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This story is adapted from a version published by Cardiff University. .

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.

Researchers from CU �鶹ӰԺ and Cardiff University in the United Kingdom have found that developing countries, especially, rely on international action to improve air quality, because much of their pollution comes from outside their borders.��

The new study, , analyzed cross-border pollution “exchanges” for 168 countries and revealed that if countries do not collaborate effectively on climate policy, it could lead to greater health inequality for poorer nations that have less control over their own air quality.��

The team’s work focuses on the impact of exposure to fine particulate matter, what scientists call “PM2.5,” which is the leading environmental risk factor for premature deaths globally.

“Some climate policies could inadvertently make air pollution inequalities worse, specifically for developing nations that might rely heavily on their neighbors for clean air,” said Daven Henze, senior author of the new study and professor at the Paul M. Rady Department of Mechanical Engineering at CU �鶹ӰԺ.

“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.”

Lead author Omar Nawaz at the Cardiff University 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 research team used advanced atmospheric modeling and NASA satellite data to simulate different future emissions scenarios for the year 2040. The researchers used this data and a health burden estimation to understand how countries could make an impact through climate policy.

“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,” said Nawaz.

According to the researchers’ projections, the balance of pollution flowing across borders could shift, even if total global air pollution declines.

These insights could inform policymaking and global aid work that seeks to address climate change.��

In a sustainable socioeconomic development scenario, for example, pollution flowing across the U.S.-Mexico border would substantially decrease. Mexico would contribute much more to the health benefits that come from this shift than the United States.

The team plans to do further research 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.

“Ozone is transported even further in the atmosphere than PM2.5, contributes to significant health burdens, and shares common emission sources with PM2.5. We thus have follow-up studies in the works to investigate the interplay between climate policies and long-range health co-benefits associated with both species simultaneously,” said Henze.