Understanding Microplastics Discourse Through Social Sensing: Insights from Geotagged Social Media

Microplastics have emerged as a growing global environmental and public health concern due to their widespread presence and increasing potential for human exposure through food, water, and air. Recent scientific evidence and expanding media coverage have heightened public awareness and debate surrounding their ecological and health impacts. However, a systematic understanding of how public attention and discourse related to microplastics vary across time and regions remains limited. Social sensing provides a promising framework to address this gap by leveraging large-scale digital trace data to capture collective attention and perception. This study analyzed geotagged microplastics-related tweets between 2017 and 2022 to characterize spatiotemporal patterns of public attention, dominant themes, and sentiment across global and regional contexts. Using an integrated spatiotemporal and content-based approach, we identified shifts in discussion intensity, thematic emphasis, and regional engagement, and examined their associations with local sociodemographic characteristics. Results show that public attention follows an issue-attention cycle rather than a steady increase. Three dominant themes emerged: Advocacy, Risk and Exposure, and Scientific Communication, with advocacy-related discussions consistently dominant. Across all themes, the proportion of neutral tweets declined over time, suggesting a shift toward more evaluative and opinion-oriented discourse. In the United States, neutral-sentiment discourse exhibited significant spatial heterogeneity and varies with education, race/ethnicity, and income. Overall, this study presents a scalable social sensing framework that leverages geotagged social media big data to track how environmental issues are discussed across time and space, with broader applications for studying public communication related to other emerging and controversial issues.