting both urban populations and national economies.

While the study offers valuable insights into the economic impacts of transportation emissions and public health, it is important to acknowledge its limitations. The analysis is based on existing literature and case studies, which may not fully capture the unique challenges and opportunities faced by individual cities. Further empirical research, particularly context-specific studies, is needed to refine and tailor policy recommendations for diverse urban settings. Additionally, this review paper does not address all factors influencing air quality and transportation, such as political and social dynamics, which may play a significant role in shaping policy outcomes. Therefore, continued exploration of these issues is essential for developing more targeted and effective strategies for sustainable urban transportation.