Abstract Summary
Plastic pollution in the natural environment poses a growing threat to ecosystems and human health, prompting urgent needs for monitoring, clean-ups, and new policies. One key aspect is the identification and definition of plastic hotspots to effectively prioritize resource allocation and mitigation strategies. Yet, the delineation of hotspots varies significantly across plastic pollution studies, and a definition is often lacking or inconsistent without a clear purpose and boundaries of the term. In our study, we applied four common hotspot definitions to plastic pollution datasets ranging from urban areas to a global scale. For each scale, hotspots were defined according to 1) values above the average of the dataset, 2) values in the highest interval, 3) outliers, and 4) values exceeding the 90th percentile. Our findings reveal that these hotspot definitions encompass between 0.8% to 93.3% of the total plastic pollution, covering < 0.1% to 50.3% of the total locations. Given this wide range of results and the possibility of temporal inconsistency in hotspots, we emphasize the need for standardized criteria and a holistic approach to describe plastic hotspots. Therefore, we designed a step-wise framework to define hotspots by determining the purpose, units, spatial scale, temporal scale, and threshold values. Incorporating these steps in research and policymaking yields a unified understanding of hotspots, facilitating the development of effective interventions and mitigative measures.
