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If nations reduce their greenhouse gas emissions, they could slow climate change. Those actions would also have the added benefit of saving over two million lives globally that might be lost because of harmful air pollutants by 2050, according to preliminary data in new CU ������ý���� research.

The findings come from an ongoing study led by Patrick Wiecko, a doctoral student in the Environmental Engineering Program. He will present the data at the American Geophysical Union annual conference (AGU25) in New Orleans on Dec. 18. The results have not been peer-reviewed.

Patrick Wiecko

Air pollutants such as nitrogen dioxide (NO2), fine particulate matter (PM 2.5), and ozone are among the main components of the smog that often shrouds urban skies. These pollutants can penetrate deep into the lungs and bloodstream, leading to cardiovascular and respiratory diseases, asthma and premature death.

Globally, chronic exposure to these air pollutants each year, including 150,000 in the United States.

These numbers could rise or fall depending on how nations choose to curb emissions over the next few decades, Wiecko said. The same sources that emit greenhouse gases, such as the burning of fossil fuels��in vehicles, power plants and factories, are also major contributors of air pollutants.

Wiecko and his team analyzed how the number of deaths associated with air pollution would change under three different global emission scenarios: one in which nations cooperate on the global stage to drastically reduce their emissions, one that maintains “business as usual” emissions, and one in which nations ramp up emissions without considering their global impacts.

Using a computer program, the researchers simulated how emitted pollutants move and react in the atmosphere, considering meteorological factors such as wind, temperature, sunlight and humidity.

The researchers paired those projections with global health data to estimate how shifts in air quality under the three scenarios could affect premature deaths by 2050.

Their model showed that in 2019, PM 2.5 was responsible for 4.3 million deaths worldwide, ozone for 880,000 and nitrogen dioxide for 2 million. If the world makes significant efforts toward reducing emissions and developing green technologies by 2050, it could save 2.7 million lives globally, including 86,000 in the United States and 1.1 million in China.

“Countries like China that have made huge progress in shifting away from fossil fuels—by electrifying their vehicle fleets, for example—could see substantial health benefits,” Wiecko said.

But if the world backtracks its coordinated climate efforts and fails to keep warming below 1.5°C, some nations might see more deaths from air pollution. In India, for example, 65,000 more people would die from deteriorating air quality. ��

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Under the 2015 Paris Agreement, countries have pledged to reduce emissions and limit global warming to 1.5°C (2.7°F) above pre-industrial levels by the end of the century to avert the worst impacts of climate change. But the shows the global average temperature is likely to rise by 2.5 to 2.9°C if countries stick to current policies.

Because air pollution crosses borders, the team also examined how many deaths each nation could prevent by cutting emissions, both at home and abroad.��Under the low-emission scenario, for example, the United States could see 86,000 fewer deaths. Domestic efforts account for 72,000 of those saved lives, while the remaining 14,000 depend on pollution-cutting measures implemented by neighboring countries.

“A lot of the costs of emissions are felt elsewhere,” Wiecko said.

He added that air pollution not only damages lungs, but also harms crops and ecosystems.

“It’s going to impact other parts of our society, like crop failure stemming from higher ozone concentrations,” Wiecko said. “Even if we don’t always see it or feel it, we’re all connected by the air we share, and we all have a role in cleaning it up.”