Air pollution is one of the most pressing global challenges that affects lives worldwide. In many countries, severe air pollution is still one of the most crucial burdens of economic development (Jayachandran 2009, Greenstone and Hanna 2014, Chen et al. 2013, Greenstone and Jack 2015, Jack 2017, Ito and Zhang 2020, Khanna et al. 2021, Neidell et al. 2022, Gao et al. 2022, Berkouwer and Dean 2022). Previous studies have linked air pollution with negative health outcomes, such as low fertility rates and increased mortality.
A fundamental challenge in curbing air pollution is its transboundary nature. International organisations including the World Bank recognise the international spillover effects of air pollution as a first-order problem (World Bank 2022). However, the economics literature has not incorporated this spillover effect when evaluating the cost of air pollution and the benefit of environmental regulation. For example, the benefits of recent ambitious environmental policies in China and India may have a substantial impact on environmental quality in the surrounding countries, but these spillovers are not typically considered while evaluating these policies.
In our paper, we study the international spillover effects of air pollution and examine the extent to which conventional economic analysis would understate the cost of air pollution as well as the benefit of environmental regulation (Heo, Ito and Kotamarthi 2023). Our framework integrates recent advances in atmospheric science into econometric estimation and microdata on mortality and health. We use the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) to obtain data on hourly particle trajectories from China to South Korea. Combining these particle trajectory data with hourly PM2.5 data in China and Korea, we estimate how the transboundary PM2.5 from China affects PM2.5 in South Korea. We then connect these data with the universe of individual-level mortality data and emergency-department-visit data in South Korea to quantify the mortality and health impacts of transboundary air pollution.
Geographical characteristics of South Korea and China
In East Asia, autumn and winter are characterised by prevailing west winds (‘the Westerlies’), which mean that South Korea receives persistent west winds from China. In these seasons, we find that PM2.5 is substantially higher in the northwest region of South Korea than in the southeast region. By contrast, these regions have similar PM2.5 levels in spring and summer.
We use HYSPLIT to quantitatively confirm this relationship by simulating hourly backward trajectories from China to South Korea. The northwestern cities in South Korea, such as Incheon and Seoul, have trajectories coming from China more than half of the time in our sample period. By contrast, cities in the southeast, such as Busan, experience trajectories from China at a lower frequency.
Figure 1 PM2.5 in China and South Korea
Figure 2 Examples of backward trajectories