By Emily Ayshford


When countries produce air pollution, it doesn’t just stay within its borders. But just how that pollution travels, and how it affects the economies and well-being of residents in neighboring countries, has been difficult to show.

A collaboration between University of Chicago and the U.S. Department of Energy’s Argonne National Laboratory researchers set out to change that. Using advanced models that track particle pollution and combining them with health and mortality data, the collaborators found that the air pollution has a direct impact on the health of residents of South Korea.

Together, Koichiro Ito, associate professor at UChicago’s Harris School of Public Policy; Rao Kotamarthi, a senior scientist at Argonne; and Seonmin Will Heo, a former UChicago graduate student, found that not only does Chinese air pollution lead to an increase in deaths in South Korea—especially for infants and the elderly—it also leads to more emergency room visits for asthma and nasal inflammation.

On the upside, the researchers also show that China’s “war on pollution” policies aimed at reducing air pollution have worked, resulting in less transboundary air pollution and fewer deaths in South Korea than before the policies were put in place.

“This is an issue we have wanted to study for a long time, and now we have the right models and data to show just how air pollution affects neighboring countries,” Ito said. “We show that it increases mortality, but we also who that policies to reduce pollution have a positive effect on neighboring countries, as well.”

Tracking air pollution and its effect on health

Chinese communities rely on coal-powered power plants, and, in the cold months, coal-burning heating sources. These fuel sources produce fine particulate matter (PM2.5) which rise into the air and can affect people’s health when levels are high. These particulates both stay within China and cross borders into neighboring nations. In East Asia, transboundary air pollution is boosted in the fall and winter by prevailing west winds, called “the westerlies.” That means during those seasons, South Korea receives persistent winds from China, and therefore more air pollution.

To find out just how much of this pollution traveled from China, Ito connected with Kotamarthi, an expert in high-performance computing and air transport models, at a conference sponsored by UChicago’s Joint Task Force Initiative and the Energy Policy Institute (EPIC) designed to spur collaborations between UChicago and Argonne.

To track the pollution, the researchers used the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), a tool from the National Oceanic and Atmospheric Administration that simulates air particle trajectories on both local and global scales.

Together with UChicago’s Research Computing Center, the researchers ran millions of trajectories for these particles and found that, as a result of these winds, northwest South Korea has much higher air pollution compared to southeast South Korea.

They then combined that data with mortality data from South Korea’s national statistical agency. For the period of 2013-2017, they found that a 1 microgram per cubic meter increase in PM2.5 led to an increase in mortality. Specifically, it translated into an additional 31.2 deaths for every million people annually. The increase in mortality was greatest for infants (a 2.1 % increase in mortality) and those with respiratory and cardiovascular disease (a 1.1 % increase in mortality).

They also found that the same increase in air pollution resulted in an increase in daily emergency room visits for asthma and rhinitis (nasal inflammation).

“The granularity of the data really shows us the cause and effect,” Ito said. “It also showed us that pollution affects outcome of the residents for the next 60 to 70 days. Those days matter the most.”

A reduction in pollution saved lives

But the research also shows improvement in air quality. Since 2014, China has rolled out a nationwide air pollution reduction program. The program resulted in a 9.6 microgram per cubic meter decrease in transboundary air pollution from China to South Korea from 2015 to 2019. That resulted in fewer deaths (about 300 fewer deaths for every million people a year), and the researchers calculate that it saved South Korea more than $2.6 billion per year.

Still, the researchers found that under this policy, Chinese air pollution decreased more in cities where the pollution was more likely to stay in the country, and less in cities where it was likely to be pushed out by the westerly winds.

“The results are pretty stunning,” Kotamarthi said. “It shows you really do have to worry about air pollution as a global problem. Developing countries like India have not yet had the same reduction in pollution, so this is also an important topic for other parts of Asia, as well.”

The project benefitted from early funding from UChicago Joint Task Force Initiative, which helps Argonne and Fermilab achieve mission success by opening channels of frequent communication and collaboration across institutions.

“This is an interdisciplinary project in many ways, and if there wasn’t initial funding, it wouldn’t have happened,” Kotamarthi said. “This is a wonderful way to develop interdisciplinary research between the lab and the university.”

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