Navigating environmental cooperation on air pollution amid political competition in East Asia

East Asian countries have recently upgraded their regional cooperation for clean air through the Acid Deposition Monitoring Network in East Asia, with elaborate arrangements for monitoring and capacity-building assistance for multiple pollutants. This represents a departure from the earlier informal regimes with vague arrangements on acid deposition. However, despite this notable shift, this formalization in the regional governance for clean air remains largely unexplored in the existing literature. This study fills this gap by analysing the dynamics of formalization through aid from theories of regime complexity and legalization. It focuses on the decade from 2012 to 2021, employing documentary analysis and interviews. The results reveal that governments actively pursue their state interests by adjusting institutional arrangements through regime competition and selection that drive formalization. Sharing cognition of the hazardousness of multiple pollutants achieved through interactions between regional and global institutions serves as a catalyst for reaching an agreement on the arrangements.