This glossary explains the vocabulary used across the river plastic emissions map, methodology notes, and river profiles. It is designed for readers comparing modeled emission data, field observations, and practical prevention programs.
Riverine plastic emissions
The annual mass of plastic waste transported by rivers into the ocean. Estimated at 0.8–2.7 million metric tons per year globally (Meijer et al. 2021).
Source: Meijer et al. 2021
Mismanaged plastic waste
Plastic waste that is not properly collected, sorted, or disposed of, and is therefore at risk of entering the environment.
Source: UNEP 2021
Modeled outfall
A point where a river discharges into the ocean, with plastic emission estimates derived from geospatial modeling rather than direct measurement.
Source: Meijer et al. 2021
Ocean-bound plastic
Plastic waste at high risk of reaching the ocean because it is unmanaged, near waterways or coastlines, and not captured by formal collection systems. The term is used in prevention and recovery programs, while riverine emission models estimate one major transport pathway.
Related: mismanaged plastic waste and emission modeling methodology
Plastic flux
The amount of plastic moving past a point in a river over a given period. Field studies may estimate flux by counting floating items, measuring river velocity, and scaling observations over time.
Related: rainfall and flooding effects
Aquatic plastic leakage
All plastic entering aquatic environments from all pathways: rivers, coastal areas, and direct dumping. Broader than riverine emissions alone. Estimated at ~22 Mt/yr.
Source: OECD 2022
Ocean plastic stock
The accumulated mass of plastic in marine environments from all historical sources: floating debris, seafloor deposits, and microplastics.
Source: UNEP 2021
Watershed
The land area that drains into a particular river or body of water. Also called a drainage basin or catchment area.
Emission rank
The position of a river outfall relative to others, ordered by modeled annual plastic emission (mt/yr).
Source: Meijer et al. 2021
Distance to coast
A key variable in river plastic emission models. Rivers with shorter paths to the ocean deliver plastic more efficiently.
Source: Meijer et al. 2021
Microplastics
Plastic fragments smaller than 5 mm. Can result from fragmentation of larger plastics or be manufactured at small sizes (e.g. nurdles, microbeads).
Source: UNEP 2021
Confidence interval
A range of values that reflects uncertainty in a model estimate. The 0.8–2.7 Mt/yr range for riverine emissions represents a confidence interval, not imprecision.
Macroplastics
Plastic items or fragments larger than 5 mm, such as bottles, packaging, sachets, bags, and foam. Macroplastics are often the focus of river cleanup and interception because they can be collected before fragmenting into microplastics.
Source: UNEP 2021
Extended producer responsibility
A policy approach that makes producers responsible for the post-consumer stage of packaging and products. In plastic pollution prevention, EPR can fund collection, recycling, reuse systems, and verified recovery programs.
Related: mismanaged plastic waste
Collection point
A location where recovered plastic is gathered, sorted, weighed, and prepared for transport into recycling or processing systems. Collection points can help prevent plastic from reaching drains, rivers, and coastlines.
Related: river plastic prevention context
Traceability
The ability to document where recovered plastic came from, how it moved through collection and processing, and what claims can be made about it. Traceability supports accountability in programs designed to stop plastic before it reaches waterways.