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Hung and Nghiem

offset the negative effects of urban growth. Cui et al., Health effects span both acute and chronic domains.
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Guo et al., and Nasreen et al., affirmed the decreasing Acute impacts include eye, nose, and throat irritation,
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(inhibiting) impact of different factors (the Russia- asthma exacerbation, and increased hospital admissions
Ukraine war, financial development) on improving for respiratory and cardiac conditions. Chronic
environmental quality in general, respectively. In outcomes encompass asthma development, chronic
another study, Bakry et al. confirmed the reducing obstructive pulmonary disease, lung cancer, stroke,
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impact of digital finance on emission in a group of and heart disease, in addition to emerging evidence of
developing countries. impacts on neurological and reproductive health.
This variation points to the existence of an In developing countries where pollution levels
environmental Kuznets curve for air pollution, where frequently exceed WHO guidelines by substantial
pollution initially worsens with urbanization and margins, the health burden becomes particularly
industrialization but can improve beyond certain income severe. Apte et al. found that health impacts per unit
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thresholds as cleaner technologies become affordable and of pollution exposure were greater in highly polluted
environmental regulations strengthen. Dong et al., using environments, suggesting non-linear dose-response
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panel data from 126 countries, identified this inverted-U relationships that amplify risks in contexts, such as
relationship between urbanization and PM2.5, with urban Vietnam. The same research, focusing specifically
agglomeration effects and technological progress helping on low- and middle-income countries, also identified
reduce pollution at later development stages. stronger associations between air pollution and adverse
Several mechanisms explain how urbanization drives health outcomes compared to high-income countries,
pollution increases. Urban concentration of people and potentially reflecting higher baseline pollution levels,
economic activity intensifies energy consumption, greater population vulnerability, and limited healthcare
vehicle use, and industrial output – all generating access. 21
substantial emissions. Guan et al. highlighted Beyond PM2.5, other urban pollutants pose significant
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how urbanization typically increases fossil fuel health risks. Nitrogen dioxide (NO2), primarily from
consumption for electricity, heating, and industry, while vehicle engines and power generation, irritates lungs,
simultaneously expanding transportation emissions as aggravates asthma, and increases respiratory infection
rural populations migrate to cities. risk. Chronic NO2 exposure associates with reduced
Importantly, urban form matters significantly for lung function and contributes to secondary pollutant
pollution outcomes. Chen et al. demonstrated that formation including ozone and nitrate particles.
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densely populated, well-planned cities with mixed Epidemiological studies link long-term NO2 exposure
land use can achieve lower per capita emissions than to elevated all-cause, cardiovascular, and respiratory
sprawling, low-density urban areas. This suggests mortality risks.
that compact growth combined with public transit Sulfur dioxide (SO2) from coal burning and
can mitigate pollution, whereas urban sprawl tends to industrial processes triggers bronchoconstriction and
increase vehicle dependence and energy consumption. asthma attacks even at relatively low concentrations.
Short-term SO2 spikes correlate with increased hospital
2.2. Air pollution and public health visits for respiratory and cardiac issues, while long-term
The health impacts of air pollution have been exposure contributes to chronic respiratory illness and
extensively documented through epidemiological secondary particulate formation.
research worldwide, with PM2.5 showing particularly These pollutants often co-occur and may act
strong associations with adverse health outcomes across synergistically. NO2 and SO2 can exacerbate PM2.5
all age groups and health conditions. effects by injuring respiratory tissues and reducing
A comprehensive review of 263 studies by Zhang physiological defenses. Ozone (O3), a secondary
et al. confirmed robust associations between PM2.5 pollutant forming from nitrogen oxides and volatile
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exposure and increased risks of respiratory diseases, organic compounds under sunlight, causes respiratory
cardiovascular disorders, and pre-mature mortality. inflammation and reduced lung function in urban
Pope III et al. estimated that every 10 μg/m areas.
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increase in long-term PM2.5 exposure associates with
approximately 6% higher all-cause mortality globally, 2.3. Research on Vietnam
though this relationship appears non-linear with steeper Research on air pollution and health in Vietnam has
slopes at higher pollution levels. expanded considerably in recent years, though it

Volume 22 Issue 3 (2025) 200 doi: 10.36922/AJWEP025130088