Association of under-five child diarrheal disease in the Philippines due to landfill size, as related to China’s 2017 Operation National Sword Policy

Introduction: China's Operation National Sword policy (2018) dramatically shifted international waste flows from China to Southeast Asian countries, including the Philippines. This study examines the relationship between this policy shift and childhood diarrhea incidence in the Philippines through landfill exposure pathways. Methods: We analyzed DHS data from 2003, 2008, 2017, and 2022, including 31,468 children under age 5. A difference-in-differences approach examined landfill proximity exposure using shortest distance with 1/d² decay function. Fixed effects controlled for survey year and administrative region. Results: Diarrhea probability decreased consistently over time (2-3% per period). Counterintuitively, pre-policy closer landfill proximity associated with reduced diarrhea risk (2.94% decrease), while post-policy proximity increased risk (2.90% increase). Sub analyses stratified by water source and landfill categories often lost statistical significance. Discussion: Unexpected pre-policy findings suggest complex confounding factors beyond model capabilities. Sample size reductions in restricted analyses revealed substantial inferential limitations. Conclusion: This first examination of ONS policy effects on child health in receiving countries highlights the need for more sophisticated analytical approaches incorporating environmental monitoring and longitudinal designs.