Review article https://doi.org/10.1038/s41591-025-03929-8
Air pollution interventions for health
Received: 12 March 2025
Accepted: 30 July 2025
Published online: 21 August 2025
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John S. Ji 1 ,
Maria Neira6
Francesca
Dominici 2,3, Nelson Gouveia 4, Frank J. Kelly 5 &
Air pollution, a leading environmental health risk, claims millions of lives yearly, impacting health across the lifespan. Despite widespread acknowledgement of air pollution-related disease burdens, eliminating air pollution remains challenging. Many regions are reliant on fossil fuels or biomass for basic survival, and developed economies striving to reduce air pollution face persistent barriers. Climate change complicates intervention eforts, as rising temperatures and extreme weather (for example, wildfres, dust storms) intensify air pollution. Traditional interventions may falter under worsening climate conditions, requiring integrated mitigation, adaptation and resilient infrastructure to yield environmental and health benefts. In this narrative Review, we evaluate multilevel interventions at the national, community and individual levels, discussing what works and does not work, with illustrative case examples. No single intervention sufces; efcacy depends on context, shaped by enforcement and equity. Integrated strategies are needed to address the root causes of air pollution and mitigate the devastating health impacts.
Air pollution is a leading environmental risk factor that impairs health across the lifespan and causes millions of premature deaths annually1. The World Health Organization (WHO) estimates that 99% of the global population breathes air that fails to meet WHO safety guidelines, with low- and middle-income countries (LMICs) having the highest exposure due to fossil fuel reliance and infrastructure2–5. Epidemiological and mechanistic studies reveal that air pollution disrupts nearly every organ system, driving adverse effects on the lungs6, heart7, brain, central nervous system8, immune system9 10 and others11 (Fig. 1). Quasi-experimental studies demonstrate that air pollution is associated with pregnancy complications and adverse birth outcomes, such as preeclampsia, gestational diabetes, congenital malformations, preterm birth and low birth weight12–22. As a leading yet modifiable risk factor for myriad negative health effects, air pollution demands urgent, evidence-based interventions to advance global health equity and reduce its devastating toll.
The ‘State of Global Air 2024’ report found that air pollution accounted for 8.1 million deaths globally in 2021, making it the second leading risk factor for death behind high blood pressure1. Alarmingly, more than 700,000 deaths in children under 5 years of age were linked
to air pollution, representing 15% of all global deaths in this age group. Although these adverse health outcomes in children are largely driven by acute conditions such as lower respiratory infections, the overall disease burden from air pollution is dominated by long-term impacts. Chronic diseases, including heart disease, stroke, diabetes, lung cancer and chronic obstructive pulmonary disease, account for nearly 90% of the disease burden from air pollution. Despite its ubiquity, air pollution remains underrecognized as a health determinant. Its complexity arises from a dynamic mixture of particulate matter, nitrogen dioxide (NO2), ozone (O3) and other pollutants from combustion, traffic and secondary reactions, driving acute crises and chronic risks, with mixture effects complicating control (Fig. 2).
Air pollution intertwined with climate change poses complex challenges from evolving transportation emissions, pollutant mixtures and climate-driven air quality shifts, which challenge current intervention policies. Climate change drives new emission sources, like wildfires and O3 from warming, while urbanization concentrates exposure in ‘megacities’; of note, more than half of the global population will live in megacities by 2050 (refs. 23–25).
1Vanke School of Public Health, Tsinghua University, Beijing, China. 2Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA. 3Harvard Data Science Initiative, Cambridge, MA, USA. 4Faculty of Medicine, Department of Preventive Medicine, University of São Paulo, São Paulo, Brazil. 5Environmental Research Group, School of Public Health, Faculty of Medicine, Imperial College London, London, UK. 6Department of Environment, Climate Change and Health, World Health Organization, Geneva, Switzerland. e-mail: johnji@tsinghua.edu.cn
NO x Air pollutant VOCs
Blood–brain barrier
Cross Enter
Endothelial injury Enter systemic circulation
• Vasoconstriction
• Promotion of pro-thrombotic states
• Dysregulation of NO synthesis
• Autonomic nervous system dysregulation
• Changes in ion channel function
Cardiovascular impact
• High blood pressure
• Atherosclerosis
• Stroke
• Myocardial infarction
• Cardiac arrhythmia and cardiac arrest
Fig. 1 | Pathophysiology of air pollution exposure and its multisystem health effects. Air pollutants, including SO2, NOx, O3, polycyclic aromatic hydrocarbons, heavy metals and fine particles, enter the body primarily through inhalation via the alveoli. These pollutants initiate a cascade of pathophysiological processes: (1) neurological impact: pollutants cross the blood–brain barrier, causing neuroinflammation, microglial activation, altered neuronal migration, synaptic plasticity deficits and myelination issues, contributing to neurodegenerative diseases, IQ reduction, autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) and mental health. (2) Pulmonary impact: ultrafine particles trigger reactive oxygen species (ROS) production, inflammatory cytokine release (IL-1β, IL-6 and CRP) and systemic inflammation,
In this Review, we explore air pollution interventions, focusing on what works and what does not at the individual, community and national levels. We highlight the environmental and health co-benefits of well-designed interventions, showcase positive examples of urban and city-level actions and consider the role of legislation. The urgency of interventions for air pollution mitigation cannot be overstated; it is a matter of life and death, requiring action at all pollution scales at the individual, community and national levels.
National and international interventions
Air pollution requires coordinated interventions at national and international levels to achieve scalable reductions. National policies such as the US Clean Air Act26, China’s Blue Sky Defense War27, EU Ambient Air Quality Directives28, India’s Graded Response Action Plan (GRAP; https://caqm.nic.in)29, open burning bans and global agreements (driven by national regulatory frameworks) set legally binding pollution limits. These interventions not only reduce air pollution exposure but also drive technological innovation, economic co-benefits and environmental justice improvements. Furthermore, international agreements such as the Paris Agreement (https://unfccc.int/process-and-meetings/ the-paris-agreement) highlight the necessity of global cooperation in tackling air pollution beyond national borders. A global air quality framework should have harmonized standards, but challenges experienced with many national and international policies include cross-border enforcement, industry pushback, inconsistent standards
• Synaptic plasticity
• Microglial activation
• Altered neuronal migration
• Neuroinflammation
• Myelination
• Bronchial reactivity
• Mucociliary clearance
Tissue injury
• ROS
• Inflammatory cytokines
Neurological impact
• Neurodegenerative diseases
• IQ reduction
• ASD
• ADHD
• Mental health
Pulmonary Impact
• COPD
• Pulmonary fibrosis
• Asthma Chronic bronchitis
• Respiratory infections
Epigenetic modifications
• Systemic inflammation
• DNA methylation
• DNA damage
Systemic disease
• Cancer
• Metabolic disease and diabetes
• Cardiovascular disease
• Subfertility and preterm birth
leading to bronchial reactivity, impaired mucociliary clearance and conditions such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, asthma, chronic bronchitis and respiratory infections. (3) Cardiovascular impact: pollutants cause endothelial injury, vasoconstriction, dysregulation of NO synthesis and promotion of pro-thrombotic states, increasing risks of high blood pressure, atherosclerosis, stroke and myocardial infarction. (4) Systemic disease: chronic exposure leads to epigenetic modifications, DNA methylation, DNA damage and systemic inflammation, promoting cancer and metabolic diseases including diabetes. The figure highlights the interconnected mechanisms linking air pollution exposure to multisystem health effects.
and weak enforcement. Below, we discuss key national and international policies and their respective advantages and limitations.
The US Clean Air Act
The US Clean Air Act is a benchmark for air quality regulation, with decades of enforceable standards and recent 2024 updates demonstrating considerable health and economic benefits, making it a prime example of effective national policy26. The Act was first enacted in 1970 and substantially amended in 1990, authorizing the US Environmental Protection Agency (EPA) to establish and enforce National Ambient Air Quality Standards for six key pollutants: PM2.5, O3, NO2, sulfur dioxide (SO2), carbon monoxide (CO) and lead. Over the past five decades, implementation of US Clean Air Act regulations has substantially reduced air pollution, improved respiratory and cardiovascular health and increased life expectancy30. In February 2024, the EPA lowered the annual PM2.5 standard from 12.0 μg m−3 to 9.0 μg m−3 in response to growing epidemiological evidence linking even low-level PM2.5 exposure to premature mortality and cardiovascular disease. This revision is projected to prevent 4,500 premature deaths per year by 2032 while also reducing asthma exacerbations, hospital admissions and lost workdays31,32. Indeed, the revised National Ambient Air Quality Standards for PM2.5 is expected to prevent approximately 800,000 cases of asthma exacerbations by 2032 (ref. 33). The success of this Act is attributed to enforceable standards, adaptive revisions based on epidemiological evidence and a focus on health-driven outcomes.
Alveoli
interventions
air legislation
on open burning
emission regulations
air quality framework
solutions
Air pollution early warning systems
Fossil fuel phaseout and energy transition LEZs and ULEZs
Fig. 2 | Air pollution interventions by pollutant type. The figure illustrates the different approaches to reducing particulate matter (PM; for example, PM2.5 and PM10) and gaseous pollutants (for example, NO2, O3 and SO2). Top, key sources of primary and secondary air pollutants and how these interact with each other and with climate effects. Tailoring interventions to local air quality profiles to
It has driven cleaner vehicle technologies and catalyzed economic benefits, with an estimated public health net benefit of $22 billion to $46 billion34. A study using Medicare data, covering the health records of 73 million older adults (aged 65+) from 2000 to 2016, showed that lower PM2.5 exposure reduced deaths across all groups, with greater benefits for Black and low-income communities, who face higher pollution exposures and burdens35.
Coal-fired electricity generation units are a major cause of air pollution, with 460,000 deaths attributed to PM2.5 from these units in the USA from 1999 to 2016 and exposure to this PM2.5 carrying 2.1 times the mortality risk compared to PM 2.5 from other sources 36 Coal, historically a relatively inexpensive fuel, is burned to provide electricity worldwide, even as the USA and other nations debate whether it should remain a part of the energy portfolio, amid public health and climate concerns. In April 2024, the US EPA announced the final Carbon Pollution Standards for Fossil Fuel-Fired Power Plants 37 , designed to cut emissions from the power sector drastically. The rule mandates that existing coal-fired power plants operating beyond 2039 achieve a 90% reduction in carbon emissions by 2032 through carbon capture and storage. Similarly, new natural gas-fired plants
control measures Lead-free gasoline policy
Face masks (N95, P2, KN95)
purifiers
Clean cooking transitions (LPG adoption) Behavioral modifications
address dominant pollutants in specific regions is crucial (for example, focusing on gaseous pollutant reduction in areas with high O3 levels). Bottom, national-, community- and individual-level interventions alongside their primary sources and pollutant transformations to guide targeted policy decisions.
must implement 90% carbon capture and sequestration by 2032. These regulations are expected to reduce 1.4 billion tons of carbon emissions by 2047, aligning with US climate goals, and deliver up to $370 billion in combined climate and public health benefits over two decades38 .
Phaseout of leaded gasoline. The global phaseout of leaded gasoline has been one of the most successful international environmental health interventions, dramatically reducing airborne lead levels and providing a model for coordinated global action. Leaded gasoline, introduced in the 1920s, was widely used in internal combustion engines as an additive to improve engine performance by increasing octane levels. However, tetraethyl lead, the compound used in leaded gasoline, is a neurotoxin affecting synaptic calcium channels39. There is a causal relationship between blood lead levels (a biomarker with a half-life of around 30 days40) and lowered IQ, learning disabilities and behavioral issues20. Chronic exposure in adults has been linked to cardiovascular diseases, hypertension and kidney damage. Lead exposure also disrupts the central nervous system, with studies indicating a higher risk of neurodegenerative diseases and developmental delays
(HONO)
(N2O)
(CH4)
Furthermore, lead has been shown to interfere with the biosynthesis of hemoglobin, resulting in anemia44
The US EPA spearheaded the efforts to eliminate lead from gasoline, with the Clean Air Act of 1970 marking the beginning of regulatory action45; by the early 1990s, unleaded gasoline had become the standard. The phaseout was facilitated by the introduction of cleaner, alternative fuels and the promotion of catalytic converter technologies that require unleaded gasoline. The United Nations Environment Programme launched the Partnership for Clean Fuels and Vehicles46 to support the transition from leaded to unleaded fuels in developing countries. This initiative successfully encouraged a global movement, with many LMICs adopting regulations to phase out leaded gasoline by the 2010s. In the 1990s, China and India transitioned from leaded to unleaded gasoline as part of broader efforts to modernize their automotive industries and improve air quality. By 2006, leaded gasoline had been discontinued in most sub-Saharan regions. The phaseout of leaded gasoline has led to a dramatic reduction in airborne lead levels globally. In the USA, studies from the National Health and Nutrition Examination Survey by the Centers for Disease Control and Prevention found that blood levels of lead in US children decreased by 90% from the 1970s to the early 2000s47.
China’s Blue Sky Defense War
China’s air pollution reduction efforts, including the Air Pollution Prevention and Control Action Plan (https://go.nature.com/4mGJKls; 2013–2017) and the Blue Sky Defense War ( https://go.nature. com/3JbuBdc; 2018–2020, officially the Three-Year Action Plan to Win the Blue Sky Defense War), target PM2.5 and other pollutants. These are a series of policies including emission retrofits in coal-fired power plants (which reduced SO2, nitrogen oxides (NOx) and primary PM2.5 emissions and phased out small, high-emission factories), coal-to-gas transition for residential heating and industrial processes, expanded renewable energy (hydropower, wind, solar) and transportation regulations (including phasing out high-emission diesel trucks and incentivizing electric vehicles)48.
These initiatives aim to improve air quality and public health without undermining economic growth27 49. The China Center for Disease Control and Prevention conducted a comprehensive review of the acute health effects of fine PM and evaluated the effectiveness of air pollution control measures; they note that, while national PM2.5 concentrations declined from 72 μg m−3 in 2013 to 33 μg m−3 in 2020, this remains well above the WHO-recommended limit of 5 μg m−3. Epidemiological studies indicate that each 10-μg m−3 increase in PM2.5 exposure is associated with a 0.22% rise in non-accidental mortality and a 0.26% increase in cardiovascular hospitalizations (or 0.31% specifically for ischemic heart disease hospitalizations)50. Air pollution drives considerable morbidity long before manifesting in mortality, thus emphasizing the urgent need for sustained intervention.
Despite persistent heavy pollution episodes in economically prosperous city clusters, where annual PM 2.5 concentrations often exceeded the national standard of 35 μg m−3 (ref. 51), targeted interventions have driven major improvements. Between 2013 and 2017, PM 2.5 concentrations declined by 39.6% in Beijing–Tianjin–Hebei, 34.3% in the Yangtze River Delta and 27.7% in the Pearl River Delta52 53 Several key strategies worked. First, ultralow emission retrofits in coal-fired power plants substantially reduced SO 2, NO x and primary PM2.5 emissions, while industrial upgrades phased out small, high-emission factories and replaced coal-fired industrial boilers with gas-fired or electric alternatives. The coal-to-gas transition for residential heating and industrial processes further cut PM 2.5 exposure, particularly in northern China, where wintertime coal combustion was a major contributor to pollution. Simultaneously, expanding renewable energy sources (hydropower, wind and solar) reduced reliance on fossil fuels. Transportation sector regulations phased out high-emission diesel trucks and incentivized electric
vehicle adoption, leading to a decline in transportation-related PM2.5 emissions.
The temporary air quality improvements during major international events such as the Beijing 2008 Olympics and the 2014 APEC Summit demonstrated China’s ability to address air pollution. Beijing experienced considerable air quality improvements during these events, facilitated by factory closures, traffic controls and reduced emissions from key sectors. These ‘Beijing Blue’ and ‘APEC Blue’ skies demonstrated what could be achieved through short-term intensive interventions; however, these improvements were often temporary and reverted shortly after the events concluded54–56. During the events, air quality monitoring was enhanced through high-density, real-time surveillance networks, enabling more accurate pollution forecasting and emergency response measures (such as temporary factory shutdowns and traffic restrictions) during severe pollution episodes57–61.
Ultimately, China’s air pollution control policies have delivered substantial health co-benefits alongside air quality improvements. A nationwide case-crossover study across 292 Chinese cities found that the Air Pollution Prevention and Control Action Plan (2013) reduced PM2.5 and black carbon concentrations by 28.61% and 20.35%, respectively, from 2013 to 2017, leading to a 30% average reduction in annual attributable fractions for nine major cause-specific hospital admissions, with the largest decrease observed for depression62.
India’s GRAP
India’s GRAP, implemented in 2017, is an emergency air pollution control measure aiming to curb extreme air pollution episodes in Delhi and the surrounding National Capital Regions29. GRAP activates targeted interventions, such as restricting vehicle use and construction activities, when air pollution levels exceed critical thresholds. While the GRAP has led to a reduction in the percentage of days with PM2.5 exceeding 120 μg m−3, its impact has been spatially variable, proving more effective in northern and eastern districts (Panipat and Meerut) but less so in southern and western areas (Bharatpur and Alwar), where enforcement challenges persist63. Using a difference-in-differences approach, a study evaluated the GRAP’s causal effects by comparing PM2.5 reductions in Delhi and the National Capital Region with similar non-GRAP regions, controlling for climate factors such as precipitation, temperature and wind speed. Estimates indicated that pollution caused 2.3 million premature deaths in India in 2019, with 1.6 million attributed to air pollution alone64
More broadly, India remains among the countries worst affected by air pollution. Estimates show that air pollution can reduce life expectancy by up to 10 years64; although this estimate, derived from a natural experiment comparing coal-heating impacts, may be confounded by geographic and socioeconomic factors and conflates household and ambient pollution, limiting its global applicability65. While India has implemented policies like the Pradhan Mantri Ujjwala Yojana (https:// pmuy.gov.in/) to reduce household air pollution, the country still lacks a centralized enforcement system for pollution control. Despite short-term improvements from the GRAP, industrial emissions, urbanization and transboundary pollution continue to drive persistently high PM2.5 levels, necessitating broader, long-term strategies for sustained air quality improvements.
Open burning bans
Open burning of waste and agricultural residues remains a major and persistent source of air pollution, particularly in regions where regulatory enforcement of control is weak. Open burning releases a complex mix of hazardous pollutants including PM2.5, dioxins, volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons, all of which are already linked to respiratory diseases, cardiovascular conditions and cancer66,67. While policies banning stubble burning, municipal waste incineration and biomass burning exist in several regions68–70, lowering air pollution when multiple emission sources exists remains
a key challenge. Farmers often resort to burning crop residues due to limited access to mechanized alternatives, while inadequate waste management infrastructure drives the widespread burning of municipal and industrial waste.
There is a need for region-specific solutions to address the enforcement challenges that limit the effectiveness of open burning bans. Complementing top-down enforcement, addressing open burning requires a deeper understanding of behavioral drivers and regional differences. Studies have shown that, in many LMICs, burning persists owing to necessity rather than noncompliance, driven by inadequate waste management systems, economic constraints and traditions66,71,72. While high-income countries have successfully reduced burning through enforcement and viable alternatives, these strategies cannot be directly transplanted to low-resource settings. Instead, region-specific solutions, such as community-based programs, economic incentives for sustainable agricultural practices and investments in waste management infrastructure and mechanization, are crucial for lasting change. Moreover, sub-Saharan Africa remains an understudied region in air pollution interventions despite being disproportionately affected by burning emissions. Research and policy efforts must prioritize these gaps to develop effective, scalable solutions.
Global agreements and air pollution governance
Global agreements, such as the Paris Agreement and regional frameworks such as the Convention on Long-Range Transboundary Air Pollution (LRTAP; https://go.nature.com/4mgVpaO), underscore the necessity of international cooperation in addressing transboundary air pollution and integrating air quality with climate goals. While the Paris Agreement (2015) is primarily a climate treaty, it has profound co-benefits for air pollution reduction and health improvement by incentivizing countries to transition away from fossil fuel-based energy systems. Many of the policies aligned with climate mitigation, such as phasing out coal-fired power plants, promoting clean transportation and expanding renewable energy, simultaneously reduce PM2.5, NOx and other harmful pollutants, potentially yielding immediate public health benefits73. Synergistic interactions between air pollution and extreme temperatures amplify negative health impacts, as high PM2.5 and heat jointly increase mortality risks. A 2025 study in India found that extreme heat and PM2.5 exposure tripled cardiovascular mortality risks, with urban areas most affected74. Similar effects were observed in China and the USA, where PM2.5 and O3 risks rise with temperature75,76 These interactions underscore the need for integrated climate–air quality policies. However, air pollution lacks the legal commitment of climate frameworks, leaving governance gaps3. However, despite these overlaps, air pollution has not received the same legal and political commitment as climate change mitigation, leaving substantial gaps in international air quality governance.
Existing regional air quality agreements, such as the LRTAP in North America and Europe and frameworks like the ASEAN Agreement on Transboundary Haze Pollution in Southeast Asia, have built policy foundation in reducing air pollution. The LRTAP, established in 1979, has cut sulfur emissions by 70% in Europe through binding protocols77. The EU’s revised Ambient Air Quality Directive (https://eur-lex.europa. eu/eli/dir/2024/2881/oj), effective December 2024, sets stricter limits for pollutants including PM10, SO2 and O3, aligning with WHO guidelines by 2030 (ref. 78). It aims to halve premature deaths from air pollution by 2030 compared to 2005, enhancing monitoring and enforcement. At the same time, these agreements are limited by their regional scope, inconsistent enforcement and focus on specific pollutants. In economically vulnerable regions, where air pollution burdens are highest, comparable frameworks or resources for implementation are often lacking. A simultaneous challenge is that global agreements have the risk of withdrawal, in which the progress made in reducing air pollution through climate-aligned policies could be severely undermined. Many air quality improvements, such as phasing out coal-fired
power plants, electrifying transportation and expanding renewable energy, are largely driven by climate action and carbon neutrality commitments. Without sustained policy commitment, gains could be reversed, exposing populations to health risks. Lessons from successful national and regional policies, such as those outlined above, demonstrate that ambitious regulation, enforcement mechanisms and sustained investment can rapidly improve air quality. A dedicated international framework would provide the necessary legal and financial structures to benefit health and climate action and provide a financial return on investment79
City and community interventions
Cities and communities are where pollution sources, such as traffic, industry and household energy use, are concentrated and where air quality interventions can yield considerable population-level benefits. Local governments have successfully implemented policies like congestion pricing, low-emission zones (LEZs) and fuel transitions to mitigate pollution and improve health.
A landmark study of the Great Smog of London (1952) provided some of the first documentation of robust epidemiological evidence demonstrating the direct health effects of extreme air pollution, with retrospective analyses revealing 4,000–12,000 premature fatalities and widespread morbidity from cardiorespiratory diseases. Notably, excess deaths persisted even after the smog had cleared, indicating both acute and delayed health effects of severe air pollution exposure80–82. The lasting legacy of this event catalyzed one of the earliest examples of air pollution policy driven by epidemiological evidence and was also the impetus for the UK 1956 Clean Air Act (https://www. legislation.gov.uk/ukpga/Eliz2/4-5/52/enacted ), which curtailed domestic coal burning in London and other major cities. The implementation of smokeless zones, controls imposed on industries, increased availability and use of natural gas and changes in the industrial and economic structure of the UK led to a considerable reduction in concentrations of smoke and SO2 in recent decades83,84
This legislation paved the way for modern air quality regulations worldwide, which go beyond pollution control — for example, involving early warning systems and urban greening interventions. Efforts to mitigate the health impacts of air pollution involve either root cause interventions, which target emission sources, or exposure interventions, which shield individuals from pollutants. The sections below highlight some key examples of these approaches at the city and/or community level.
Emission reduction interventions
Traffic-related air pollution control measures. The adoption of LEZs has resulted in measurable reductions in NO2 and PM2.5, highlighting effective urban traffic management strategies with global applicability. LEZs restrict access for high-polluting vehicles in designated areas and have been widely implemented in Europe, North America and Asia to curb vehicular pollution of PM2.5 and NO2 concentrations, lowering mortality risks. In London, the major contribution of road traffic to NOx (40%) and PM10 (66%) emissions in 2003 (ref. 85) prompted the introduction of the Congestion Charging Scheme that same year to reduce vehicle numbers and a city-wide LEZ in 2008 to modernize vehicle fleets86. The Ultra Low Emission Zone (ULEZ), launched in central London in 2019 and expanded to outer London by 2023 (ref. 87), achieved a 96.2% vehicle compliance rate by February 2024, as reported by the Greater London Authority88. This expansion mitigates pollution leakage by covering a larger airshed, ensuring cleaner air across Greater London. Paris’s ‘Paris Breathes’ initiative combines LEZs, road pricing for high emitters and electric vehicle promotion to target traffic pollution89. However, a 2017 EU study found that diesel vehicles emitted 4.6 million tons of excess NOx beyond laboratory-tested limits in 2015, linked to 11,500 premature deaths from PM2.5 and O3, highlighting gaps in Euro 6 and Euro VI standards for emissions90. Enforcing stricter
standards could nearly eliminate these emissions. Yet, such programs, like others worldwide, grapple with environmental justice concerns91–93
Expanding clean public transport options requires a reduced reliance on high-emission vehicles. In Bogotá, Colombia, the introduction of TransMiCable (a cable car system connecting a peripheral neighborhood to the city’s Bus Rapid Transit network) was linked to declines in air pollution exposure94 because it serves as an alternative to automobile transportation. Related measures, including vehicle rationing and speed controls aim to reduce emissions during peak pollution periods. A well-known policy is Mexico City’s ‘Hoy No Circula’, which restricts vehicle use based on license plate numbers on specific days, initially reduced air pollution. However, it has seen mixed effects due to adaptive behaviors such as increased car ownership95–97. New Delhi’s odd–even vehicle rationing scheme showed mixed results on improving air quality, with some hourly reductions in PM2.5 and PM10 levels but limited overall impact due to overnight emissions and weather conditions98
Green space and nature-based solutions Afforestation initiatives (by which nonforested land is converted to forest), such as the urban forest initiative MillionTreesNYC and the planted windbreaking forest strips of China’s Three-North Shelterbelt, showcase the potential of green infrastructure to mitigate air pollution99–101, despite context-specific challenges. Green space has direct health benefits through the biophilia hypothesis102. Urban greening, such as parks, green walls and street trees, has been proposed to filter pollutants, lower ambient temperatures and enhance air circulation, promoting healthy behavior and mental health and well-being103–106. However, the effectiveness of green space interventions on air quality varies widely depending on tree species, planting design, meteorological conditions and urban morphology. Green infrastructure plays a complex yet crucial role in urban air quality management. Trees and vegetation can capture airborne pollutants, with leaves and plant surfaces acting as natural filters for PM, black carbon and NO2, thereby improving local air quality. By regulating temperature and airflow, urban greening reduces heat buildup and limits the formation of secondary pollutants like ground-level O3. Strategically placed green barriers, such as tree-lined streets and hedges, can buffer vehicle emissions, lowering pollution exposure in high-traffic areas. However, the effectiveness of these interventions is highly site specific and depends on urban design, meteorology and plant species selection. In dense urban settings, trees can trap pollutants rather than dispersing them, exacerbating local air pollution in ‘urban canyons’107. Some plant species also emit biogenic VOCs, which can contribute to O3 and secondary aerosol formation, counteracting their pollution-reducing effects108. Moreover, the ability of green spaces to improve air quality is influenced by wind patterns and climate conditions, with dense vegetation potentially reducing ventilation in stagnant air conditions. Real-world interventions highlight these trade-offs107
In London, policies promoting green roofs, vertical gardens and tree planting aim to reduce NO2 and PM2.5 levels and enhance urban resilience109. MillionTreesNYC has demonstrated some reductions in air pollution exposure while providing co-benefits such as heat mitigation110. Large-scale afforestation projects have helped lower PM2.5 concentrations in Beijing, although some areas experienced increased nighttime pollution retention due to reduced airflow111,112. These findings emphasize the importance of context-aware urban greening strategies, where species selection, placement and integration with other air pollution control measures are designed to meet ecological needs113. A critical question remains: what ‘dose’ of green space delivers optimal health benefits, particularly through air pollution reduction? More greenery often correlates with fewer emission sources (for example, less paved surfaces or traffic), amplifying its indirect impact on air quality114. However, direct health benefits, reduced asthma rates or improved mental well-being also depend on the quality, accessibility
and distribution of green spaces, not just their quantity115,116. Effective strategies must integrate species selection (favoring plants with low biogenic VOC emissions), strategic placement (maximizing pollutant buffering while ensuring ventilation) and complementary measures (like emission control policies)108 117 118
Large ecological tree planting also impacts natural sand dust, contributing to air pollution in arid regions. China’s Three-North Shelterbelt Program (also known as the ‘Sanbei’ project), launched in 1978, restored grasslands across northern China to curb sandstorms and dust storms. From 1978 to 2017, Sanbei increased forest coverage from 5.1% to 13.6% and reduced soil erosion by 44.7 million hectares, stabilizing deserts and weakening dust conditions in southern counties119. Techniques like straw grid planting in Gansu Province affix sand, reducing airborne dust. While direct health impact data are limited, reduced PM10 exposure likely mitigates asthma and bronchitis exacerbations120.
Exposure reduction interventions
Early warning systems. Air pollution early warning systems in cities demonstrate that real-time monitoring and public advisories can reduce exposure during high-pollution events, even with inconsistent adherence. Many cities now operate air pollution early warning systems to provide real-time alerts on PM2.5, O3 and wildfire smoke levels, allowing residents to take protective measures when necessary. Cities such as Los Angeles, Beijing, London and Delhi have implemented high-resolution monitoring networks that trigger advisories on school closures, outdoor activity restrictions and indoor air quality protection121–123. During wildfire smoke episodes, public health advisories recommend either staying indoors in spaces with high-efficiency particulate air (HEPA) filtration, which removes at least 99.97% of airborne particles as small as 0.3 μm, including smoke particles, or relocating to cleaner air zones, depending on the duration and severity of the pollution. To enhance resilience against high-pollution events, cities are integrating early warning systems with broader air quality management strategies. This includes mobile air quality index alerts, public mask distribution and designated ‘clean air shelters’ in schools, elderly care centers and low-income housing areas. Real-time air quality monitoring and early warning systems can help individuals and communities make informed decisions during wildfire events. Digital platforms such as AirNow (US), FireSmoke Canada and Australia’s AirRater app provide localized smoke forecasts and exposure risk assessments124. However, public adherence to air quality advisories remains inconsistent, often due to a lack of trust or conflicting health priorities125. Public health campaigns and mobile alerts may improve adherence, particularly for vulnerable groups. A key priority must be the expansion of air quality monitoring and research in LMICs, where extreme air pollution is rising. This is critical to enhance surveillance, inform policy and replicate the research-driven progress seen in Europe, North America and China126.
Individual-level interventions
Reducing household air pollution is among the most effective and accessible root cause strategies to improve air quality and therefore health. Transitioning to cleaner household energy sources helps to prevent chronic diseases and save lives127 128. More broadly, indoor air pollution, encompassing outdoor pollutants infiltrating homes, can be addressed through measures like window closure or air filtration129–131 For ambient air pollution (for example, PM2.5, O3, NO2) from traffic, industry and biomass burning, individual-level solutions such as air purifiers, masks and behavioral changes provide temporary exposure reduction. However, while these may alleviate risks during acute events like wildfires, they neither curb secondary pollution (for example, smog from precursors) nor address underlying emission drivers23 132 .
A systematic review by the Cochrane Collaboration assessed individual-level interventions, such as wearing masks, behavioral changes and heeding air quality alerts, to reduce exposure to outdoor
air pollution133. The review highlighted a lack of robust evidence regarding the efficacy and safety of these interventions, especially for individuals with chronic respiratory conditions. The American Thoracic Society proposed a series of personal interventions, including staying indoors, limiting physical activity during high-pollution periods and using air purifiers, to reduce individual exposure, but importantly, these do not address the broader issue of ambient air pollution and may not be sustainable or practical for generating long-term health benefits21,22,134. Upstream strategies, including emission reductions and policy changes, are seen as more effective solutions for long-term air quality improvement135.
Individual actions complement systemic interventions by reducing emissions from household sources or mitigating exposure to ambient and climate-driven pollution. Emission reduction actions, like transitioning to clean cooking fuels, target pollution at the source, while exposure reduction actions, such as air purifiers and face masks, protect against residual pollutants. This section evaluates key interventions for their health impacts and scalability.
Emission reduction interventions
From biomass to clean cooking with liquefied petroleum gas. The transition from biomass fuels to liquefied petroleum gas (LPG) can substantially reduce household air pollution and associated health effects, particularly in LMICs where biomass fuels are widely used. Biomass fuels include wood and dung, which, when undergoing combustion, lead to concentrated PM2.5 and black carbon emission, polluting indoor and outdoor air quality. Unlike broader indoor air pollution from sources like tobacco smoke or building materials, household air pollution specifically results from cooking, heating or lighting with solid fuels in poorly ventilated homes. The Global Burden of Disease Study 2021 estimates that household air pollution caused 3.11 million premature deaths and 111 million disability-adjusted life-years (DALYs) in 2021 (3.9% of all DALYs), predominantly in sub-Saharan Africa and south Asia, with approximately one-third of DALYs mediated through adverse reproductive outcomes such as low birth weight and short gestation136
Multicenter randomized controlled trials (RCTs) provide evidence of the health benefits of transitioning to cleaner fuels like LPG. The Household Air Pollution and Health trial, conducted in India, Guatemala, Peru and Rwanda, involved 3,200 households, targeting pregnant women and older adult women, and provided LPG stoves and an 18-month fuel supply to enable participants to switch from biomass fuel. A series of key findings include significant reductions in low birth weight, preterm births and severe pneumonia in infants and improved cardiovascular health and lower blood pressure in older adults. In addition, biomarker analysis revealed reduced levels of carcinogenic metabolites and respiratory impairment markers, correlating with substantial declines in exposure to PM2.5, black carbon and CO137. The Ghana Randomized Air Pollution and Health Study found a 32% reduction in mean PM2.5 exposure in pregnant mothers in the LPG (intervention) arm compared with a control arm but no significant reduction in birth weight or pneumonia incidence, likely due to persistent community-level pollution138.
Fuel transitions eliminate household biomass combustion, addressing a major root cause of indoor air pollution in LMICs. However, the same factors that make cleaner fuels beneficial also make their adoption difficult. While LPG use improves health by reducing exposure to harmful pollutants, affordability constraints, unreliable supply chains and entrenched cooking traditions often limit sustained adoption. Even when households adopt LPG, many continue using biomass as a backup due to cost concerns and fuel availability, diluting the health benefits. Overcoming these barriers requires policies that not only improve access to cleaner fuels but also address economic, infrastructural and social constraints that reinforce dependence on polluting energy sources.
Transportation mode switching. Promoting active transportation like cycling can have dual benefits of reducing emissions and improving health, supported by urban design and policy incentives. A systematic review found that car commuters face 1.22 times higher air pollution exposure than cyclists, but active commuters (cyclists, pedestrians) inhale higher pollutant doses due to increased ventilation and trip duration. Despite this, cyclists gain up to 1 year in life expectancy compared to car commuters, as physical activity benefits outweigh pollution risks139. Urban design supporting active transport, such as dedicated bike lanes and pedestrian-friendly infrastructure, reduces exposure by enabling low-traffic routes. Individual behavior change requires supportive policies, such as bike-sharing programs and workplace incentives, to overcome barriers like cost and accessibility. While effective for reducing emissions and improving cardiovascular health, active transport must be paired with systemic emission controls to minimize exposure risks140. Scalability is limited by urban sprawl, safety concerns and cultural preferences for motorized transport, particularly in LMICs141.
Exposure reduction interventions
Air purifiers and ventilation. Improving indoor air quality through air purification has emerged as a strategy to reduce exposure to PM2.5 and its associated health risks142,143. Evidence from RCTs highlights the potential benefits and limitations of this intervention144. In a US-based study conducted in a low-income senior care facility, portable air filtration systems equipped with HEPA filters significantly reduced personal PM2.5 exposure (from 15.5 μg m−3 to 7.4 μg m−3) and lowered systolic blood pressure by 3.2 mmHg145. These findings suggest that even short-term use of portable air filtration can provide cardioprotective benefits for older adults. A randomized, double-blind crossover trial conducted in Shanghai demonstrated that air purification reduced PM2.5 concentrations by 57%, significantly improving circulating biomarkers of inflammation, coagulation and vasoconstriction. The study also observed reductions in blood pressure and fractional exhaled nitric oxide (NO) among healthy young adults146. These benefits, most pronounced in highly polluted regions and for those spending substantial time indoors, highlight air purification’s effectiveness as an exposure reduction strategy. A systematic review of RCTs demonstrated consistent reductions in systolic blood pressure (averaging 4 mmHg) with the use of home air purifiers, further highlighting their role in mitigating cardiovascular risks147
However, air purifiers show variable efficacy for other health effects. A recent trial in residential aged care facilities in Australia found no significant reduction in acute respiratory infections among residents using HEPA air purifiers. While a subgroup analysis revealed a modest reduction in the incidence of acute respiratory infections among participants who completed the study (from 35.6% to 24.0%), the overall results suggest limited efficacy. Additionally, a meta-analysis on cardiovascular outcomes noted limitations in air purification studies, including small sample sizes and short follow-up durations for external generalizability148. In sum, these findings indicate that, while air purifiers can reduce pollutant exposure and improve cardiovascular health in some settings, their effectiveness for respiratory infections and broader health outcomes is variable. Further large-scale, long-term studies are needed to confirm these benefits and optimize inter vention designs.
Face masks for extreme air pollution N95 and similar standard masks can help protect individuals against PM2.5 during acute pollution events like wildfires, despite limitations for chronic exposure and gaseous pollutants. A Cochrane review found that N95 respirators may reduce short-term cardiovascular risks by filtering PM2.5133. Wildfire smoke is characterized by high concentrations of fine PM (PM2.5), with dominant particle sizes ranging from 0.4 to 0.7 μm, which poses substantial respiratory and cardiovascular risks149. Well-fitted N95 respirators, KN95
Multilevel interventions for air pollution reduction
National and international interventions
• Clean air legislation: the US Clean Air Act reduced coal-related PM2.5 levels and is projected to prevent 4,500 premature deaths annually under revised 2024 standards31 35
• Industrial emission regulations: China’s Blue Sky Defense War led to a 39.6% reduction in PM2.5 levels in key regions through coal-to-gas transitions and ultralow emission retrofits in power plants50,62
• Fossil fuel phaseout and energy transition: the US EPA’s 2024 Carbon Pollution Standards require 90% carbon capture for new natural gas and coal power plants, aligning with climate and air quality goals38.
• Bans on open burning: while essential to controlling PM2.5 in LMICs, enforcement remains a challenge; sustainable alternatives (for example, mechanized residue management for farmers) are needed for efectiveness66 67
• Global air quality framework: advocates for an international treaty on air pollution, modeled after the Paris Agreement, to set binding global air quality targets and integrate pollution control into climate policies3,79
Community- and city-level interventions
• LEZs and ULEZs: London’s ULEZ expansion reduced vehicular NO2 and PM2.5 emissions, but leakage efects (pollution shifting to nonregulated areas) require comprehensive enforcement strategies87 88 90
• Trafic control measures: Bogotá’s TransMiCable and Mexico City’s speed limit regulations improved local air quality, demonstrating co-benefits of transit-oriented policies94 95
masks and P2 masks filter at least 95% of PM2.5, offering an effective barrier against wildfire-related particulate exposure. However, their efficiency depends on proper fit, continuous usage and replacement schedules, which may limit their practicality for prolonged use, particularly in older adults and those with respiratory conditions150 151 . Moreover, face masks do not filter gaseous pollutants (for example, CO, VOCs, formaldehyde), which are also prevalent in wildfire smoke and pose additional health risks. A recent study found that masks incorporating activated carbon, Spunbond and meltblow materials (made from thermoplastic polymers that are melted and blown into fine fibers) are more effective in absorbing toxic gases such as COx, NOx and SOx than traditional masks, suggesting that masks with these advanced materials may offer some protection against the gaseous pollutants found in wildfire smoke152
However, face masks are not a viable intervention for chronic exposure to ambient air pollution. Unlike acute wildfire smoke episodes, urban air pollution consists of a complex mix of primary emissions from traffic, industry and biomass burning, along with secondary pollutants such as O3 and NO2. These pollutants require systemic interventions. Moreover, complicating factors of face mask use are the demand for tight, secure fit and comfort, affecting utilization153
Future directions
There needs to be a strategic focus on addressing the root cause of air pollution. Interventions should first address emission reduction and then exposure mitigation. Emission reduction interventions, such as transitioning from biomass to clean cooking fuels and phasing out coal-based energy, directly tackle pollution sources, yielding health
• Urban greening and nature-based solutions: green spaces can act as air pollution bufers by filtering PM2.5 and NO2, but efects are highly context dependent. In dense urban settings, vegetation can trap pollutants107113 119, exacerbating local air quality.
• Air pollution early warning systems: real-time air quality index (AQI) alerts and wildfire smoke advisories (for example, AirNow, FireSmoke Canada and AirRater app) guide protective behaviors, although public adherence remains inconsistent, partly due to variations in AQI standards and interpretations across regions124 125
• Lead-free gasoline policy: the global phaseout of leaded gasoline successfully reduced airborne lead exposure, with measurable improvements in public health, particularly in children45 47 .
Individual-level interventions
• Air purifiers: HEPA filtration significantly reduces PM2.5 exposure and improves cardiovascular health in controlled indoor settings. However, benefits are dependent on time spent indoors and filtration eficiency144,146,147
• Face masks (N95, P2, KN95): efective for short-term protection during high-pollution events like wildfires but not viable for long-term ambient exposure mitigation133 150 152
• Clean cooking transitions (LPG adoption): the Household Air Pollution and Health trial showed significant reductions in household air pollution exposure and improved infant and maternal health. However, adoption remains limited by cost, fuel availability and cultural factors137138
• Behavioral modifications: air quality alerts, staying indoors and reducing outdoor activity during peak pollution periods can lower exposure but do not address emissions at their source133 134
benefits like reduced infant mortality and cardiovascular risks. These approaches are particularly vital in developing economies, where reliance on fossil fuels and biomass drives disproportionate health burdens. Exposure reduction strategies, such as air purifiers and N95 masks, offer temporary relief during acute events like wildfires but are less effective for chronic exposure or gaseous pollutants. Their scalability is limited by cost, access and inconsistent adherence, as seen in results showing variable respiratory benefits from air purifiers. While these measures are valuable for managing short-term crises, they are not substitutes for systemic emission controls.
Climate change intensifies secondary pollutants (for example, O3) and introduces new pollution sources like wildfires, necessitating integrated climate–air quality policies to align emission reductions with health and resilience goals. Given the heterogeneity of interventions, outcomes and methods used in existing studies, there is a pressing need for standardized study designs, uniform evaluations and advanced analytical methods, including big data and sophisticated modeling, to better establish the effectiveness of air pollution interventions154. To address the complex interplay of air pollution and health, environmental epidemiology needs advancements to tackle challenges like coexposures, collinearity and confounding, while quantifying lag effects through improved study designs and strengthen causal inference. In the real world, simpler quasi-experimental designs may enhance transparency and credibility in establishing causality, whereas more sophisticated approaches, although potentially more robust, can sometimes obscure interpretability and reduce stakeholder buy-in.
Ongoing discourse over whether more evidence or action is needed is secondary to the urgent need for implementation science
to bridge research and practice. Global frameworks, especially climate change agreements, help align emission reduction efforts with air quality co-benefits. Empirical evidence underscores that the success of air pollution interventions hinges on robust policy enforcement in the local context. By combining global coordination with localized action, we can seize immediate opportunities, address region-specific challenges and forge a path toward cleaner air and better health.
Conclusion
Air pollution is deeply interconnected with the climate crisis, posing a dual threat to human health and environmental stability. Transitioning to clean energy, phasing out fossil fuels, and embracing sustainable urban planning offer powerful opportunities to improve air quality while bolstering climate resilience. Moving forward, we must amplify proven, evidence-based solutions, ensuring that clean air becomes a universal right, accessible to all communities, regardless of geography or circumstance (Box 1).
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Acknowledgements
We gratefully acknowledge Z. Tao for formatting and drafting the figures, Y. H. Jia for organizing literature searches, N. L. Sieber for contributions to human physiology in Fig. 1 and J. J. Zhang and S. Wang for their expertise in the environmental chemistry of Fig. 2. J.S.J. is supported by the National Natural Science Foundation of China (NSFC) grant (82422064).
Competing interests
The authors declare no competing interests.
Additional information
Correspondence and requests for materials should be addressed to John S. Ji.
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