Air pollution poses a significant threat to human health. One challenge countries encounter in reducing air pollution is that some of it may be caused by sources in neighboring countries and be carried over borders. This is the case in South Korea, where westerly winds carry pollution from China during the fall and winter months. In this way, countries like South Korea may not have full control over the pollution hurting their citizens.

The authors employ recent advances in atmospheric science to collect data on the hourly particulate matter (PM2.5) pollution trajectories from China to South Korea. They combine these trajectory data with hourly particulate pollution in China and South Korea and estimate how the transboundary pollution from China effects particulate pollution in South Korea. They then connect these data with mortality and emergency room visit data in South Korea to quantify the health impacts of transboundary air pollution.