Municipal plastic waste represents not only a management and technological challenge but also a potential source of ecobiological pressure on riverine and riparian ecosystems. Inadequate separate collection, uncontrolled accumulation and fragmentation of plastic materials may facilitate the release of macroplastics and microplastics into freshwater ecosystems, where they can interact with macroinvertebrates, fish, microbial communities, bottom sediments, soils and riparian habitats. The aim of this study was to identify and characterise the potential pathways through which municipal plastic waste may enter riverine ecosystems, synthesise the possible mechanisms of its interaction with biota, and develop a preliminary conceptual framework for identifying priorities for ecobiological monitoring. A theoretical and analytical approach was applied, combining a targeted narrative review of recent scientific literature, a “pressure – pathway – receptor – response” framework, and an illustrative application of the developed by the authors plastic waste collection efficiency index to two hypothetical scenarios of municipal waste collection. The synthesis of the scientific literature showed that municipal plastic waste may interact with biota through physical habitat contamination, particle ingestion, transport of associated pollutants, formation of the plastisphere, and alterations in microbial processes in water, bottom sediments and soils. The illustrative application of the index to the two hypothetical scenarios yielded values of 0.67 and 0.64 and demonstrated how different combinations of service coverage and infrastructure accessibility affected the overall assessment. These scenario-based values do not characterise specific municipalities and do not quantify actual plastic leakage, concentrations in the aquatic environment, biological toxicity or biodiversity degradation. The study proposes a conceptual ecobiological framework for prioritising separate collection, local microplastic monitoring, assessment of bottom sediments, bioindication, and subsequent field verification in river basins affected by pressure from municipal plastic waste
macroinvertebrates; plastisphere; bottom sediments; bioindication; floodplains