Building a national plastic waste inventory applying citizen science in Brazil

Environmental pollution is a complex problem that requires multisector stakeholder engagement. In the present study, we present results from the Blue Keepers program, which prioritizes data production to initiate dialogue and engage the private sector towards actions established through Sustainable Development Objectives. Phase 1 of the program included a robust diagnosis of plastic leakage across all municipalities in the country. In Phase 2, 109 field samplings took place in 20 municipalities in 11 different states to better understand local realities and, through citizen science, engage local partners in the discussion. Plastic was the most common material found among the 106,010 items collected in aquatic and coastal environments. Assessments in beaches, mangroves, and igarapé streams showed different items among the most ubiquitous, demonstrating potentially different sources for this pollution. The framework presented here for monitoring solid waste pollution in aquatic and coastal environments underscores three critical elements for successful initiatives focused on plastic pollution: 1) the scaling potential of citizen science for comprehensive monitoring; 2) the importance of science-based approaches for meaningful stakeholder engagement, including the private sector; and 3) the foundational role of robust databases in supporting evidence-based decision-making across governance levels. As global attention to marine plastic pollution continues to grow, the Blue Keepers model offers valuable methodological innovations and partnership strategies that can inform initiatives worldwide, contributing to the collective effort to combat plastic pollution.