Climate policy must consider cross-border pollution “exchanges” to address inequality and achieve health benefits, research finds
First-of-its-kind study assesses how health benefits of aggressive climate policy travel across international borders
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Schematics of the metrics used to quantify inequalities associated with transboundary air pollution across different climate futures. (a) Transboundary fractions (TF) characterize the extent of co-benefits in a country that come from external action; co-benefits are the premature deaths avoided owing to reduced PM2.5 concentrations. (b) Exchanges (EXC) compare co-benefits from emission reductions between a pair of countries or regions; the contribution to total benefits exchanged (TEC) indicates how much a country contributes to the total gross co-benefits exchanged between two countries. Figure 1 was created using Python and the Matplotlib, Cartopy, GeoPandas, and Contextily libraries. Country borders and coastlines are from Natural Earth (public domain), and the basemap is from CartoDB Positron (CC BY 4.0).
view moreCredit: O. Nawaz, Cardiff University and D. Henze, University of Colorado Boulder.
Ambitious climate action to improve global air quality could save up to 1.32 million lives per year by 2040, according to a new study.
The research, led by Cardiff University, shows how developing countries rely heavily on international cooperation to see these benefits, because much of their pollution originates outside their borders.
The first-of-its-kind study analysed these cross-border pollution “exchanges” for nearly every country – 168 in total.
Their findings, published in Nature Communications, reveal how a fragmented world, with little collaborative climate mitigation policymaking, would lead to greater health inequality for poorer nations who have less control over their own air quality.
Their work focuses on the impact of fine particulate matter (PM2.5), exposure to which is the leading environmental risk factor for premature deaths globally.
Lead author Dr Omar Nawaz from Cardiff University’s School of Earth and Environmental Sciences, said: “While we know climate action can benefit public health, most research has ignored how this affects the air pollution that travels across international borders and creates inequalities between countries.
“Our analysis shows how climate mitigation decisions made in wealthy nations directly affect the health of people in the Global South, particularly in Africa and Asia.”
The team, which includes researchers at the University of Colorado Boulder, used advanced atmospheric modelling and NASA satellite data to simulate different future emissions scenarios for the year 2040.
Together with a health burden estimation, these data enabled the researchers to understand who benefits—and assess different levels of dependency—when countries implement climate mitigation policies.
“We wanted to see how the health benefits of action on climate change could differ when there is greater or weaker global cooperation,” explains Dr Nawaz.
“We were surprised to find that although Asia sees the most total benefits from climate action to its large share of the population, African countries are often the most reliant on external action, with the amount of health benefits they get from climate mitigation abroad increasing in fragmented future scenarios.”
The team’s projections also show the balance of pollution flowing across borders may shift, even when total global air pollution declines.
This is vital information for policymakers and global aid organisations as they seek to address climate change challenges amidst domestic and international priorities.
Co-author Professor Daven Henze of the Department of Mechanical Engineering at the University of Colorado Boulder added: “Some climate policies could inadvertently make air pollution inequalities worse, specifically for developing nations that might rely heavily on their neighbours for clean air. It’s thus not sufficient to focus only on domestic co-benefits. More inclusive climate strategies entail explicitly accounting for evolving transboundary inequalities.
“Holistic climate policy should therefore evaluate how dependent a nation is on others’ emissions reductions, how mitigation scenarios reshape air-pollution flows across borders, and whether global efforts are helping or harming equity.”
The team plans to develop their analysis further by exploring how climate change itself alters the weather patterns that transport this pollution, as well as looking at other pollutant types like ozone and organic aerosols.
Their paper, ‘National climate action can ameliorate, perpetuate, or exacerbate international air pollution inequalities’, is published in Nature Communications.
ENDS
Notes to editors
Paper
The paper will appear online via the journal website at 10am GMT/5am ET on Thursday 12 February 2026.
The digital object identifier (DOI) number for this paper will be 10.1038/s41467-026-68827-0
Interviews
Interviews with the research team are available on request.
For more information contact:
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Cardiff University
Cardiff University is recognised in independent government assessments as one of Britain’s leading teaching and research universities and is a member of the Russell Group of the UK’s most research-intensive universities. The 2021 Research Excellence Framework found 90% of the University’s research to be world-leading or internationally excellent. Among its academic staff are two Nobel Laureates, including the winner of the 2007 Nobel Prize for Medicine, Professor Sir Martin Evans. Founded by Royal Charter in 1883, today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University’s breadth of expertise encompasses: the College of Arts, Humanities and Social Sciences; the College of Biomedical and Life Sciences; and the College of Physical Sciences and Engineering. Its University institutes bring together academics from a range of disciplines to tackle some of the challenges facing society, the economy, and the environment. More at www.cardiff.ac.uk
Country-level estimates of transboundary co-benefits across four combinations of shared socioeconomic pathways (SSP) and representative concentration pathways (RCP). (a) Transboundary fractions for individual countries in a sustainable and strong climate mitigation scenario (SSP1-26), (b) the relative change in transboundary fractions associated with a weaker RCP, i.e., from SSP1-26 to SSP1-45; red values indicate where transboundary fractions have increased whereas blue values indicate decreases, (c) the relative change in transboundary fractions from a less equal SSP, i.e., from SSP1-26 to SSP3-26, (d) the relative change in transboundary fractions from both a weaker RCP and less equal SSP, i.e., from SSP1-26 to SSP3-45. Figure 3 was created using Python and the Matplotlib, Cartopy, GeoPandas, and Contextily libraries. Country borders and coastlines are from Natural Earth (public domain), and the basemap is from CartoDB Positron (CC BY 4.0).
Total and transboundary co-benefits associated with different climate scenarios. (a) The total deaths avoided for each of the shared socioeconomic pathway (SSP) and representative concentration pathway (RCP) scenarios relative to SSP3-Baseline in 2040 ordered from the most to least equitable scenarios. Colors indicate the receptor region in which the co-benefits occurred (i.e., where the deaths were avoided). Socioeconomic trends and mitigation strategies are included on the y-axis. Error bars refer to the lower and upper bound uncertainty from the health impact assessment for the total co-benefits. (b) The co-benefits specifically attributable to external action for each of the receptor regions (i.e., the transboundary co-benefits). The fraction of co-benefits that are transboundary broken down by (c) socioeconomic development type and (d) mitigation strategy. Data in (a) and (b) are presented as central estimates and lower and upper bounds based on confidence intervals in the health data
Exchanges (EXC) of climate co-benefits within and between different regions across the five shared socioeconomic pathways (SSP). (a) Exchanges for Europe and Africa, for SSP1-26 in 2040 (left). Contributions are indicated through a logarithmic colormap ranging from 1 to 1000 deaths avoided. Darker colors indicate greater co-benefits in the receptor country attributable to emission reductions in the source country; self-contributions (i.e., the diagonal) are excluded. (b) EXC within Asia and between Asia and Africa; here contributions are indicated in a logarithmic colormap that ranges from 10 to 10000 deaths avoided. (c) Heatmaps of transboundary exchanges of climate action within and between Europe and Africa in 2040 for the scenarios SSP2-26, SSP3-26, SSP4-26, and SSP5-26 relative to SSP1-26. The colormaps are linear and range from -60 to +60 fewer or more deaths avoided compared to SSP1. (d) Heatmaps of transboundary exchanges of climate action within Asia and between Asia and Africa in 2040 for the scenarios SSP2-26, SSP3-26, SSP4-26, and SSP5-26 relative to SSP1-26. The colormaps are linear and range from -120 to +120 fewer or more deaths avoided compared to SSP1. For all subplots, interregional exchanges (i.e., Africa to Europe and Asia to Africa) are provided in an absolute sense – not relative to SSP1. White stars are placed to indicate the top 5% highest (absolute) values for each heatmap.
The change in the percentage of co-benefits exchanged (TEC × 100%) between regional and country pairs that is contributed by the higher GDP (first name). For the regional exchanges from the shared socioeconomic pathway (SSP) scenario SSP3-45 to SSP1-45 in 2040 (a), the arrow points from the less equal scenario (SSP3-45) to the more equal scenario (SSP1-45) and the gray dot represents SSP3-45 and the white dot represents SSP1-45. For the country exchanges (b), the arrow and dots are the same but the background shading indicates in which region the exchange occurs as labelled in the legend below the subplots; grey indicates exchange between different regions. Panels (c) and (d) are the same as (a) and (b), respectively, but for middle-of-the-road development (SSP2 vs SSP1) instead of fragmentation development.
Credit
O. Nawaz, Cardiff University and D. Henze, University of Colorado Boulder.
Journal
Nature Communications
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
National climate action can ameliorate, perpetuate, or exacerbate international air pollution inequalities
Article Publication Date
12-Feb-2026
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